The platform element of the conodont Amydrotaxis praejohnsoni n. sp. shows statistically significant morphological changes from the base to the top of the delta Zone (Lower Devonian). The changes occur particularly in mean denticle number, height and character of the anterior denticles, and shape of the basal cavity. The earliest forms have fewer denticles ( = 7.1), an enlarged, high anterior denticle, and a broadly flared posterior basal cavity, whereas late forms have more denticles ( = 9.4), equal-sized anterior denticles, and a narrow posterior basal cavity. There is no stasis phase in the species history, but rather a mosaic pattern in which the observed changes in the character states are seemingly independent of each other and proceed at variable rates.

A new genus and species of raninid crab, Rogueus orri, is described from the Tenmile Member of the Lookingglass Formation in southwestern Oregon. Based upon previous studies of foraminiferans, the rock unit has been assigned an early middle Eocene age. Distinct from other raninids with its sinuous fronto-orbital margin, bifid rostrum, and uniquely branched anterolateral teeth, Rogueus orri may be descended from Notopocorystes (Cretacoranina) fritschi.

Previously undescribed specimens of Pachycephalosaurus wyomingensis allow partial description of the anterior braincase and a preliminary examination of change of dome shape with age. The two morphs of dome shape recognized in adults are also present in juvenile specimens with dome lengths half that of mature adults. A new specimen of Stegoceras edmontonense in the same geographic and stratigraphic provenance as P. wyomingensis establishes that the two pachycephalosaur genera could exist sympatrically.

Previously described faunas of Early Silurian through Late Pennsylvanian age from the Alexander terrane have been endemic, or have variously suggested North American or Asiatic affinities, leaving the paleogeographic history of the terrane uncertain although indicating a location closer to North America than to Asia (Armstrong, 1970; Douglass, 1971; Savage, 1981, 1985, 1989; Savage et al., 1978; Savage and Barkeley, 1985; Soja, 1988; Vaskey, 1982). The occurrence reported here of the Canadian Arctic brachiopods Nanukidium cf. N. cunninghamensis and Atrypoidea scheii in the Alexander terrane during the Late Silurian could be additional evidence supporting the view that the Alexander terrane was not far removed from the North American craton during middle Paleozoic time.

New specimens of Beckwithia typa, from the upper Middle Cambrian of Utah, show that, contrary to previous descriptions, the animal had at least 10 tergites (possibly 12) and probably a tail-spine. There is no evidence for a fused tail-plate, the one character that made Beckwithia appear anomalous with respect to other aglaspidid arthropods. It did, however, differ from most other aglaspidids in having a single series of axial spines along the trunk, but this cannot be regarded as a basis for continued separation of Beckwithia into a monogeneric family. A possible relationship with Kodymirus vagans is suggested by the presence of axial spines, although there may have been significant differences in the nature of the ventral sclerites. Beckwithia? major from the Upper Cambrian of Wisconsin is known only from fragmentary specimens and no evidence of a fused tail-plate has been found. Beckwithia? daubikhensis from the Khanka Massif, Soviet Union, is unlikely to be a member of this genus; the single specimen on which the taxon was based may be a poorly preserved Khankaspis bazhanovi.

A new species, Enchodus brevis (Enchodontoidei: Enchodontidae), is described from lower Cenomanian beds in Ein-Yabrud, near Jerusalem. The species is characterized by the following features: the shortest enchodontid body; an ectopterygoid bearing one smooth canine terminal tooth; barbed dentary teeth; a huge front tooth of dentary with two anterior cutting edges; two supraneurals; second preural vertebra without a neural spine; and absence of lateral line scales except for a long hook-like terminal scale at the caudal peduncle. The systematic position of the new species suggests the emendment of the generic diagnosis.

A new Fourier method is presented to quantify shapes too complex to be described by conventional polar Fourier analysis. The length along a closed curve serves as the independent variable. The centroid of the curve is determined and for each point on the curve two different dependent variables are defined, based on: 1) the angle defined by the starting point, the centroid, and the point on the curve; and 2) the radial distance from the centroid to the point on the curve. The method is used to describe the trilobite cranidium, and 12 harmonic coefficients are found to summarize 99 percent of the shape information contained in the cranidial outline. In an application to trilobite evolution during the Cambrian and Ordovician, it is found that higher taxa of trilobites become progressively more distinct morphologically. This result is in agreement with previous qualitative observations, and is attributable to an increase in morphologic dispersion among higher taxa, but not to a decrease in morphologic dispersion within higher taxa.

A new species of fossil isopod, Palaega goedertorum, is described from late Eocene to early Miocene rocks of the Twin River Group, the Astoria Formation, and unit B of Wolfe and McKee (1968) in the state of Washington. These fossil forms are similar to living forms referred to the genus Bathynomus A. Milne-Edwards, 1879; hence, Bathynomus is considered a junior subjective synonym of Palaega Woodward, 1870. Since extant species of Palaega are known only from bathyal habitats, these occurrences tend to corroborate the deep-water paleoenvironmental setting of these rock units. This is the first report of Palaega from the eastern Pacific region.

Currently some controversy exists in the micropaleontological community concerning the statistically correct number of counts required for quantitative examinations, particularly with respect to the effect of variations in the number of species between samples and the significance of varying fractional abundances on the reliability of results. This analysis of the various statistical methods used to determine the number of required counts has shown that the number of species has no relationship to the number of counts required to measure accurately fractional abundances. As part of the study, logarithmic contours plotting percentage abundance against the total number of specimens, which provide abundance errors at a 95 percent confidence level, have been generated. The plot is displayed logarithmically to emphasize the significance of rare microfossil elements that dominate most assemblages, and which are important in many paleoenvironmental studies. Based on the plot, it is recommended that researchers utilize counts of at least 50 for indicator species having a fractional abundance of approximately 50 percent or greater; 300 counts for species which comprise approximately 10 percent of a sample; 500–1,000 counts for species that make up 5 percent of a sample; and counts of several thousand for defining species that comprise 1 percent of a sample. It is important to note, however, that where similar biofacies are involved, higher counts are required to accurately distinguish them. It is also recommended that researchers include fractional error abundances with their estimated abundances to provide an indication of their accuracy.

Detached rostral teeth of fossil sawfishes of the family Sclerorhynchidae Cappetta (1974) are relatively common in Late Cretaceous marine strata of Texas. Most such teeth are referable to various species of Ischyrhiza and Onchopristis (Slaughter and Steiner, 1968). The extraordinarily large rostral teeth described herein are not referable to any sawfish presently known from North America. They belong to Onchosaurus pharao (Dames, 1887), which is known elsewhere from Egypt, Nigeria, Zaire, Angola, and Brazil (Arambourg, 1940; Tabaste, 1963; Cappetta, 1987). The specimens are the largest reported for any sawfish.

Standards have been empirically developed to describe various morphological characters of eurypterids. The standards pertain to the following characters: 1) shape of the prosoma; 2) shape of the metastoma; 3) shape of the eyes; 4) position of the eyes; 5) types of prosomal appendages; 6) types of swimming leg paddles; 7) structure of the doublure; 8) differentiation of the opisthosoma; 9) structure of the genital appendages; 10) shape of the telson; and 11) types of ornamentation.

For the first time, a uniform, standardized taxonomy is proposed for classification and identification of most genera. The taxonomy is based on the observation that most higher taxonomic levels for arthropods are based on the structure and arrangement of the appendages. Details of the taxonomy rely on the morphological standards proposed here.

The order Eurypterida Burmeister, 1843, is here defined by the presence of only six pairs of prosomal appendages, the first pair being the chelicera, the next five pairs being the gnathobasic, uniramus legs. Suborders are characterized by the gross morphology of the chelicera. Superfamilies and families are characterized by the use of a single character complex, specifically the structure and arrangement of the second through sixth pairs of prosomal appendages. Genera are recognized by more specific standards.

A new classification of the order Eurypterida is proposed. Three new superfamilies, Kokomopteroidea, Megalograptoidea, and Brachyopterelloidea, and five new families, Brachyopterellidae, Adelophthalmidae, Lanarkopteridae, Erieopteridae, and Hardieopteridae, are proposed.

The crinoid Ectenocrinus has unusual trimeric columnals which make it instantly recognizable. In northern New York State such columnals first appear in the deep shelf facies of the lower Trenton Group (the Sugar River Limestone). In these strata the columnals display nearly triangular shapes with triangular lumina and represent a new species, E. triangulus. A small minority of the columnals of these early forms are round with five-pointed lumina.

A definite cline had developed by middle Trentonian time. Deep-water columnals display the ancestral triangular form, whereas adjacent, shallow-water forms are rounder and have the five-pointed or pentagonal lumina. These round types came to be the beneficiaries of middle Trentonian facies changes. This was a time when the eastern bank margin steepened and narrowed. The deep shelf habitat shrank to the east and disappeared. Trapped in this shrinking sea floor setting, the populations of the deep-water members of the cline dwindled and disappeared before late Trentonian time. Only the round form with a pentagonal lumen survived. This form, Ectenocrinus simplex, was a great success; its numbers increased and its range expanded throughout the remainder of Trentonian time.

The transition from Ectenocrinus triangulus to E. simplex is seamless. No boundary, other than an arbitrary one, can be recognized. A simple and gradual shift of phenotype abundance characterized the event.

Small vertebrates were recovered from the matrix encasing specimens of giant sauropod dinosaurs (Supersaurus, Ultrasaurus, Dystylosaurus) collected from the “Dry Mesa” Quarry (Brushy Basin Member, Morrison Formation, western Colorado). Most of the remains appear to pertain to a single form of pterodactyloid pterosaur, Mesadactylus ornithosphyos, n. gen. and sp., the holotype of which is a synsacrum. A bone end from this quarry, first identified as an avian proximal tibia and named Palaeopteryx thomsoni, is reidentified as the distal radius of a small deinonychosaur or bird. A small femur of a small deinonychosaur or bird and additional material of other small vertebrates from this quarry are figured and described.

Chondrophorines have a long but exceedingly sporadic history: they dot the late Precambrian and Paleozoic and are common in modern oceans, but have not been reported from the Mesozoic or Cenozoic save for a possible Triassic occurrence (Stanley, 1986) and a single Cretaceous appearance (Stanley and Kanie, 1985). Stanley (1982) suggested that much of the fossil record of the group may languish unrecognized and misidentified in museum drawers because of its generally molluscanlike aspect and poor representation in the literature. This suspicion is validated by the discovery of a velellid chondrophorine pneumatophore in the vertebrate collections of the University of California Museum of Paleontology (UCMP).

When i described the Mazon Creek tanaidacean crustacean and named it Cryptocaris hootchi Schram, 1974, two problems presented themselves. First, all specimens but one were in private collections, and none of their owners then seemed inclined to donate them to an established natural history museum. Second, the collections of the Field Museum of Natural History in Chicago at that time contained only a single specimen, P32053, of what appeared to be the Mazon Creek tanaidacean. This specimen is peculiarly preserved and of only mediocre quality. Consequently, I based the description of the Mazon Creek tanaidacean almost entirely on the privately held specimens, noting their numbers and private repositories, but designated the Field Museum specimen, P32053, as the holotype. A subsequent review of all fossil tanaidaceans (Schram et al., 1986) focused exclusively on the privately held specimens collected from Mazon Creek sites.

Paolia vetusta Smith, 1871a, from the Hindostan whetstone beds of Indiana (Namurian), thought to have been lost since 1918, has been found and currently is housed at Hanover College, Hanover, Indiana. Paolia vetusta is illustrated photographically for the first time. The major character difference between Smith's (1871a) figure and the actual specimen is the lack in the latter of an extensive archedictyon extending over the entire specimen. Currently, the family Paoliidae is defined as having Sc terminating on R. Paolia vetusta clearly shows Sc terminating on C. Therefore, the Sc terminus should have no taxonomic significance at the family level.

Two alternative hypotheses for proximal column growth are tested in Taxocrinus cf. T. whitfieldi, a late Mississippian flexible crinoid. The first hypothesis states that new columnals are added at the base of the proximal column (immediately above the generating columnal), whereas the second hypothesis has columnals of the proximal column inserted beneath the aboral cup. In both hypotheses, middle column columnals are inserted beneath the generating columnal and are independent from the proximal column.

External features used to determine points of columnal insertion include wedge-shaped columnals and sharp changes in columnar morphology. Sagittal sections reveal the presence of small columnals, some of which can be interpreted as the last columnals inserted prior to death. Data collected on Taxocrinus cf. T. whitfieldi confirm the first hypothesis. This hypothesis may be applicable to other crinoids with xenomorphic columns.