Dolabrosaurus aquatilis n. gen. and sp., a small amphibious or aquatic reptile from the Upper Triassic Chinle Formation of north-central New Mexico, is described on the basis of portions of the vertebral column and partial fore- and hindlimbs of a single specimen. Comparison with other Triassic reptiles indicates that D. aquatilis is most closely related to Drepanosaurus unguicaudatus, a small, enigmatic lepidosauromorph from the Upper Triassic Zorzino Formation of the Italian Alps. Both species are assigned to a new family, Drepanosauridae, with Dolabrosaurus recognized as more primitive in some aspects of its vertebral and pedal morphology. The precise assignment of Drepanosauridae within the Lepidosauromorpha remains uncertain.

A vertebra from the Judith River Formation (Campanian) of Saskatchewan, found with other Upper Cretaceous vertebrate remains, is referred to the loon-like hesperornithiform Baptornis, and is the first recorded occurrence of this genus from continental deposits. It is also the first bird described from the Judith River Formation of western Canada.

A megafossil flora, composed of 12 form taxa, has been collected from the Upper Mississippian–Lower Pennsylvanian Surprise Canyon Formation in the Grand Canyon, Arizona. It is the first known flora of this age to be recorded in Arizona, and includes Lepidodendron aculeatum Sternberg, L. mannabachense Presl, L. volkmannianum Sternberg, Lepidostrobus sp. cf. L. ornatus Brongniart, Lepidostrobophyllum sp., Knorria sp., Cyperites sp., Stigmaria ficoides (Sternberg), Calamites (Mesocalamites) cistiiformis Stur, Calamites sp., Pecopteris cf. P. aspera, and Wardia sp. (seed). The 22 species of palynomorphs previously reported from this formation suggest that the local flora was more diverse than the paucity of plant megafossil specimens indicates.

The Society of Sedimentary Geology (SEPM) joins with the Department of Geosciences and Keller Conference Center, Penn State University, in hosting the Society's 1993 Theme Meeting on the biotic, sedimentary, and geochemical indicators of past global change. The goal of this meeting is to bring together researchers studying the stratigraphic record with researchers using physically based models. Tentative Symposia topics include:

Although numerical methods are highly useful in paleontological studies, potential problems arise with application of parametric statistical methods to paleontological data. Most common statistical tests assume data are normally distributed and that multiple populations have equal variances (homoscedasticity). Paleontological data frequently do not satisfy these assumptions, thereby affecting results of tests and potentially misleading scientific interpretations. Nonparametric tests should be used when assumptions of parametric tests are violated. Normal scores tests, which utilize expected normal deviates (rankits) substituted for original data, are the most powerful nonparametric tests. Despite their potential utility, normal scores tests have received little attention, primarily because of difficulties encountered with rankit conversion.

Recent advances in microcomputer technology provide viable methods for rankit conversion, thus making normal scores tests accessible for routine application. Normal scores tests provide a practical method of dealing with nonnormality and heteroscedasticity common in paleontological data.

Paleoecological analysis of three attached spiriferid species (Punctospirifer kentuckyensis, Crurithyris planoconvexa, and Hustedia mormoni) and six free-living chonetid brachiopod species (Chonetinella flemingi, Chonetinella verneuiliana, Lissochonetes geinitzianus, Mesolobus mesolobus, Neochonetes fragilis, and Quadrochonetes geronticus) from Middle and Upper Pennsylvanian strata of north-central Texas has been undertaken using, in part, population dynamics information derived initially from size-frequency distributions. The brachiopod populations in this study are believed to represent in situ assemblages formed by noncatastrophic mortality. Spiriferid species occurred in large populations characterized by positively skewed size-frequency distributions in which few individuals attained the maximum potential size reported for a given species. Chonetid species, in contrast, occurred in smaller numbers characterized by negatively to low positively skewed size-frequency distributions in which greater numbers of individuals attained maximum potential size.

The differences observed in the population structure of these two groups can best be explained as reflecting different adaptive lifestyle strategies that are shared at the ordinal level. Morphological features common to chonetid species enabled individuals to live freely at the sediment-water interface and perhaps reorient their position if disturbed. Based on size-frequency analysis, low-density populations of chonetids appear to produce relatively larger numbers of survivors in the adult and maximum size classes. Spiriferids were constrained to attachment surfaces occupied at the time of larval settlement, and individuals presumably had no mechanism to regain life position if overturned or if this surface became unstable. These physical limitations seem to be reflected in a population structure in which higher density populations were required to overcome the high mortality rates incurred by individuals. This appears to be a case in which size-frequency distributions have not been significantly altered by taphonomic overprint and in which size-frequency analysis can be used to detect differences in the life histories and population structure of brachiopod species.

The concept of the Ordovician gastropod genus Maclurites Le Sueur, 1818, at present includes much variation. Maclurina Ulrich in Ulrich and Scofield, 1897, is removed as a subjective synonym of Maclurites and reestablished as a separate genus. Species of Maclurites with spiral grooves on the outer whorl surface and a relatively small umbilicus are transferred to Maclurina. Maclurina manitobensis (Whiteaves, 1890) forms a distinctive part of the Late Ordovician-age “Arctic Ordovician fauna.” An unusually large specimen (25 cm in diameter) from the Bighorn Dolomite (Upper Ordovician), Wyoming, is illustrated; this Wyoming specimen is the volumetrically largest Paleozoic gastropod ever reported.

New specimens of aglaspidid arthropods, mainly from the Upper Cambrian St. Lawrence Formation of Wisconsin (Upper Dikelocephalus Zone), show that appendages previously assigned to the genotype Aglaspis barrandei actually belong to a new genus and species Flobertia kochi. Chraspedops fragilis is transferred to a new genus Tuboculops. The generic attribution of Aglaspis dorsetensis and Aglaspis franconensis is queried. The distinction at species level is queried for Setaspis spinulosus and S. regularis and also for Aglaspoides sculptilis and A. semicircularis, although no formal changes are recommended. Aglaspis simplex is transferred to Glypharthrus simplex and Glypharthrus deadwoodensis is synonymized with Glypharthrus vulpes. Restorations are presented of Aglaspis barrandei, Aglaspis spinifer, and Glypharthrus thomasi. Aglaspis spinifer probably had a total of four head appendages. Well-preserved aglaspidid specimens often evince tergal processes that are apparently unique to this taxon and these may have acted as apodemes.

Trilobites occur in two generically distinct faunas in the Permian strata of West Texas. The stratigraphically lower fauna, composed of Ditomopyge decurtata (Gheyselinck), Ditomopyge sp., Triproetus angustus n. sp., Triproetus tumidus n. sp., Triproetus altasulcus n. sp., is present in Wolfcampian and early Leonardian strata. The stratigraphically upper fauna, present in late Leonardian and Guadalupian strata, is comprised of Delaria antiqua (Girty), Delaria granti n. sp., Delaria brevis n. sp., Delaria westexensis n. sp., Delaria chinatiensis n. sp., Novoameura vitrumons n. sp., Anisopyge perannulata (Shumard), and Anisopyge cooperi n. sp.

The lower fauna originated in the late Pennsylvanian, inhabited shallow-water environments, was relatively pandemic, and is interpreted to have become extinct as a result of marine regression during the early to middle Leonardian. The endemic upper fauna originated in deep waters of the Marfa and Delaware Basins during the late Leonardian, and, concurrent with sea level rise, migrated and diversified into the shelf-margin reefs of the late Leonardian and Guadalupian. Regression during the Late Permian resulted in extinction of this second Permian trilobite fauna.

Six extant and nine fossil species of the raninid Lyreidus de Haan, including Lyreidus (Lyreidus) lebuensis n. sp. and Lyreidus (Lysirude) hookeri n. sp., are recognized. Based on morphology of the anterolateral margin and sternum, the species are referred to two subgenera, Lyreidus (Lyreidus) and Lyreidus (Lysirude). The genus first appears in shallow-water, high-latitude, southern hemisphere localities in New Zealand, Antarctica, and Chile in the early Eocene. Subsequently, the nominate subgenus is confined to the southern hemisphere until the Neogene when it dispersed into the Indo-West Pacific region. Lyreidus (Lysirude) is documented by early and middle Eocene occurrences in Antarctica and New Zealand; however, all subsequent occurrences, fossil and recent, are in the northern hemisphere. The disjunct modern distribution within the genus is confined to this subfamily; species are known from the western North Atlantic and the Indo-West Pacific.

Nine species of fossil isopods have been studied from Cretaceous to Pleistocene rocks of North America. This represents all known species from the Mesozoic and Cenozoic fossil record on this continent. Four species of Palaega were studied. Palaega goedertorum Wieder and Feldmann, 1989, from upper Eocene to lower Miocene rocks of Washington state, has served recently as the basis for restructuring the genus. Emendations are made to species descriptions of Palaega guadalupensis and P. williamsonensis from the Cretaceous rocks of Texas. The fourth species of Palaega, P. lamnae, also from the Cretaceous rocks of Texas, although of doubtful affinities with this genus, was not removed due to lack of sufficient information to reassign it. Two new species are described, Cirolana enigma, from Lower Cretaceous rocks of South Dakota, and Archaeoniscus texanus, from the Cretaceous of Texas. This is the first report of Cirolana from the fossil record. Two sphaeromatid isopods were included: one, Sphaeroma burkartii from Tertiary rocks of Mexico, was not located for study; the other, Eocopea oculata, is from Miocene rocks of southern California. Two specimens of the valviferan genus Saduria, from Pleistocene deposits in Canada, were also studied.

Four hybocrinid and disparid crinoids from the Middle Ordovician Dunleith Formation (Galena Group) of northern Iowa and southern Minnesota are described: Hybocrinus conicus Billings, Ohiocrinus levorsoni n. sp., Caleidocrinus (Huxleyocrinus) gerki n. sp., and Ectenocrinus simplex (Hall). The first three taxa are rare. Ectenocrinus simplex is an abundant and protean form ranging from the Shermanian to the Maysville and from the Appalachians to the Midcontinent. One Middle Ordovician specimen from the Dunleith is a complete small adult with stem and a lichenocrinid holdfast. The column was largely upright with the crown located about 25 cm above the seafloor. The Middle Ordovician crinoids differ somewhat from the later Cincinnatian material where only young E. simplex exhibit lichenocrinid holdfasts. Older crinoids became detached and were eleutherozoic well before the column was 25 cm long. Thus, the Cincinnatian individuals lost the attachment device earlier during ontogeny than their ancestors in the Middle Ordovician. Unlike most associated crinoids, E. simplex formed a roughly conical filtration net. The arms of E. simplex are extensively branched. Ten main arms bear unbranched ramules on alternate brachials, and the arm structure converges on the pinnulate pattern. Narrow food grooves and short covering plates are present. Analogies with living crinoids indicate that small food particles were caught by small and close-spaced tube-feet. The formation of new plates and ramules at the arm tips increases the size of the food-gathering system throughout ontogeny. The food-gathering capacity comprises the number of food-catching tube-feet times the width of the food grooves, and it measures the number and size of food particles that can be caught. Both size and capacity of the food-gathering system are positively allometric compared to crown volume and the amount of tissue that must be nourished. This is mainly caused by the addition of new ramules at the arm tips, which generates an exponentially increasing plate supply rate. Examination of numerous specimens from various geographic and stratigraphic horizons with multivariate statistics shows that the species was homogeneous throughout its range aside from the differences in living habits mentioned above.

Paraorthacodus conicus (Davis, 1890) of the family Palaeospinacidae, but previously believed to be a mako shark (family Lamnidae), and P. andersoni (Case, 1978), until now reported only from the Judith River Formation of Montana, are both described from the Late Cretaceous of the Kristianstad Basin, southern Sweden. The name Synechodus nerviensis Leriche, 1929, is a junior synonym of P. conicus and Synechodus striatus Case, 1978, is likewise a junior synonym of P. andersoni.