The extinction of the Olenellina on Laurentia can be located within centimeters in the C-shale or uppermost Combined Metals Limestone members of the Pioche Formation in eastern Nevada. Olenellid species diversity beneath the extinction boundary is not diminished. One of the richest Laurentian intervals for articulated olenellids is in the 50 centimeters of shale immediately below the extinction boundary at Ruin Wash. Additional morphological information about some of the species comes from a silicified fauna 1.8 m below the extinction boundary at Hidden Valley. The olenellid fauna from the 2-meter interval below the extinction boundary is described. Questions about current generic and subgeneric relationships are discussed. Among general observations, intraspecific variability unrelated to size or taphonomic effects is minimal for most species; at least two species may have been capable of enrollment; and visual surfaces of one species show no evidence of facets. New species include: Olenellus (Olenellus?) fowleri, Olenellus (Paedeumias) chiefensis, Olenellus (Paedeumias) terminatus, Bolbolenellus brevispinus, and Nephrolenellus geniculatus. Olenellus (Olenellus) gilberti Meek and Olenellus (Olenellus) howelli Meek are revised.

Over the course of the last two decades, the baenid taxon Plesiobaena has typically been thought to consist of two named species, Plesiobaena antiqua (Campanian) and Plesiobaena putorius (Paleocene), along with an unnamed species from the Maastrichtian, but the interrelationship of these three taxa was never explored in an explicit phylogenetic context. Herein we present or re-describe a number of relevant specimens and provide a cladistic analysis of Baenidae using species only as terminal taxa. The phylogenetic analysis clearly reveals that Plesiobaena in the traditional sense is a paraphyletic assemblage relative to the clade formed by Gamerabaena sonsalla and Palatobaena spp., thus demanding some nomenclatural adjustments. In particular, Plesiobaena putorius is moved to a new genus, Cedrobaena, and the unnamed taxon from the Maastrichtian is formally named Peckemys brinkman. Many of the new Cedrobaena putorius and Peckemys brinkman specimens described herein were found at the Turtle Graveyard locality in Slope County, North Dakota, along with four other turtle taxa, increasing the turtle diversity of this locality to at least six taxa. Although this indicates that Turtle Graveyard is the world's most diverse fossil turtle thanatocoenosis, a comparable diversity is found in modern river systems in the southeastern United States today. Our phylogenetic analysis indicates that seven out of nine latest Cretaceous baenid turtle lineages survived into the Paleocene, four of which are interpreted as being durophagous.

A low-diversity shelly fauna occurs in the Deep Spring Formation of the White–Inyo Mountains of eastern California and in Esmeralda County, Nevada. Although poorly preserved, specimens can be recovered through acid digestion of the limestone matrix. The fauna is composed of three tubes of uncertain affinities and a hyolith. Nevadatubulus dunfeei n. gen. and sp., a distinctive, randomly curved and annulated tube, is abundant and far outnumbers the remaining three elements: Coleoloides inyoensis n. sp., Sinotubulites cienegensis McMenamin, and the hyolith Salanytheca sp. The original composition of the faunal elements appears to have been calcite or aragonite, but recrystallization has destroyed any ultrastructure. No phosphatic elements occur with the fauna nor have phosphatic fossils been recovered from the underlying Wyman and Reed Formations or the other members of the Deep Spring Formation.

The fauna occurs 1,500 meters below the first trilobite body fossils and may be coeval with faunas from the basal Cambrian Tommotian Stage of the Siberian Platform. Wyattia, the only previously described pre-trilobite shelly fossil from the region, occurs in approximately the same stratigraphic interval but was not recovered in our samples.

The appendicular skeleton of the Lower Permian temnospondyl Eryops megacephalus Cope, 1877, described and figured in detail, is similar to that of most temnospondyls, except that it is highly ossified. It displays terrestrial adaptations, including a reduced dermal pectoral girdle and comparatively large limbs, characterized by well-developed processes for muscle attachment. While many features that were previously unknown or uncommon among temnospondyls were identified, no apomorphies of the appendicular skeleton particular to Eryops were found. Some characteristics of the endochondral postcranial skeleton found in well-ossified temnospondyls, such as Eryops, are absent in less well ossified temnospondyls due to immaturity or paedomorphism. The effects of heterochronic processes on the morphology of the postcranial skeleton of temnospondyls and the implications for cladistics are discussed; the appendicular skeleton of Eryops is considered hypermorphic. Within the Temnospondyli, the Eryops appendicular skeleton is most similar to that of the Dissorophoidea, and most dissimilar to both the most plesiomorphic temnospondyls and the secondarily aquatic Mesozoic stereospondyls. The appendicular skeletons of well-ossified Late Permian and Mesozoic temnospondyls are not as robust as that of Eryops.

Surprisingly, Eryops, in common with other well-ossified temnospondyls, shares many derived features of the appendicular skeleton with seymouriamorphs and diadectomorphs. The presence of these previously unrecognized synapomorphies (relative to stem tetrapods and embolomeres) provides evidence for an alternative hypothesis of relationships of early tetrapods, suggesting that the Temnospondyli and seymouriamorphs plus diadectomorphs are sister taxa.

African machairodont specimens previously referred to three species of Megantereon are considered to represent a single species in turn argued to be conspecific with the Eurasian species Megantereon cultridens (Cuvier). The area of origin of Megantereon remains unclear, but doubt is expressed about claims for an earliest appearance of the genus in North America. It is probable that the North American species M. hesperus is a junior synonym of M. cultridens.

Two regional composite sections in the Frasnian, Upper Devonian, of New York State result from graphic correlation of conodont species. The first extends from Frasnian conodont zones 3 to 7, the second from Frasnian zones 11 to 13c (we prefer this terminology to “Montagne Noire” or “MN” zonation as the zone-defining species occur throughout the Devonian tropics). Key beds, widely traceable bases of prominent black shales, have been used with only a few exceptions to position the lines of correlation (LOC) in the graphs. Other key beds, not used for positioning, fall exactly on the LOC supporting the hypothesis of their synchrony. Fifty-five conodont species in the New York regional composites are compared with their ranges in the global Frasnian Composite Standard proving no major discrepancies. The taxonomy of Ancyrodella nodosa Ulrich and Bassler, widely misidentified in the past, has been clarified through restudy of the type specimens, resulting in its distinction from A. hamata Ulrich and Bassler (=A. buckeyensis Stauffer). A new species of Polygnathellus Bassler, which is restricted to Frasnian Zone 4, is kept in open nomenclature because the rarity of specimens is insufficient to determine the extent of intraspecifc variation and whether one or two species are represented in our New York and Western Australian collections.

This paper describes a unique deepwater brachiopod fauna from the upper part of the Talung Formation at the Dongpan Section, southern Guangxi, South China. This brachiopod fauna includes 10 species belonging to 10 genera. New taxa are Anidanthus mucronata n. sp., Dongpanoproductus elegans n. gen. and sp., Costatumulus dongpanensis n. sp., and Spinomarginifera semicircridge n. sp. This fauna is characterized by small, thin-shelled species with high abundance and low diversity, and therefore is different in generic and species composition from the coeval faunas of the Late Permian limestone facies in South China. The brachiopod fauna can be safely assigned to the latest Changhsingian as indicated by the presence of abundant Paracrurithyris pigmaea, the immediately underlying radiolarian Neoalbaillella optima Zone of late Changhsingian age, and the overlying ammonoid Ophiceras sp. cf. O. tingi Tien of the lowest Triassic. This fauna is most likely to have lived in a deepwater environment as indicated by coexistence with the radiolarian Latentifistularia, small thin-shelled brachiopods, and the dominance of silica-bearing mudstone.

The ca. 780–740 Ma Chuar Group, Grand Canyon, Arizona, provides an exceptional record of life during the diversification of crown-group eukaryotes, just prior to the first Cryogenian glaciation. We document in detail the assemblage of organic-walled microfossils preserved in fine-grained siliciclastics throughout the unit. In contrast with earlier studies, we primarily used SEM to document fossil morphologies, augmented by transmitted light microscopy, FIB-SEM, and TEM. This resulted in the discovery of new species and the recognition of broad-ranging, intraspecific biological and taphonomic variation in other species. Twenty-two species and five unnamed morphotypes are described, including three new species: Kaibabia gemmulella, Microlepidopalla mira, and Volleyballia dehlerae; two new combinations: Galerosphaera walcottii and Lanulatisphaera laufeldii; and 17 previously described forms. The possible colonial green alga Palaeastrum dyptocranum Butterfield in Butterfield, Knoll, and Swett, 1994 and the index fossil Cerebrosphaera globosa (Ogurtsova and Sergeev, 1989) Sergeev and Schopf, 2010 (=C. buickii Butterfield, 1994) are described for the first time from Chuar rocks. Lanulatisphaera laufeldii, a locally abundant and globally widespread species characterized by submicrometer filamentous processes that form a reticulate network, may be a useful marker for the time interval just before the appearance of vase-shaped microfossils (VSMs) ca. 740 Ma.

Organic-walled microfossil assemblages decline in diversity upsection, coincident with the appearance of VSMs and intermittent euxinia within the basin. Whether this pattern is due to preservational bias related to greater water depth or the higher TOC of upper Chuar rocks or instead reflects biotic turnover related to the spread of euxinic water masses in the basin is unknown.

Many evolutionary trends are described in the post-Paleozoic echinoids and their functional advantages are discussed. In the ambulacra, the compound plate first appeared in the Late Triassic, becoming more pronounced during the Mesozoic, and reaching its zenith in the Cenozoic. Compounding enabled the echinoid to have more numerous tubefeet, strengthened the test, and increased the size of the ambulacral tubercles and spines. These larger spines provided greater protection from predators and faster locomotion. Petals first appeared in the Middle Jurassic and were developed for more efficient respiration. The first depressed petals occurred in the Late Jurassic, and by Late Cretaceous many echinoids had depressed petals culminating in deep petals in the Cenozoic. These depressions channeled water over the respiratory tubefeet, increased the width of the ambulacra and their tubefeet, and enabled these tubefeet to be protected from predators by the arching of spines over them. An anterior groove is slightly developed by the Middle Jurassic, distinct in the Cretaceous, and deepest in the Cenozoic. This groove provided a passage for food, and shelter for the large penicillate tubefeet. Phyllodes first occur in the Lower Jurassic in both the regular and irregular echinoids. During the Mesozoic the number of pores in the phyllodes in the irregular echinoids was reduced, and in most species one pore was eliminated of a porepair. The phyllodes provided a large number of feeding tubefeet near the peristome. In the apical system of the irregular echinoids, the periproct broke out during the Lower Jurassic. Its movement posteriorly served to separate the echinoid's excrement from its feeding and respiratory areas. The number of genital plates was reduced to a single plate in the cassiduloids by the Late Cretaceous, but this reduction occurred later in the holasteroids and spatangoids; many species living today have more than one genital plate. The Triassic and Early Jurassic echinoids were small; but during the latter part of the Jurassic, larger species occur, particularly among the irregulars and echinothurioids. All the Triassic echinoids except one were circular in marginal outline, but during the Jurassic the test in many irregulars became elongate enabling the echinoid to develop unidirectional movement. The flattening of the test permitted the echinoid to cover its test more easily, making the animal less conspicuous, less affected by wave motion, and placing more of the food-gathering tubefeet in contact with the seafloor. The Triassic lantern had grooved teeth and a shallow foramen, but by the Lower Jurassic some lanterns had a deeper foramen magnum. By the Middle Jurassic keeled teeth are present, and by the Late Cretaceous some lanterns have joined epiphyses. These changes permitted the lantern to be more mobile and strengthened the teeth and epiphyses. The lantern supports in all Triassic echinoids are outgrowths of interambulacral plates, but in the Lower Jurassic many species have ambulacral supports. By the Middle Jurassic these supports are joined together in some species to form an arch. These changes also increased the mobility and power of movement of the lantern. Gill notches first appeared in the Lower Jurassic (Hettangian) and were well developed by the Toarcian. The tubercles and their spines were large in the Triassic and gradually decreased in size in some species through the Mesozoic. This reduction enabled these echinoids with smaller spines to cover their tests with sediment. The rate of introduction of new plates was low in the Triassic, increasing during the Jurassic. This increase was mainly in the ambulacra and served to increase the number of tubefeet. Among the holasteroids-spatangoids some of the ventral interambulacral plates increased in size relative to adjacent plates during the Mesozoic and Cenozoic forming the labrum and plastron. These changes permitted the development of the “heart-shaped” test, and an anterior shift of the peristome. Diversity of echinoids increased since the Triassic with the development of different kinds of echinoids able to inhabit many varied habitats. All Triassic echinoids lived on top of the substrate, but in the Jurassic irregular echinoids began to burrow in the sediment. They increased in number of species during the Mesozoic and now are more numerous in species than the regular echinoids.

The difference between Jurassic and Triassic species is not as abrupt as formerly thought, and all Jurassic echinoids are considered to have had a cidaroid ancestor.

Deutler's classic work (1926) provides the basis for an analysis of plate growth in echinoids. Deutler showed that the concentric growth rings found within each plate may be used to reconstruct the ontogeny of the entire plate pattern.

New observations of growth-line configurations, particularly in Strongylocentrotus pallidus (Sars), have been used to derive a general model for echinoid growth. The plate mosaic is assumed to be the result of close packing of the growing plates. The shape of a given plate thus depends on its size and position relative to surrounding plates.

The rate of meridional growth of a plate can be shown to change regularly with increasing distance from the echinoid's apical system. Migration of plates away from the apical system thus causes change in the rate of plate growth. The rate of plate migration is strongly influenced, in turn, by the rate of supply of new plates at the apical system.

A mathematical model has been developed from these considerations which, when treated by digital computer (with x-y plotter output), produces ideal plate patterns (including growth rings). The constants in the model may be varied to produce a broad spectrum of echinoid plate patterns.

The Dinwoody Formation of the western United States represents an important archive of Early Triassic ecosystems in the immediate aftermath of the end-Permian mass extinction. We present a systematic description and a quantitative paleoecological analysis of its benthic faunas in order to reconstruct benthic associations and to explore the temporal and spatial variations of diversity, ecological structure and taxonomic composition throughout the earliest Triassic of the western United States. A total of 15 bivalve species, two gastropod species, and two brachiopod species are recognized in the study area. The paleoecological analysis shows that the oldest Dinwoody communities are characterized by low diversity, low ecological complexity and high dominance of few species. We suggest that this low diversity most likely reflects the consequences of the mass extinction in the first place and not necessarily the persistence of environmental stress. Whereas this diversity pattern persists into younger strata of the Dinwoody Formation in outer shelf environments, an increase in richness, evenness and guild diversity occurred around the Griesbachian–Dienerian boundary in more shallow marine habitats. This incipient recovery towards the end of the Griesbachian is in accordance with observations from other regions and thus probably represents an interregional signal. In contrast to increasing richness within communities (alpha-diversity), beta-diversity remained low during the Griesbachian and Dienerian in the study area. This low beta-diversity reflects a wide environmental and geographical range of taxa during the earliest Triassic, indicating that the increase of within-habitat diversity has not yet led to significant competitive exclusion. We hypothesize that the well-known prevalence of generalized taxa in post-extinction faunas is primarily an effect of reduced competition that allows species to exist through the full range of their fundamental niches, rather than being caused by unusual and uniform environmental stress.

Fossiliferous deposits of the Greenhorn Limestone (Upper Cretaceous) are found on the Comanche National Grassland in southeastern Colorado. The lowest portion of the Greenhorn Limestone, the base of the Lincoln Limestone Member, contains calcarenite beds rich in disarticulated remains of marine vertebrates. We examined the composition of the vertebrate paleofauna from one particular location (Tobe locality) through surface collecting and acid solution of rocks. The paleofauna is taxonomically diverse, consisting of 22 chondrichthyans, at least 15 osteichthyan fishes, and six aquatic reptiles. Molluscan taxa indicate that the basal Lincoln Limestone in southeastern Colorado was deposited sometime between middle Middle Cenomanian (ca. 95 Ma) and late Middle Cenomanian (ca. 94.7 Ma), and the composition of the vertebrate fauna (primarily chondrichthyan taxa) agrees with this interpretation. The Tobe locality was situated far from the shorelines of the Western Interior Seaway, with relatively high-energy waves impinging upon the seafloor, concentrating biogenic remains. Fossil remains within the calcarenite appear to have undergone minor time-averaging, based upon erosional rounding and breakage present in numerous specimens. Nevertheless, the deposit contains one of the best representative Middle Cenomanian vertebrate communities so far described from the Western Interior Seaway of North America. Considering that the paleofauna consists of taxa diverse in size, morphology, and inferred ecology, the trophic structure of the paleocommunity was probably complex.

New material of polyglyphanodontine lizards from the Late Cretaceous has been found in various localities in western North America. Several transversely oriented teeth representing a new species of Dicothodon were recovered from the Turonian of southern Utah. These specimens necessitate reassignment of Polyglyphanodon bajaensis to Dicothodon (Polyglyphanodon) bajaensis. From the Campanian of Utah, additional teeth and jaw fragments referable to Manangysaurus saueri have been recovered and this species is reassigned here to Peneteius (Manangysaurus) saueri. Also, an isolated tooth referable to Peneteius has been recovered from the Campanian of southern Texas. The results of a phylogenetic analysis support a monophyletic grouping of the transversely-toothed taxa with Bicuspidon as the sister taxon of Polyglyphanodontini new taxon, which is comprised of Polyglyphanodon, Dicothodon, and Peneteius. The phylogenetic analysis also places “teiid” lizards from the Cretaceous of Asia and North America in a monophyletic group, Borioteiioidea new taxon, which is the sister taxon to the Teiioidea (Teiidae + Gymnophthalmidae). This new hypothesis of the interrelationships of these taxa requires the reevaluation of several characteristics that were previously considered diagnostic for a more inclusive Teiidae. Another implication of our results is that Teiidae (sensu stricto) has no demonstrable pre-Tertiary occurrence. It appears that Teiioidea and Borioteiioidea diverged from a common ancestor by the Early Cretaceous. The Teiioidea entered South America and are currently represented by the Teiidae and Gymnophthalmidae, whereas Borioteiioidea radiated throughout North America with subsequent dispersal to Asia and Europe.

The living members of the Argopecten gibbus stock include the bay and calico scallops, Argopecten irradians (Lamarck) and A. gibbus (Linné), both common in the western Atlantic and Gulf of Mexico; the less common A. nucleus (Born) of the Caribbean, southern Gulf of Mexico, Antilles, and southeastern Florida; and the common A. circularis (Sowerby) and A. purpuratus (Lamarck) of the eastern Pacific. The fossil members of the stock include the ancestors of these living species together with Argopecten eboreus (Conrad), an extinct species or species-group not ancestral to any of the later taxa. This study seeks to determine evolutionary relationships within the Argopecten gibbus stock by working back through the fossil record from a model of the morphological and ecological relationships of living species and subspecies. Biologically, the study is limited to an analysis of the morphology and ecology of the living taxa deduced from population samples. Paleontologically, it is limited to an analysis of morphological variation among samples of fossil populations collected from upper Cenozoic strata (Alum Bluff Group of the middle Miocene through the Pleistocene) exposed on the Atlantic and Gulf Coastal Plains of the United States. The time span investigated is about 18 million years, according to the latest published scale of absolute time.

Differences between samples were studied and evaluated by means of morphometric data consisting of 70 measurements and form ratios of the outline, ligamenture, and musculature of each valve. Using an electronic digital computer, data were subjected to univariate and bivariate analyses, and samples were compared using machine-plotted, bivariate scatter diagrams, reduced major axes, and other graphical techniques. Data from right and left valves were treated separately, except that they were recombined in the study of characters that differ between valves, thereby furnishing new information on intervalve features.

The postulated phylogeny shows a poorly known species, Argopecten species b, in the early middle Miocene (Oak Grove Sand), that is apparently very near the origin of the stock. This species evolved phyletically through A. nicholsi (Gardner) of the Shoal River Formation and A. choctawhatcheensis (Mansfield) of the Arca Faunizone into A. comparilis (Tuomey & Holmes) of the upper Miocene (Tamiami, Pinecrest, Duplin, and Yorktown Formations). A. comparilis was apparently broadly adapted and widely distributed, living in bays, sounds, and open marine waters in the western Atlantic, Gulf of Mexico, and Caribbean and probably extending through seaway passages to the Pacific, where it gave rise phyletically to A. circularis. By the end of the Miocene, on the eastern side of the Americas, this variable species had split, giving rise to a primitive bay scallop, A. anteamplicostatus (Mansfield), that, like the living bay scallop (its phyletic descendant), was probably ecologically restricted to the semienclosed waters of bays and sounds, and to another species, A. vicenarius (Conrad), probably restricted to open marine waters like the living calico scallop. The primitive bay scallop was apparently unable to reach the Pacific, but the open-marine species seems to have given rise to both the Pacific A. purpuratus and the Atlantic calico scallop, A. gibbus. The living Pacific A. circularis is morphologically primitive in that it resembles the Miocene species A. comparilis more than it does any of the later species on the eastern side of the Americas and is ecologically primitive in that it is broadly adapted and able to live both in bays and sounds and in open marine waters. During the Pleistocene, A. nucleus, a tropical bay scallop, is inferred to have split from A. gibbus and to have become morphologically convergent on the true bay scallop, A. irradians. A. eboreus, a common scallop on the eastern side of the Americas in the Miocene and Pliocene, represents a highly variable yet morphologically persistent lineage that neither split nor gave rise phyletically to other species and that became extinct during the early Pleistocene. In certain features of morphology, the A. gibbus lineage is convergent on the A. eboreus lineage, indicating that the extinct species may also have been restricted to open marine waters.

On the basis of the materials analyzed thus far, the evolution (both phyletic change and splitting) of the stock has been faster on the Atlantic side of the Americas than on the Pacific side, with the living Pacific species resembling late Miocene and early Pliocene Atlantic species. Because barrier islands seem to have played a key role in speciation within the stock, it would appear that evolutionary differences may have been caused by the active coastal tectonism of the Pacific side destroying such island barriers before genetic differences between inshore and offshore scallop populations could arise.

With regard to nomenclature, the name Argopecten is shown to be a senior synonym of Plagioctenium; the generic name Aequipecten is rejected for American species related to Argopecten gibbus; and it is concluded that the generic name Chlamys, sensu lato, is better applied as the subfamily name Chlamydinae. The species name Argopecten vicenarius (Conrad), unused since 1898, is reinstated as the only available name for an important taxon occurring in the Caloosahatchee Marl of Florida and the Waccamaw Formation of the Carolinas.

Coccoid and filamentous microfossils in the Borden Rift Basin on northwestern Baffin Island and western Bylot Island are reported from 14 localities at six general stratigraphic levels in the Society Cliffs Formation, and one in the Victor Bay Formation. At least seven of 12 fossiliferous Society Cliffs samples, and one of two Victor Bay samples, are from cherty dolostones formed in shallow restricted, peritidal evaporitic environments. The remaining six fossiliferous samples accumulated in somewhat deeper, less restricted waters. The assemblage is preserved in black chert nodules and layers and comprises 30 taxa, including the filamentous forms Archaeotrichion? sp., Tenuofilum septatum, Eomycetopsis robusta, Siphonophycus inornatum, S. kestron, Rhicnonema antiquum, Brachypleganon sp., Eomicrocoleus sp., Uluksanella baffinensis n. gen. and sp., Talakania? sp., the coccoid taxa Eosynechococcus medius, E. grandis, Archaeoellipsoides obesus, Sphaerophycus parvum, S. medium, Myxococcoides minor, M. grandis, Melasmatosphaera spp., Phanerosphaerops capitaneus, Palaeoanacystis sp., Tetraphycus hebeiensis, Eogloeocapsa bella, Gloeodiniopsis magna, G. sp. 1, G. mikros, Polybessurus bipartitus, Cymatiosphaera? sp., the fusiform Eupoikilofusa? sp., and rare specimens of two unidentified and problematic taxa.

Previous reports of Cambrian bryozoans have proved not to be bryozoans. No pre-Ordovician bryozoans have been recognized. The oldest unequivocal bryozoans known from North America, Britain, and Russia are evidently of early Arenigian age. New bryozoans recently collected from the Fenxiang Formation in the Daping and Guanzhuangping sections, situated in the area east of the Yangtze Gorges, are described here, including one new genus, Orbiramus, and six new species, Nekhorosheviella nodulifera, N. semisphaerica, Orbiramus normalis, O. ovalis, O. minus, and Prophyllodictya prisca. These are assigned to the Trepostomida, apart from the last species which belongs to the Cryptostomida. The new bryozoans are from the conodont Paltodus deltifer deltifer Zone of the late Tremadocian age, the first three species possibly being present in the P. deltifer pristinus Subzone at the base. Therefore, they are the oldest bryozoans known from anywhere in the world. Extensive reefs resulting from a major regression in the late Tremadocian were dominated by bryozoans in the upper Fenxiang Formation. The bryozoans lived in a shoal environment and accumulated essentially in situ, showing no signs of significant transportation.

The Coelophysis dinosaur quarry at Ghost Ranch, near Abiquiu, New Mexico, is unique among Triassic fossil sites for its yield of numerous complete and partial skeletons of a single species of theropod dinosaur (Coelophysis bauri). Since its discovery in 1947 by E. H. Colbert in the red siltstone beds of the Upper Triassic Chinle Formation, the quarry has yielded the remains of at least 1,000 individuals from approximately 30 cubic meters of excavated material. The main bone-bearing strata are abandoned channel deposits that are part of a siltstone overbank sequence. The Coelophysis remains found at the quarry are remarkably whole and well preserved, though they range in degree of articulation from complete skeletons to isolated limbs and bones. Skeletons, partial skeletons, and bones are crudely aligned and show little evidence of predator or scavenger disturbance or surface weathering. Geologic and taphonomic evidence suggests that the dinosaurs preserved in the Ghost Ranch quarry were transported to the site as carcasses by fluvial currents. The carcasses blocked a small channel and were subsequently buried by silts. Petrographic study and neutron activation analysis reveal no evidence of volcanic ash, paleopathologic osteology, or unusual chemistry in the quarry bone and sediments. The virtual monospecificity, taphonomy, and ecology of the assemblage suggest that the dinosaurs perished due to a regional environmental crisis, such as drought.

The discovery of a fish bone layer immediately overlying the K-T iridium anomaly on Seymour Island, Antarctic Peninsula, which may represent the first documented mass kill associated with the impact event, together with new faunal data across the boundary has provided new insight into events at the end of the Cretaceous. The utilization of a geographical approach and a new graphical representation of range data has revealed that events at the end of the Cretaceous were not instantaneous, but occurred over a finite period of time. Although the fish bone layer may contain victims of the impact event, the absence of ammonites in either the iridiumbearing layer or the overlying fish layer suggests that the extinction event at the end of the Cretaceous was the culmination of several processes beginning in the late Campanian. The impact was the proverbial “straw that broke the camel's back,” leading to the extinction of many others forms of life that might have survived the period of global biotic stress during the waning stages of the Mesozoic if there had not been an impact. The absence of mass extinction following catastrophic geologic events in a biotic robust world, such as the Middle Ordovician Millbrig-Big Bentonite volcanic event suggests that the biosphere is remarkably resilient to major geologic catastrophes with mass extinction events occurring only when there is a conjunction of geologic events none of which might be capable of producing a global mass extinction by itself.

More than 40 species of siliceous microfossils are present in both T-3 core Fl-437 (Cretaceous) and in core Fl-422 (Eocene) from the central Arctic Ocean. Previous identifications of the silicoflagellates were the basis of the ages for these cores, but diatoms of the two cores, previously unidentified, suggest that Fl-437 could be as old as Campanian rather than middle to late Maastrichtian and that Fl-422 may be early to middle Eocene rather than middle to late Eocene. Identification of archaeomonads and ebridians completes the cataloging of the known biosiliceous assemblages of the older Arctic Ocean.

Strong seasonality for the Late Cretaceous and early Cenozoic Arctic Ocean is suggested from alternating layers of vegetative cells and resting spores in both cores. The abundance of fossils is interpreted as evidence for seasonal upwelling in a nutrient-rich and much warmer Arctic Ocean. No evidence of seasonal ice or of ice-rafting is present. The profound climate change from the warmer older Arctic Ocean to the ice-covered condition of the present occurred after deposition of the sediment of Fl-422.

Moderately well preserved Permian (late Wolfcampian, Leonardian, Guadalupian, and Djulfian) and Early(?) Triassic radiolarian faunas from sedimentary mélange cherts of the Grindstone terrane in central Oregon are nearly identical to coeval chert faunas in Japan. These Permian faunas are similar to those used in constructing the radiolarian zonations for Japan and the Tethyan regions. Although several Oregon taxa have been reported from limestone sequences in the central United States, most of the Oregon forms have only been found in cherty rocks and nearly half have not previously been reported from North America. Forty-two taxa belonging to 19 genera (Albaillella Deflandre, Deflandrella De Wever and Caridroit, Entactinia Foreman, Entactinosphaera Foreman, Follicucullus Ormiston and Babcock, Haplentactinia Foreman, Hegleria Nazarov and Ormiston, Ishigaum De Wever and Caridroit, Kashiwara Sashida and Tonishi, Latentibifistula Nazarov and Ormiston, Latentifistula Nazarov and Ormiston, Nazarovella De Wever and Caridroit, Neoalbaillella Takemura and Nakaseko, Parentactinia Dumitrica, Praedeflandrella Kozur and Mostler, Pseudoalbaillella Holdsworth and Jones, Pseudotormentus De Wever and Caridroit, Quinqueremis Nazarov and Ormiston, and Triplanospongos Sashida and Tonishi) are systematically treated. Co-occurrences of some species in Oregon indicate that their ranges in North America may differ from those in Japan. This paper also contains the first illustrated record of Early(?) Triassic radiolarians from North America.