Julia T. Sankey

LATE CAMPANIAN SOUTHERN DINOSAURS, AGUJA FORMATION, BIG BEND, TEXAS

Abstract One of the southernmost North American late Campanian microvertebrate assemblages was collected from the upper Aguja Formation, Big Bend National Park, Texas. The dinosaurs provide additional evidence that distinct southern and northern terrestrial vertebrate provinces occurred contemporaneously during this time due to latitudinal differences in temperature and rainfall. Southern areas, such as west Texas, were warm dry, with non-seasonal climates, and with open-canopy woodlands; they appear to be less fossil-rich and less diverse than northern areas. Nine dinosaurs are present, based on isolated teeth: pachycephalosaurid; hadrosaurid; ceratopsian; tyrannosaurid; Saurornitholestes cf. langstoni (Sues, 1978); Richardoestesia cf. gilmorei (Currie et al., 1990); a new species of Richardoestesia, which is named here; and a undetermined theropod unlike any previously described. Previous reports of Troodon sp. from the Talley Mt. and Terlingua microsites are mistaken; they are a pachycephalosaurid. Many of the dinosaur teeth are small, and are probably from juveniles or younger individuals, evidence that dinosaurs nested in the area. Paleoecologically, the upper Aguja was probably more similar to the lower and more inland faunas of the Scollard Formation (∼66 Ma) of Alberta than to contemporaneous northern faunas: both had drier, open environments and lower dinosaur abundance. This connection between climate and dinosaur abundance suggests that climatic factors were important in the Late Cretaceous dinosaur extinctions.

NEW TAXA OF TRANSVERSELY-TOOTHED LIZARDS (SQUAMATA: SCINCOMORPHA) AND NEW INFORMATION ON THE EVOLUTIONARY HISTORY OF “TEIIDS”

Abstract 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.

Comparative morphology of the ilium of anurans and urodeles (Lissamphibia) and a re-assessment of the anuran affinities of Nezpercius dodsoni Blob et al., 2001

ABSTRACT Ilia of anurans (frogs) and urodeles (salamanders) are commonly recovered from microvertebrate fossil localities. Ilia in these clades are distinctive when complete and articulated with the rest of the pelvic girdle, but when preserved as isolated and broken fossils they may appear superficially similar. Reliable identification of urodele ilia is further hampered by limited information about the basic structure and contacts of the bone and its variation within the clade. Here we demonstrate that the ilium is more variable among urodeles than previously realized and provide the first detailed inventory of features that are potentially useful for differentiating ilia of anurans and urodeles. Many of these features relate to differences between the two clades in the orientation of the ilium and its contacts with other bones and with soft tissues. Based on the results of our survey, we re-interpret the holotype and two referred ilia of Nezpercius dodsoni (Late Cretaceous; Montana, U.S.A.) as being from an indeterminate urodele, not an anuran as originally described. Additional examples of Late Cretaceous urodele ilia are documented to highlight some of the variation seen in fossil urodele ilia and to aid in the proper identification of such specimens.

LATE HOLOCENE PLANTS, CATAVINA, BAJA CALIFORNIA

Thirty-six plant taxa were identified from macrofossils and pollen in a late Holocene (1,770 years B.P.) woodrat (Neotoma) midden from a granite boulder field near Catavina, Baja California, Mexic0. The fossils document the presence of Sonoran Desert (Viscaino subdivision) vegetation and a relatively modern climatic regime in the late Holocene. However, abundances and distributions of plants were different from today. Excluding rare Pinus pollen (long distance transport), only about 51% of the midden plants still occur within 100 m of the site. Another 8 species have moved into the area. Apparently, greater moisture allowed soil development on bou1- ders and the expansion of plants, especially Prosopzs glandulosa, away from the mesic washes. The modern climate is drier than 1,770 years ag0.

Fossil canids from the Mehrten Formation, Late Cenozoic of Northern California

ABSTRACT The Hemphillian-age Mehrten Formation has yielded several fossil dogs (family Canidae). Initial study had identified all larger canids as Borophagus secundus ( = Osteoborus cyonoides), a bone-crushing borophagine (a diverse subfamily of extinct canids), and all smaller canids as Canis cf. C. davisi, a canine (a subfamily including all living canids). Later analysis split B. secundus into two taxa and reassigned Canis cf. C. davisi to Eucyon davisi, yet omitted fragmentary remains of possible vulpines. Despite this wealth of Mehrten canid materials, a detailed systematic treatment is lacking. More recently, additional specimens have become available, further necessitating a systematic examination of the canids at this site. The present study finds four canid species: two borophagines (Borophagus parvus and B. secundus) and two canines (E. davisi and Vulpes stenognathus, newly identified). We support the division of ‘B. secundus’ into the smaller B. parvus and the larger, more hypercarnivorous B. secundus and find two morphotypes within B. parvus. A specimen from the Coyote Hill fauna, earliest in the Mehrten sequence, is reassigned to B. secundus, extending the temporal range of the species in California into the early Hemphillian. Borophagus parvus co-occurs with B. secundus only in the lower Modesto Reservoir Member; higher in the sequence, B. parvus co-occurs only with canines. Despite the apparent turnover in its co-inhabitants, B. parvus exhibits no size change. Given that the characteristics of B. parvus and B. secundus are intermediate among other Borophagus, the Mehrten canids may represent a rapid transition early in the evolution of the Borophagus lineage.

First bone-cracking dog coprolites provide new insight into bone consumption in Borophagus and their unique ecological niche

Borophagine canids have long been hypothesized to be North American ecological ‘avatars’ of living hyenas in Africa and Asia, but direct fossil evidence of hyena-like bone consumption is hitherto unknown. We report rare coprolites (fossilized feces) of Borophagus parvus from the late Miocene of California and, for the first time, describe unambiguous evidence that these predatory canids ingested large amounts of bone. Surface morphology, micro-CT analyses, and contextual information reveal (1) droppings in concentrations signifying scent-marking behavior, similar to latrines used by living social carnivorans; (2) routine consumption of skeletons; (3) undissolved bones inside coprolites indicating gastrointestinal similarity to modern striped and brown hyenas; (4) B. parvus body weight of ~24 kg, reaching sizes of obligatory large-prey hunters; and (5) prey size ranging ~35–100 kg. This combination of traits suggests that bone-crushing Borophagus potentially hunted in collaborative social groups and occupied a niche no longer present in North American ecosystems.