Presented herein is the first morphological analysis of turtle relationships to examine the monophyly of many turtle groups by using only single species as terminals and by integrating a large number of primitive fossil taxa. The data matrix consists of 136 osteological parsimony informative characters with 169 derived character states for 45 fossil and 22 living species of the clade Testudinata. The results corroborate the monophyly of a large number of previously hypothesized clades, but refute the accepted hypothesis regarding the basal split of living turtles. In particular, the primitive turtles Proterochersis robusta, Kayentachelys aprix, Mongolochelys efremovi, Meiolania platyceps, and Kallokibotion bajazidi are removed from their current position as crown turtles and placed along the phylogenetic stem of this clade. The age of the turtle crown is thereby adjusted from the Late Triassic to the Late Jurassic, which is relevant to testing molecular clock hypotheses. This revised topology has important implications for the evolution of several character complexes, because it implies that the common ancestor of all living turtles must have had a partially braced brain case and a primitive trochlear mechanism. Other noteworthy conclusions include the tentative exclusion of protostegids from Chelonioidea, the placement of Platysternon megacephalum outside of Chelydridae, and the tentative interpretation of Sandownia harrisi as a basal eucryptodire.

Since the 1969 description of Deinonychus antirrhopus Ostrom, cooperative pack hunting behavior for this species and, subsequently, for many other nonavian theropods, has attained wide acceptance. In this paper we assess the hypothesis of mammal-like cooperative pack hunting in D. antirrhopus and other nonavian theropods by examining the behaviors of extant diapsids. Through phylogenetic inference and character optimization, we conclude that this hypothesis is both unparsimonious and unlikely for these taxa and that the null hypothesis should therefore be that nonavian theropod dinosaurs were solitary hunters or, at most, foraged in loose associations. Moreover, we present new evidence from the D. antirrhopus type locality of probable intraspecific aggression in this species. Additionally, our study suggests that some evidence that has previously been proposed in support of highly gregarious, mammal-like behavior in nonavian theropods (e.g., certain theropod-dominated fossil assemblages, preserved bite-mark injuries on some specimens, and the preponderance of theropod trackways at some sites) may alternatively be interpreted as evidence that nonavian theropod behavior was more agonistic, cannibalistic, and diapsid-like than has been widely believed.

Although sometimes treated as synonyms, Eurypterus remipes (Fiddlers Green Formation) and Eurypterus lacustris (Williamsville Formation) have usually been considered separate species. Conclusions have often been based on statistical methods used to examine sets of carapace measurements. Here, morphological evidence of the cuticular sculpture of the telson margin and the prominent embayment on the lateral carapace margin supports their status as separate species. These differences are consistent throughout ontogeny and between sexual dimorphs. In the interest of establishing taxonomic stability and of providing standards for comparison of morphology, neotypes have been selected for both E. remipes and E. lacustris. Two new morphological characters from the type A genital appendage and the operculum support a close relationship between E. remipes and E. lacustris. New and earlier evidence suggest that the population representing E. remipes developed into the slightly younger E. lacustris population through the process of heterochrony, and that they represent chronospecies rather than evolutionary species.

Balaenophilus umigamecolus are reported for the first time in the eastern Pacific, from the Jalisco coast of western Mexico. Two new hosts are represented: the olive ridley turtle, Lepidochelys olivacea, and the black turtle, Chelonia mydas agassizi. Data indicate a distinct correlation between the presence of B. umigamecolus copepods and Stomatolepas praegustator, barnacles that grow imbedded in turtle skin. This relationship may have implications for marine turtle health.

In this paper we summarize the history of the American School of Prehistoric Research, discuss the sites visited during the program's tenure from 1921–1934, and provide an analysis based on taxonomy and skeletal elements of the large mammalian faunal remains from one of those sites, La Quina. A listing of all La Quina large mammalian fauna deposited at the Yale Peabody Museum is presented.