Detailed investigation of the essentially complete uppermost Miocene through Lower Pleistocene sequence in Deep Sea Drilling Project (DSDP) Hole 603C, western North Atlantic, has revealed the presence of the new dinoflagellate cyst species Lejeunecysta hatterasensis, Lejeunecysta interrupta, Corrudinium devernaliae, and Pyxidinopsis vesiculata, as well as the acritarchs Leiosphaeridia rockhallensis Head new species and Leffingwellia costata new genus and species. Independent magnetobiostratigraphic control of DSDP Hole 603C constrains the ranges of these new species. Lejeunecysta interrupta n. sp. appears to range no higher than lowermost Pliocene at 5.2 Ma, Pyxidinopsis vesiculata n. sp. has a range top at about 4.5 Ma in the Lower Pliocene, Corrudinium devernaliae n. sp. has a well-defined range of 4.7–4.1 Ma within the Lower Pliocene, and Leiosphaeridia rockhallensis n. sp. has a similarly well-defined range of 4.4–3.9 Ma within the Lower Pliocene. The presence of Leiosphaeridia rockhallensis n. sp. in the Ramsholt Member of the Coralline Crag Formation, eastern England, supports an Early Pliocene age for this member.

In late Paleozoic solitary Rugosa, the zigzag microstructure as defined by Schindewolf (1942) is related to presence of an elevated magnesium content within biogenic calcite (intermediate magnesian calcite, IMC) and its subsequent loss during diagenesis by microdissolution and neomorphism. This particular microstructure has been recognized with certainty only in some Carboniferous and Permian rugose corals (e.g., Lophophyllidium spp.). Septal and other skeletal microstructures in those corals are dominantly (oblique) sloping-lamellar, which is also interpreted as diagenetic in origin. Two directions of oblique lamellae commonly occur in thickened skeletal elements, forming chevrons that make up zigzag microstructure with its orientation determined by presence of microdolomite blebs within skeletal calcite. Geochemical studies of corals from the Mississippian Imo Formation of Arkansas, the Pennsylvanian Buckhorn asphalt of Oklahoma and Pennsylvanian Kendrick Shale of Kentucky all indicate that magnesium content in skeletal calcite of the corals was elevated, with a maximum in the neighborhood of six to eight mole percent CaCO3, thereby forming intermediate magnesium calcite. Corals with this zigzag microstructure apparently only occurred during the late Paleozoic interval of “aragonite seas”; as a result, this diagenetic behavior of rugose corals can serve as a proxy for secular change in marine chemistry and/or climate.

Early Devonian (Emsian) gastropods from the Zhusileng Formation of Zhusilenghaierhan Region, West Inner Mongolia, China, consisting of 18 taxa, including Neimongolidiscus circumumbilicus new genus and species, Pseudopharkidonotus sinensis new genus and species, Nodulospira danmianshanensis new genus and species, Zhusilengospira turbiniformis new genus and species, Zhusilengospira compactum new genus and species, Taemasotrochus nodosa new species, and Scalaetrochus sinensis new species. Endemic forms dominate the fauna, which shows some genus level affinities with Eastern Australia, the Kitikami Mountains of Japan. The fauna does feature small numbers of cosmopolitan taxa.

New heterostrophic gastropods are reported from the lowermost part of the Dayie Formation (Early Triassic, Leping, Jiangxi province, China). A new genus Jiangxispira (Streptacididae) is described. Jiangxispira yangouensis new genus and new species has an almost discoidal, heterostrophic protoconch that is typical of the largely Paleozoic Streptacididae, yet the teleoconch resembles that of certain Mesozoic opisthobranchs belonging to the Superfamily Cylindrobullinoidea. This character combination in Jiangxispira may indicate a phylogenetic link between the Paleozoic Streptacididae (Allogastropoda) and the Mesozoic Cylindrobullinoidea (Opisthobranchia). Small opisthobranchs form an important component of Early Triassic gastropod faunas. The opisthobranchs seemingly benefited from selective processes operating during the Permo-Triassic mass extinction and the reorganization of gastropod faunas during the subsequent recovery period.

Three new genera and six new species of shallow-marine gastropods are named from Upper Cretaceous strata found mainly in California. The trochids Cidarina cretacea new species and Cidarina beta new species, the ficid Bulbificopsis garza new genus and new species, and the cancellariid Mataxa arida new species are from the Maastrichtian part of the Moreno Formation of north-central California. This is the earliest record of Cidarina, whose previous chronologic range was middle Eocene to Recent. Bulbificopsis is the first record of a Cretaceous ficid from the Pacific slope of North America, and Mataxa was previously known only from Upper Cretaceous strata in the southeastern United States and northeastern Brazil. The buccinid Eripachya jalama new species and the fasciolariid Calkota daileyi new genus and new species are from the lower upper Campanian Jalama Formation in southern California. Calkota is also recognized herein as occurring in upper Maastrichtian strata of North Dakota and South Dakota. The new melongenid genus, Pentzia, established for Fulgur hilgardi White, 1889, is from Campanian strata throughout California; middle Campanian strata on Sucia Island, Washington; and upper Campanian to lower Maastrichtian strata in northern Baja California, Mexico.

The ctenonotellid ostracode species Brezelina palmata (Krause, 1889) and the tetradellid species Ogmoopsis bocki (Öpik, 1935) are represented by seven and five molting stages, respectively. Both species display an association of velar and size dimorphism in the three last instars. The analysis of the juvenile morphology of O. bocki provides evidence for a close relationship with the earliest known palaeocope ostracode species Nanopsis nanella (Moberg and Segerberg, 1906). The population age structure of B. palmata in synchronous beds at two localities reveals different types of thanatocoenoses, supporting the hypothesis of a deepening gradient along the Baltic-Ladoga Klint.

A new scolopendromorph centipede (Myriapoda: Chilopoda), Cratoraricrus oberlii n. gen. and sp., is described from the Nova Olinda Member of the Lower Cretaceous Crato Formation of northeast Brazil. The specimen is tentatively referred to the Scolopendridae based on possession of bisegmented tarsi and paramedian longitudinal grooves on the sternites. This specimen represents one of only four verifiable Mesozoic taxa.

The Cambrian–Ordovician boundary is a type 1 depositional sequence boundary with dramatic local erosional incision in restricted marine facies on the easternmost New York Promontory. The systemic boundary is bracketed below by Late Cambrian, upper Cordylodus proavus Zone (s.s). conodonts from carbonates of the upper Little Falls Formation (=Whitehall Formation, abandoned). Presumed Lower Ordovician ellesmeraceratoid cephalopods from the upper Little Falls are uppermost Cambrian and among the oldest known in North America. The overlying deepening–shoaling cycle of the Tribes Hill Formation (=Cutting and Great Meadows Formations, abandoned) is the local expression of a lowermost Ordovician (Rossodus manitouensis Zone) depositional sequence recognizable across Laurentia. Complete replacement of conodonts takes place in the late Tremadocian or Tremadocian–Arenigian boundary interval with onlap of the “Fort Ann Formation” across the paleokarst cap of the Tribes Hill. The trilobites Hystricurus sp. and Symphysurina myopia Westrop new species occur in less restricted, thrombolitic facies of the middle Tribes Hill that have the highest conodont diversity. Ulrichodina Furnish, 1938, emend. is regarded as the senior synonym of the conodont Colaptoconus Kennedy, 1994 (=Glyptoconus Kennedy, 1980).

The largest known trilobite fossil, a virtually complete articulated dorsal shield of the asaphid Isotelus rex new species, has been recovered from Upper Ordovician (Cincinnatian, Richmondian) nearshore carbonates of the Churchill River Group in northern Manitoba. At over 700 mm in length, it is almost 70 percent longer than the largest previously documented complete trilobite, and provides the first unequivocal evidence of maximum trilobite length in excess of one-half metre. Comparisons with other fossil and extant members of the phylum suggest that in terms of maximum linear dimensions it was among the biggest arthropods ever to have lived. Sediments of the Churchill River Group were deposited in an equatorial epeiric setting and the extremely large size of I. rex n. sp. thus marks a striking example of low-latitude gigantism, in sharp contrast to the widespread phenomenon of “polar gigantism” in many modern marine benthic arthropods. Lack of extensive epibiontic colonization of the exoskeletal surface and the presence of large distinctive trace fossils in the same unit suggest that I. rex n. sp. may have been a semi-infaunal predator and scavenger that employed a shallow furrowing and probing mode of benthic feeding. The extinction of the isotelines (and virtually the entire asaphide lineage) at the end of the Ordovician cannot be related to the near contemporaneous achievement of exceptionally large adult size in some representatives. Failure to survive the terminal Ordovician extinction event was most likely a consequence of a pelagic larval life-style that proved ill-adapted to the rapid onset of global climatic cooling and loss of tropical shelf habitats.

The glyptocystitoid rhombiferan Sprinkleocystis ektopios new genus and species is described from the Middle Ordovician (Caradoc) Benbolt Formation of Tennessee. This species is characterized by having four ambulacra bearing only terminal brachioles, the absence of lateral 5, and protuberant pectinirhombs and periproct. Many of its features are considered typical of the family Cheirocrinidae whereas others are more characteristic of the Glyptocystitidae. Its small size and simple ambulacral and pectinirhomb structures suggest a paedomorphic evolutionary origin, and its thecal morphology further suggests that the validity of a separate Cheirocrinidae and Glyptocystitidae may need reevaluation.

All 19 known species of the primitive cladid crinoid genera Atelestocrinus, Cyathocrinites, Goniocrinus, Parisocrinus, Pellecrinus, and Zygotocrinus from the early Osagean Burlington Limestone of the North American midcontinent are reviewed and redescribed or, where necessary, redefined. Nine of these species are illustrated for the first time herein. Sixteen are considered valid, including C. deroseari n. sp. Of the remaining three species, one is left in open nomenclature, and two are considered nomen dubia. Pellecrinus is recognized for the first time from the Burlington Limestone, although the specimens can not be identified to the species level and are left in open nomenclature.

Cyathocrinites ranges from the Middle Silurian to at least the Middle Mississippian. During the Early Mississippian Cyathocrinites experienced an evolutionary radiation with a maximum diversity of nine species in the Burlington Limestone. Phylogenetic relationships were investigated in a parsimony-based phylogenetic analysis by combining morphologic data from the Burlington species with data from the four other species of Cyathocrinites from the late Osagean and early Meramecian of the east-central United States. The Kinderhookian C. chouteauensis (Miller and Gurley, 1896) served as the outgroup. A phylogenetic analysis of 14 species of Mississippian Cyathocrinites yielded a single most parsimonious tree with a length of 28 steps (C. I. = 0.607, H. I. = 0.392, R. I. = 0.718, R. C. = 0.436). Results of this analysis suggest that at least two major clades existed within Mississippian Cyathocrinites. One clade contains C. sampsoni (Miller, 1891b), C. gilesi (Wachsmuth and Springer, 1878), C. farleyi (Meek and Worthen, 1866), and C. barydactylus (Wachsmuth and Springer, 1878). The second clade contains C. iowensis, C. kelloggi (White, 1862), C. barrisi (Hall, 1861a), C. rigidus, C. deroseari n. sp., C. asperrimus (Springer, 1911), C. lamellosus (White, 1863), and C. harrodi (Wachsmuth and Springer, 1880). Cyathocrinites multibrachiatus forms a polytomy with these two clades. Members of the first clade exhibit a unique overall morphology present only during the Mississippian, suggesting the clade arose during this time. Members of the second clade, plus C. multibrachiatus, exhibit some characters present in Cyathocrinites species as old as the Middle Silurian and, thus, may have its roots among Silurian and Devonian species.

A low-diversity crinoid fauna is described from the Fitchville Formation, Lower Mississippian (Late Devonian to Early Mississippian) of Utah County, Utah. Based on the crinoid fauna, composed of Nunnacrinus olsoni new species, Paracosmetocrinus lundi new species, and Platycrinites sp., this fauna is interpreted as being from the Kinderhookian, Upper Fitchville Formation. This occurrence of Nunnacrinus extends the geographic and facies range of this genus in western North America and the geographic range of Paracosmetocrinus within western North America.

The conodont fauna from nine sections across a platform-to-basin transect in northeastern British Columbia includes species of Early Ordovician (Tremadocian) to Early Silurian (Llandovery) age. A collection of 9,110 conodont elements was recovered from 205 samples taken from nine stratigraphic sections that preserve the platform succession of the Kechika, Skoki, Beaverfoot, McCusker and Nonda Formations and their off-shelf equivalents, the Ospika, Robb, Kenny and Laurier Formations of the Road River Group. The fauna is assigned to 106 species representing 67 genera; the Ordovician species are representative of two faunal realms. One new genus, left in open nomenclature, is described. Five new species include Drepanoistodus latus and four new species left in open nomenclature assigned to the following genera: Walliserodus, Multioistodus?, Pseudooneotodus, and Belodina. The Midcontinent Realm zones recognized include, in ascending order, the Acodus kechikaensis, Oepikodus communis, Jumudontus gananda, Tripodus laevis to Plectodina aculeata zones, Phragmodus undatus and Gamachignathus ensifer? zones. Zonal species of the Atlantic Realm are Microzarkodina flabellum, Eoplacognathus suecicus, Baltoniodus variabilis, Pygodus anserinus, and Amorphognathus tvaerensis. The Silurian fauna, of lower diversity than the Ordovician fauna, is representative of the Distomodus staurognathoides and Pterospathodus amorphognathoides zones.

Superbly preserved tarsi of a new, undescribed, primitive member of Diadectidae and of Diadectes, the best known member of the family, are described. The major distinction between them is the retention of sutures in the astragalus of the former which clearly indicate an origin from the fusion of three separate ossifications considered homologues of the primitive amphibian tibiale, intermedium, and proximal centrale. Among the Diadectomorpha (includes also Limnoscelidae and Tseajaiidae) only Diadectidae possesses an astragalus, which is considered a synapomorphy of the family within this grouping. Furthermore, the sister-group relationship of the new, undescribed diadectid to the other diadectids demonstrates a transformational, phylogenetic homology of the astragalus via the ontogenetic fusion of the primitive amphibian tarsal bones. The astragalus of diadectids is identical to those of late Paleozoic terrestrial amniotes in structure and relationship to neighboring elements. This, plus the wide acceptance of a close relationship between Diadectomorpha and Amniota, is cited as suggestive of an identical developmental origin of their astragali.

In diadectids, including fully mature individuals, an unusual reduction or absence of ossification of some central and distal tarsal bones has resulted in an unique tarsus with large unoccupied areas and a structural pattern in which the only bony link between the tarsus and the digits is via the fourth distal tarsal, producing a crude facsimile of the lacertilian mesotarsal joint. Such a joint would have permitted, as in lacertilians, a wide range of movements which may have served several important functions: 1) maintaining an anteriorly directed pes to maximize the force of its posterior thrust during limb retraction, 2) placement of the pes close to the body midline for greater stride length and more efficient support and greater maneuverability during locomotion.