Comparisons of biotopes based on ternary plots and cluster analyses of living ostracode assemblages with those from subfossil assemblages from a small reef flat show that biostratinomic processes modify the assemblages before they are incorporated into the sediment of the reef flat. Selective preservation changes the assemblages by preferentially preserving robust carapaces over fragile carapaces. The thin-shelled Paradoxostomatidae, which are abundant in the algae-dwelling assemblages, are largely destroyed by biostratinomic processes and are represented by only a few individuals in the subfossil assemblages.

Mixing of algae-dwelling assemblages and sediment-dwelling assemblages results in a lower relative proportion of many species in the subfossil assemblages than in the living assemblages. The Leptocytheridae, which comprise a large portion of the sediment-dwelling fauna, are reduced in relative proportion in the subfossil assemblages as a result of dilution of the sediment-dwelling fauna with an abundant, algae-dwelling fauna.

Transportation of ostracode remains by wave-induced currents removes the patchiness that is characteristic of the biotopes of the living ostracode assemblages but does not completely homogenize the assemblage despite the close spacing of sampling and the small areal extent of the biotopes studied.

Five Jurassic through Oligocene sea stars are described; all are assignable to modern genera and two (Tethyaster jurassicus; Mediaster hayi) represent new species. Tethyaster and Pseudarchaster are morphologically similar but represent separate orders; occurrence of both in Jurassic sediments suggests close common ancestry. Many post-Paleozoic sea stars appear enduring, perhaps because of broad ecological tolerances and construction; the fossils described here probably are not unique as asteroid living fossils.

Rudists arose in the Late Jurassic and survived for nearly 100 m.y. before becoming extinct at the end of the Cretaceous. Over this interval they diversified gradually during the Late Jurassic and Early Cretaceous, rapidly in the mid-Cretaceous, then more slowly in the Late Cretaceous. Total rates of origination and extinction during the Late Jurassic and Early Cretaceous were uniform and comparable to those reported for other groups. The Late Cretaceous, however, was characterized by high and widely fluctuating total origination and extinction rates. Per taxon rates reveal a similar pattern except for high and variable rates in the Jurassic. The number of genera increased from the Oxfordian to a peak in the Cenomanian, decreased in the Turonian and Coniacian coinciding with a minor mass extinction event, and rose to a zenith in the Maastrichtian. Unlike other groups investigated, the rudists were at their highest level of diversity immediately prior to their disappearance.

Rudist genera survived for a mean of 12 m.y., whereas families survived for a mean of 48 m.y. Survivorship curves for generic cohorts, based upon survival of all rudist genera that evolved during each stage, exhibit a concave shape when the effects of mass extinction and variance at low diversities are considered. Causal factors involved in the final disappearance of the rudists remain unclear; however, their tropical provinciality in the Late Cretaceous contributed to their vulnerability to mass extinction.

A well-preserved and locally abundant crinoid fauna has been discovered in the lower part of the Champlainian (Middle Ordovician) Glenhaven Member of the Guttenberg Formation in the Upper Mississippi Valley region. The material consists of the dicyclic inadunates Cupulocrinus levorsoni n. sp., C. jewetti (E. Billings) and monocyclic camerate Pycnocrinus gerki n. sp.

An unusually complete large pycnodont fish from the Mooreville Chalk of Green County, Alabama, is figured and compared to several previously described specimens. Material from the specimen apparently places Grypodus Hay = Ancistrodon Roemer, Hadrodus Leidy, and Propenser Applegate into synonymy. The specimen is referred to Hadrodus hewletti (Applegate). A complete dentition is present and most of the thick, tuberculated ganoid scales that covered the body are preserved. Exact location of the dorsal fin has been determined and many of the fragile gill rakers are represented.

A new genus and species of amynodontid rhinoceros, Rostriamynodon grangeri, from the early Late Eocene of Inner Mongolia, People's Republic of China, is the most primitive amynodontid recognized to date. Rostriamynodon exhibits the major diagnostic characteristics of amynodontids: quadratic M3, preorbital fossa, and loss of upper and lower P1. It differs from more advanced members of the family in its long preorbital region and lower cheek tooth morphology. Comparisons with other Eocene ceratomorphs show the crucial position Rostriamynodon has in determining phylogenetic relationships between rhinocerotoids and tapiroids. Evidence is presented for the monophyly of the Rhinocerotoidea, including amynodontids.

Five new ostracode genera and their type species are described from among 42 taxa obtained from silicified residues from the Quadrithyris brachiopod Zone and the upper pesavis and lower sulcatus conodont Zones of the McMonnigal Limestone at Ikes Canyon, Dianas Punch Bowl quadrangle, Nye County, Nevada. These are the beyrichiaceans Pseudomyomphalus spicatus n. gen., n. sp., and Dolichoscaphoides copelandi n. gen., n. sp., the hollinacean Eurekabolbina torquata n. gen., n. sp., the kloedenellacean Elenamarginia polenovae n. gen., n. sp. and the quasillitacean Prosumia peterseni n. gen., n. sp. Three of the five genera also occur in the partially correlative Windmill Limestone of Eureka County, Nevada, and may prove useful for interbasinal correlation.

The functional interpretation of Drepanosaurus unguicaudatus, an Upper Triassic lepidosaurian from the Italian Alps, is given here. The peculiar anatomical structure of the post-cranial skeleton would point to a burrowing animal.

Fossil land mammals were collected by G. G. Simpson in 1933–1934 at and near the Tapera de López in central Chubut Province, Patagonia, southern Argentina, from rocks now mapped as the Sarmiento Formation. These fossils are assigned to land mammal faunas of Casamayoran (Early Eocene), Mustersan (Middle Eocene), and Deseadan (late Early Oligocene through Early Miocene) age.

40K-40Ar age determinations of eight basalt and two tuff units associated with the Deseadan age local fauna at Scarritt Pocket establish a geochronologic framework that calibrates the biostratigraphic record at this locality. The radioisotope dates obtained at Scarritt Pocket range from 23.4 Ma to about 21.0 Ma, and equate with earliest Miocene time. The Scarritt Pocket local fauna is the youngest dated Deseadan age fauna yet known in South America.

Seven other localities have, or were reputed to have, local faunas of Deseadan age associated with dated volcanic units. Six of these localities are in Argentina (Gran Barranca, Cerro Blanco, Valle Hermoso, Pico Truncado, Cañadón Hondo, Quebrada Fiera de Malargüe) and one in Bolivia (Estratos Salla in the Salla-Luribay Basin). The stratigraphic relationships of the volcanic units with these local faunas is discussed, and the taxonomic content of each is reassessed.

The Deseadan Land Mammal Age is defined by the earliest record of the land mammal genus Pyrotherium, which is from below a basalt dated at 33.6 Ma at Pico Truncado. Other early records of Pyrotherium occur below basalts dated at about 29 Ma at the Gran Barranca and Valle Hermoso, and from a 28.5 Ma level of the Estratos Salla. Thus, the lower boundary for Deseadan time is about 34 Ma.

The youngest record of Pyrotherium is in the upper levels of the Estratos Salla dated at about 24 Ma. However, the Scarritt Pocket local fauna, which lacks Pyrotherium, permits placement of the upper boundary for Deseadan time at about 21.0 Ma. Late Deseadan time is surely, and the end of Deseadan time is apparently, marked by the last record of such groups as Proborhyaeninae (Proborhyaena), Rhynchippinae (Rhynchippus), Archaeohyracidae (Archaeohyrax), and the genera Platypittamys (Octodontidae), Scarrittia (Leontiniidae), Propachyrucos and Prohegetotherium (Hegetotheriidae), and Argyrohyrax (Interatheriidae), as these taxa are recorded in the Scarritt Pocket local fauna. Thus, Deseadan time extends from about 34.0 Ma to about 21.0 Ma, making it the Land Mammal Age with the longest known duration in South America.

A new full description of the bivalve Shikamaia akasakaensis Ozaki (genotype species of Shikamaia) is presented, providing the first documentation of its hinge and ligament, and resolving many uncertainties about Shikamaia, the first described genus of the Permian bivalve family Alatoconchidae. The genus Shikamaia has a unique ligament, modified from typical duplivincular ligaments in occupying only half of the cardinal area, and having ligament sheets that extend themselves towards the beak with continued growth. This ligament is strikingly different from the ligaments of other alatoconchid genera. All alatoconchids are believed to have a common ancestry, but the magnitude of difference in their hinges warrants dividing the family into two subfamilies. The subfamily Saikraconchinae is erected new.

Eight Early Silurian inadunate crinoids are described. These include: a pisocrinid, genus and species undetermined; (?)Myelodactylus sp.; Kanabinocrinus thyaros n. gen., n. sp.; Euspirocrinus heliktos n. sp.; (?)Euspirocrinus sp.; Eoparisocrinus siluricus n. comb. (n. gen.); Dendrocrinus daytonensis n. sp.; and dendrocrinid, genus and species undetermined. Parisocrinus siluricus, Parisocrinus mulletensis, and Euspirocrinus obconicus are all reassigned to Eoparisocrinus. Parisocrinus is restricted to members of Devonian and Mississippian age. The genus Parisocrinus is discussed, and its type species P. perplexus is illustrated.

Pisocrinid, genus and species undetermined, (?)Myelodactylus sp., and Kanabinocrinus thyaros represent the oldest member of the family in which each belongs. The phylogenetic relationships of these and other taxa are discussed.

A new species of phyllocarid arthropod, Tropidocaris salsiusculus, is described from the Upper Devonian Hampshire Formation near Rowlesburg, West Virginia. The organism was found in association with numerous trace fossils, at least one of which could have been produced by T. salsiusculus, and body fossils, including Lingula sp., several bivalve mollusks and smooth ostracods. Collectively, these organisms suggest a brackish-water environment of deposition. This report represents only the third record of phyllocarids from West Virginia.

A specimen of the ammonoid Perrinites Böse, 1919, was collected from the McCloud Limestone east of the summit of Tombstone Mountain, Shasta County, California. This is the first record of the genus in California, an important addition to the meager Permian cephalopod fauna of the state previously reported by Miller, Furnish, and Clark (1957) and Wilson (1984). It was found 1,100 feet (335 m) above the base of the formation in a coarse-grained limestone (Los Angeles County Museum of Natural History, Invertebrate Paleontology Section locality 6184) within fusulinid zone H of Skinner and Wilde (1965), considered to be late early or early middle Leonardian in age.

A low diversity fauna of microscopic crinoids from the Kinderhookian (Mississippian) McCraney Limestone at Seehorn Hollow, western Illinois, is described and illustrated by stereomicrographs. The crinoids include first record of the camerate crinoid genus Hexacrinites (H. mississippiensis n. sp.) above the Devonian. The other three taxa are all inadunates and include the monocyclic microcrinoid Allagecrinus mccraneyensis n. sp., which has up to 14 arms, and two dicyclic poteriocrinoids, Hypselocrinus maccabei (Miller and Gurley, 1894) and an indeterminate genus of the Scytalocrinidae.

Three late Devonian ammonoid-bearing levels are described from the area of Cleveland, Ohio. These appear to represent the German Platyclymenia, Clymenia and Wocklumeria Stufen, clear evidence for which has been lacking previously in eastern North America. The lowest level, around the base of the Cleveland Shale, yields Sporadoceras, Cyrtoclymenia, Platyclymenia and a new species, Pleuroclymenia (?) ohioense. The middle level, near the top of the Cleveland Shale, bears Cymaclymenia, Sporadoceras and Prionoceras. The highest level, just above the base of the Bedford Shale, has Prionoceras quadripartitum. This species, and a fauna of the basal Bedford, have been located also in the area of Columbus, Ohio. An Epiwocklumeria (?) sp. is recorded from Indiana. Attention is drawn to the international importance of the late Famennian and Lower Carboniferous ammonoid sequence which can now be recognized in Ohio.