Non-technical Summary
The study of Ordovician (ca. 485 to 443 million years ago) ostracods (small bivalved crustaceans) from eastern North America has been neglected for more than 40 years, prompting the need for taxonomic updates. Here we examined the taxonomy and biogeography of well-preserved silicified ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. Fifty-two species are described in detail including three new species: Vogdesella longidorsa n. sp., Eokloedenella duodepressa n. sp. and Aviacypris valcourensis n. sp. Results indicate close faunal relationships between Laurentia (ancient continent generally consisting of the present-day North America and Greenland) and Baltica (ancient continent generally consisting of the present-day Northern and Eastern Europe) during the Late Ordovician. Meanwhile, the fauna shares some common elements with nearby Siberia and Avalonia, and further connections with Kazakhstan and Peri-Gondwana blocks can also be traced.
Introduction
Ostracods have thrived from the Early Ordovician to the present, being a successful and resilient clade of crustaceans (Horne, Reference Horne, Holmes and Chivas2002; Williams et al., Reference Williams, Siveter, Salas, Vannier, Popov and Ghobadi Pour2008) and are good proxies for biogeographical and paleoecological analyses (Yasuhara et al., Reference Yasuhara, Tittensor, Hillebrand and Worm2017; Yasuhara, Reference Yasuhara2019). Ordovician ostracods represent the very early evolutionary stage of this group and play an important role in marine benthic communities during the Great Ordovician Biodiversification Event (GOBE) (Braddy et al., Reference Braddy, Tollerton, Racheboeuf, Schallreuter, Webby, Paris, Droser and Percival2004; Harper et al., Reference Harper, Cascales-Miñana and Servais2020). Abundant Ordovician ostracods from the Baltica and Laurentia have been known since the middle nineteenth century (Conrad, Reference Conrad1843; Eichwald, Reference Eichwald1855), while only sparse and discontinuous descriptions have been documented from other regions, such as terranes from the Peri-Gondwana (see Table 1 for references). The globally heterogeneous nature of taxonomic study of Ordovician ostracods largely constrains discussions on their macroevolutionary patterns.
Faunas compared in this research
Where ostracods have been well sampled, taxonomic redundancy resulting from insufficient revision has become a major obstacle that further hinders diversity analysis. Recent reviews (Huang et al., Reference Huang, Yasuhara, Horne, Perrier, Smith and Brandão2022) show great inconsistencies in registered and accepted names between the World Ostracoda Database (WOD, Brandão et al., Reference Brandão, Antonietto, Nery, Pereira, Praxedes, Santos and Karanovic2024) and the Paleobiology Database (PBDB, http://paleobiodb.org), the latter of which comprises a relatively complete occurrence record for Laurentian ostracods. This is because, despite the fact that many Ordovician ostracod species were described from Laurentia in the late nineteenth to middle twentieth centuries (e.g., Ulrich, Reference Ulrich and Ulrich1889, Reference Ulrich1890, Reference Ulrich1894; Ulrich and Bassler, Reference Ulrich and Bassler1906, Reference Ulrich and Bassler1908, Reference Ulrich and Bassler1923; Harris, Reference Harris1931a, Reference Harrisb, Reference Harris1957; Kay, Reference Kay1934, Reference Kay1940; Swain, Reference Swain1957, Reference Swain1962; Kraft, Reference Kraft1962), simple morphology and incomplete preservation has resulted in the underestimation of diversity. For example, Williams and Vannier (Reference Williams and Vannier1995) found that more than a hundred featureless, straight-hinged ostracod species had been chronically assigned to an umbrella genus Aparchites, which actually included many different genera. Thus, systematic reexaminations of ostracod taxonomy are urgently necessary.
Here we describe newly collected, well-preserved, and silicified materials from the Crown Point Formation of Valcour Island, New York State, and provide taxonomic revisions. Previously, Swain (Reference Swain1957, Reference Swain1962) described six ostracod faunas from the eastern United States, including three in Pennsylvania, two in New York and one in Vermont, recognizing 36 species from the Valcour fauna. Later, Copeland (Reference Copeland1982) recorded an additional four new species from the Crown Point Formation, indicating great potential for high ostracod diversity of the formation. Indeed, our comprehensive analysis further increases the diversity of the Valcour fauna by 30%, and has implications for our understanding of local faunal composition, as well as global biogeographical patterns.
Geologic setting
The study area is Valcour Island, in Lake Champlain, northeastern New York State, which is paleogeographically located on the southern marginal area of Laurentia (Fig. 1) (Blakey, Reference Blakey2013; Torsvik and Cocks, Reference Torsvik and Cocks2017; McLaughlin and Stigall, Reference McLaughlin, Stigall, Servais, Harper, Lefebvre and Percival2023). The Ordovician system in this area is represented by the carbonate Chazy Group (Cushing, Reference Cushing1905; Oxley and Kay, Reference Oxley and Kay1959), including the Day Point, Crown Point, and the Valcour formations in ascending order.
(1) Paleogeographical map of Laurentia showing sampled locality (indicated by red rhombus) and other faunas mentioned in this paper (gray rhombuses). Ok, Oklahoma; Mi, Minnesota; Ke, Kentucky; Vi, Virginia; Pe, Pennsylvania; NY, New York; On, Ontario; Ma, Northwest Territories, Mackenzie; MP, Nunavut, Melville Peninsula; BI, Nunavut, Baffin Island; Gi, Scotland, Girvan District. See Table 1 for references. Light-gray shaded area with dotted line represents the Southern Marginal Province of Laurentia ostracods (Mohibullah et al., Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012). Black lines and dashed lines indicate the modern state boundaries and national border, respectively. Base map modified from Blakey (Reference Blakey2013), Torsvik and Cocks (Reference Torsvik and Cocks2017), and McLaughlin and Stigall (Reference McLaughlin, Stigall, Servais, Harper, Lefebvre and Percival2023). (2, 3) Location maps of Valcour Island and the sampled section (indicated by red rhombuses).
The Chazy Group, which traditionally was assigned to the Middle Ordovician, was the basis for the North American Chazyan Stage. However, the group is now recognized to range into the early Sandbian (Late Ordovician, Nemagraptus gracilis Zone), based on conodont and graptolite studies (Sweet et al., Reference Sweet, Ethington and Barnes1970; Ross et al., Reference Ross, Adler, Amsden, Bergström and Bergström1982; Harris et al., Reference Harris, Dumoulin, Repetski, Carter, Cooper, Droser and Finney1995; Bergström and Ferretti, Reference Bergström and Ferretti2017). Most authors followed this age designation (e.g., Mohibullah et al., Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012; Dix et al., Reference Dix, Nehza and Okon2013; Meidla et al., Reference Meidla, Tinn, Salas, Williams, Siveter, Vandenbroucke, Sabbe, Harper and Servais2013; Selleck and Mehrtens, Reference Selleck, Mehrtens and Franzi2015), but Cornell (Reference Cornell2008) argued that the Chazy Group is completely Sandbian age based on a distinct hiatus between the Day Point Formation and the underlying Beekmantown Group, as supported by a trilobite study (Landing and Westrop, Reference Landing and Westrop2006). Considering the reliable nature of conodont and graptolite for biostratigraphical correlation, we agree with the age designation that the group ranges into the Late Ordovician.
Materials and methods
Ostracod samples documented in this research were newly collected from the grayish limestone of the Crown Point Formation, which has a total thickness of 95.4 m (313 ft) (Shaw, Reference Shaw1968). Sampling was conducted under the permit TR 2179/9267 (to MJH) from the New York State Department of Environmental Conservation in 2015. Twelve beds from a 10-meter interval of the lower Crown Point Formation were sampled and processed with buffered diluted formic acid. Silicified specimens (N = 23,451) were manually picked out of residues using a binocular microscope, with 2717 of them being indeterminate fragments. Uncoated specimens were digitally imaged using a HITACHI S3400N variable pressure scanning electronic microscope in low-vacuum mode at the Electron Microscope Unit of the University of Hong Kong.
The classification scheme used in this study follows Scott (Reference Scott and Moore1961), Vannier et al. (Reference Vannier, Siveter and Schallreuter1989), Mohibullah et al. (Reference Mohibullah, Williams and Zalasiewicz2014), and Siveter et al. (Reference Siveter, Briggs, Siveter and Sutton2024). The morphological terminology is from Jaanusson (Reference Jaanusson1957), Scott (Reference Scott and Moore1961), and Henningsmoen (Reference Henningsmoen1965).
Repositories and institutional abbreviations
Specimens discussed in this paper are housed in the American Museum of Natural History, New York, USA (AMNH); Museum of Comparative Zoology, Harvard University, Massachusetts, USA (MCZ); National Museum of Natural History, Washington DC, USA (USNM); and the Geological Survey of Canada, Ottawa, Canada (GSC). Figured specimens are housed in the New York State Museum (catalogue numbers NYSM 19523–19736).
Results
Fifty-two species of 42 genera were identified from the Crown Point Formation (Figs. 2–4) on Valcour Island. The Valcour fauna is characterized by the dominance of beyrichiocopids (25 species of 21 genera) and podocopids (17 species of 14 genera) (Fig. 4). The most abundant components of the fauna are the podocopid Krausella variata Kraft, Reference Kraft1962, and the beyrichiocopid Cryptophyllus oboloides (Ulrich and Bassler, Reference Ulrich and Bassler1923) (Fig. 3). The podocopid Elliptocyprites longula Swain, Reference Swain1962, the platycopid Primitiella anterorotunda Kraft, Reference Kraft1962, and the beyrichiocopids Eurychilina placida Swain, Reference Swain1962, and Eurybolbina bulbinoda (Swain, Reference Swain1962) are moderately abundant (Fig. 3), while the remaining species have relatively low abundances.
Stratigraphical range of ostracods from the Crown Point Formation at Valcour Island, northeastern New York State. Numbers below the lithology are sample reference numbers.
Ostracod faunal results from the Crown Point Formation at Valcour Island, northeastern New York State, showing relative abundance (%) of the six most abundant species, and changes in the proportional faunal composition and the endemicity through the samples.
General composition of the Valcour fauna from the Crown Point Formation at Valcour Island, northeastern New York State at the Order level and the endemicity level.
Discussion
Biogeographical significance
The Valcour fauna belongs to the Southern Marginal Province of Laurentian ostracods during the Late Ordovician (Fig. 1), which is characterized by a notable degree of endemism at the species level (Mohibullah et al., Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012)—57.7% of the species (Fig. 4, Table 2) found in the Champlain Lake area are endemic, consistent with the characteristic endemicity pattern observed in the province (Mohibullah et al., Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012). At the genus level, however, the present fauna demonstrates close relationships with faunas within Laurentia (Figs. 1, 5; Table 1) and has as many as 40 genera in common with adjacent paleocontinents (Figs. 5, 6; Table 1).
Endemic species list of the Valcour Fauna from the Crown Point Formation at Valcour Island, northeastern New York State
Genera of the Valcour fauna and their occurrences (black dots; circles indicate uncertain taxonomy) in other areas. See Table 1 for references. Ok., Oklahoma; Mi., Minnesota; Ke., Kentucky; Vi., Virginia; Pe., Pennsylvania; On., Ontario; Ma., Northwest Territories, Mackenzie; M.P., Nunavut, Melville Peninsula; B.I., Nunavut, Baffin Island; Gi., Scotland, Girvan District; Bal., Baltica; Ava., Avalonia; Sib., Siberia; Kaz., Kazakhstan; Pr., Argentine Precordillera; S.C., South China; A.T.A., Armorican Terrane Assembly; Al., Iranian Alborz; Au., Australia; Si., Sibumasu; In., India.
Genus-level relations between the studied Valcour fauna and selected faunas from other regions (see Table 1 for references). Black lines indicate numbers of commonly shared genera between the connected regions. Number in Laurentia represents the number of commonly shared genera between the Valcour fauna and other Laurentian faunas. Kaz, Kazakhstan; ATA, Armorican Terrane Assembly; Al, Iranian Alborz; SC, South China; Si, Sibumasu; Au, Australia; Pr, Argentine Precordillera. Base map modified from Torsvik and Cocks (Reference Torsvik and Cocks2017).
The apparent contradiction of exhibiting low endemicity at the genus level while displaying high endemicity at the species level suggests a history of frequent faunal exchange with a fast speciation rate during the early Sandbian age in the southern region of Laurentia. This aligns well with the greatly increased ostracod migration rates persisting from the late Darriwilian to the late Sandbian, which are calibrated by ostracod dispersal based on graptolite biozones (Williams et al., Reference Williams, Floyd, Salas, Siveter, Stone and Vannier2003). Noticeably, strong affinities at the genus level between Laurentia and Baltica during the Late Ordovician also have been recognized in brachiopods (Harper and Stewart, Reference Harper and Stewart2008; Sohrabi and Jin, Reference Sohrabi and Jin2013; Candela, Reference Candela2014), trilobites (Fortey and Cocks, Reference Fortey and Cocks2003), and bryozoans (Anstey et al., Reference Anstey, Pachut and Tuckey2003). Among these, brachiopods also show inconsistencies across taxonomic scales with homogeneity in generic composition but different congeneric species that nonetheless share ancestors from the Continental Margin Brachiopod Fauna (Jin et al., Reference Jin, Sohrabi and Sproat2013).
Twenty-seven genera of Valcour fauna ostracods have been documented from faunas of a similar age in Baltica (e.g., Henningsmoen, Reference Henningsmoen1954; Jaanusson, Reference Jaanusson1957; Sidaravičiene, Reference Sidaravičiene1992; Olempska, Reference Olempska1994; Meidla, Reference Meidla1996; see Table 1 for references) (Figs. 5, 6), showcasing the strong connections with Baltica, as exemplified by Schallreuter and Siveter (Reference Schallreuter and Siveter1985) and Williams et al. (Reference Williams, Floyd, Salas, Siveter, Stone and Vannier2003). Apart from widespread taxa such as Longiscula, Steusloffina, Pseudulrichia, and Aechmina, the Valcour fauna also comprises some newly introduced elements such as Collibolbina and others (Fig. 5). Additionally, species exclusive to Laurentia and Baltica (Fig. 4) further demonstrate the migration route between these two paleocontinents.
The faunal affinities between the current fauna and those of Gondwana, the Peri-Gondwana region, Avalonia, Siberia, and Kazakhstan are evinced by sharing some widespread genera (Figs. 5, 6, Table 1), as well as Tricornina, Budnianella, Macrocyproides, and Elliptocyprites. Tricornina first appeared in the late Darriwilian unnamed strata of northern Taimyr (Melnikova, Reference Melnikova2000) and was discovered in the Valcour fauna (this paper) and the Late Ordovician erratic boulders of Germany (Blumenstengel, Reference Blumenstengel1965), suggesting that the genus might have originated in Siberia. Budnianella, found only in the Valcour fauna (this paper), Virginia (Kraft, Reference Kraft1962), and Siberia (Melnikova, Reference Melnikova2000), highlights another link between Laurentia and Siberia. In addition, Macrocyproides has been documented from South China (Li, Reference Li1989; Wang, Reference Wang2015; Zhang, Reference Zhang2023), and Elliptocyprites is known from the Argentine Precordillera (Salas, Reference Salas2002b), central Iran (Schallreuter et al., Reference Schallreuter, Hinz-Schallreuter, Balini and Ferretti2006), and Australia (Schallreuter, Reference Schallreuter1988), revealing additional affinities with the Gondwana and Peri-Gondwana regions (Fig. 6). In general, the Valcour fauna bears the greatest affinity with those in Baltica, but also shares some common elements with those in nearby Siberia and Avalonia. Further connections can be detected by genera shared with Kazakhstan and with some Peri-Gondwana blocks including South China, Armorican Terrane Assembly, Iranian Alborz, and Argentine Precordillera. Limited relationships with Gondwana could be due to both the considerable paleodistance between the two and/or sampling bias due to lack of study in Gondwana.
Paleoenvironmental implications
Paleoenvironments associated with the Ordovician ostracod faunas from multiple terranes have been extensively analyzed in many aspects (e.g., Vannier et al., Reference Vannier, Siveter and Schallreuter1989; Williams and Siveter, Reference Williams and Siveter1996; Floyd et al., Reference Floyd, Williams and Rushton1999; Williams et al., Reference Williams, Floyd, Miller and Siveter2001a, b; Mohibullah et al., Reference Mohibullah, Williams and Zalasiewicz2014; Salas et al., Reference Salas, Waisfeld and Muñoz2019). The dominance of beyrichiocopids and podocopids in highly diverse faunas often occurs in shallow, stable, carbonate depositional environments (Vannier et al., Reference Vannier, Siveter and Schallreuter1989), such as faunas found in the Baltoscandia region (Meidla, Reference Meidla1996; Tinn et al., Reference Tinn, Meidla and Ainsaar2006). The depositional environments of the fossiliferous Crown Point Formation are known to range from stable, shallow-water conditions, represented by articulated trilobites (Shaw, Reference Shaw1968, Reference Shaw and Trip1969), to storm-dominated shelf settings with more agitated waters, based on fossiliferous bioclastic wackstones, packstones, and grainstones (Mehrtens and Selleck, Reference Mehrtens, Selleck, McLellan and Karabinos2002). The high diversity of the current fauna, combined with the dominance of beyrichiocopids and podocopids, aligns with a stable carbonate environment.
Biostratigraphical remarks
Age-diagnostic graptolites and conodonts have not been reported from the studied formation, leading to an ambiguous age determination. Both Mohibullah et al. (Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012) and Meidla et al. (Reference Meidla, Tinn, Salas, Williams, Siveter, Vandenbroucke, Sabbe, Harper and Servais2013) have considered the formation to be early Sandbian in age within the Nemagraptus gracilis Zone, and the current composition of the fauna strongly supports this age assignment.
At the genus level, Eoaquapulex, Platyrhomboides, and Monoceratella first appeared in other Sandbian formations in Laurentia (Lincolnshire and Edinburg formations of Virginia; Loysburg Formation of Pennsylvania; Balclatchie and Ardwell formations of the Scotland Girvan District; Bromide Formation of Oklahoma; see Table 1 for references), suggesting a stratigraphical range that begins in the N. gracilis Zone. At the species level, the Valcour fauna bears a strong resemblance to the fauna recorded from the Lincolnshire and Edinburg formations of Virginia (Kraft, Reference Kraft1962), sharing 10 common species: Ectoprimitia diminucarina Kraft, Reference Kraft1962, Eurychilina mattea Kraft, Reference Kraft1962, Primitiella anterorotunda Kraft, Reference Kraft1962, Eokloedenella posterodepressa Kraft, Reference Kraft1962, Krausella variata Kraft, Reference Kraft1962, Budnianella shenandoahense Kraft, Reference Kraft1962, Platyrhomboides virginiensis Kraft, Reference Kraft1962, Eoaquapulex frequens (Steusloff, Reference Steusloff1894), Eohollina depressa (Kay, Reference Kay1940), and Aparchites fimbriatus (Ulrich, Reference Ulrich1892). Conodonts and graptolites from these formations suggest a Sandbian age (Cooper and Cooper, Reference Cooper and Cooper1946; Bergström, Reference Bergström1971), which are here considered to be age equivalent to the Crown Point Formation.
Systematic paleontology
Abbreviations
CA, cardinal angle; L, maximum length; H, maximum height.
Class Ostracoda Latreille, Reference Latreille1802
Order Beyrichiocopida Pokorný, Reference Pokorný1954
Suborder Palaeocopina Henningsmoen, Reference Henningsmoen1953b
Superfamily Hollinoidea Swartz, Reference Swartz1936
Family Tvaerenellidae Jaanusson, Reference Jaanusson1957
Genus Dicranella Ulrich, Reference Ulrich1894
Type species
Dicranella bicornis Ulrich, Reference Ulrich1894.
Dicranella fimbriata Copeland, Reference Copeland1982
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–12) Dicranella fimbriata Copeland, Reference Copeland1982: (1–4) NYSM 19523, juvenile; (1) left lateral view; (2) right lateral view; (3) dorsal view; (4) ventral view. (5, 6) NYSM 19524, tecnomorph; (5) left lateral view; (6) internal view. (7, 8) NYSM 19525, heteromorph; (7) right lateral view; (8) internal view, showing the dolon. (9) NYSM 19526, tecnomorph, left lateral view. (10) NYSM 19527, juvenile, right lateral view. (11) NYSM 19528, juvenile, right lateral view. (12) NYSM 19529, juvenile, right lateral view. (13–19) Bromidella spiveyi Harris, Reference Harris1957: (13–15) NYSM 19530, heteromorph; (13) right lateral view; (14) internal view, showing the dolon; (15) magnified fragment of the star-shaped pustules, scale bar = 50 μm. (16, 17) NYSM 19531, tecnomorph; (16) right lateral view; (17) internal view. (18) NYSM 19532, juvenile, right lateral view. (19) NYSM 19533, juvenile, right lateral view. Scale bar = 500 μm.
Reference Copeland1982 Dicranella fimbriata Copeland, p. 13, pl. 6, figs. 1, 2; pl. 9, figs. 18, 19.
Holotype
Heteromorphic right valve (USNM 306765) from the Crown Point Formation of Valcour Island, New York, locality PB79.
Description
Valve slightly preplete and equal, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior one slightly larger than the posterior one. Two distinct protuberances developed on the surface of the valve, forming a ‘U’-shaped pattern with a deep middle sulcus. Anterior protuberance shorter than the posterior one in adult specimens, and both protrude over the dorsal margin. In juveniles, both protuberances at the same height. Velar structures developed as a subtle anteroventral frill. Marginal spines short and thick along the free margin. The surface of the valve finely papillose to granular, granules on velum aligned in parallel rows especially in female specimens. Sexual dimorphism observed. Female develops a dolon anteroventrally to posteroventrally without the dolonate groove, formed by the frill.
Remarks
The present specimens are assigned to Dicranella fimbriata based on the distinct protuberances, the finely papillose surface, and the outlines of the valve. This species differs from the type species D. bicornis from the Trenton Group of Minnesota in the shape of the protuberances and the development of velar ridge. From the same region, D. spinosa Ulrich, Reference Ulrich1894, bears a longer shape of the valve, and the anterior protuberance is more like a node; the outline of D. marginata Ulrich, Reference Ulrich1894, is similar to the present species, but both the protuberances are lower than the dorsal margin or slightly above it; the present species resembles D. bigeneris Ulrich, Reference Ulrich1894, in the shape of the valve and the ‘U’-shaped pattern, but the latter has a strongly developed velar ridge, and the protuberances are also lower than the dorsal margin. Dicranella fragilis Harris, Reference Harris1957, from the Bromide Formation of Oklahoma develops two thin and long protuberances and is a smaller size and is thus differentiated from the present species. Dicranella macrocarinata Harris, Reference Harris1931a, from the same region has no marginal spines.
Genus Bromidella Harris, Reference Harris1931a
Type species
Bromidella reticulata Harris, Reference Harris1931a.
Bromidella spiveyi Harris, Reference Harris1957
Reference Harris1957 Bromidella spiveyi Harris, p. 237, pl. 8, fig. 2.
Reference Swain1962 Eurychilina multipustulosa Swain, p. 727, pl. 109, figs. 6a, b.
Reference Copeland1982 Bromidella spiveyi; Copeland, p. 10, pl. 2, figs. 22, 23.
Holotype
Heteromorphic left valve (MCZ 4632) from the McLish Formation of Arbuckle Mountains, Oklahoma, locality Oklahoma Highway 99, Simpson section.
Description
Valve amplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Adductorial pit narrow, situated at the anterior part of the valve with a rounded preadductorial node. Velar structure develops as elongated spines along the free margin. Dorsal plica well developed as a ridge. The surface of the valve ornamented with dense star-shaped pustules. Sexual dimorphism observed. Female develops a dolon anteroventrally to posteroventrally without the dolonate groove. The external surface of the dolon is smooth, possibly caused by preservation. The velar spines on the dolon are shorter and closer to each other than normal ones.
Remarks
Swain (Reference Swain1962) introduced a new species within Eurychilina Ulrich, Reference Ulrich and Ulrich1889, for specimens from Valcour Island, according to the velar structure. He argued that the velar spines could be connected as a complete frill that was not preserved due to the imperfect silicification. However, the smooth surfaces of the spines in our new materials show no sign of connection between the spines, and the well-preserved star-shaped pustules indicate high-fidelity mineral replacement. Copeland (Reference Copeland1982) also suggested that Eurychilina multipustulosa Swain, Reference Swain1962, is a synonym of Bromidella spiveyi, and we agree with the revision in this study.
Bromidella spiveyi differs from all species within the genus in having the signate star-shaped pustules on the surface of the valve.
Genus Eoaquapulex Levinson, Reference Levinson1968
Type species
Diplopsis socialis Levinson, Reference Levinson1961.
Eoaquapulex frequens (Steusloff, Reference Steusloff1894)
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–3) Eoaquapulex frequens (Steusloff, Reference Steusloff1894): (1, 2) NYSM 19534, heteromorph; (1) right lateral view; (2) internal view. (3) NYSM 19535, heteromorph, left lateral view. (4–6) Collibolbina simplex (Krause, Reference Krause1892): (4) NYSM 19536, right lateral view. (5) NYSM 19537, left lateral view. (6) NYSM 19538, juvenile, right lateral view. (7–18) Eohollina depressa (Kay, Reference Kay1940): (7–10) NYSM 19539, tecnomorph; (7) right lateral view; (8) left lateral view; (9) dorsal view; (10) ventral view. (11) NYSM 19540, juvenile, left lateral view. (12) NYSM 19541, juvenile, right lateral view. (13) NYSM 19542, tecnomorph, left lateral view. (14) NYSM 19543, tecnomorph, left lateral view. (15, 16) NYSM 19544, tecnomorph; (15) left lateral view. (16) internal view. (17, 18) NYSM 19545, heteromorph; (17) left lateral view. (18) internal view, showing the dolon. Scale bar = 500 μm.
Reference Steusloff1894 Isochilina frequens Steusloff, p. 784, pl. 58, fig. 4.
Reference Kummerow1924 Aparchites? frequens; Kummerow, p. 415, pl. 20, fig. 4.
Reference Henningsmoen1954 Oepikella frequens; Henningsmoen, p. 93, pl. 5, figs. 7–9.
Reference Kraft1962 Oepikella frequens; Kraft, p. 32, 33, pl. 3, fig. 15; pl. 4, figs. 1–14.
Reference Nõlvak, Meidla and Hints1989 Diplopsis frequens; Nõlvak et al., p. 90, fig. 2.
Reference Meidla, Sarv, Kaljo and Nestor1990 Eoaquapulex frequens; Meidla and Sarv, p. 69, pl. 8, fig. 5.
Reference Sidaravičiene1992 Eoaquapulex frequens; Sidaravičiene, p. 104, pl. 27, figs. 11, 12.
Reference Meidla1996 Eoaquapulex frequens; Meidla, p. 41, pl. 5, fig. 12.
Holotype
Not designated.
Description
Valve amplete and subequal, with dorsal margin straight and ventral margin convex. CAs largely obtuse, the anterior one smaller than the posterior one. The surface of the valve smooth. Sexual dimorphism observed. Velar structure develops as narrow ridge in male valves. Velar ridge extends ventrally into a strong elongate dolon without distinct dolonate groove, forming a subtrapezoidal in lateral view of the female valve.
Remarks
The present specimens are assigned to Eoaquapulex frequens based on the elongated dolon, the smooth surface, the large size, and the outline of the valve. The original work (Steusloff, Reference Steusloff1894) did not designate the type specimen, and this assignment is based on specimens from the Lincolnshire Formation, Virginia (Kraft, Reference Kraft1962). Based on the velar structure, the species was removed from the leperditicopid genus Isochilina Swartz, Reference Swartz1949 (Henningsmoen, Reference Henningsmoen1954). Levinson (Reference Levinson1961) differentiated the newly established genus Diplopsis from the genus Oepikella by the angularity of the cardinal angles and the absence of marginal spines. Later (Levinson, Reference Levinson1968) revised the name Diplopsis to Eoaquapulex due to the homonym issue with Diplopsis Fauvel, Reference Fauvel1902. This species is thus revised to the genus Eoaquapulex accordingly.
Eoaquapulex frequens differs from the type species E. socialis in parallel dorsal and ventral margin.
Family Tetradellidae Swartz, Reference Swartz1936
Genus Collibolbina Schallreuter, Reference Schallreuter1964
Type species
Lomatobolbina collis Schallreuter, Reference Schallreuter1964.
Collibolbina simplex (Krause, Reference Krause1892)
Reference Krause1892 Entomis simplex Krause, p. 390, pl. 21, fig. 6.
Reference Schallreuter1967 Collibolbina simplex; Schallreuter, p. 442.
Reference Schallreuter1994 Collibolbina plana; Schallreuter, p. 496, 498, 526, 528, 506, 514, 518, 520, pl. 6, fig. 1; pl. 11, fig. 4; pl. 13, fig. 3; pl. 14, figs. 3–5.
Reference Põldvere, Kleesment, Paalits, Meidla and Bauert1998 Aulacopsis simplex; Põldvere et al., fig. 6.
Reference Tinn and Meidla1999 Aulacopsis simplex; Tinn and Meidla, p. 29, pl. 1, fig. 2.
Reference Tinn and Meidla2001 Aulacopsis simplex; Tinn and Meidla, p. 132, 135, figs. 2, 4e.
Reference Tinn2002 Aulacopsis simplex; Tinn, p. 23, 26, 35, 39, 40, figs. 6(8), 7, 9.
Reference Tolmacheva, Egerquist, Meidla, Tinn and Holmer2003 Aulacopsis simplex; Tolmacheva et al., figs. 2, 5.
Reference Tinn and Meidla2004 Aulacopsis simplex; Tinn and Meidla, p. 208, 210, 221, figs. 2, 3, pl. 1, fig. 14.
Reference Schallreuter and Hinz-Schallreuter2013 Collibolbina simplex; Schallreuter and Hinz-Schallreuter, p. 161, fig. 6.
Holotype
Heteromorphic left valve from the “Lower Ordovician” of Dalecarlia, Sweden. The type specimen was photographed but then lost; Schallreuter and Hinz-Schallreuter (Reference Schallreuter and Hinz-Schallreuter2011) designated a neotype (GG 400-G123-9) (Institut für Geographie und Geologie, Ernst Moritz Arndt-Universität Greifswald, Greifswald, Germany) from the Black Orthoceras Limestone of Gislövshammar, Scania, Sweden.
Description
Valve preplete and subequal, with dorsal margin straight and ventral margin convex. Anterior CA more obtuse than the posterior one. Velar spines develop posteroventrally. Surface smooth. Middle sulcus indistinct, shallow, long, and sigmoidal. Anterior lobe and posterior lobe evenly swollen, forming a platform on the lateral surface.
Remarks
The present specimens are assigned to Collibolbina simplex based on the shallow and sigmoidal middle sulcus, the flat lobes, and the outlines of the valve. Schallreuter and Hinz-Schallreuter (Reference Schallreuter and Hinz-Schallreuter2013) revised this species from Aulacopsis Hessland, Reference Hessland1949, to Collibolbina based on the shallow and weak middle sulcus. That revision is accepted here because Aulacopsis develops a fissure-like middle sulcus (Hessland, Reference Hessland1949).
Collibolbina simplex differs from all species within the genus in having a weak and shallow middle sulcus.
Family Hollinidae Swartz, Reference Swartz1936
Genus Eohollina Harris, Reference Harris1957
Type species
Beyrichia irregularis Spivey, Reference Spivey1939.
Eohollina depressa (Kay, Reference Kay1940)
Reference Harris1931b Ulrichia initialis Harris, p. 58, 59, pl. 13, fig. 5.
Reference Kay1940 Bromidella depressa Kay, p. 237, 263, pl. 34, figs. 12–15.
Reference Harris1957 Eohollina depressa; Harris, p. 208, pl. 7, figs. 1, 2.
Reference Kraft1962 Bromidella depressa; Kraft, p. 43, pl. 15, figs. 8–17.
Reference Copeland1965 Eohollina depressa; Copeland, p. 9, pl. 8, figs. 14–16, 21–23.
Reference Copeland1982 Eohollina depressa; Copeland, p. 10, pl. 2, figs. 18, 19; pl. 6, figs. 9, 10; pl. 7, fig. 5.
Reference Swain, Cornell and Sloan1987 Bromidella depressa; Swain and Cornell, p. 106, 107; pl. 9, fig. 6; pl. 10, fig. 1; pl. 11, figs. 8–17.
Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012 Eohollina depressa; Mohibullah et al., p. 6, fig. 5H.
Holotype
Heteromorphic right valve (AMNH-FI-88438) (formerly 27592 C, Columbia University, New York, USA) from the Ion Member, Decorah Formation of Cannon Falls, Minnesota.
Description
Valve slightly preplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior one slightly broader than the posterior one. Velar structure developed as a narrow frill. Middle node-like lobe (L2) and the posterodorsal lobe (L3) separated by anteromedian sulcus. Longitudinally elongated anterior lobe (L1) connected with L2 and the large posteroventral lobe (L4) ventrally. The surface of the valve densely pustulose. Sexual dimorphism observed. Female develops a dolon formed by the frill anteroventrally to posteroventrally without the dolonate groove, forming a swollen ventral lobe-like area.
Remarks
The present specimens are assigned to Eohollina depressa based on the distinct lobe arrangement on the surface of the valve. This species has been described by many authors and reported as an index fossil of the Late Ordovician Bromide Formation. Kay (Reference Kay1940) originally assigned this species to Bromidella based on the lobation of the valve and the general outline, but Bromidella is characterized by a prominent dorsal plica (curved dorsal ridge), and the present species develops no such feature. Harris (Reference Harris1957) described the new genus Eohollina as the close counterpart of a Devonian and Carboniferous lobated genus Hollina Ulrich and Bassler, Reference Ulrich and Bassler1908, suggested an ancestral relationship between the two genera, and revised the present species to Eohollina accordingly. We follow the revision here in the study.
The surface ornaments of the valve are variable due to different preservation conditions. Kay (Reference Kay1940) described “smooth” surface, and Harris (Reference Harris1957, p. 208) stated “perforated except for occasional traces of papilli on the large posteroventral lobe.” Swain and Cornell (Reference Swain, Cornell and Sloan1987) considered the surface to be densely pustulose as in the Valcour specimens, but the figure from Mohibullah et al. (Reference Mohibullah, Williams, Vandenbroucke, Sabbe and Zalasiewicz2012) showed a smooth surface. Eohollina depressa differs from the type species E. irregularis in the more subtle posterodorsal lobe and the narrower frill.
Superfamily Eurychilinoidea Ulrich and Bassler, Reference Ulrich and Bassler1923
Family Oepikellidae Jaanusson, Reference Jaanusson1957
Genus Ectoprimitia Bouček, Reference Bouček1936
Type species
Primitia corrugata Krause, Reference Krause1892.
Ectoprimitia diminucarina Kraft, Reference Kraft1962
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–9) Ectoprimitia diminucarina Kraft, Reference Kraft1962: (1–4) NYSM 19546, preadult; (1) right lateral view; (2) left lateral view; (3) dorsal view; (4) ventral view. (5) NYSM 19547, adult, right lateral view. (6, 7) NYSM 19548, adult; (6) left lateral view; (7) internal view. (8) NYSM 19549, left lateral view. (9) NYSM 19550, left lateral view. (10–22) Platybolbina? sp.: (10–13) NYSM 19551, juvenile; (10) left lateral view; (11) right lateral view; (12) dorsal view; (13) ventral view. (14) NYSM 19552, juvenile, right lateral view. (15–17) NYSM 19553, heteromorph; (15) left lateral view; (16) internal view, showing the dolon; (17) magnified fragment of the double layered frill, scale bar = 50 μm. (18) NYSM 19554, juvenile, left lateral view. (19) NYSM 19555, juvenile, left lateral view. (20, 21) NYSM 19556 tecnomorph; (20) right lateral view. (21) internal view. (22) NYSM 19557, tecnomorph, right lateral view. Scale bar = 500 μm.
Reference Kraft1962 Ectoprimitia? diminucarina Kraft, p. 72, pl. 5, fig. 15; pl. 6, figs. 1–5.
Holotype
Right valve (USNM 136606) from the Edinburg Formation of Strasburg Junction, Virginia.
Description
Valve amplete and subequal, with dorsal margin straight and ventral margin convex with a slight depression in the middle area. CAs obtuse, the anterior one larger than the posterior one. Adductorial pit narrow, situated at the middle part of the valve with a rounded and indistinct preadductorial node. Velar structure developed as a narrow frill along the marginal area. Right valve overlaps the left along the free margin behind the velum, forming a flat marginal surface. The surface of the valve smooth. Subrectangular in lateral view.
Remarks
Kraft (Reference Kraft1962) doubtfully assigned this species to Ectoprimitia based on the ventral convexity, noting that this species is strongly convex ventrally whereas the genus is characterized by a slightly depressed ventral area. However, the figured specimen (Kraft, Reference Kraft1962, pl. 6, fig. 3) shows a slight depression at the ventral area and no prominent convexity. This feature as well as the subtriangular outline are considered to fit the genus description in Hessland (Reference Hessland1949), which is followed here in this study. The present specimens are assigned to this species based on the smooth surface, the development of the velar frill, the indistinct preadductorial node, and the outline of the valve.
Ectoprimitia diminucarina differs from the type species E. corrugata in having a smooth surface, subrectangular outline, and narrow frill. It is similar to E. tenuireticulata from Sweden in the outline of the valve, but the latter has a slightly reticulate surface.
Genus Platybolbina Henningsmoen, Reference Henningsmoen1953b
Description
Valve slightly preplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse, the anterior one larger than the posterior one. Shallow and indistinct sulcal depression located in the middle area of the valve with an indistinct preadductorial node. Velar structure develops as a characteristically broad frill, which is separated into two parts along the entire free margin. The inside part of the frill is flat whereas the outside is radially striated. From the internal view, the frill is double layered, developing aligned pores. Valve overlapping unknown. Frill curved laterally, forming a broad and flat marginal surface. The surface of the valve smooth. Juvenile valve develops a posterodorsal spine and striated frill only, and preadults develop a narrower inside frill. Sexual dimorphism observed. Female develops a dolon anteroventrally without the dolonate groove.
Remarks
Despite the fact that features of the present specimens (shallow sulcal depression, the indistinct preadductorial node, the strongly developed velar frill, and the outline of the valve) largely match with the definition of the genus, the sexual dimorphism is different from that of other species within the genus. Heteromorphs of the genus develop more convex, swollen, and wider frills than do tecnomorphs. However, the present female specimens develop a dolon, and this designation is thus tentative.
Platybolbina? sp. differs from all species within the genus in having the double layered, separated, and complete frill, and the dolon.
Family Eurychilinidae Ulrich and Bassler, Reference Ulrich and Bassler1923
Genus Eurychilina Ulrich, Reference Ulrich and Ulrich1889
Type species
Eurychilina reticulata Krause, Reference Krause1889.
Eurychilina placida Swain, Reference Swain1962
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–10) Eurychilina placida Swain, Reference Swain1962: (1, 2) NYSM 19558, tecnomorph; (1) left lateral view; (2) internal view. (3, 4) NYSM 19559, heteromorph; (3) left lateral view; (4) internal view, showing the dolon. (5–8) NYSM 19560, juvenile; (5) right lateral view; (6) left lateral view; (7) dorsal view; (8) ventral view. (9) NYSM 19561, juvenile, right lateral view. (10) NYSM 19562, juvenile, left lateral view, with molting scar. (11–15) Eurychilina mattea Kraft, Reference Kraft1962: (11, 12) NYSM 19563, tecnomorph; (11) left lateral view; (12) internal view. (13–15) NYSM 19564, heteromorph; (13) left lateral view; (14) magnified fragment of the granular lateral surface, scale bar = 50 μm; (15) internal view, showing the dolon. Scale bar = 500 μm.
Reference Swain1962 Eurychilina placida Swain, p. 730, pl. 109, figs. 7a–f.
Reference Copeland1982 Eurychilina? placida; Copeland, p. 34–39, pl. 7, figs. 14–22; pl. 8, fig. 3; pl. 9, fig. 3.
Holotype
Tecnomorphic right valve (USNM PAL 140611) from the Crown Point Formation of Valcour Island, New York.
Description
Valve amplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse, the anterior one larger than the posterior one. Well-defined adductorial pit located in the middle area of the valve with a distinct rounded preadductorial node. Velar structure developed as broad, radially striated frill along the entire free margin. Left valve overlaps right valve. Two indistinct ridges developed on the free margin. The surface of the valve smooth. Dorsal plica strongly developed. Light and indistinct groove of the molting scar can be observed on several specimens. Sexual dimorphism observed. Female develops a dolon anteroventrally with a faint dolonate groove.
Remarks
The widespread genus Eurychilina is highly variable on the dolonate structure (including the dolonate groove) and the surface ornaments. Kraft (Reference Kraft1962) recognized three groups within the genus based on the variation in the preadductorial node (strongly developed, faintly developed, and dorsally developed). Eurychilina placida belongs to the strongly developed group. The present specimens are assigned to E. placida based on the smooth surface, the strongly developed preadductorial node, the dorsal plica, and the outline of the valve. Some specimens show a molting scar on the lateral surface of the valve as a thin and indistinct groove.
Eurychilina placida differs from all species within the genus in having a smooth surface of the valve.
Eurychilina mattea Kraft, Reference Kraft1962
Reference Kraft1962 Eurychilina mattea Kraft, p. 36, pl. 10, figs. 9–14.
Reference Copeland1982 Eurychilina? mattea; Copeland, p. 34–39, pl. 7, fig. 23; pl. 9, figs. 14, 15.
Holotype
Right valve (USNM 136589) from the Edinburg Formation of Strasburg Junction, Virginia.
Description
Valve amplete, with dorsal margin straight and ventral margin convex. CAs obtuse, the anterior one larger than the posterior one. Well-defined adductorial pit located in the middle area of the valve with a distinct rounded preadductorial node. Velar structure developed as broad, finely striated frill spines along the entire free margin. On the free margin, a row of marginal spines developed only ventrally. The surface of the valve densely granular, with larger granules on the surface in general, and smaller granules on the preadductorial node. A row of special small granules is present in between large granules, indicating the molting scar. Dorsal plica slightly developed. Sexual dimorphism observed. Female develops a dolon anteroventrally without a dolonate groove; the surface of the female frill with the dolon smooth.
Remarks
The present specimens are assigned to Eurychilina mattea based on the densely granular surface, the strongly developed preadductorial node and the outline of the valve. The present species highly resembles E. placida from the same formation in most of the features, except that it develops a granular surface, more striated frill, and marginal spines. Nonetheless, because the expression of the ornamentation depends on the quality of the preservation, it is possible that the two species are conspecific.
Eurychilina mattea differs from all species within the genus in having a densely granular surface of the valve.
Eurychilina cf. E. partifimbriata Kay, Reference Kay1940
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–8) Eurychilina cf. E. partifimbriata Kay, Reference Kay1940: (1, 2) NYSM 19565, juvenile; (1) right lateral view; (2) ventral view. (3) NYSM 19566, juvenile, right lateral view. (4) NYSM 19567, juvenile, left lateral view. (5) NYSM 19568, juvenile, left lateral view. (6) NYSM 19569, juvenile, left lateral view. (7) NYSM 19570, preadult, left lateral view. (8) NYSM 19571, heteromorph, left lateral view. (9–19) Eurybolbina bulbinoda (Swain, Reference Swain1962): (9–12) NYSM 19572, adult; (9) left lateral view; (10) right lateral view; (11) dorsal view; (12) ventral view. (13–15) NYSM 19573, adult; (13) left lateral view; (14) ventral view; (15) magnified fragment of the papollose lateral surface, scale bar = 10 μm. (16, 17) NYSM 19574, adult; (16) left lateral view; (17) internal view, showing the pores. (18) NYSM 19575, preadult, right lateral view. (19) NYSM 19576, preadult, right lateral view. Scale bar = 500 μm.
cf. Reference Kay1940 Eurychilina partifimbriata Kay, p. 251, pl. 31, figs. 6–8.
Reference Copeland1982 Eurychilina? placida; Copeland, p. 38, 39, pl. 9, fig. 8.
cf. Reference Swain, Cornell and Sloan1987 Eurychilina partifimbriata; Swain and Cornell, p. 109, pl. 9, figs. 3a, b; pl. 13, figs. 8, 10, 16.
Description
Valve slightly preplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Shallow adductorial pit located in the middle area of the valve with a rounded preadductorial node. Velar structure develops as striated narrow frill, starting anterodorsally and getting broader ventrally. Characteristically, the frill terminates abruptly at the posteroventral part of the valve. A row of marginal spines developed along the free margin. Surface of the valve smooth. Juveniles develop a small posterodorsal spine, projecting above the dorsal margin. Adults bear dorsal plica. Sexual dimorphism observed. Female develops a dolon anteroventrally without a dolonate groove.
Remarks
The present specimens are similar to Eurychilina partifimbriata Kay, Reference Kay1940, in having the truncated velar frill and the shallow adductorial pit. However, E. partifimbriata has a finely pustulose surface of the valve, and a more swollen shape in dorsal and ventral views (Kay, Reference Kay1940, pl. 31, figs. 6, 8). This assignment is thus tentative.
Eurychilina cf. E. partifimbriata differs from all species within the genus in having an abruptly terminated velar frill.
Genus Eurybolbina Copeland, Reference Copeland1982
Type species
Eurybolbina krafti Copeland, Reference Copeland1982.
Eurybolbina bulbinoda (Swain, Reference Swain1962)
Reference Swain1962 Eurychilina bulbinoda Swain, p. 726, 727, pl. 109, figs. 4a, b.
non Reference Kraft1962 Eurychilina bulbinoda Kraft, p. 38, pl. 10, figs. 4–8.
Reference Copeland1982 Eurybolbina bulbinoda; Copeland, p. 12, pl. 7, figs. 3, 4, 6–8.
Holotype
Left valve (USNM 306701) from the Day Point Formation of Valcour Island, New York.
Description
Valve preplete, with dorsal margin straight and ventral margin convex. CAs obtuse, the anterior one larger than the posterior one, and the posterior one ended into a short spine projecting posterodorsally. Left valve larger than the right valve, overlapping the entire free margin, forming a broad marginal surface. Broad and shallow adductorial pit situated in the middle area of the valve, and a rounded, relatively large preadductorial node located close to the dorsal margin. Velar structure develops as narrow frill along the free margin, broadest anteroventrally. The surface of the valve densely papillose. From the internal view, scattered pores can be observed. Sexual dimorphism unknown.
Variability
The velar frill varies in width. Some specimens abruptly narrow the frill from posteroventral part to posterodorsal part, whereas some have a more elongated frill, which gradually narrows posterodorsally.
Remarks
Copeland (Reference Copeland1982) differentiated four species of Ctenobolbina Ulrich, Reference Ulrich1890, by their lack of the characteristic alate process on the lateral-ventral part of the valve, considering them to be a new genus Eurybolbina. Kraft (Reference Kraft1962) originally described the species Eurychilina bulbinoda Kraft, Reference Kraft1962, with a broad and complete frill from the Lincolnshire and Edinburg formations of Virginia. Swain (Reference Swain1962) questionably assigned specimens from the Crown Point Formation of New York as Eurychilina bulbinoda, because the latter bears a narrower and incomplete frill. Copeland (Reference Copeland1982) later included the specimens from New York in the newly established genus Eurybolbina, and we follow that revision here.
Eurybolbina bulbinoda differs from the type species E. krafti Copeland, Reference Copeland1982, and E. clintonensis (Swain, Reference Swain1962) in having a densely papillose surface whereas both latter species have a reticulated surface. Eurybolbina mackenziensis (Copeland, Reference Copeland1978) develops a large preadductorial node located at the middle part of the valve, which differentiates it from the present species.
Genus Piretia Jaanusson, Reference Jaanusson1957
Type species
Piretia geniculata Jaanusson, Reference Jaanusson1957.
Piretia shawi Copeland, Reference Copeland1982
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–16) Piretia shawi Copeland, Reference Copeland1982: (1–3) NYSM 19577, heteromorph; (1) left lateral view; (2) internal view, showing the dolon; (3) magnified fragment of the incisure on the frill, scale bar = 50 μm. (4, 5) NYSM 19578, tecnomorph; (4) left lateral view; (5) internal view. (6) NYSM 19579, heteromorph, right lateral view. (7) NYSM 19580, juvenile, dorsal view. (8) NYSM 19581, heteromorph, right lateral view. (9) NYSM 19582, tecnomorph, left lateral view. (10) NYSM 19583, preadult, right lateral view. (11) NYSM 19584, heteromorph, right lateral view. (12) NYSM 19585, tecnomorph, right lateral view. (13) NYSM 19586, juvenile, right lateral view. (14) NYSM 19587, juvenile, right lateral view. (15) NYSM 19588, juvenile, right lateral view. (16) NYSM 19589, juvenile, left lateral view. Scale bar = 500 μm.
Reference Copeland1982 Piretia shawi Copeland, p. 12, pl. 6, figs. 11–19.
Holotype
Left valve (USNM 306692) from the Day Point Formation of Valcour Island, New York, locality PB5.
Description
Valve amplete and subequal, with dorsal margin straight and long and ventral margin convex. CAs obtuse, the anterior one larger than the posterior one. Shallow and sigmoidal middle sulcus located in the middle area of the valve with a small preadductorial node. Velar structure developed as broad and tubulous frill along the entire free margin, terminating with a posterodorsal spine. Tubules united anterodorsally. From the internal view, small and aligned incisures developed on the end of the tubulous frill. A subtle velar ridge developed before the tubulous frill, forming the base of the frill. The general surface of the valve smooth, but granular on the velar ridge. Sexual dimorphism observed. Female develops a broader velar ridge with an anteroventral dolon underneath. The dolon connected with the tubulous frill.
Remarks
The present specimens are assigned to Piretia shawi based on the characteristic tubulous frill and the outline of the valve. Copeland (Reference Copeland1982) assigned the species to Piretia Jaanusson, Reference Jaanusson1957, based on its deep and sigmoidal middle sulcus, but some figured specimens (e.g., Copeland, Reference Copeland1982, pl. 6, figs. 11–16, 18) also bear a shallow middle sulcus, as do the present specimens. This could be the result of intraspecific variation or preservation.
Piretia shawi differs from all species within the genus in having the characteristically tubulous frill. One specimen (NYSM 19580, Figure 12.7) is preserved such that the two valves are open.
Family Acronotellidae Swartz, Reference Swartz1936
Genus Monoceratella Teichert, Reference Teichert1937
Type species
Monoceratella teres Teichert, Reference Teichert1937.
Monoceratella cf. M. teres Teichert, Reference Teichert1937
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–9) Monoceratella cf. M. teres Teichert, Reference Teichert1937: (1–3) NYSM 19590, adult; (1) right lateral view; (2) ventral view; (3) dorsal view. (4, 5) NYSM 19591, adult; (4) left lateral view; (5) internal view. (6) NYSM 19592, juvenile, right lateral view. (7) NYSM 19593, juvenile, right lateral view. (8) NYSM 19594, juvenile, right lateral view. (9) NYSM 19595, preadult, right lateral view. (10–16) Tricornina (Ovornina) valcourensis (Copeland, Reference Copeland1982): (10, 11) NYSM 19596, juvenile; (10) right lateral view; (11) dorsal view. (12, 13) NYSM 19597, adult; (12) left lateral view; (13) dorsal view. (14) NYSM 19598, juvenile, left lateral view. (15) NYSM 19599, juvenile, left lateral view. (16) NYSM 19600, juvenile, right lateral view. Scale bar = 500 μm.
Reference Copeland1982 Monoceratella cf. teres; Copeland, pl. 7, fig. 1; pl. 9, fig. 12, 13.
Description
Valve preplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Left valve larger than the right, overlapping along the complete free margin. Surface smooth. An obtuse and short spine projects laterally, forming a swollen area posteroventrally. Middle sulcus curved and shallow, extending close to the ventral margin. Indistinct node in front of the middle sulcus. Preadult dimorphism observed. Preadult valves develop a short spine posterodorsally, projecting above the dorsal margin, and the adult valves bear a slightly swollen area behind the middle sulcus accordingly.
Remarks
Copeland (Reference Copeland1982) figured the species without description. The present species closely resembles Monoceratella teres in the posteroventral spine, the shallow middle sulcus, and the outline of the valve, but the latter has a less-swollen ventrum and a thinner, longer posteroventral spine. The designation is thus tentative. The present species is similar to Winchellatia minnesotensis Kay, Reference Kay1940, from the Decorah Formation of Minnesota in the outline of the valve, the posteroventral spine, the long middle sulcus and the presulcus node. However, the Monoceratella cf. M. teres specimens have a simple contact margin area without any velar structure.
Superfamily Uncertain
Family Tricorninidae Blumenstengel, Reference Blumenstengel1965
Genus Tricornina Bouček, Reference Bouček1936
Type species
Tricornina navicular Bouček, Reference Bouček1936.
Subgenus Ovornina Gründel, Reference Gründel1966
Tricornina (Ovornina) valcourensis (Copeland, Reference Copeland1982)
Reference Copeland1982 Ovornina (Margoplanitia) valcourensis Copeland, p. 18, pl. 8, figs. 22–25.
Holotype
Left valve (USNM 306744) from the Day Point Formation of Valcour Island, New York, locality PB5.
Description
Valve preplete, with dorsal margin straight and ventral margin convex. Anterior CA obtuse, posterior CA acute and slightly rounded. Distinctively long, thin, and hollow lateral spine situated at the mid-ventral part of the valve, protruding posteriorly. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Tricornina (Ovornina) valcourensis (Copeland, Reference Copeland1982) based on the distinctive lateral spine and the outline of the valve. The genus Tricornina, originally described from Silurian specimens, has a rather long stratigraphical range from the Ordovician to Devonian (Gündel, 1966). Gündel (1966) reviewed the family Tricorninidae and proposed a new genus Ovornina for specimens that only developed a lateral spine without cardinal spines. Later, Schallreuter (Reference Schallreuter2005) and Schallreuter et al. (Reference Schallreuter, Hinz-Schallreuter, Balini and Ferretti2006) revised Ovornina as a subgenus of Tricornina. We follow the most recent revision.
Tricornina (Ovornina) valcourensis differs from the other Ordovician species T. (O.) haehneli Blumenstengel, Reference Blumenstengel1965, in having a more flattened surface, and its greatest height is located at the anterior third of the valve.
Family Uncertain
Ostracod gen. et sp. indet.
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–9) Aparchites fimbriatus (Ulrich, Reference Ulrich1892): (1–4) NYSM 19601, preadult; (1) left lateral view; (2) right lateral view; (3) dorsal view; (4) ventral view. (5) NYSM 19602, juvenile, left lateral view. (6) NYSM 19603, juvenile, left lateral view. (7) NYSM 19604, juvenile, left lateral view. (8) NYSM 19605, adult, left lateral view. (9) NYSM 19606, preadult, right lateral view. (10–14) Aparchites pembertonensis Swain, Reference Swain1957: (10) NYSM 19607, juvenile, right lateral view. (11) NYSM 19608, juvenile, left lateral view. (12) NYSM 19609, juvenile, right lateral view. (13) NYSM 19610, preadult, left lateral view. (14) NYSM 19611, adult, right lateral view. (15–17) Baltonotella circulantis (Harris, Reference Harris1957): (15) NYSM 19612, adult, lateral view. (16) NYSM 19613, preadult, lateral view. (17) NYSM 19614, juvenile, lateral view. (18, 19) Macronotella scofieldi? Ulrich, Reference Ulrich1894: (18) NYSM 19615, juvenile, right lateral view. (19) NYSM 19616, juvenile, right lateral view. (20) NYSM 19617, ostracod gen. et sp. indet., left lateral view. Scale bar = 500 μm.
Description
Valve preplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Surface partly punctate on the ventral half of the valve, with a rounded area indicating the adductorial muscle. Velar structure developed as short, striated frill anteroventrally. Sexual dimorphism unknown.
Remarks
Only one specimen was recovered. Based on the position of the adductorial muscle scar, the present specimen is a left valve. The “straight-hinge” outline and the velar structure suggest that it is a palaeocopiniid species. The present specimen also bears some similarities to the aparchitiids in the outline of the valve, and in having limited velar structures and a simply ornamented surface.
Suborder Leicopina Schallreuter, Reference Schallreuter1973
Superfamily Aparchitioidea Jones, Reference Jones1901
Family Aparchitidae Jones, Reference Jones1901
Genus Aparchites Jones, Reference Jones1889
Type species
Aparchites whiteavesi Jones, Reference Jones1889.
Aparchites fimbriatus (Ulrich, Reference Ulrich1892)
Reference Ulrich1892 Leperditia fimbriata Ulrich, p. 268, pl. 9, figs. 34–36.
Reference Ulrich1894 Aparchites fimbriatus; Ulrich, p. 645, pl. 45, figs. 10–12.
Reference Ulrich1894 Leperditella canalis; Ulrich, p. 637, pl. 43, figs. 1–3.
Reference Kay1940 Aparchites carinatus; Kay, p. 244, pl. 29, figs. 29–32.
Reference Swain1957 Aparchites fimbriatus; Swain, p. 560, 561, pl. 61, figs. 13d, e.
Reference Swain, Cornell and Hansen1961 Aparchites fimbriatus; Swain et al., p. 351–353, pl. 46, figs. 1c–h.
Reference Copeland1982 “Aparchites” fimbriatus; Copeland, p. 34, pl. 7, fig. 11.
Holotype
Left valve (USNM 41834) from the Maquoketa Formation of Fillmore County, Minnesota.
Description
Valve amplete and unequal, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Right valve larger than the left valve, overlapping the entire free margin. Velar ridge developed along the free margin on the left valve, more prominent ventrally. Undecorated free margin on the right valve, overlapping the left valve, forming a flat marginal surface. Preadult dimorphism developed strongly. Distinct, broad, and striated velar frill developed on both valves of the preplete juveniles, protruding anterodorsally and posterodorsally above the dorsal margin. During growth, the frill on the left valve partly exfoliated into spines and denticles on the velar ridge, whereas the one on the right valve exfoliated completely. The surface of the valve punctate with pores. A rounded, impunctate muscle scar located at the anterior-median part of the valve. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Aparchites fimbriata (Ulrich, Reference Ulrich1892) based on the unequal valves, the characteristic preadult dimorphism, the punctate surface, and the outline of the valve. Aparchites fimbriata differs from the type species A. whiteavesi Jones, Reference Jones1889, in having the punctate surface, unequal valves, velar ridge, and a more elliptical shape of the valve. Aparchites pembertonensis Swain, Reference Swain1957, from the Loysburg and Benner formations of Pennsylvania bears a smooth surface.
Aparchites pembertonensis Swain, Reference Swain1957
Reference Swain1957 Aparchites pembertonensis Swain, p. 560, pl. 61, figs. 12a, b; pl. 62, fig. 11.
Reference Copeland1982 “Aparchites” fimbriatus; Copeland, p. 36, pl. 8, fig. 20.
Holotype
Right valve (USNM) from the Loysburg Formation of Pemberton Quarry, Pennsylvania. The type specimen is deposited with an unknown catalog number.
Description
Valve slightly preplete, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior CA larger than the posterior one. Preadult dimorphism developed. A subtle swelling developed mid-dorsally, forming an indistinct umbonate dorsum in adult valves. The surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Aparchites pembertonensis Swain, Reference Swain1957, based on the dorsal swelling, the smooth surface, and the outline of the valve. The present species is similar to Schmidtella Ulrich, Reference Ulrich1892, in having an umbonate dorsum (Swain, Reference Swain1957), but unlike Schmidtella, does not develop a faint depressed area on the surface of the valve, indicating the previous molt.
Aparchites pembertonensis is similar to the type species A. whiteavesi Jones, Reference Jones1889, in the outline of the valve, but the latter develops no dorsal swelling. Aparchites pembertonensis differs from A. fimbriatus (Ulrich, Reference Ulrich1892) in having the dorsal swelling and a preplete valve.
Genus Baltonotella Sarv, Reference Sarv1959
Type species
Macronotella kuckersiana Bonnema, Reference Bonnema1909.
Baltonotella circulantis (Harris, Reference Harris1957)
Reference Harris1957 Paraparchites? circulantis Harris, p. 142, 143, pl. 6, figs. 1a–c.
Reference Kraft1962 Aparchites suborbicularis; Kraft, p. 31, pl. 3, figs. 7–13.
Reference Williams and Vannier1995 Baltonotella circulantis; Williams and Vannier, p. 12, pl. 1, figs. 1–5.
Holotype
Right valve (MCZ 4508) from the Bromide Formation of the Arbuckle Mountains, Oklahoma, locality Oklahoma Highway 77, Simpson section.
Description
Valve amplete, with dorsal margin slightly umbonate and ventral margin convex, forming a circular shape of the valve. CAs indistinctly obtuse and subequal. Narrow and striated velar frill developed along the free margin. Preadult dimorphism developed, with surface of the juvenile valve being unornamented. Surface of the adult valve pitted. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Baltonotella circulantis (Harris, Reference Harris1957) based on the umbonate dorsal margin, the pitted surface, and the circular outline of the valve. Williams and Vannier (Reference Williams and Vannier1995) revised the present species to Baltonotella without giving a systematic description, but noted that the umbonate dorsal margin is a characteristic feature of the genus. We thus follow that revision.
Baltonotella circulantis differs from other species within the genus in having the circular outline of the valve and coarsely pitted surface.
Genus Macronotella Ulrich, Reference Ulrich1894
Type species
Macronotella scofieldi Ulrich, Reference Ulrich1894.
Macronotella scofieldi? Ulrich, Reference Ulrich1894
Reference Ulrich1894 Macronotella scofieldi Ulrich, p. 684, pl. 43, figs. 30–34.
Reference Ulrich and Bassler1923 Macronotella scofieldi; Ulrich and Bassler, p. 315, 316, figs. 22–27.
Reference Kesling, Crafts, Darby, Shubak and Smith1960 Macronotella scofieldi; Kesling et al., p. 304, 305, pl. 1, figs. 1–3; pl. 2, figs. 1, 2; pl. 3, figs. 1–4.
Reference Swain, Cornell and Hansen1961 Macronotella scofieldi; Swain et al., p. 355, 356, pl. 47, figs. 3a, b.
Description
Valve slightly preplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Surface of the valve characteristically pitted. Rounded, unpitted muscle scar located at the middle of the valve. No velar structure observed.
Remarks
Only two relatively small valves were recovered. Based on the characteristically pitted surface and the outline of the valve, the present specimens are tentatively regarded as juveniles of Macronotella scofieldi Ulrich, Reference Ulrich1894.
Macronotella scofieldi? differs from M. elegans Harris, Reference Harris1957, from the Oil Creek Formation of Oklahoma in having a longer dorsal margin. Macronotella mcgeheei Harris, Reference Harris1957, develops a more densely punctate surface, and M. upsoni Harris, Reference Harris1957, bears a slightly swollen dorsal margin. Hessland (Reference Hessland1949) recognized two species of the present genus from the Darriwilian “Orthoceras Limestone” of Sweden (from Holen Limestone to Folkeslunda Limestone, see Nielsen et al., Reference Nielsen, Ahlberg, Ebbestad, Hammer, Harper, Lindskog, Rasmussen, Stouge, Servais, Harper, Lefebvre and Percival2023), M. planosalebrosa Hessland, Reference Hessland1949, and M. reticulata Hessland, Reference Hessland1949, both of which develop shallow and indistinct pits that differentiate them from Macronotella scofieldi?.
Suborder Binodicopina Schallreuter, Reference Schallreuter1972
Superfamily Aechminoidea Bouček, Reference Bouček1936
Family Aechminidae Bouček, Reference Bouček1936
Genus Aechmina Jones and Holl, Reference Jones and Holl1868
Type species
Aechmina cuspidata Jones and Holl, Reference Jones and Holl1868.
Aechmina maccormicki Copeland, Reference Copeland1973
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–7) Aechmina maccormicki Copeland, Reference Copeland1973: (1) NYSM 19618, adult, left lateral view. (2) NYSM 19619, adult, right lateral view. (3) NYSM 19620, preadult, right lateral view. (4) NYSM 19621, preadult, right lateral view. (5) NYSM 19622, preadult, left lateral view. (6) NYSM 19623, preadult, left lateral view. (7) NYSM 19624, juvenile, left lateral view. (8, 9) Pseudulrichia cf. ullehmanni Schallreuter, Reference Schallreuter1981: (8) NYSM 19625, right lateral view. (9) NYSM 19626, right lateral view. (10–12) Pseudulrichia? sp.: (10) NYSM 19627, right lateral view. (11) NYSM 19628, right lateral view. (12) NYSM 19629, left lateral view. (13, 14) Circulina sp.: (13) NYSM 19630, right lateral view. (14) NYSM 19631, left lateral view. (15–20) Vogdesella longidorsa n. sp.: (15–18) NYSM 19632, holotype, adult; (15) left lateral view; (16) right lateral view; (17) dorsal view; (18) ventral view. (19) NYSM 19633, paratype, adult, left lateral view. (20) NYSM 19634, paratype, adult, right lateral view. Scale bar = 200 μm.
Reference Copeland1973 Aechmina maccormicki Copeland, p. 19, 20, pl. 1, fig. 8; pl. 3, figs. 5–7.
Reference Williams, Stone, Siveter and Taylor2001b Aechmina maccormicki; Williams et al., p. 594, fig. 3a–d.
Holotype
Right valve (GSC 31430) from the Ellis Bay Formation of Anticosti Island, Quebec.
Description
Valve amplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. A prominent horn-shaped spine protruded posteriorly from the middle-dorsal part of the valve, creating a shallow middle sulcus accordingly. The surface of the valve weakly reticulate. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Aechmina maccormicki Copeland, Reference Copeland1973, based on the characteristic posteriorly bending spine, and the general outline of the valve. The figured specimens from previous work (Copeland, Reference Copeland1973, pl. 3, figs. 5–7) have a more robust spine, which can also be slightly thinner (Williams et al., Reference Williams, Stone, Siveter and Taylor2001b, figs. 3a–d). This feature is regarded as intraspecific variation here in this study.
Aechmina maccormicki differs from the type species A. cuspidata Jones and Holl, Reference Jones and Holl1868, in having a much shorter spine. The species is similar to A. groenwalli Troedsson, Reference Troedsson1918, in having a posteriorly bending protuberance, but the protuberance in the latter is rounded and elliptical.
Genus Pseudulrichia Schmidt, Reference Schmidt1941
Type species
Leperditia bivertex Ulrich, Reference Ulrich1879.
Pseudulrichia cf. P. ullehmanni Schallreuter, Reference Schallreuter1981
cf. Reference Schallreuter1981 Pseudulrichia ullehmanni Schallreuter, p. 69, Fig. 9.
Description
Valve slightly preplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Two distinct nodes developed dorsally on the lateral surface. Anterior node round and small. Posterior node spiny and protruding posterodorsally above the dorsal margin. Middle sulcus shallow. Surface of the valve reticulate. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Pseudulrichia Schmidt, Reference Schmidt1941, based on the distinctive two nodes, the absence of a velar structure and the outline of the valve. The present specimens closely resemble P. ullehmanni Schallreuter, Reference Schallreuter1981, in having similarly shaped dorsal nodes and slightly preplete shape of the valve. However, the latter develops a smooth valve, and it was described in Baltica. The assignment of the present specimens is thus tentative.
Pseudulrichia cf. P. ullehmanni is characterized by the reticulate surface and the preplete outline, which differentiates it from other species within the genus.
Psudulrichia? sp.
Description
Valve amplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Two prominent and spiny nodes developed on the lateral surface, close to the dorsal margin. An indistinct rounded node situated behind the anterior spiny node, forming a short sulcus in front of the broad and shallow middle sulcus. A crescentic, subtle ridge developed anteroventrally to posteroventrally, connecting with the posterior spiny node ventrally. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Pseudulrichia Schmidt, Reference Schmidt1941, based on the two spiny nodes, the absence of a velar structure, and the outline of the valve. However, the development of a third node, which is fused with the anterior node, and a pseudovelum-like ridge on the present specimens indicate a close relationship with Klimphores Schallreuter, Reference Schallreuter1966. Since only three specimens were recovered, the assignment is tentative.
The present species highly resembles Pseudulrichia? sp. described from the Rockcliffe Formation of Ottawa, Ontario (Copeland et al., Reference Copeland, Parkins and Nowlan1989) in having the crescentic ridge and spiny nodes, but the latter has a more elongated valve and no third node. Pseudulrichia? sp. differs from all species within the genus in bearing a small, rounded third node.
Family Circulinidae Neckaja, Reference Neckaja1966
Genus Circulina Neckaja, Reference Neckaja1966
Description
Valve postplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. General surface of the valve flattened, with an indistinct annular ridge developing anterodorsally to posterodorsally. The annular ridge opened dorsally, terminating as two rounded nodes. Middle area of the valve depressed. The surface of the valve reticulate. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Circulina Neckaja, Reference Neckaja1966, based on the flattened surface, the annular ridge, and the middle depression. Only two specimens were recovered, and the reticulation of the valve surface is not well preserved. Circulina sp. differs from the type species Circulina fimbriata Neckaja, Reference Neckaja1966, in having a reticulate surface and a more indistinct and broader ridge. The small and rounded middle depression of this species is similar to that of C. nuda Neckaja, Reference Neckaja1966.
Genus Vogdesella Baker, Reference Baker1924
Holotype
Adult carapace, NYSM 19632 (Fig. 15.15–15.18) from the Crown Point Formation of the Valcour Island, New York State, USA.
Paratypes
Adult left valve, NYSM 19633 (Fig. 15.19); adult right valve, NYSM 19634 (Fig. 15.20).
Diagnosis
Vogdesella with a characteristic elongated dorsal margin, a very indistinct middle depression, and a flattened valve.
Occurrence
Sandbian (Late Ordovician) Crown Point Formation of the Valcour Island, New York State, USA.
Description
Valve amplete to slightly postplete and subequal, with elongated dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Very indistinct depression situated at the mid-dorsal part of the valve. Surface of valve smooth. From the ventral and dorsal view, valve flattened with an angular pseudovelum-like ridge between lateral surface and steep marginal surface. Sexual dimorphism unknown.
Etymology
From Latin longa (adjective, nominative singular, gender feminine) and dorsum (noun, nominative singular, gender neuter), referring to the elongated dorsum of this species.
Dimensions
NYSM 19632 (holotype), L = 438 μm, H = 306 μm; NYSM 19633 (paratype), L = 443 μm, H = 316 μm; NYSM 19634 (paratype), L = 449 μm, H = 306 μm.
Remarks
The present specimens are assigned to Vogdesella Baker, Reference Baker1924, based on the indistinct middle depression, the subequal valves, the absence of a marginal structure, and the outline of the valve. Schallreuter (Reference Schallreuter1980) recognized Pariconchoprimitia based on the absence of a middle depression and the presence of a muscle patch, but the validity was questioned by Meidla (Reference Meidla1996) due to the close similarity to Vogdesella. Meidla (Reference Meidla1996) suggested that they were synonymous, because the middle depression and muscle patch can be both present and absent in some species of both genera. We agreed with the suggestion.
Vogdesella longidorsa n. sp. closely resembles Pseudbollia obsoleta Jones, Reference Jones1985, from the Caradoc Series of Wales in having a flattened surface of the valve and a steep marginal surface, and a similar outline of the valve. However, the latter develops two rounded nodes that exhibit the generic feature and is thus considered not to be congeneric with the present species.
Vogdesella longidorsa n. sp. differs from all species within the genus in having an elongated dorsal margin.
Suborder Eridostracina Adamczak, Reference Adamczak1961
Family Cryptophyllidae Adamczak, Reference Adamczak1961
Genus Cryptophyllus Levinson, Reference Levinson1951
Type species
Eridoconcha oboloides Ulrich and Bassler, Reference Ulrich and Bassler1923.
Cryptophyllus oboloides (Ulrich and Bassler, Reference Ulrich and Bassler1923)
Ostracods from the Crown Point Formation of the Valcour Island, northeastern New York State. (1–12) Cryptophyllus oboloides (Ulrich and Bassler, Reference Ulrich and Bassler1923): (1–5) NYSM 19635, specimen with 5 layers; (1) right lateral view; (2) left lateral view; (3) dorsal view; (4) ventral view; (5) magnified fragment of the layered molts on the anterior cardinal angle, scale bar = 20 μm. (6) NYSM 19636, specimen with 2 layers, right lateral view. (7) NYSM 19637, specimen with 5 layers, right lateral view. (8) NYSM 19638, specimen with 3 layers, right lateral view. (9) NYSM 19639, specimen with 6 layers, right lateral view. (10, 11) NYSM 19640, specimen with 4 layers; (10) left lateral view; (11) internal view, showing the layered molts. (12) NYSM 19641, specimen with 8 layers, right lateral view. (13–22) Primitiella anterorotunda Kraft, Reference Kraft1962: (13–16) NYSM 19642, juvenile; (13) right lateral view; (14) left lateral view; (15) dorsal view; (16) ventral view. (17, 18) NYSM 19643, adult; (17) left lateral view; (18) magnified fragment of the posterior reticulation, scale bar = 50 μm. (19) NYSM 19644, preadult, right lateral view. (20) NYSM 19645, preadult, left lateral view. (21) NYSM 19646, juvenile, left lateral view. (22) NYSM 19647, juvenile, left lateral view. Scale bar = 500 μm.
Reference Ulrich and Bassler1923 Eridoconcha oboloides Ulrich and Bassler, p. 296, fig. 14.6–14.8.
Reference Levinson1951 Cryptophyllus oboloides; Levinson, p. 558, pl. 77, figs. 9a, b.
Reference Swain1957 Cryptophyllus oboloides; Swain, p. 565, pl. 62, figs. 15a–f.
Reference Swain, Cornell and Hansen1961 Cryptophyllus oboloides; Swain et al., p. 363, pl. 48, figs. 10a, b.
Reference Adamczak1961 Cryptophyllus oboloides; Adamczak, p. 47, 56, figs. 5D, 9E.
Reference Jones and Olempska2013 Cryptophyllus oboloides; Jones and Olempska, p. 346, fig. 4.5–4.7.
Holotype
Carapace (USNM 82388) from the Decorah Formation of St. Paul, Minnesota.
Description
Valve amplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Molt retention well developed, forming thin and concentric grooves that represent the free margin of earlier-stage molts. Dorsal margin prominently umbonate in multi-layered specimens, caused by the stacking of valves. Number of molt layer not necessarily related to the size of the valve. Specimens with two, three, four, five, six, and eight layers observed. The surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Cryptophyllus oboloides (Ulrich and Bassler, Reference Ulrich and Bassler1923) based on the characteristic molt retention, the thin grooves, and the outline of the valve. Previous works (Levinson, Reference Levinson1951; Olempska, Reference Olempska2012; Jones and Olempska, Reference Jones and Olempska2013) showed that its layered valve and hingement resulted from retention, making it more closely related to arthropods than bivalves. Although some authors (e.g., Schmidt, Reference Schmidt1941; Adamczak, Reference Adamczak1976) suggested an affinity with non-marine branchiopods, eridostracines are still assigned with ostracods, but this may be reconsidered if preserved appendages are discovered (Olempska, Reference Olempska2012; Jones and Olempska, Reference Jones and Olempska2013). Levinson (Reference Levinson1951) differentiated Cryptophyllus from Eridoconcha Ulrich and Bassler, Reference Ulrich and Bassler1923, based on the “trough” structures. Cryptophyllus develops a thin groove between each molt while Eridoconcha has a “U”-shaped trough formed by the marginal ridge of each molt (Fig. 17). We follow the designation.
Sketch drawing of Cryptophyllus Levinson, Reference Levinson1951, and Eridoconcha Ulrich and Bassler, Reference Ulrich and Bassler1923, showing difference between thin groove and “U”-shaped trough (modified from Jones and Olempska, Reference Jones and Olempska2013). (1, 2) Cryptophyllus oboloides (Ulrich and Bassler, Reference Ulrich and Bassler1923): (1) lateral view; (2) end view, showing thin grooves between each layer. (3, 4) Eridoconcha simpsoni Harris, Reference Harris1931a: (3) lateral view; (4) end view, showing “U”-shaped trough between each layer. Scale bar = 100 μm.
Cryptophyllus magnum (Harris, Reference Harris1931a) develops a large valve size and an umbonal spine, and is thus differentiated from the present species. Cryptophyllus oboloides differs from C. gutta Schallreuter, Reference Schallreuter1968a, and C. pius Truuver and Meidla, Reference Truuver and Meidla2015, from the Baltica in the outline of the valve.
Order Platycopida Sars, Reference Sars1866
Suborder Cytherelliformes Skogsberg, Reference Skogsberg1920
Superfamily Leperditelloidea Ulrich and Bassler, Reference Ulrich and Bassler1906
Family Primitiidae Ulrich and Bassler, Reference Ulrich and Bassler1923
Genus Primitiella Ulrich, Reference Ulrich1894
Type species
Primitiella constricta Ulrich, Reference Ulrich1894.
Primitiella anterorotunda Kraft, Reference Kraft1962
Reference Kraft1962 Primitiella anterorotunda Kraft, p. 72, pl. 5, figs. 8–12.
Holotype
Carapace (USNM 136629) from the Lincolnshire Formation of Strasburg, Virginia.
Description
Valve preplete, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior one larger than the posterior one. Right valve larger than the left, overlapping along the entire free margin. Velar ridge developed on the right valve, with short velar spines posteroventrally. Velar structure of the left valve developed as a narrow frill anteroventrally, and a row of short spines posteroventrally. Faint and indistinct depression located at the mid-dorsal part of the valve. Surface of the valve generally smooth, with reticulation developed posteriorly on the adult valve. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Primitiella anterorotunda Kraft, Reference Kraft1962, based on the undefined middle depression, the narrow velar frill, the unequal Cas, and the outline of the valve. The original description of the genus by Ulrich (Reference Ulrich1894, p. 648) was brief, lacking details on the marginal structures, but he described the type species, Primitiella constricta Ulrich, Reference Ulrich1894, as having “free edges with a narrow border.” The present species differs from the type species in having the velar frill and partly reticulate surface of the valve. The present species differs from other species within the genus in having a more elongated valve, posterior reticulation, a narrow velar frill, and an extended free margin on the right valve.
Primitiella? sp.
Ostracods from the Crown Point Formation of the Valcour Island, northeastern New York State. (1–15) Eokloedenella posterodepressa Kraft, Reference Kraft1962: (1–4) NYSM 19648, preadult; (1) right lateral view; (2) left lateral view; (3) dorsal view; (4) ventral view. (5, 6) NYSM 19649, preadult; (5) right lateral view; (6) magnified fragment of the posterior reticulation, scale bar = 20 μm. (7, 8) NYSM 19650, preadult; (7) right lateral view; (8) internal view, showing the double layered structure. (9, 10) NYSM 19651, adult; (9) right lateral view; (10) internal view, showing the double layered structure. (11) NYSM 19652, preadult, left lateral view. (12) NYSM 19653, juvenile, right lateral view. (13) NYSM 19654, juvenile, right lateral view. (14) NYSM 19655, preadult, right lateral view. (15) NYSM 19656, adult, left lateral view. (16–20) Eokloedenella duodepressa n. sp.: (16) NYSM 19657, juvenile, right lateral view. (17) NYSM 19658, paratype, juvenile, right lateral view. (18) NYSM 19659, juvenile, left lateral view. (19) NYSM 19660, holotype, adult, right lateral view. (20) NYSM 19661, paratype, adult, left lateral view. (21–24) Primitiella? sp.: (21) NYSM 19662, left lateral view. (22) NYSM 19663, left lateral view. (23) NYSM 19664, right lateral view. (24) NYSM 19665, right lateral view. Scale bar = 500 μm.
Description
Valve preplete, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior one larger than the posterior one. Valve shape elongated. Surface of the valve smooth. No marginal structure observed. Sexual dimorphism unknown.
Remarks
The present specimens are tentatively assigned to Primitiella based on the outline of the valve. The present specimens show limited features and are possible juveniles of other species.
Family Leperditellidae Ulrich and Bassler, Reference Ulrich and Bassler1906
Genus Eokloedenella Kraft, Reference Kraft1962
Type species
Eokloedenella posterodepressa Kraft, Reference Kraft1962.
Eokloedenella posterodepressa Kraft, Reference Kraft1962
Reference Kraft1962 Eokloedenella posterodepressa Kraft, p. 56, 57, pl. 8, figs. 8–12.
Holotype
Right valve (USNM 136583) from the Edinburg Formation of Strasburg, Virginia.
Description
Valve preplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior one larger than the posterior one. Short and deep adductorial pit situated at the anterior part of the valve. A steep slope developed posterodorsally, bearing reticulation on the surface. Surface of adult valve smooth in general except for the steep slope. Thin ridges parallel to the free margin developed on the juvenile valve surface. Double layered structure observed along the ventral margin internally, resembling duplicature in podocopids. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Eokloedenella posterodepressa Kraft, Reference Kraft1962, based on the deep adductorial pit, the posterodorsal depression, the posterior reticulation, and the outline of the valve. Kraft (Reference Kraft1962) proposed the genus and considered it as a member of the family Kloedenellidae Ulrich and Bassler, Reference Ulrich and Bassler1908, possibly representing a primitive group without the incurved ventrum. However, Guber and Jaanusson (Reference Guber and Jaanusson1964) argued that Eokloedenella bears no evidence of the posteroventral brood chamber characteristic of kloedenellids and suggested that it should be assigned to Leperditellidae. Copeland (Reference Copeland1974) agreed with the suggestion and we also follow the revision.
Eokloedenella posterodepressa differs from E. canadensis (Bassler, Reference Bassler and Twenhofel1928) from the Ellis Bay Formation of Anticosti Island in having a less steep posterior depression, a partly reticulate surface of the valve and a more elongated shape of the valve. Eokloedenella whittakerensis Copeland, Reference Copeland1974, from the Middle Ordovician of the District of Mackenzie bears an amplete valve, a finely papillose surface and an indistinct adductorial pit, which differentiates it from the present species.
Eokloedenella duodepressa new species
Holotype
Adult right valve, NYSM 19660 (Fig. 18.19) from the Crown Point Formation of the Valcour Island, New York State, USA.
Paratypes
Adult left valve, NYSM 19661 (Fig. 18.20); juvenile right valve, NYSM 19658 (Fig. 18.17).
Diagnosis
Eokloedenella with two distinctive anterior and posterior depressions. Adductorial pit short with a rounded preadductorial node.
Occurrence
Sandbian (Late Ordovician) Crown Point Formation of the Valcour Island, New York State, USA.
Description
Valve preplete and subequal, with dorsal margin straight and ventral margin convex. CAs obtuse, anterior one larger than the posterior one. Short adductorial pit situated at the anterior part of the valve, with a small and rounded preadductorial node. Two steep slopes developed anteroventrally and posterodorsally, respectively. Surface of adult valve develops thin ridges. Juvenile valve smooth. Sexual dimorphism unknown.
Etymology
From Latin duo (numeral, nominative plural, gender neuter) and depressa (adjective, nominative plural, gender neuter), referring to the two depressions on both anterior and posterior parts of this species.
Dimensions
NYSM 19660 (holotype), L = 581 μm, H = 343 μm; NYSM 19661 (paratype), L = 567 μm, H = 335 μm; NYSM 19658 (paratype), L = 365 μm, H = 211 μm.
Remarks
The present specimens are assigned to Eokloedenella Kraft, Reference Kraft1962, based on the deep adductorial pit, the anteroventral and posterodorsal depressions and the outline of the valve. The present species differs from all species within the genus in having the diagnostic anterior depression. Eokloedenella duodepressa n. sp. is similar to E. posterodepressa Kraft, Reference Kraft1962, in having a small size of the valve and anterior depression; it also bears no reticulation on the surface of the depressions.
Genus Schmidtella Ulrich, Reference Ulrich1892
Type species
Schmidtella crassimarginata Ulrich, Reference Ulrich1892.
Schmidtella affinis Ulrich, Reference Ulrich1894
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–10) Schmidtella affinis Ulrich, Reference Ulrich1894: (1–4) NYSM 19666, adult; (1) right lateral view; (2) left lateral view; (3) dorsal view; (4) ventral view. (5, 6) NYSM 19667, adult; (5) right lateral view; (6) internal view, showing the double layered structure. (7, 8) NYSM 19668, adult; (7) right lateral view; (8) internal view, showing partly preserved double layered structure. (9, 10) NYSM 19669, preadult; (9) left lateral view; (10) internal view without the second layer. (11, 12) Schmidtella sp.: (11) NYSM 19670, lateral view. (12) NYSM 19671, lateral view. (13–16) Lomatopisthia simplex (Harris, Reference Harris1957): (13) NYSM 19672, right lateral view. (14) NYSM 19673, left lateral view. (15) NYSM 19674, left lateral view. (16) NYSM 19675, left lateral view. (17) Martinssonozona? sp., NYSM 19676, lateral view. Scale bar = 500 μm.
Reference Ulrich1894 Schmidtella affinis Ulrich, p. 641, pl. 43, figs. 45–47.
Reference Kay1940 Schmidtella affinis; Kay, p. 241, pl. 29, figs. 1–4.
Reference Harris1957 Schmidtella affinis; Harris, p. 162, pl. 3, figs. 1a–c.
Reference Copeland1974 Schmidtella affinis; Copeland, p. 27, pl. 3, figs. 12–15, pl. 5, figs. 10, 11.
Holotype
Right valve (USNM 41296) from the Prosser Formation of Goodhue County, Minnesota.
Description
Valve postplete and subequal, with ventral margin convex. Dorsal margin umbonate, with hinge straight. CAs obtuse and subequal. A faint and concentric groove with broad depressed area located on lateral surface of the valve, parallel to the free margin. Posterior border slightly extended, forming the postplete shape of valve. Surface of the valve smooth. From the internal view, double layered structure observed. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Schmidtella affinis Ulrich, Reference Ulrich1894, based on the slightly postplete shape of valve, the concentric depression along the ventral margin, the posteriorly extended border and the outline of the valve. Schmidtella affinis differs from the type species Schmidtella crassimarginata Ulrich, Reference Ulrich1892, in having a posteriorly extended border, a less distinct ventral depression, and a postplete valve. Schmidtella concentrodepressa Kraft, Reference Kraft1962, strongly resembles the present species in the posteriorly extended border, but the latter develops a more convex dorsum. Schmidtella umbonata Ulrich, Reference Ulrich1894, develops a strongly umbonate dorsal margin and subcircular valve, differentiating it from the present species. In contrast with S. sublenticularis (Jones, Reference Jones1890) and S. robervali Copeland, Reference Copeland1973, Schmidtella affinis develops the concentric groove which is caused by the shedded molt.
Schmidtella sp.
Description
Valve amplete, with ventral margin convex. Dorsal margin slightly umbonate, with hinge straight. CAs obtuse and subequal. A short and depressed area located anteroventrally, paralleling with the free margin. Surface of the valve regularly furrowed. Furrows parallel with the free margin and dorsal margin. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Schmidtella based on the anteroventral depression and the outline of the valve. However, only two specimens were recovered, and one broken specimen lacks the anteroventral depression. This specimen could be a shedded molt, but further study on the present species is needed, so the assignment is tentative. Schmidtella sp. differs from all species within the genus in having the characteristically furrowed surface of the valve.
Superfamily Kloedenelloidea Ulrich and Bassler, Reference Ulrich and Bassler1908
Family Lomatopisthiidae Guber and Jaanusson, Reference Guber and Jaanusson1964
Genus Lomatopisthia Guber and Jaanusson, Reference Guber and Jaanusson1964
Type species
Thomasatia simplex Harris, Reference Harris1957.
Lomatopisthia simplex (Harris, Reference Harris1957)
Reference Harris1957 Thomasatia simplex Harris, p. 248, 249, pl. 8, figs. 15, 17a, b.
Reference Guber and Jaanusson1964 Lomatopisthia simplex; Guber and Jaanusson, p. 27–30, pl. 3, figs. 5–15.
Reference Copeland1982 Lomatopisthia simplex; Copeland, p. 36, pl. 8, fig. 5.
Reference Williams1991 Lomatopisthia simplex; Williams, p. 13–16, pl. 14, figs. 1–5; pl. 16, figs. 1–4.
Reference Williams and Siveter1996 Lomatopisthia simplex; Williams and Siveter, p. 79, Fig. c.
Holotype
Left valve (MCZ 4641) from the Tulip Creek Formation of Arbuckle Mountains, Oklahoma, locality Oklahoma Highway 99, Simpson section.
Description
Valve amplete, with dorsal margin straight. Ventral margin straight, parallel with the dorsal margin, forming a subrectangular shape of valve. CAs obtuse, subequal and weakly defined. Anterior lobe reached to the dorsal margin, curved and parallel to the anterior margin. Anterior lobe (L1) and middle knob-like rounded node (L2) separated by the short and deep anterior sulcus (S1). Middle sulcus (S2) broad and deep, gradually fused with the L1 and wide lobe (L3) ventrally. Posterior lobe (L4) developed as a curved arch, parallel to the posterior margin. Surface of the valve smooth. Sexual dimorphism observed. Inflated posterior lobe developed in female valve, which gives a larger height of the valve.
Remarks
The present specimens are assigned to Lomatopisthia simplex (Harris, Reference Harris1957) based on the development of the lobes and the middle node, the posterior dimorphism, and the outline of the valve. This species was originally assigned to Thomasatia Kay, Reference Kay1934, based on the lobate morphology. After examining new materials with posterior sexual dimorphism, Guber and Jaanusson (Reference Guber and Jaanusson1964) proposed the new genus Lomatopisthia for the group and suggested that the posterior dimorphism nature of the present species indicated an affinity with the family Kloedenellidae. We follow that revision.
Lomatopisthia simplex differs from L. bromidensis (Harris, Reference Harris1957) and L. auricula (Harris, Reference Harris1957) in having a broad L3 without a prominent S3, and L. auricula develops velar spine posteriorly.
Suborder Punciocopina Schallreuter, Reference Schallreuter1968b
Superfamily Kirkbyoidea Ulrich and Bassler, Reference Ulrich and Bassler1906
Family Kirkbyidae Ulrich and Bassler, Reference Ulrich and Bassler1906
Genus Martinssonozona Schallreuter, Reference Schallreuter1968b
Type species
Martinssonozona ordoviciana Schallreuter, Reference Schallreuter1968b.
Martinssonozona? sp.
Description
Valve subamplete, with dorsal margin straight. Ventral margin concave in the middle part of the valve. CAs obtuse and subequal. Surface of the valve covered with fine ridges parallel to the dorsal and ventral margins, weakly reticulate. Sexual dimorphism unknown.
Remarks
The present specimens are tentatively assigned to Martinssonozona Schallreuter, Reference Schallreuter1968b, based on the fine ridges, the concave ventral margin, and the outline of the valve. However, the absence of a “kirkbyan pit” (Schallreuter, Reference Schallreuter1968b) and the distinct reticulation in present specimens makes the designation questionable. The present specimens are possibly juveniles. Martinssonozona? sp. differs from the type species Martinssonozona ordoviciana Schallreuter, Reference Schallreuter1968b, in lacking a deep and narrow adductorial pit and a strongly reticulate valve surface formed by both horizontal and longitudinal ridges.
Order Leperditicopida Scott, Reference Scott and Moore1961
Family Leperditiidae Jones, Reference Jones1856
Genus Eoleperditia Swartz, Reference Swartz1949
Type species
Cytherina fabulites Conrad, Reference Conrad1843.
Eoleperditia labellosa (Jones, Reference Jones1891)
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–5) Eoleperditia labellosa (Jones, Reference Jones1891): (1) NYSM 19677, preadult, right lateral view. (2) NYSM 19678, preadult, left lateral view. (3) NYSM 19679, adult, left lateral view. (4) NYSM 19680, adult, left lateral view. (5) NYSM 19681, adult, left lateral view. (6, 7) Tirisochilina cf. T. anna (Jones, Reference Jones1858): (6, 7) NYSM 19682, adult; (6) right lateral view; (7) magnified fragment of the pitted surface, scale bar = 100 μm. Scale bar = 1.00 mm.
Reference Jones1891 Isochilina labellosa Jones, p. 64, pl. 10, figs. 16, 17, 19.
Reference Swain1957 Eoleperditia labellosa; Swain, p. 546, 547, pl. 59, fig. 4.
Holotype
Not designated.
Description
Valve slightly postplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Surface of the valve weakly punctate. An indistinct and impunctate area situated at the mid-anterior part of the punctate valve, representing the muscle scar. Eye tubercle small, distinct, and raised, located in front of the muscle scar. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Eoleperditia labellosa (Jones, Reference Jones1891) based on the small and raised eye tubercle, the punctate surface, and the outline of the valve. No holotype was designated, and the present assignment was based on specimens from the New Market limestone of Kauffman, Pennsylvania (Swain, Reference Swain1957). The species was originally assigned to Isochilina Jones, Reference Jones1858. Swain (Reference Swain1957) included the species in Eoleperditia based on the absence of the anterodorsal chevron scar and the flattened marginal surface. We follow such revision. In the present specimens, some relatively small valves bear smooth surfaces; however, Swain (Reference Swain1957) described a smooth specimen with a length of 2.05 mm, suggesting that the punctation could be related to the preservation.
Eoleperditia labellosa differs from the type species E. fabulites (Conrad, Reference Conrad1843) in having the distinct and raised eye tubercle and indistinct muscle scar. Eoleperditia nana (Jones, Reference Jones1891) developed a larger valve size than those of the present species. Both E. inflativentralis Harris, Reference Harris1957, and E. spicata Harris, Reference Harris1957, from the Simpson Group of Oklahoma have spiny cardinal angles, which distinguish them from the present species.
Family Isochilinidae Swartz, Reference Swartz1949
Genus Tirisochilina Berdan, Reference Berdan1976
Type species
Tirisochilina juabaria Berdan, Reference Berdan1976.
Tirisochilina cf. T. anna (Jones, Reference Jones1858)
cf. Reference Jones1858 Leperditia anna Jones, p. 247, pl. 9, fig. 18.
cf. Reference Berdan1976 Tirisochilina anna; Berdan, p. 61, pl. 9, fig. 13.
Reference Copeland1982 Tirisochilina anna; Copeland, p. 38, pl. 9, figs. 9–11.
Description
Valve slightly postplete, with dorsal margin straight and ventral margin convex. CAs obtuse and subequal. Surface of the valve finely punctate. Small pores observed in some punctation. Smooth, large and rounded area situated at the mid-anterior part of the valve, representing the muscle scar. Eye tubercle very indistinct and faint, located anterodorsally, one-third distance from the anterior margin, one-fifth distance from the dorsal margin. Sexual dimorphism unknown.
Remarks
The assignment of the present specimens is tentative. Berdan (Reference Berdan1976) reexamined leperditicopids from the Ibex area of Utah, revised Leperditia anna Jones, Reference Jones1858, to a species of Tirisochilina based on the absence of the stopping pits on the marginal area. We follow such revision. The present specimens closely resemble Tirisochilina anna in having the punctate surface, the absence of the stopping pits and chevron scar, the rounded muscle scar, and the outline of the valve. However, according to the original description of the species (Jones, Reference Jones1858), the eye tubercle is distinct and raised, and this assignment is thus tentative. Although figured specimens from Jones (Reference Jones1858, pl. 9, fig. 18) and Berdan (Reference Berdan1976, pl. 9, fig. 13) were too poorly illustrated to demonstrate the distinct eye tubercle, figured specimens in Copeland (Reference Copeland1982, pl. 9, figs. 9–11) clearly showed no eye tubercle. We thus consider the designation in Copeland (Reference Copeland1982) as questionable, and the specimens should be conspecific with the present specimens.
Tirisochilina cf. T. anna differs from the type species T. juabaria Berdan, Reference Berdan1976, in having a smaller size and an indistinct eye tubercle. Tirisochilina obesiporosa (Harris, Reference Harris1957) from the Joins Formation of Oklahoma has a subquadrate outline of the valve and well-developed eye tubercle, which differentiates it from the present species.
Order Podocopida Sars, Reference Sars1866
Suborder Metacopina Sylvester-Bradley, Reference Sylvester-Bradley and Moore1961
Superfamily Bairdiocypridoidea Shaver, Reference Shaver and Moore1961
Family Krausellidae Berdan, Reference Berdan and Moore1961
Genus Krausella Ulrich, Reference Ulrich1894
Type species
Krausella inaequalis Ulrich, Reference Ulrich1894.
Krausella variata Kraft, Reference Kraft1962
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–12) Krausella variata Kraft, Reference Kraft1962: (1–4) NYSM 19683, adult; (1) right lateral view; (2) left lateral view; (3) ventral view; (4) dorsal view. (5, 6) NYSM 19684, adult; (5) right lateral view; (6) internal view, showing the double layered structure. (7, 8) NYSM 19685, juvenile; (7) right lateral view; (8) magnified fragment of the pores, scale bar = 50 μm. (9) NYSM 19686, juvenile, right lateral view. (10) NYSM 19687, juvenile, right lateral view. (11, 12) NYSM 19688, adult; (11) left lateral view; (12) internal view. (13–18) Acanthoscapha champlainensis Swain, Reference Swain1962: (13–16) NYSM 19689, adult; (13) left lateral view; (14) right lateral view; (15) ventral view; (16) dorsal view. (17) NYSM 19690, adult, left lateral view. (18) NYSM 19691, juvenile, left lateral view. (19–28) Pachydomelloides valcourensis Swain, Reference Swain1962: (19–22) NYSM 19692, preadult; (19) left lateral view; (20) right lateral view; (21) dorsal view; (22) ventral view. (23) NYSM 19693, juvenile, right lateral view. (24) NYSM 19694, juvenile, right lateral view. (25, 26) NYSM 19695, adult; (25) right lateral view; (26) internal view, showing the double layered structure. (27, 28) NYSM 19696, preadult; (27) left lateral view; (28) internal view. Scale bar = 500 μm.
Reference Kraft1962 Krausella variata Kraft, p. 63–66, pl. 17, figs. 1–23; pl. 18, figs. 1a, b.
Reference Swain1962 Krausella variata; Swain, p. 738, pl. 111, figs. 7a–f.
Reference Williams, Floyd, Miller and Siveter2001a Krausella variata; Williams et al., p. 504, fig. 5f, g, j.
Reference Mohibullah, Vandenbroucke, Williams, Floyd, Meidla, Zalasiewicz and Siveter2011 Krausella variata; Mohibullah et al., p. 60, fig. 4c.
Reference Mohibullah, Williams and Zalasiewicz2014 Krausella variata; Mohibullah et al., p. 27, 28, pl. 6, figs. 5–7.
Holotype
Carapace (USNM 136593) from the Edinburg Formation of Strasburg, Virginia.
Description
Valve amplete to slightly postplete, unequal and asymmetrical. Left valve elliptical, with both dorsal and ventral margins convex. Right valve elongated and subtriangular, with dorsal margin convex and ventral margin slightly concave. Prominent spine extended posteriorly at the end of the right valve; posterior spine thinner in the juvenile valve. Left valve larger than the right valve, overlapping the right valve along the entire free margin. Surface of the valve smooth. Pores observed on well-preserved specimen. Double layered structure observed from internal view. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Krausella variata Kraft, Reference Kraft1962, based on the asymmetrical valve, the subtriangular right valve, the posterior spine, and the smooth surface of the valve. Some specimens (see Mohibullah et al., Reference Mohibullah, Vandenbroucke, Williams, Floyd, Meidla, Zalasiewicz and Siveter2011, Reference Mohibullah, Williams and Zalasiewicz2014) develop a strongly arched dorsal margin on the right valve, forming a triangular outline.
Krausella variata differs from the type species Krausella inaequalis Ulrich, Reference Ulrich1894, from the Trenton Limestone of Illinois in having an elliptical shaped valve in dorsal or ventral view, and a relatively smaller left valve. Krausella variata resembles K. arcuata Ulrich, Reference Ulrich1894, in having the similar subtriangular right valve, but the latter has a more elongated left valve than that of the present species.
Family Beecherellidae Ulrich, Reference Ulrich1894
Genus Acanthoscapha Ulrich and Bassler, Reference Ulrich and Bassler1923
Type species
Beecherella navicula Ulrich, Reference Ulrich1891.
Acanthoscapha champlainensis Swain, Reference Swain1962
Reference Swain1962 Acanthoscapha champlainensis; Swain, p. 735, pl. 110, figs. 4a–g.
Holotype
Left valve (USNM PAL 140597) from the Crown Point Formation of Valcour Island, New York.
Description
Valve amplete and unequal, with dorsal margin straight and ventral margin characteristically concave. Broad flange-like areas developed anteroventrally and posteroventrally. Left valve slightly larger than the right valve, overlapping slightly at the concavity of the ventral margin. CAs well defined by acuminated anterodorsal and posterodorsal ends. CAs terminated as elongated spines protruding anteriorly and posteriorly, forming a boat-shaped, lanceolate outline of the valve. Surface of the valve smooth. Mesostene duplicature well developed internally. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Acanthoscapha champlainensis Swain, Reference Swain1962, based on the characteristically boat-shaped outline of the valve, the anterodorsal and posterodorsal spines on the left valve, the mesostene duplicature (inner calcified lamella that is narrow in the middle, see Schallreuter and Hinz-Schallreuter, Reference Schallreuter and Hinz-Schallreuter2011), and the limited valve overlapping. The present species strongly resembles Kozuriscapha rectangulata Salas, Reference Salas2002b, from the Las Aguaditas Formation of Argentina in lateral view (Salas, Reference Salas2002b, fig. 2I–L), but the latter has a convex ventral margin without the mesostene duplicature.
Acanthoscapha champlainensis is the only known Ordovician species of Acanthoscapha so far. The Devonian type species Acanthoscapha navicula (Ulrich, Reference Ulrich1891) has a slightly arched and convex dorsal margin, and the Silurian A. bohemica (Bouček, Reference Bouček1936) has a prominently elongated valve.
Family Pachydomellidae Berdan and Sohn, Reference Berdan, Sohn and Moore1961
Genus Pachydomelloides Swain, Reference Swain1962
Type species
Pachydomelloides valcourensis Swain, Reference Swain1962.
Pachydomelloides valcourensis Swain, Reference Swain1962
Reference Swain1962 Pachydomelloides valcourensis Swain, p. 739, pl. 111, figs. 8a–c.
Holotype
Left valve (USNM PAL 140591) from the Crown Point Formation of Valcour Island, New York.
Description
Valve amplete to slightly preplete, unequal. Left valve slightly larger than the right valve, overlapping the right valve ventrally. Hinge line straight. Ventral margin of the left valve strongly convex, forming a subelliptical shape of the valve. Right valve subtrapezoidal, with ventral margin strongly concave. Posterior part of valve with characteristically abrupt depression, forming an elevated, longitudinal area ornamented with indistinct reticulation. General surface of the valve smooth. Double layered structure observed from internal view. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Pachydomelloides valcourensis Swain, Reference Swain1962, based on the characteristically posterior depression, the asymmetrical valve, and the outline of the valve. Pachydomelloides valcourensis differs from P. inaequalis Salas, Reference Salas2002b, from the Las Aguaditas Formation of Argentina in having a subtrapezoidal right valve and a more prominent posterior depression.
Family Budnianellidae Kraft, Reference Kraft1962
Genus Budnianella Bouček, Reference Bouček1936
Type species
Budnianella caroli Bouček, Reference Bouček1936.
Budnianella shenandoahense Kraft, Reference Kraft1962
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–5) Budnianella shenandoahense Kraft, Reference Kraft1962: (1, 2) NYSM 19697, adult; (1) right lateral view; (2) ventral view. (3) NYSM 19698, preadult, left lateral view. (4) NYSM 19699, juvenile, left lateral view. (5) NYSM 19700, juvenile, right lateral view. (6–10) Budnianella ellipticalis Swain, Reference Swain1962: (6) NYSM 19701, adult, right lateral view. (7) NYSM 19702, preadult, right lateral view. (8, 9) NYSM 19703, preadult; (8) left lateral view; (9) ventral view. (10) NYSM 19704, juvenile, left lateral view. (11–15) Elliptocyprites longula Swain, Reference Swain1962: (11–14) NYSM 19705, adult; (11) left lateral view; (12) right lateral view; (13) dorsal view; (14) ventral view. (15) NYSM 19706, preadult, lateral view. (16–21) Macrocyproides trentonensis (Ulrich, Reference Ulrich1894): (16–19) NYSM 19707, juvenile; (16) left lateral view; (17) right lateral view; (18) dorsal view; (19) ventral view. (20) NYSM 19708, adult, left lateral view. (21) NYSM 19709, adult, right lateral view. (22–26) Phelobythocypris lindstroemi (Jones, Reference Jones1890): (22–25) NYSM 19710, adult; (22) left lateral view; (23) right lateral view; (24) dorsal view; (25) ventral view. (26) NYSM 19711, preadult, right lateral view. (27, 28) Phelobythocypris cylindrica (Hall, Reference Hall1871): (27) NYSM 19712, right lateral view. (28) NYSM 19713, right lateral view. Scale bar = 500 μm.
Reference Kraft1962 Budnianella shenandoahense; Kraft, p. 60, pl. 16, figs. 1a–d, 2a–c.
Reference Swain1962 Budnianella shenandoahense; Swain, p. 735, 736, pl. 110, figs. 5a–e.
Reference Copeland1982 Budnianella shenandoahense; Copeland, p. 36–39, pl. 8, fig. 19; pl. 9, fig. 4.
Holotype
Left valve (USNM 136627) from the Lincolnshire Formation of Strasburg, Virginia.
Description
Valve slightly preplete and subequal, with hinge line straight and ventral margin slightly convex. Ventral margin of adult valve somehow parallel with the hinge line, forming a subrectangular shape of the valve. Juvenile valve subtriangular. Broad flange-like areas developed anteriorly and posteriorly, with middle part of the valve swollen. Thin and horizontal ridge situated on the lateral surface of the valve, parallel with the ventral margin, alate-like in ventral view. Ridge extended anteriorly to posteriorly across the entire swollen part of the adult valve, whereas that of the juveniles extends only halfway. Ventral free margin flattened, forming a narrow contact area. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Budnianella shenandoahense Kraft, Reference Kraft1962, based on the horizontal ridge, the flattened ventral margin, and the outline of the valve. Although the mesostene duplicature was not observed in the present specimens, the broad flange-like areas are likely to be where duplicature was developed. Budnianella shenandoahense differs from all species in the genus in having the characteristically horizontal ridge on the lateral surface of the valve.
Budnianella ellipticalis Swain, Reference Swain1962
Reference Swain1962 Budnianella ellipticalis Swain, p. 736, pl. 110, figs. 6a–e.
Holotype
Right valve (USNM PAL 140633) from the Crown Point Formation of Valcour Island, New York.
Description
Valve amplete and subequal, with hinge line straight and ventral margin straight to slightly concave, parallel with the hinge line. Cardinal angles poorly defined, forming an elliptical shape of the valve. Broad flange-like areas developed anteriorly and posteriorly, with middle part of the valve swollen. The ventral free margin flattened, forming a narrow contact area. Left valve overlapping the right valve ventrally on the flattened area. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Budnianella ellipticalis Swain, Reference Swain1962, based on the flattened ventral margin and the outline of the valve. The present species differs from the type species B. caroli Bouček, Reference Bouček1936, in having a smooth surface of the valve. Budnianella shenandoahense Kraft, Reference Kraft1962, and B. nodosa Swain, Reference Swain1962, both bear an ornamented lateral surface with ridge and nodes, which distinguishes them from B. ellipticalis.
Family Bairdiocyprididae Shaver, Reference Shaver and Moore1961
Genus Elliptocyprites Swain, Reference Swain1962
Type species
Elliptocyprites parallela Swain, Reference Swain1962.
Elliptocyprites longula Swain, Reference Swain1962
Reference Swain1962 Elliptocyprites longula Swain, p. 742, pl. 111, fig. 10.
Holotype
Left valve (USNM PAL 140599) from the Crown Point Formation of Valcour Island, New York.
Description
Valve amplete and subequal. Left valve slightly larger than the right valve, overlapping the right valve along the entire free margin. Hinge line straight. Ventral margin parallel with the hinge line, forming an elongated elliptical shape of the valve. Posterior boarder unnoticeably acuminated posteroventrally. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Elliptocyprites longula Swain, Reference Swain1962, based on the small valve size and the outline of the valve. Swain (Reference Swain1962) differentiated E. parallela Swain, Reference Swain1962, from the present species based on the size of the valve. The present specimens are consistently small in size (<1.00 mm), and there is no solid evidence to indicate that E. longula is the juvenile form of E. parallela. The type species also differs from the present species in having a distinctly concave ventral margin on the right valve. Thus, we consider Elliptocyprites longula to be valid.
Elliptocyprites longula differs from E.? magna Salas, Reference Salas2002b, from the Las Aguaditas Formation of Argentina in having the elongated shape of the valve.
Genus Macrocyproides Spivey, Reference Spivey1939
Type species
Macrocyproides clermontensis Spivey, Reference Spivey1939.
Macrocyproides trentonensis (Ulrich, Reference Ulrich1894)
Reference Ulrich1894 Aparchites minutissimus trentonensis Ulrich, p. 646, pl. 43, figs. 18–20.
Reference Kay1940 Aparchites trentonensis; Kay, p. 244, pl. 29, fig. 33.
Reference Swain, Cornell and Hansen1961 Macrocyproides trentonensis; Swain et al., p. 371, 372, pl. 48, fig. 11; pl. 50, figs. 5a–d.
Reference Kraft1962 Macrocyproides cf. clermontensis; Kraft, p. 68, pl. 18, figs. 13a–d.
Reference Swain1962 Macrocyproides trentonensis; Swain, p. 740, pl. 111, figs. 2a–c.
Holotype
Right valve (USNM 41302) from the Decorah Formation of Goodhue County, Minnesota.
Description
Valve preplete and subequal. Right valve slightly larger than the left valve, overlapping the left valve posteriorly and ventrally. Hinge line straight. Dorsal margin strongly convex, with ventral margin concave, forming a subtriangular shape of the valve. Anterior boarder broadly rounded whereas posterior boarder narrowly rounded. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Macrocyproides trentonensis (Ulrich, Reference Ulrich1894) based on the strongly convex dorsal margin, the narrowly rounded posterior boarder, and the general outline of the valve. The present species was initially assigned to the “bag genus” Aparchites (see Williams and Vannier, Reference Williams and Vannier1995) due to its featureless surface. Swain et al. (Reference Swain, Cornell and Hansen1961) revised the present species to Macrocyproides based on the clearly concave ventral margin that is visible when oriented correctly, suggesting that it was originally described upside down. We follow this revision.
Macrocyproides trentonensis differs from the type species M. clermontensis Spivey, Reference Spivey1939, in having a subtriangular shape of valve, and the latter develops a less concave ventral margin.
Genus Phelobythocypris Warshauer and Berdan, Reference Warshauer and Berdan1982
Type species
Leperditia (Isochilina) cylindrica Hall, Reference Hall1871.
Phelobythocypris lindstroemi (Jones, Reference Jones1890)
Reference Jones1890 Bythocypris? lindstroemi Jones, p. 548, pl. 21, figs. 11a–c.
Reference Copeland1970 “Bythocypris” lindstroemi?; Copeland, p. 26, 27, pl. 5, fig. 21.
Reference Copeland1973 “Bythocypris” lindstroemi?; Copeland, p. 30, 32, 40, pl. 1, fig. 3; pl. 2, fig. 4; pl. 6, fig. 7.
Holotype
Not designated. The type stratum is the Ellis Bay Formation of Anticosti Island, Canada.
Description
Valve amplete and subequal. Left valve slightly larger than the right valve, overlapping the right valve along the entire free margin. Hinge line straight, one-third of the total length of the valve. Dorsal margin straight and ventral margin significantly concave. Anterior border rounded, and posterior border more narrowly rounded. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The holotype of the species was not designated, and this assignment was based on the specimens from the Vaureal Formation of Anticosti Island, Canada (Copeland, Reference Copeland1970, Reference Copeland1973). The present specimens are considered to be conspecific with specimens figured in Copeland (Reference Copeland1970, Reference Copeland1973) based on the overlapping and the outline of the valve. Warshauer and Berdan (Reference Warshauer and Berdan1982) assigned the present species to the genus Phelobythocypris based on its reniform outline, overlapping feature, and the smooth surface. We here follow the revision.
Phelobythocypris cylindrica (Hall, Reference Hall1871)
Reference Hall1871 Leperditia (Isochilina) cylindrica Hall, p. 27, pl. 8, fig. 12.
Reference Hall and Whitfield1875 Leperditia (Isochilina) cylindrica; Hall and Whitfield, p. 101, pl. 4, fig. 5.
Reference Ulrich and Ulrich1889 Bythocypris cylindrica; Ulrich, p. 48, pl. 9, fig. 6.
Reference Ulrich1894 Bythocypris cylindrica; Ulrich, p. 687, pl. 44, figs. 29–35.
Reference Keenan1951 Bythocypris cylindrica; Keenan, p. 567, pl. 78, figs. 4, 8–13.
Reference Copeland1965 Bythocypris? cylindrica; Copeland, p. 45, pl. 2, figs. 2–4.
Reference Copeland1970 “Bythocypris” cylindrica; Copeland, p. 23, pl. 4, fig. 25.
Reference Copeland1973 “Bythocypris” cylindrica; Copeland, p. 36, pl. 4, fig. 3.
Reference Copeland1974 Bairdiocypris cylindrica; Copeland, p. 10, 46, pl. 6, fig. 7.
Reference Warshauer and Berdan1982 Phelobythocypris cylindrica; Warshauer and Berdan, p. 68, 69, pl. 18, figs. 8–18.
Reference Copeland, Parkins and Nowlan1989 Phelobythocypris cylindrica; Copeland et al., p. 17, pl. 2, fig. 18.
Holotype
Not designated.
Description
Valve postplete. Dorsal margin convex and ventral margin slightly concave. Anterior border narrowly rounded, posterior border more broadly rounded, forming a subreniform outline of the valve. CAs weakly defined. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Phelobythocypris cylindrica (Hall, Reference Hall1871) based on the narrowly acuminated anterior part of the valve, the slightly concave ventral margin, and the outline of the valve. This assignment was based on specimens from the Clays Ferry and Lexington formations of Kentucky, USA (Warshauer and Berdan, Reference Warshauer and Berdan1982). It is problematic to assign fossil specimens without soft parts to the recent genus Bythocypris Brady, Reference Brady1880, based only on the reniform outline and the smooth surface of the valve (Hessland, Reference Hessland1949). Warshauer and Berdan (Reference Warshauer and Berdan1982) revised the present species, proposing a new genus Phelobythocypris to represent the ancestral group that is “deceitful,” due to the lack of the duplicature and the muscle scar. We follow that revision.
Phelobythocypris cylindrica differs from P. lindstroemi (Jones, Reference Jones1890) in having a broader posterior boarder and a postplete valve. The latter bears a more concave ventral margin.
Family Longisculidae Neckaja, Reference Neckaja1966
Genus Platyrhomboides Harris, Reference Harris1957
Type species
Platyrhomboides quadratus Harris, Reference Harris1957.
Platyrhomboides virginiensis Kraft, Reference Kraft1962
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–6) Platyrhomboides virginiensis Kraft, Reference Kraft1962: (1–4) NYSM 19714, adult; (1) right lateral view; (2) left lateral view; (3) dorsal view; (4) ventral view. (5) NYSM 19715, adult, right lateral view. (6) NYSM 19716, juvenile, left lateral view. (7–12) Longiscula cf. L. perfecta Meidla, Reference Meidla1993; (7) NYSM 19717, left lateral view. (8–11) NYSM 19718, (8) left lateral view; (9) right lateral view; (10) dorsal view; (11) ventral view. (12) NYSM 19719, left lateral view. (13–17) Rectella? sp.: (13–16) NYSM 19720, adult, (13) right lateral view; (14) left lateral view; (15) dorsal view; (16) ventral view. (17) NYSM 19721, preadult, left lateral view. (18–24) Dornbuschia? sp.: (18–21) NYSM 19722, preadult; (18) left lateral view; (19) right lateral view; (20) dorsal view; (21) ventral view. (22) NYSM 19723, juvenile, right lateral view. (23) NYSM 19724, juvenile, left lateral view. (24) NYSM 19725, adult, right lateral view. Scale bar = 500 μm.
Reference Kraft1962 Platyrhomboides virginiensis Kraft, p. 61, 62, pl. 16, figs. 3–5.
Reference Swain1962 Platyrhomboides virginiensis; Swain, p. 740, pl. 110, figs. 8a–e; pl. 111, figs. 1a–d.
Holotype
Left valve (USNM 136624) from the Edinburg Formation of Strasburg, Virginia.
Description
Valve amplete and subequal. Left valve slightly larger than the right valve, overlapping the right valve ventrally. Hinge line straight. Ventral margin parallel to the hinge line, forming an elongated trapezoidal shape of the valve. A lateral ridge situated between the lateral and ventral surface from anterior to posterior border, slightly curved posteriorly. Ventral marginal surface flattened strongly, with a narrow, triangular contact area defined by a shallow ridge on the right valve indicating the degree of valve overlapping. Dorsal ridges developed on both valves. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Platyrhomboides virginiensis Kraft, Reference Kraft1962, based on the characteristic trapezoidal shape of the valve, the dorsal and ventral ridges, and a flattened, subhexagonal shape in ventral view. Kraft (Reference Kraft1962) considered the prominent dorsal ridges on both left and right valves to be diagnostic of P. virginiensis from the Lincolnshire and Edinburg formations of Virginia. Copeland (Reference Copeland1982) suggested that the specimens from both Swain (Reference Swain1962) and Kraft (Reference Kraft1962) should be identified as P. quadratus Harris, Reference Harris1957, considering that the dorsal ridge can also be a valid feature but is abraded in some specimens. However, in ventral view, the valve of P. quadratus (Harris, Reference Harris1957, pl. 10, fig. 4b) is clearly fusiform in shape with a smoothly curved ventral margin, whereas that of P. virginiensis (Kraft, Reference Kraft1962, pl. 16, figs. 3d, 4a; this paper) has a flattened, subhexagonal shape. Thus, we support maintaining the validity of P. virginiensis.
Genus Longiscula Neckaja, Reference Neckaja1958
Type species
Longiscula arcuaris Neckaja, Reference Neckaja1958.
Longiscula cf. L. perfecta Meidla, Reference Meidla1993
cf. Reference Meidla1993 Longiscula perfecta Meidla, p. 298–301, pl. 3, figs. 10–12; pl. 4, figs. 1–3; pl. 5, figs. 1–12.
cf. Reference Meidla1996 Longiscula perfecta; Meidla, p. 117, pl. 24, figs. 1–3.
Description
Valve amplete and subequal. Left valve slightly larger than the right valve, overlapping the right valve ventrally and anterodorsally. Hinge line straight. Dorsal margin arched highly, forming a subtriangular shape of the valve. Ventral margin slightly concave. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are similar to the holotype of Longiscula perfecta Meidla, Reference Meidla1993, in the valve overlapping and the general outline of the valve. However, the latter has a larger size of the valve. Without reasonable justification, the assumption of the present specimens being juveniles of L. perfecta cannot be made. The assignment is thus tentative.
Longiscula cf. L. perfecta differs from the type species L. arcuaris Neckaja, Reference Neckaja1958, in having a more rounded anterior border, and a shorter but higher shape of the valve.
Genus Rectella Neckaja, Reference Neckaja1958
Description
Valve amplete and subequal. Left valve slightly larger than the right valve, overlapping the right valve limitedly posterodorsally. Hinge line straight. Dorsal margin straight and ventral margin slightly concave, almost parallel to each other, forming a subquadrate shape of the valve. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are tentatively considered to be a species of Rectella Neckaja, Reference Neckaja1958, based on the partial overlapping and the subquadrate shape of the valve. However, Rectella species are characterized by stop-ridges on the right valve, a feature not observed in the present specimens. Furthermore, the present specimens bear no ventral overlapping, which is also different from Rectella species. Only two specimens were recovered, and the assignment is tentative.
Genus Dornbuschia Schallreuter, Reference Schallreuter1968c
Description
Valve amplete and unequal. Left valve larger than the right valve, overlapping the right valve along the entire free margin. Hinge line straight. Dorsal margin straight and ventral margin slightly concave. CAs poorly defined. Anterior border rounded, whereas posterior border acuminated strongly posteroventrally, forming a subtrapezoidal outline of the valve. A prominent spine extended posteroventrally on the right valve. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The characteristic duplicature of Dornbuschia Schallreuter, Reference Schallreuter1968c, is not observed in the present specimens. Thus, this designation is tentative based on the valve overlapping, the posteroventral acumination, and the subtrapezoidal shape of the valve. The present specimens show close similarity with species of Krausella Ulrich, Reference Ulrich1894, in having the posterior spine on the right valve. However, Krausella develops a convex dorsal margin and a strongly asymmetrical valve while the left valve is elliptical. Bairdianella? posteroextensa Kraft, Reference Kraft1962, from the Lincolnshire and Edinburg formations of Virginia bears a resemblance with the present specimens regarding the posterior acumination and the outline of the valve, but the former has symmetrical valves without the posteroventral spine, which distinguishes it from the present species.
Dornbuschia? sp. differs from all other species in the genus in having the posteroventral spine on the right valve.
Genus Aviacypris Schallreuter, Reference Schallreuter1977
Type species
Aviacypris avia Schallreuter, Reference Schallreuter1977.
Aviacypris valcourensis new species
Ostracods from the Crown Point Formation of Valcour Island, northeastern New York State. (1–9) Aviacypris valcourensis n. sp.; (1–4) NYSM 19726, paratype, juvenile; (1) left lateral view; (2) right lateral view; (3) dorsal view; (4) ventral view. (5) NYSM 19727, juvenile, left lateral view. (6) NYSM 19728, juvenile, right lateral view. (7, 8) NYSM 19729, paratype, preadult; (7) left lateral view; (8) internal view, showing the mesostene duplicature. (9) NYSM 19730, holotype, adult, left lateral view. (10, 11) Aviacypris cf. A. planta Schallreuter and Hinz-Schallreuter, Reference Schallreuter and Hinz-Schallreuter2011: (10) NYSM 19731, right lateral view. (11) NYSM 19732, left lateral view. (12–17) Steusloffina plattsburgensis (Swain, 1962): (12–15) NYSM 19733, preadult; (12) left lateral view; (13) right lateral view; (14) dorsal view; (15) ventral view. (16) NYSM 1974, juvenile, left lateral view. (17) NYSM 19735, adult, left lateral view. (18–20) Valcouropsis shawi Copeland, Reference Copeland1982: (18–20) NYSM 19736, adult; (18) left lateral view; (19) internal view, showing the double layered structure; (20) ventral view. Scale bar = 500 μm.
Reference Copeland1982 ?Budnianella ellipticalis; Copeland, p. 34–39, pl. 7, figs. 9, 10; pl. 8, fig. 10; pl. 9, fig. 17.
Holotype
Adult left valve, NYSM 19730 (Fig. 23.9) from the Crown Point Formation of the Valcour Island, New York State, USA.
Paratypes
Preadult left valve, NYSM 19729 (Fig. 23.7, 23.8); juvenile carapace, NYSM 19726 (Fig. 23.1–23.4).
Diagnosis
Aviacypris with a subrectangular shape of the valve, and two obtuse and subequal CAs.
Description
Valve subequal, with dorsal margin straight and ventral margin concave. CAs obtuse and subequal, forming a subrectangular shape of the valve. Hinge very long. Left valve slightly larger than the right valve, overlapping the right valve ventrally. Juvenile valve strongly preplete without the umbonate dorsum. Adult valve slightly postplete to amplete, with a umbonate posterodorsum. Surface of the valve smooth. From the internal view, mesostene duplicature well developed. Sexual dimorphism unknown.
Etymology
After the name of the Valcour Island.
Dimensions
NYSM 19730 (holotype), L = 1350 μm, H = 543 μm; NYSM 19729 (paratype), L = 1034 μm, H = 430 μm; NYSM 19726 (paratype), L = 563 μm, H = 258 μm.
Remarks
The present specimens are assigned to Aviacypris Schallreuter, Reference Schallreuter1977, based on the mesostene duplicature and the outline of the valve. Aviacypris valcourensis n. sp. differs from all other species within the genus in having the characteristically subrectangular outline of the valve.
Aviacypris cf. A. planta Schallreuter and Hinz-Schallreuter, Reference Schallreuter and Hinz-Schallreuter2011
cf. Reference Schallreuter and Hinz-Schallreuter2011 Aviacypris planta Schallreuter and Hinz-Schallreuter, p. 224, pl. 4, figs. 14, 15.
Description
Valve postplete, with dorsal margin straight and ventral margin concave. CAs unequal, anterior CA larger than the posterior one. Hinge very long. Surface of the valve smooth. Mesostene duplicature well developed. Sexual dimorphism unknown.
Remarks
The present specimens resemble the holotype of Aviacypris planta Schallreuter and Hinz-Schallreuter, Reference Schallreuter and Hinz-Schallreuter2011, in having the unequal CAs, the ventral convexity and the postplete outline of the valve. However, the latter develops a more rounded anterior border. Only two specimens were recovered, and the designation requires further investigation.
Aviacypris cf. A. planta differs from the type species Aviacypris avia Schallreuter, Reference Schallreuter1977, in having a more rounded posterior border. Both A. truncata Schallreuter and Hinz-Schallreuter, Reference Schallreuter and Hinz-Schallreuter2011, and A. coartata Schallreuter and Hinz-Schallreuter, Reference Schallreuter and Hinz-Schallreuter2011, from the glacial erratic boulders of Sweden develop weakly defined CAs and an elongated subelliptical outline, which distinguishes them from Aviacypris cf. A. planta.
Family Steusloffinidae Schallreuter, Reference Schallreuter1984
Genus Steusloffina Teichert, Reference Teichert1937
Type species
Steusloffina ulrichi Teichert, Reference Teichert1937.
Steusloffina plattsburgensis (Swain, Reference Swain1962)
Reference Swain1962 Monoceratina? plattsburgensis – Swain, p. 737, pl. 111, figs. 3a–d.
Holotype
Right valve (USNM PAL 140581) from the Crown Point Formation of Valcour Island, New York.
Description
Valve preplete and subequal. CAs obtuse and unequal, posterior CA larger than the anterior one. Left valve slightly larger than the right valve, overlapping the right valve along the entire free margin. Dorsal margin slightly convex with an indistinct umbo and ventral margin convex. Anterior border broadly rounded, and posterior border acuminated, forming a subtriangular shape of the valve. Rounded elevation developed posteroventrally, sloping steeply to the ventral margin, forming a flattened ventral surface. Surface of the valve smooth. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Steusloffina plattsburgensis (Swain, Reference Swain1962) based on the valve overlapping, the posteroventral elevation, and the subtriangular outline of the valve. The species was tentatively assigned to the Carboniferous genus Monoceratina Roth, Reference Roth1928, due to the lack of the characteristic middle sulcus. However, the subtriangular outline, valve overlapping, and the nonsulcal lateral surface of the present species are consistent with the generic features of Steusloffina Teichert, Reference Teichert1937. We consider the present species to be a species of Steusloffina.
Steusloffina plattsburgensis differs from the type species S. ulrichi Teichert, Reference Teichert1937, in having a posteroventral elevation. Salas (Reference Salas2002b) described an uncertain Steusloffina species from the Las Aguaditas Formation of Argentina, with a similar inflated ventrum but a more convex ventral margin than that of the present species.
Suborder Uncertain
Superfamily Uncertain
Family Uncertain
Genus Valcouropsis Copeland, Reference Copeland1982
Type species
Valcouropsis shawi Copeland, Reference Copeland1982.
Valcouropsis shawi Copeland, Reference Copeland1982
Reference Copeland1982 Valcouropsis shawi Copeland, p. 17, 18, pl. 8, figs. 11–18.
Holotype
Left valve (USNM 306737) from the Day Point Formation of Valcour Island, New York, locality PB15.
Description
Valve slightly postplete with hinge straight. Dorsal margin strongly umbonate with an elongated elevation, and ventral margin convex. Similar elevation developed ventrally, forming a flattened ventral marginal surface. Anterior border broadly rounded, and posterior border more narrowly rounded. Surface of the median area of the valve smooth. Surface of the valve slightly granular to reticulate on the elevations, granules aligned rhythmically. From the internal view, double layered structure observed. Sexual dimorphism unknown.
Remarks
The present specimens are assigned to Valcouropsis shawi Copeland, Reference Copeland1982, based on the characteristic dorsal and ventral elevation, the double-walled shell, the partly granular surface of the valve, and the outline of the valve. The taxonomic position of the genus Valcouropsis is still uncertain. Copeland (Reference Copeland1982) compared the genus with Schmidtella Ulrich, Reference Ulrich1892, based on its umbonate dorsum, but the elongated outline of Valcouropsis shawi is more consistent with podocopids. We tentatively place the genus under podocopid.
Acknowledgments
We thank R.P.P. Wong, and the staff of the Electron Microscope Unit, University of Hong Kong for continuous support. We are grateful to M. Slovacek (American Museum of Natural History) for helping to prepare the samples and L. Amati (New York State Museum) for facilitating collection permits and loans. The work described in this article was partially supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region, China (project codes: RFS2223-7S02; HKU 17300821); and the Seed Funding Programme for Basic Research of the University of Hong Kong (project codes: 2302101483; 2202100581) (to MY).
Competing interests
The authors declare none.
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