Associated fauna

The Hickory Corners Member is rich in bryozoans, crinoids, bivalves, gastropods, brachiopods, and trilobites (Fig. 4). Small, solitary rugose corals (Enterolasma? sp.) are common in this limestone. Brachiopods are relatively diverse and include Hyattidina, Platystrophia, Dalejina, Coolinia, and rare Eocoelia; disarticulated sclera of the trilobites Liocalymene and Encrinurus are relatively common in the Hickory Corners Member.

Figure 4.

(1) Surface of fossil-rich limestone of the Reynales Formation; (2) thin section across bedding. (1) Scale bar = 10 mm; (2) scale bar = 5 mm.

Eocoelia, often considered to be a nearshore indicator, is typical of the ‘Eocoelia Community’ (Ziegler, Reference Ziegler1965) or benthic assemblage (BA) 2 of Boucot (Reference Boucot1975; see Boucot and Lawson, Reference Boucot and Lawson1999 for numerous examples). However, this brachiopod is rare in the Niagara County area. The upper portion of the Hickory Corners Member passes eastward (up-ramp) into the Wallington Limestone, which is rich in robust pentamerid brachiopods (Pentamerus oblongus Sowerby, Reference Sowerby and Murchison1839), as well as favositids and small stromatoporoids, a typical BA3 assemblage (Boucot, Reference Boucot1975; Boucot and Lawson, Reference Boucot and Lawson1999). Overall, the moderate diversity of brachiopod, bryozoan, and echinoderm fauna of the Hickory Corners Member is indicative of a BA3 to BA4 position.

The Reynales Formation in Niagara County, including the Hickory Corners study locality, has yielded a small but distinctive crinoid fauna (Eckert and Brett, Reference Eckert and Brett2001), including the small disparid crinoid Haptocrinus calvatus Eckert and Brett, Reference Eckert and Brett2001, long known for its distinctive pentalobate columnals, which make up a high proportion of the Hickory Corners grainstones. Hall (Reference Hall1852) figured these under an incompletely known species ‘Glyptocrinus plumosus.’ These small crinoids are associated with the coiled columns of perhaps three species of Eomyelodactylus, notably E. sparteus Eckert, Reference Eckert1990, the camerate Dynamocrinus robustus Eckert and Brett, Reference Eckert and Brett2001, and the flexible crinoid Prolixocrinus anellus Eckert and Brett, Reference Eckert and Brett2001.

The Hickory Corners faunas, especially the crinoids, show affinities to those described from the uppermost Brassfield Formation (‘Red Brassfield’) in Ohio and Kentucky (e.g., Ausich, Reference Ausich1984, Reference Ausich1986a, Reference Ausichb; Ausich and Dravage, Reference Ausich and Dravage1988). On the basis of conodonts and the brachiopods Microcardinalia and Triplecia, this unit has been suggested to be of mid-Aeronian age and thus equivalent to the Oldham Limestone of Kentucky and ‘Packer Shell’ of the Ohio Subsurface, both of which are correlated with the Reynales Formation in New York. All of these units yield moderately abundant ramose and reticulate bryozoans that have not received recent study (see Foerste, Reference Foerste1887, Reference Foerste1893, Reference Foerste1919) and warrant further comparative work.

Type species

Diploclema trentonense Ulrich in Miller, Reference Miller1889. Middle Ordovician (‘Trenton Group’), USA

Diagnosis (emended)

Branched dichotomous colonies. Autozooecia pyriform, growing in biradial pattern from the median lamina through simple exterior skeletal wall, separated by interzooecial space in endozone. In some species, interzooecial space protrudes into the exozone between autozooecia giving an impression of tubes. Autozooecial apertures rounded to oval, with low peristomes, opening distally on all sides of subcylindrical stems, arranged in quincunx order on the colony surface, surrounded by peripheral structures and nodes. The exterior skeletal walls thin, continuous except for autozooecial apertures, covering both autozooecial chambers and small portions of colony-wide extrazooecial space, consisting of prismatic material. Autozooecial diaphragms rarely occurring. Interior autozooecial walls thickly laminated, with distinct zooecial boundaries, often undulating in proximal parts of autozooecia. Communication pores absent. Pseudopores absent. Heterozooecia not known.

Occurrence

Middle Ordovician of United States. Upper Ordovician of western Argentina. Lower to middle Silurian of United States, Canada, and Europe.

Remarks

The genus Diploclema Ulrich in Miller, Reference Miller1889 is unique among cyclostome bryozoans because of its exterior wall, which has a prismatic structure and is completely different from the laminated interior wall. Diploclema can be compared with Kukersella Bassler, Reference Bassler1911 in possessing similar colony form and autozooecial shape, but Diploclema lacks axial tubes, communication pores, and pseudopores. Furthermore, the microstructure of the frontal walls of Kukersella is finely laminated whereas the frontal wall of Diploclema is prismatic.

Diploclema argutum Bassler, Reference Bassler1906 Figures 5.1–5.9, 6.1–6.3; Table 1

1906

Diploclema sparsum var. argutum Bassler, p. 17, pl. 5, figs. 8, 9.

1971

Diploclema regulariforme Kopajevich, Reference Kopajevich1971, p. 121, fig. 3.

Table 1.

Descriptive statistics of Diploclema argutum Bassler, Reference Bassler1906. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Holotype

USNM PAL 35557. Rochester Shale, Wenlock, lower Silurian; New York, USA.

Occurrence

Lower Silurian, Llandovery-Wenlock of USA (New York). Lower Silurian, Wenlock of Estonia.

Description

Branched dichotomous colonies, cylindrical and belt shaped, bifoliate, arising from encrusting bases. Cylindrical branches 0.30–0.46 mm in diameter, belt shaped 0.37–0.43 mm thick and 0.75–1.43 mm wide. Autozooecia drop shaped, narrow proximally and broadened distally, 0.40–0.60 mm long and 0.13–0.20 mm wide, separated by interzooecial space in endozone. Interzooecial space protruding to the exterior wall between autozooecia producing rounded separations 0.04–0.08 mm in diameter. Autozooecial apertures oval, 0.07–0.10 mm wide, spaced 0.34–0.44 mm from center to center longitudinally. Interior autozooecial walls thickly laminated, undulating near the surface, with distinct zooecial boundaries, 0.013–0.040 mm thick. Exterior zooecial walls granular, 0.005–0.008 mm thick.

Remarks

Bassler (Reference Bassler1906, p. 18, pl. 5, figs 8, 9) described “a distinct pore in front of zooecial aperture.” These pores were sometimes regarded as heterozooecia. Kopajevich (Reference Kopajevich1971, p. 120, text-figs. 1, 2) described ‘upper’ and ‘lower’ partitions in the autozooecia of Diploclema. This model implies zooecia with long peristomes and arched zooecia. A shallow section that cuts the peristome (upper partition) and the arched part of the zooecium (lower partition) produces the appearance of heterozooecia. A similar model was suggested by Brood (Reference Brood1975, p. 64, fig. 12). He suggested the existence of a “vertically placed tabula, which divides the zooecium in two compartments.” The outer compartment is supposed to have contact with the surface, whereas the inner compartment would be connected by pores to the outer one. However, such a morphology is not obvious from observation of the presently described abundant material from the Silurian of North America. The morphology of Diploclema is difficult to describe because its outer wall is extremely thin and cannot be observed in tangential sections. Transverse and longitudinal sections show that zooecia are rather flat, and they have neither distinct peristomes nor compartments (Fig. 6.1). Any openings of the ‘heterozooecia’ or ‘pores’ could not be observed in the tangential section. Diploclema has a kind of an interzooecial space, which separates autozooecia in endozone, and in distal parts it protrudes from the exozone and reaches the exterior wall (but does not protrude into it). This space is filled by calcite spar, which means that it had no direct contact with seawater. By contrast, autozooecial space is filled by micrite, assuming contact with the sediment via the aperture (after death and decay of the bryozoan). The impression of ‘partitions’ or ‘compartments’ inside of the autozooecia of Diploclema appears in oblique sections (Fig. 5.4), whereas strictly longitudinal sections cut only the autozooecia (Fig. 6.1).

Figure 5.

(1–9). Diploclema argutum Bassler, Reference Bassler1906: (1, 2) longitudinal section of a basal part of a colony encrusting Moyerella n. sp., SMF 23.327; (3) basal part of a colony encrusting sediment, SMF 23.344; (4) oblique longitudinal section showing autozooecia and interzooecial space (arrows), SMF 23.342; (5, 6) shallow tangential section showing autozooecial apertures, internal walls, and interzooecial space (arrows); (5) SMF 23.353; (6) SMF 23.354; (7) oblique section showing internal walls and interzooecial space, SMF 23.323; (8, 9) shallow tangential section showing autozooecial apertures, internal walls, and interzooecial space (arrows), SMF 23.323. (1) Scale bar = 1 mm; (2, 3, 7, 8) scale bars = 0.5 mm; (4–6, 9) scale bars = 0.2 mm.

Figure 6.

(1–3) Diploclema argutum Bassler, Reference Bassler1906: (1) longitudinal section showing autozooecial chambers, external walls, internal walls, and protruded interzooecial space in proximal part of autozooecia (arrows), SMF 23.333; (2) branch transverse section showing autozooecial chambers, external and internal walls, SMF 23.351; (3) branch transverse section showing autozooecial chambers, external and internal walls, SMF 23.358. (4–8) Cheilotrypa aff. C. variolata (Hall, Reference Hall1876): (4) transverse section of a hollow cylindrical colony, SMF 23.436; (5) transverse section of a hollow cylindrical colony, SMF 23.402; (6) longitudinal section of a tubular colony, SMF 23.423; (7, 8) transverse section of a hollow cylindrical colony with sheets budding “base to base” (arrow), SMF 23.428. (1–3) Scale bars = 0.2 mm; (4, 5, 7, 8) scale bars = 0.5 mm; (6) scale bar = 1 mm.

Diploclema argutum Bassler, Reference Bassler1906 is identical to D. regulariforme Kopajevich, Reference Kopajevich1971 from the Silurian (Wenlock) of Estonia. The two species coincide in their size (e.g., aperture width 0.07–0.10 mm versus 0.05–0.11 mm in D. regulariforme; autozooecial width 0.13–0.20 mm versus 0.13–0.18 mm in D. regulariforme; autozooecial length 0.40–0.60 mm versus 0.49–0.63 mm in D. regulariforme). Diploclema argutum is similar to D. sparsum (Hall, Reference Hall1852) from the Silurian (Wenlock) of New York but differs from the latter in coarser branches that are often flat and contain mesotheca instead of median axis.

Type species

Cheilotrypa hispida Ulrich, Reference Ulrich1884. Carboniferous, Mississippian, Viséan-Serpukhovian; USA.

Cheilotrypa aff. C. variolata (Hall, Reference Hall1876)
Figures 6.4–6.8, 7.1–7.5; Table 2

1876

Trematopora variolata Hall, p. 113, pl. 11, figs. 9, 10.

1882

Trematopora variolata; Hall, p. 234, pl. 10, figs. 9, 10.

Table 2.

Descriptive statistics of Cheilotrypa aff. C. variolata (Hall, Reference Hall1876). N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value.

Occurrence

Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Description

Cylindrical colonies formed by encrusting unpreserved objects, 1.25–2.50 mm in diameter, with a lumen 0.42–1.35 mm in diameter. Encrusting sheets 0.26–1.10 mm in thickness, locally budding ‘base to base’ (Fig. 6.7, 6.8). Encrusted objects represent apparently dichotomizing rigid cylindrical objects (algae?) with regular narrow portions (Fig. 6.6). Autozooecia growing from 0.005–0.010 mm thick epitheca, bending sharply at their bases toward colony surface. Autozooecial apertures circular to oval. Basal diaphragms rare to absent. Lunaria well developed, horseshoe shaped. Vesicles abundant, five to eight surrounding each autozooecial aperture, irregularly shaped, medium in size, often large at the base, polygonal in tangential section, box-like to hemispheric, with plane or concave roofs in exozone. Autozooecial walls granular, 0.003–0.005 mm thick. Extensive extrazooecial material in exozone developed, 0.20–0.33 mm thick. Maculae consist of vesicular skeleton covered by laminated calcitic material, 0.38–0.70 mm in diameter.

Remarks

Three species of Cheilotrypa are known from the Silurian of North America: C. varia (Hall, Reference Hall1876), C. variolata (Hall, Reference Hall1876), and C. ostiolata (Hall, Reference Hall1852) (all from the Wenlock of Indiana and New York). Whereas the former two species were described without use of thin sections, Cheilotrypa ostiolata was identified and described internally by Perry and Hattin (Reference Perry and Hattin1960) from the Osgood Formation (Wenlock) of Indiana. According to the descriptions and illustrations of C. varia and C. variolata in Hall (Reference Hall1882), the present species appears most similar to C. variolata. Hall (Reference Hall1882, p. 234) gives branch diameters of 2–7 mm and aperture diameters of 0.25 mm for C. varia and branch diameters of 1–1.5 mm and aperture width of 0.20 mm for C. variolata. The aperture width is still larger than in the present species (0.09–0.15 mm). Cheilotrypa sp. differs from C. ostiolata from the Silurian of New York in smaller autozooecia (autozooecia width 0.09–0.15 mm versus 0.15–0.20 mm in Cheilotrypa ostiolata).

Type species

Callopora florida Hall, Reference Hall1852. Niagaran Group, Rochester Shale, Sheinwoodian, Wenlock, Silurian; Lockport, New York, USA.

Holotype

Specimen 5572 (Indiana University Paleontological Collection). Osgood Formation (Telychian-Sheinwoodian), Silurian; Indiana, USA.

Figure 7.

(1–5) Cheilotrypa aff. C. variolata (Hall, Reference Hall1876): (1) oblique section of a hollow cylindrical colony, SMF 23.423; (2) shallow tangential section showing autozooecial apertures with lunaria, SMF 23.379; (3) deep tangential section showing autozooecial apertures with lunaria and vesicles, SMF 23.423; (4) tangential section of autozooecial aperture, SMF 23.423; (5) oblique section of a hollow cylindrical colony, SMF 23.425. (6–9) Hennigopora apta Perry and Hattin, Reference Perry and Hattin1960: (6) oblique section of a colony, SMF 23.466; (7) longitudinal section showing autozooecia and vesicles, SMF 23.466; (8, 9) tangential section showing autozooecia, acanthostyles, and vesicles; (8) SMF 23.462; (9) SMF 23.465. (1–3, 8) Scale bars = 0.5 mm; (4) scale bar = 0.1 mm; (5–7) scale bars = 1 mm; (9) scale bar = 0.2 mm.

Table 3.

Descriptive statistics of Hennigopora apta Perry and Hattin, Reference Perry and Hattin1960. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Occurrence

Osgood Formation (Telychian-Sheinwoodian), Silurian; Indiana, USA. Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Description

Encrusting colony, 1.25 mm thick. Autozooecia growing from thin epitheca, bending in the early exozone to the colony surface. Autozooecial diaphragms rare; straight, thin. Autozooecial apertures rounded polygonal, strongly petaloid due to indenting acanthostyles. Vesicles generally large, separating autozooecia in one row, 8–11 surrounding each autozooecial aperture, with rounded roofs, polygonal in tangential section. Acanthostyles abundant, relatively large, often deeply indenting autozooecial chambers, three to five surrounding each autozooecial aperture. Autozooecial walls displaying obscure granular microstructure, 0.005–0.015 mm thick. Maculae not observed.

Remarks

Hennigopora apta Perry and Hattin, Reference Perry and Hattin1960 differs from H. florida (Hall, Reference Hall1852) in having smaller autozooecial apertures (0.17–0.25 mm versus 0.28–0.35 mm in H. florida).

Type species

Homotrypa curvata Ulrich, Reference Ulrich1882. Upper Ordovician (Cincinnatian); North America.

Holotype

SMF 23.470–SMF 23.473 (four thin sections), SMF 23.474 (rock sample).

Figure 8.

(1–9) Homotrypa niagarensis n. sp.: (1) colony in rock, holotype SMF 23.474; (2) branch oblique section, holotype SMF 23.470; (3) rock thin section with transverse and oblique sections of branches, holotype SMF 23.472; (4) branch oblique section, paratype SMF 23.488; (5, 6) longitudinal section of exozone showing autozooecia with diaphragms and cystiphragms, holotype SMF 23.470; (7) longitudinal section of outer exozone showing autozooecial chambers with series of cystiphragms, paratype SMF 23.483; (8, 9) tangential section showing autozooecial apertures and acanthostyles (arrow), holotype SMF 23.473. (1) Scale bar = 10 mm; (2) scale bar = 3 mm; (3, 4) scale bars = 5 mm; (5, 8) scale bars = 1 mm; (6, 9) scale bars = 0.5 mm; (7) scale bar = 0.2 mm.

Table 4.

Descriptive statistics of Homotrypa niagarensis n. sp. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Paratypes

SMF 23.475–SMF 23.502.

Diagnosis

Ramose branched colonies with narrow exozones; autozooecia long, bending at intermediate angles in exozone, having rounded polygonal apertures; basal diaphragms in exozone; cystiphragms large, abundant in exozone; mesozooecia rare to common, small; acanthostyles rare to common, large; autozooecial walls thick, laminated with distinct medial lining.

Occurrence

Osgood Formation (Telychian-Sheinwoodian), Silurian; Indiana, USA. Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Description

Branched colonies, branch diameter 2.20–6.10 mm. Exozone 0.27–1.10 mm wide, endozone 1.56–3.94 mm wide, distinct. Secondary overgrowths uncommon. Autozooecia long in the endozone, having larger diameters than in exozone, polygonal in transverse section of endozone, bending gently and intersecting branch surface at angles of 57°–62°. Autozooecial apertures rounded polygonal. Autozooecial diaphragms rare to absent in the endozone, concentrated mostly in transitional region between endo- and exozone, common to abundant in outer exozone. Cystiphragms occurring throughout the exozone, occupying about half of the autozooecial diameter. Mesozooecia rare, locally common, small, short, restricted to the outermost part of exozone, polygonal, containing no diaphragms. Acanthostyles rare to common, large, prominent, restricted to exozone, with narrow hyaline cores and wide laminated sheaths. Autozooecial walls straight, locally weakly undulating, displaying granular microstructure, 0.002–0.003 mm thick in endozone; finely laminated with distinct medial lining, 0.05–0.11 mm thick in exozone.

Etymology

The species name refers to the Niagara River, in which vicinity the type locality is situated.

Remarks

Homotrypa niagarensis n. sp. differs from H. anticostiensis Bassler, Reference Bassler and Twenhofel1928 from the Upper Ordovician of Canada in larger autozooecial apertures (aperture width 0.13–0.20 mm versus 0.09–0.14 mm in H. anticostiensis) and in absence of maculae consisting of mesozooecia. Homotrypa niagarensis n. sp. differs from H. ramulosa Bassler, Reference Bassler1903 from the Upper Ordovician of Indiana, USA, in larger acanthostyles and larger autozooecial apertures (aperture width 0.13–0.20 mm versus 0.10–0.13 mm in H. ramulosa).

Type species

Callopora elegantula Hall, Reference Hall1852, lower Silurian (Niagaran); USA.

Occurrence

Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Figure 9.

(1) Homotrypa niagarensis n. sp.: part of branch transverse section showing thin-walled autozooecia in endozone and thick-walled autozooecia in exozone, holotype SMF 23.471. (2–6) Hallopora aff. H. elegantula (Hall, Reference Hall1852): (2) oblique section of branch with secondary overgrowth, SMF 23.504; (3) longitudinal section of exozone showing secondary overgrowth, autozooecia with diaphragms, and mesozooecia, SMF 23.504; (4) oblique section of branch showing long zooecia in endozone, SMF 23.531; (5) tangential section showing autozooecial apertures and mesozooecia, SMF 23.530; (6) longitudinal section showing autozooecia and mesozooecia, SMF 23.532. (7) Leioclema adsuetum n. sp.: longitudinal section of a branched colony with secondary overgrowth, paratype SMF 23.553. (1, 3, 6) Scale bars = 1 mm; (2, 7) scale bars = 2 mm; (4) scale bar = 3 mm; (5) scale bar = 0.5 mm.

Table 5.

Descriptive statistics of Hallopora aff. H. elegantula (Hall, Reference Hall1852). N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value.

Description

Ramose colonies, branch diameter 2.60–6.60 mm. Exozone distinct, 0.45–1.40 mm wide, endozone 1.70–4.62 mm wide. Secondary overgrowths common, 0.8–1.3 mm thick. Autozooecia long, growing parallel to branch axis for a long distance in endozone, having rounded polygonal shape in transverse section in endozone, in exozone bending sharply and intersecting branch surface at angles of 60°–90°. Autozooecial apertures rounded to oval. Autozooecial diaphragms thin, planar, rare to common in endozone, becoming common in exozone, planar, rarely inclined, developed as extension of wall cortex. Cap-like apparati and mural spines absent. Mesozooecia arising in endozone, polygonal in cross section, often separating autozooecia completely from each other in the exozone, 5–13 surrounding each autozooecial aperture. Mesozooecial diaphragms planar, densely spaced. Autozooecial walls indistinctly laminated, 0.005–0.010 mm thick in endozone; displaying distinct reverse V-shaped structure with dark autozooecial border, having well-developed wall cortex continued in diaphragms, 0.04–0.08 mm thick in exozone. Maculae consisting of macrozooecia, 1.1–1.5 mm in diameter.

Remarks

The present species is very similar to H. elegantula (Hall, Reference Hall1852). However, it differs in having smaller autozooecial apertures (0.27–0.32 mm versus 0.30–0.35 mm in H. elegantula) and smaller distances between aperture centers (0.30–0.47 mm versus 0.45–0.65 mm in H. elegantula). Hallopora aff. H. elegantula (Hall, Reference Hall1852) is very similar to H. baltica (Hennig, Reference Hennig1908) from the Silurian (Wenlock) of Gotland but differs in rare diaphragms in endozone and in closely spaced autozooecial apertures (approximately six apertures per 2 mm distance versus four in H. baltica).

The present species is also similar to the species Hallopora magnopora Foerste, Reference Foerste1887, which was originally described from the lower Silurian of Ohio and redescribed by Bassler (Reference Bassler1906) from the Rochester Shale (Wenlock) of New York. Both authors referred to “zooecia larger than is usual in species of this genus” (Foerste, Reference Foerste1887, p. 173; Bassler, Reference Bassler1906, p. 43). However, they did not provide exact measurements of the apertures. Foerste (Reference Foerste1887, p. 173) provided spacing of apertures as eight in 3 mm, and Bassler (Reference Bassler1906, p. 43) gave the value of four apertures per 2 mm. Aperture width measured from the illustrations by Bassler (Reference Bassler1906, pl. 15, fig. 1) are estimated as 0.35–0.40 mm, and these values are larger than in the present species (0.27–0.32 mm). Furthermore, according to illustrations in Bassler (Reference Bassler1906, pl. 15, figs. 1–8), H. magnopora has fewer mesozooecia than the present species.

Type species

Callopora punctata Hall, Reference Hall1858. Mississippian; Iowa, USA.

Holotype

SMF 23.535.

Table 6.

Descriptive statistics of Leioclema adsuetum n. sp. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value.

Paratypes

SMF 23.536–SMF 23.558.

Diagnosis

Ramose branched colonies with narrow distinct exozones; secondary overgrowth occurring; autozooecia long, bending at mediate angles in exozone, having rounded polygonal apertures; basal diaphragms rare to absent in exozone; mesozooecia abundant, four to nine surrounding each autozooecial aperture; acanthostyles moderately large and abundant, two to five surrounding each autozooecial aperture; autozooecial walls laminated, moderate in thickness.

Occurrence

Osgood Formation (Telychian-Sheinwoodian), Silurian; Indiana, USA. Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Description

Ramose branched colonies, branch diameter 2.55–5.88 mm. Exozone distinct, 0.34–0.72 mm wide, endozone 1.48–4.44 mm wide. Secondary overgrowth common, 0.3–0.4 mm thick. Autozooecia long, growing parallel to branch axis for a long distance in endozone, having larger diameters than in exozone, polygonal in transverse section of endozone, in exozone bending sharply and intersecting branch surface at angles of 80°–90°, having polygonal shape in cross section in endozone. Autozooecial apertures polygonal. Autozooecial diaphragms rare to absent, thin, straight or slightly deflected proximally. Mesozooecia abundant, four to nine surrounding each aperture, polygonal in cross section, strongly beaded, containing abundant planar diaphragms. Acanthostyles moderately large, abundant, two to five surrounding each aperture, originating in the distal part of exozone, often indenting autozooecia, having distinct calcite cores and dark laminated sheaths. Walls granular, 0.005–0.008 mm thick in endozones; distinctly laminated, 0.040–0.045 mm thick in the exozone.

Etymology

The species name refers to the average appearance of this species (from Latin adsuetus meaning normal, usual).

Remarks

Leioclema adsuetum n. sp. differs from L. ramulosum (Bassler, Reference Bassler1906) from the Rochester Shale of New York in more abundant acanthostyles surrounding autozooecial apertures (2–5 versus 1–2 in L. ramulosum) and in having abundant diaphragms in mesozooecia. Leioclema adsuetum n. sp. differs from L. densiporum Owen, Reference Owen1965 from the lower Silurian of England in having less abundant acanthostyles surrounding autozooecial apertures (2–5 versus 8–12 in L. densiporum).

Type species

Moyerella stellata Nekhoroshev, Reference Nekhoroshev1956. Llandovery, lower Silurian; Russia (Siberia).

Diagnosis (emended)

Thin ramose colonies, usually articulated. Axial region consisting of well-defined median axis or planar budding surface. Autozooecia shortened tubular, triangular in cross section in endozone, inflated at their bases, diverging from median axis in spiral pattern, bending abruptly in exozones. Diaphragms rare or absent. Hemisepta absent. Autozooecial apertures oval or rounded, arranged regularly in diagonal rows, commonly having peristomes. Zooecial boundaries well defined, narrow. Single large four-sided acanthostyle between longitudinally successive autozooecial apertures present. Paired heterozooecia (tectitozooecia after Kopajevich, Reference Kopajevich1975) present between successive autozooecial apertures. Tubules often present in peristomes.

Occurrence

Upper Ordovician of Argentina and Estonia; lower Silurian (Llandovery) of Siberia and Estonia and United States.

Remarks

Moyerella Nekhoroshev, Reference Nekhoroshev1956 is similar to Nematotrypa Bassler, Reference Bassler1911 in autozooecial shape and presence of acanthostyles and heterozooecia with diaphragms (tectitozooecia). However, Moyerella differs from Nematotrypa in the regular arrangement of paired heterozooecia between autozooecia and absence of hemiphragms.

Blake (Reference Blake and Robison1983, p. 561) mentioned paurostyles in the diagnosis of Moyerella. However, this kind of style is characterized by simple hyaline cores, whereas Moyerella has tubules that are deflections of the laminated skeletal material. Nekhoroshev (Reference Nekhoroshev1956, p. 47, pl. 11, fig. 3a) mentioned the presence of granules on ridges between apertures that are indeed tubules.

Holotype

SMF 23.559.

Table 7.

Descriptive statistics of Moyerella parva n. sp. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value.

Paratypes

SMF 23.560–SMF 23.633.

Diagnosis

Articulated colonies consisting of segments with pointed bases and widened proximal parts, apparently flexibly connected; segments cylindrical with narrow exozones; autozooecia moderately long, budding at low angles from the medial axis, triangular in endozone, bending abruptly in exozone; autozooecial diaphragms rare; paired heterozooecia regularly arranged between longitudinally successive autozooecial apertures; single acanthostyle between heterozooecia present; low ridges between apertures containing tubules.

Occurrence

Osgood Formation (Telychian-Sheinwoodian), Silurian; Indiana, USA. Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Description

Articulated colonies consisting of segments with pointed bases and widened proximal parts, apparently flexibly connected; segments cylindrical, 0.4–1.0 mm in diameter, with 0.1–0.3 mm wide exozones and 0.2–0.4 mm wide endozones. Branching unknown. Medial axis well developed. Autozooecia moderately long, inclined at angles of 16°–25° to the medial axis, having triangular shape in cross section in endozone, bending abruptly in exozone and intersecting the branch surface at angles of 49°–68°. Autozooecial diaphragms rare. Autozooecial apertures oval, arranged in distinct diagonal rows. Paired heterozooecia (tectitozooecia) arranged regularly between longitudinally successive autozooecial apertures, short, forming conical tubes, having triangular to pentagonal shape in cross section, 0.025–0.045 mm in width. Diaphragms in heterozooecia not observed. Autozooecial walls hyaline, 0.008–0.010 mm thick in endozone; reverse V-shaped laminated, 0.045–0.063 mm thick in exozone. Single acanthostyle between longitudinally successive autozooecial apertures present, 0.020–0.025 mm in diameter. Low ridges on the colony surface between autozooecial apertures producing four-sided pattern at junctions where acanthostyles are present. Dark tubules on ridges, 0.008–0.010 mm in diameter.

Etymology

The species name refers to the small size of this species (from Latin parva meaning small).

Remarks

Moyerella parva n. sp. is similar to M. stellata Nekhoroshev, Reference Nekhoroshev1956 from the lower Silurian (Llandovery) of Siberia but differs in possessing smaller diameter segments (0.40–1.00 mm versus 0.45–1.65 mm in M. stellata) and smaller autozooecial apertures (aperture width 0.06–0.09 mm versus 0.09–0.10 mm in M. stellata). Moreover, tectitozooecia of M. stellata have two to four diaphragms, whereas no diaphragms were observed in tectitozooecia of M. parva n. sp. Species Helopora formosa Billings, Reference Billings1866 from the Jupiter Formation (Llandovery) of the Anticosti Island is superficially similar to M. parva n. sp. in the shape of segments; however, no further details are known about this species.

Type species

Phaenopora explanata Hall, Reference Hall1852. Silurian; Canada.

Phaenopora multifida (Hall, Reference Hall1883)
Figures 11.11–11.14, 12.1–12.3; Table 8

1883

Stictopora multifida Hall, p. 268, pl. 14, fig. 4.

1887

Phaenopora multifida (Hall, Reference Hall1883); Foerste, p. 160.

1888

Phaenopora multifida (Hall, Reference Hall1883); Foerste, pl. 16, fig. 3.

1893

Phaenopora multifida (Hall, Reference Hall1883); Foerste, p. 599, pl. 29, fig 3.

Table 8.

Descriptive statistics of Phaenopora multifida (Hall, Reference Hall1883). N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Occurrence

Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA. Clinton Group, Silurian; Ohio, USA.

Description

Broad and flattened bifoliate branches, 1.0–4.5 mm wide and 0.35–1.15 mm thick. Mesotheca zigzag folded in transverse section, three layered, 0.013–0.020 mm thick. Autozooecia short, rectangular in deep tangential section. Autozooecial apertures oval to rectangular with rounded corners, arranged in 8–13 rows. Superior and observer hemisepta present, long. Metazooecia small, shallow, having triangular to pentagonal apertures, arranged regularly in pairs between apertures. Autozooecial walls finely laminated, 0.010–0.013 mm thick in endozones; laminated, fused, thick in exozones. Wide longitudinal crests on colony surface present.

Remarks

Phaenopora multifida (Hall, Reference Hall1883) differs from P. markhensis Nekhoroshev, Reference Nekhoroshev1961 from the lower Silurian (Llandovery) of Siberia in its smaller autozooecial apertures (aperture width 0.08–0.10 mm versus 0.10–0.13 mm in P. markhensis). Phaenopora multifida differs from P. contracta Astrova, Reference Astrova1959 from the Wenlock of Tuva (Russia) in thinner and narrower colonies and larger autozooecial apertures (aperture width 0.08–0.10 mm versus 0.06–0.07 mm in P. contracta).

Type species

Flustra lanceolata Goldfuss, Reference Goldfuss1829. Lower Silurian (Wenlock); Great Britain.

Ptilodictya sulcata Billings, Reference Billings1866
Figure 12.4–12.8; Table 9

1866

Ptilodictya sulcata Billings, p. 35.

1911

Ptilodictya gladiola; Bassler, p. 114, fig. 43.

1928

Ptilodictya sulcata; Bassler, p. 162, pl. 10, figs. 9–11.

1962

Ptilodictya gladiola; Kiepura, p. 405, pl. 9, fig. 1.

Table 9.

Descriptive statistics of Ptilodictya sulcata Billings, Reference Billings1866. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Lectotype

GSC 2501. Jupiter Formation (Aeronian-Telychian), Llandovery, lower Silurian; Anticosti, Canada.

Occurrence

Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA. Upper Ordovician to lower Silurian; Anticosti, Canada. Porkuni Stage (Hirnantian); Estonia.

Description

Bifoliate branched colony with pointed base, 0.72–1.35 mm wide and 0.49–0.52 mm thick in its distal part. Mesotheca zigzag folded, three layered, 0.015–0.020 mm thick; median rods lacking. Autozooecia moderately long, rectangular in deep tangential section. Autozooecial apertures rectangular with rounded corners, arranged in eight or nine rows. Short hemisepta present. Occasional thin diaphragms occurring. Heterozooecia and styles absent. Autozooecial walls in endozone laminated with dark dividing layer, 0.018–0.023 mm thick; in exozone coarsely laminated. Maculae not observed.

Remarks

The present material is similar to Ptilodictya sulcata Billings, Reference Billings1866. Ross (Reference Ross1960b) redescribed and depicted the lectotype as well as extensive additional material from the Upper Ordovician and lower Silurian of Anticosti. The present material differs in having narrower branches (branch width 0.72–1.35 mm versus 1.2–3.3 mm in the Canadian material). However, internal characteristics and aperture dimensions are identical; therefore, we identify the material from the Reynales Formation as P. sulcata.

Two more species of Ptilodictya were established from the Ordovician–Silurian deposits of North America that are quite close in their characteristics to P. sulcata: P. ensiformis (Hall, Reference Hall1852) and P. gladiola Billings, Reference Billings1866. Ross (Reference Ross1960b, p. 1068) studied the holotype of P. gladiola and supposed it being a synonym of P. ensiformis. This holotype was in bad condition, so Ross (Reference Ross1960b) could not find any morphological features for the species determination. She noted also that the majority of the material referred by Bassler (Reference Bassler and Twenhofel1928) to P. gladiola is in fact Stictoporella (Phaenopora) excellens (Billings, Reference Billings1866).

A general problem in the study of the lower Paleozoic cryptostomes is that many genera possess similar growth forms and dimensions but differ in their internal morphology. Inadequate descriptions and illustrations of original publications produce additional difficulty in discrimination of species. In some cases, study of the type material (or adequate material from type areas) has been possible. Material found at the National Museum of Natural History, Washington, D.C., contained three sets of specimens referred to Ptilodictya ensiforms (USNM PAL 35752, USNM PAL 69042, and USNM PAL 71560) and one set referred to P. gladiola (USNM PAL 57210). The latter material was referred by Bassler (Reference Bassler1911) from the Upper Ordovician of Estonia. This specimen is accompanied by a tangential thin section that reveals characteristic features of Ptilodictya. Dimensions and internal morphology of this specimen are close to those of the material from the Reynales Formation (width of autozooecial apertures 0.09–0.10 mm versus 0.07–0.08 mm in P. sulcata; spacing of apertures alongside the branch 0.21–0.29 mm versus 0.22–0.31 mm P. sulcata).

Study of photographs of the hypotype USNM PAL 69042 at the National Museum of Natural History, Washington, D.C., referred by Bassler (Reference Bassler and Twenhofel1928) to Ptilodictya ensiformis (Ordovician–Silurian of Anticosti), revealed the presence of two metazooecia between successive autozooecial apertures; therefore, this material is regarded as being Phaenopora. This species developed similar growth form with a pointed base, and it has dimensions similar to Ptilodictya sulcata and P. ensiformis.

The hypotype USNM PAL 35752 for Ptilodictya ensiformis (Hall, Reference Hall1852), referred by Bassler (Reference Bassler1906) from the Rochester Shale (Wenlock) of New York, shows typical features of Ptilodictya, but this material differs from the present species in larger autozooecial apertures (width of autozooecial apertures 0.13–0.17 mm versus 0.07–0.08 mm in P. sulcata) and wider spacing of apertures alongside the branch (0.43–0.53 mm versus 0.22–0.31 mm P. sulcata).

The specimen USNM PAL 71560, referred to by Butts (Reference Butts, Adams, Butts, Stevenson and Cook1926) as Ptilodictya ensiformis (Hall, Reference Hall1852) from the Paleozoic of Alabama, is indeed Phaenopora. This specimen has wide branches and two metazooecia between autozooecial apertures.

The species described by Kiepura (Reference Kiepura1962) as Ptilodictya gladiola Billings, Reference Billings1866 from erratic boulders of Poland shows similarities with the present material. It has branches of 0.8 mm width and apertures of ~0.08 mm width (measured from fig. 1 on pl. 9 in Kiepura, Reference Kiepura1962), which are close to present species. Internal morphology of the Polish material is unknown.

Ptilodictya sulcata is similar to P. exiliformis Suttner and Ernst, Reference Suttner and Ernst2007 from the Upper Ordovician of India (Pin Formation). The latter species has narrower branches (branch width 0.41–0.81 mm versus 0.72–1.35 mm in present material [up to ~3 mm given by other authors]). Ptilodictya differs from P. exilis Lavrentjeva in Gorjunova and Lavrentjeva, Reference Gorjunova and Lavrentjeva1993 from the Upper Ordovician (Katian) of Estonia in having smaller autozooecial apertures (aperture width 0.07–0.08 mm versus 0.10–0.13 mm in P. exilis).

Type species

Hemipachydictya copiosa Kopaevich, 1970. Ordovician–Silurian (Ashgill, Llandovery); Estonia.

Occurrence

Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Table 10.

Descriptive statistics of Metadictya sp. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Description

Bifoliate branched colony, 1.5–2.5 mm wide and 0.60–0.65 mm thick. Mesotheca straight, three layered, 0.02–0.03 mm thick; median rods present. Autozooecia moderately long, rectangular in deep tangential section. Autozooecial apertures oval to rectangular with rounded corners, arranged in 9–13 rows. Hemisepta absent. Occasional thin diaphragms occur. Heterozooecia and styles absent. Autozooecial walls in endozone laminated with dark dividing layer, 0.015–0.020 mm thick; in exozone coarsely laminated, containing numerous spherules in autozooecia walls, regularly arranged in transverse bands. Spherules 0.010–0.015 mm in diameter.

Remarks

Metadictya sp. differs from M. bifurcata (Hall, Reference Hall1883) from the lower Silurian (Llandovery) of Indiana in narrower and thinner branches (branch width 1.5–2.5 mm versus 4–5 mm in M. bifurcata; branch thickness 0.60–0.65 mm versus 2–3 mm in M. bifurcata). Foerste (Reference Foerste1887, p. 163) described material M. bifurcata from the lower Silurian of Ohio, and he gave longitudinal spacing of 5–5.5 apertures per 2 mm distance, which would closely fit with the present species (distance between aperture centers 0.34–0.40 mm [measured] versus 0.37–0.40 mm [converted] in M. bifurcata). Metadictya bifurcata (Hall, Reference Hall1883) has never been described and illustrated with use of thin sections from the type area, but this species was identified in some Ordovician localities in Europe (e.g., Bassler, Reference Bassler1911; Kiepura, Reference Kiepura1962; Spjeldnaes, Reference Spjeldnaes1984). However, the relationship of these materials to Metadictya bifurcata (Hall, Reference Hall1883) is questionable. Metadictya sp. differs from M. striatipora (Kopajevich, Reference Kopajevich, Astrova and Chudinova1970) from the lower Silurian (Llandovery) of Estonia in narrower and thinner branches as well as in smaller autozooecial apertures (aperture width 0.06–0.08 mm versus 0.11–0.28 m in M. striatipora).

Type species

Pachydictya conciliatrix Ulrich, Reference Ulrich1886. Middle Ordovician (Decorah Shale); Minnesota, USA.

Occurrence

Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Table 11.

Descriptive statistics of Trigonodictya sp. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Description

Branched bifoliate, dichotomous colonies. Branches flattened, with sharp edges, 3.5 mm wide and 0.97 mm thick. Mesotheca three layered, straight both in longitudinal and transverse sections, containing abundant median rods, 0.02–0.03 mm thick. Median rods densely spaced, 0.01–0.02 mm in diameter, continuous in dark zones separating longitudinal rows of autozooecia. Autozooecia regularly arranged in 10 alternating longitudinal rows, semicircular to trapezoid in transverse section in endozone, rectangular in deep tangential section, becoming oval on the colony surface. Autozooecial boundaries distinct, delineated laterally by continuous dark zones. Basal diaphragms rare or absent, straight. Extrazooecial skeletal deposits well developed, consisting of laminar and vesicular portions. Vesicular structures small, having flat to rounded roofs, rare to common in inner exozones. Laminar stereom with dark zones, longitudinally aligned, separating autozooecia in exozones. Monticules absent.

Remarks

Trigonodictya sp. is most similar to T. bifurcata instabilis (Foerste, Reference Foerste1887) from Llandovery of Ohio and to T. ambiqua (Ross, Reference Ross1961) from the Upper Ordovician and lower Silurian of Canada. Foerste (Reference Foerste1887, p. 164) provided the following measurements for his species: branch width 3–5 mm, branch thickness 1–2 mm, and six to seven apertures in 2 mm longitudinally. The latter value is larger than in the present species: six to seven versus four to five apertures per 2 mm. Ross (Reference Ross1961, p. 340) provided a comprehensive description of T. ambiqua accompanied by a large set of measurements. Trigonodictya sp. differs from T. ambiqua in larger autozooecial apertures (0.18–0.24 mm versus. 0.08–0.20 mm in T. ambiqua). Furthermore, T. ambiqua possesses few and small vesicular structures in endozone, which are larger and more abundant in the present species.

Type species

Retepora tenella Eichwald, Reference Eichwald1855. Upper Ordovician, Ashgill; Vormsi, Estonia.

Chasmatopora foerstei McKinney and Wyse Jackson, Reference McKinney and Wyse Jackson2010a
Figures 13.8, 14.1–14.3; Table 12

non 1852

Retepora angulata Hall, p. 49, pl. 19, fig. 3a–h.

?1875

Retepora angulata?; Hall and Whitfield, p. 111, pl. 5, figs. 2–4.

1887

Phylloporina angulata (Hall, Reference Hall1852); Foerste, p. 151, pl. 15, figs. 1, 2.

1893

Phylloporina angulata (Hall); Foerste, p. 600, pl. 28, fig. 1.

1919

Chasmatopora angulata (Hall); Foerste, p. 369.

2010a

Chasmatopora foerstei McKinney and Wyse Jackson, p. 444, text-fig. 1A–F.

2010b

Chasmatopora foerstei McKinney and Wyse Jackson, p. 41.

Table 12.

Descriptive statistics of Chasmatopora foerstei McKinney and Wyse Jackson, Reference Suárez-Andrés and McKinney2010a. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Holotype

USNM 84851 (Foerste, Reference Foerste1893, fig. 1). Clinton Group, Silurian; Soldiers’ Home Quarries, Dayton, Ohio, USA.

Occurrence

Silurian (Llandovery); Ohio and New York, USA.

Description

Reticulate colony consisting of anastomosing branches with regular oval to lens-shaped fenestrules. Branches rounded to triangular in transversal section, 0.25–0.45 mm wide. Autozooecia long, having oblong-rectangular shape in deep tangential section, well-developed vestibules, arranged in three to four alternating rows on branches. Hemisepta absent. Diaphragms common, usually situated near the bend of autozooecia in exozone. Terminal diaphragms not observed. Autozooecial apertures oval, having distinct peristomes, surrounded by 8–10 nodes. Apertural nodes 0.010–0.015 mm in diameter. Keels absent. Nodes moderately large, regularly spaced on the obverse side. Internal granular skeleton well developed, 0.015–0.020 mm thick, continuous with medial laminae, peristomes, and microstyles. Outer laminated skeleton well developed, 0.08–0.09 mm thick. Reverse side striated, containing abundant microstyles. Microstyles 0.015–0.030 mm in diameter. Heterozooecia not observed.

Remarks

Chasmatopora foerstei McKinney and Wyse Jackson, Reference McKinney and Wyse Jackson2010a differs from C. silurica (Kopajevich, Reference Kopajevich1975) from the Silurian (Llandovery) of Ukraine in its narrower branches (branch width 0.25–0.40 mm versus 0.59–0.63 mm in C. silurica). Chasmatopora foerstei is similar to C. granistriata (Ulrich, Reference Ulrich1890) from the Ordovician of the United States and Canada but differs from it in narrower branches (branch width 0.25–0.40 mm versus 0.30–0.50 mm in C. granistriata). Moreover, C. granistriata possesses keels on the obverse colony surface, which are absent in the present species.

Type species

Fenestella subantiqua d'Orbigny, Reference d'Orbigny1850. Lower Silurian (Wenlockian); England.

Fenestella jupiterensis Bassler, Reference Bassler and Twenhofel1928
Figure 14.4–14.7; Table 13

1928

Fenestella jupiterensis Bassler, p. 157, pl. 11, fig. 14, pl. 13, figs. 2, 3.

Table 13.

Descriptive statistics of Fenestella jupiterensis Bassler, Reference Bassler and Twenhofel1928. N = number of measurements; X = mean; SD = sample standard deviation; CV = coefficient of variation; Min = minimum value; Max = maximum value; units = mm.

Holotype

USNM PAL 69057. Jupiter Formation, Llandovery, Silurian; Anticosti, Canada.

Occurrence

Jupiter Formation, Llandovery, lower Silurian; Canada. Reynales Formation, Hickory Corners Member, Aeronian, Llandovery, lower Silurian; Hickory Corners, New York, USA.

Exterior description

Reticulate colony formed by straight branches joined by wide dissepiments. Fenestrules oval to rectangular. Autozooecia arranged in two rows on branches. Autozooecial apertures circular, with low peristome; 10–12 nodes in peristome, 0.008–0.010 mm in diameter; three to four apertures spaced per fenestrule length. Keel low, without nodes. Reverse side bearing nodes.

Interior description

Autozooecia relatively long, roughly rectangular in mid-tangential section with moderately long vestibule in longitudinal section. Axial wall between autozooecial rows straight; aperture positioned at distal end of chamber. Hemisepta absent. External laminated skeleton well developed on both obverse and reverse sides traversed by microstyles. Microstyles 0.010–0.015 mm in diameter. Heterozooecia not observed.

Remarks

Fenestella jupiterensis Bassler, Reference Bassler and Twenhofel1928 differs from F. elegans Hall, Reference Hall1852 from the Rochester Shale (New York) in absence of nodes on the keel and spacing of three to four apertures per fenestrule instead four to five as in the latter species. Fenestella jupiterensis is similar to another species from the Jupiter Formation, F. anticostiensis Bassler, Reference Bassler and Twenhofel1928. Unfortunately, all these species are described very briefly, without thin sections and detailed measurements. F. anticostiensis also possesses medial keel without nodes but differs in slightly larger dimensions. Bassler (Reference Bassler and Twenhofel1928, p. 156–157) gave only the numerical parameter for the spacing of fenestrules: “3 fenestrules in 3 mm longitudinally and 4 in the same space transversely.” These measurements produce estimates for average values of the distance between dissepiment centers (1 mm versus 0.73 mm in the present species) and of the distance between branch centers (0.75 mm versus 0.46 mm in the present species).