L. Barry Albright

A new North American therizinosaurid and the role of herbivory in ‘predatory’ dinosaur evolution

Historically, ecomorphological inferences regarding theropod (i.e. ‘predatory’) dinosaurs were guided by an assumption that they were singularly hypercarnivorous. A recent plethora of maniraptoran discoveries has produced evidence challenging this notion. Here, we report on a new species of maniraptoran theropod, Nothronychus graffami sp. nov. Relative completeness of this specimen permits a phylogenetic reassessment of Therizinosauria—the theropod clade exhibiting the most substantial anatomical evidence of herbivory. In the most comprehensive phylogenetic study of the clade conducted to date, we recover Therizinosauria as the basalmost maniraptoran lineage. Using concentrated changes tests, we present evidence for correlated character evolution among herbivorous and hypercarnivorous taxa and propose ecomorphological indicators for future interpretations of diet among maniraptoran clades. Maximum parsimony optimizations of character evolution within our study indicate an ancestral origin for dietary plasticity and facultative herbivory (omnivory) within the clade. These findings suggest that hypercarnivory in paravian dinosaurs is a secondarily derived dietary specialization and provide a potential mechanism for the invasion of novel morpho- and ecospace early in coelurosaurian evolution—the loss of obligate carnivory and origin of dietary opportunism.

PLESIOSAURS FROM THE UPPER CRETACEOUS (CENOMANIAN–TURONIAN) TROPIC SHALE OF SOUTHERN UTAH, PART 2:POLYCOTYLIDAE

Abstract Recent fieldwork in the Tropic Shale of southern Utah has resulted in the recovery of several specimens of short-necked plesiosaurs including both polycotylid plesiosauroids and pliosaurids. This report focuses on the former, whereas the latter are discussed in an accompanying paper. Although the Late Cretaceous Cenomanian/Turonian Stage boundary falls within the lower few meters of the Tropic Shale, all but one of the specimens were found in lower Turonian strata based on molluscan assemblages found in direct association with the skeletal material. The plesiosauroid family Polycotylidae is represented by at least three taxa: (1) the ‘typical’ late Cenomanian/early Turonian Trinacromerum; (2) Eopolycotylus rankini, gen. et sp. nov., a new genus and species that shares synapomorphies with the late Santonian/early Campanian Polycotylus latipinnus; and (3) Palmula quadratus, gen. et sp. nov., another new taxon that shares synapomorphies with unnamed taxa from the late Cenomanian of South Dakota and Japan. Cladistic analysis supports the division of the Polycotylidae into two new subfamilies, here designated the Polycotylinae and the Palmulainae. The Turonian plesiosaur fauna of the Tropic Shale, and consequently the large vertebrate fauna of the Cretaceous Western Interior Seaway, is considerably more diverse than previously realized, and there is no indication that this fauna suffered any negative consequences as a result of global scale oceanographic events, including marine extinctions, that transpired during late Cenomanian-early Turonian time.

Revised Chronostratigraphy and Biostratigraphy of the John Day Formation (Turtle Cove and Kimberly Members), Oregon, with Implications for Updated Calibration of the Arikareean North American Land Mammal Age

Although the Arikareean North American land mammal age was first typified in the Great Plains, the succession there contains significant unconformities, a generally poor magnetic record, relatively sparse radioisotopic calibration, and a major faunal hiatus. In the John Day Valley of central Oregon, however, is a thick, remarkably complete sequence of Oligocene through early Miocene strata (the John Day Formation) potentially amenable to addressing these shortcomings and long known to harbor one of the richest records of mid‐Tertiary mammals in North America. Since Prothero and Rensberger’s first magnetostratigraphic study of the John Day Formation in 1985, new advances in geochronology, together with a more comprehensive suite of paleomagnetic sections keyed to new radioisotopic and biostratigraphic data, have greatly enhanced chronostratigraphic precision. In our attempt to refine John Day chronostratigraphy, we sampled nearly 300 sites for magnetostratigraphy over a 500‐m‐thick interval and used several radioisotopically dated volcanic tuffs for our correlation with the geomagnetic polarity timescale. Many of the rocks analyzed showed unusual magnetic behavior, possibly due to the known zeolitization in this region, thereby precluding an abundance of class 1 polarity determinations. Nevertheless, preliminary results indicate that the Turtle Cove Member stratigraphically upward through the lower Kimberly Member extends from late chron C12n through C7n.1r, or from about 30.6 to 24.1 Ma. Intensive radioisotopic and magnetostratigraphic characterization of these strata provides a framework by which the associated biostratigraphy is assessed for biochronological significance relative to fossiliferous successions of the Great Plains, in turn resulting in reassessment of Arikareean subbiochron (Ar1–Ar4) boundaries. We present a revision of those boundaries that differs from their traditional timing as a hypothesis for testing in other locations.

PLESIOSAURS FROM THE UPPER CRETACEOUS (CENOMANIAN–TURONIAN) TROPIC SHALE OF SOUTHERN UTAH, PART 1: NEW RECORDS OF THE PLIOSAUR BRACHAUCHENIUS LUCASI

Abstract Recent fieldwork in the Tropic Shale of southern Utah has resulted in the recovery of two new specimens of the short-necked pliosaurid Brachauchenius lucasi Williston, 1903. Both specimens were recovered in Lower Turonian strata a few meters above the Cenomanian-Turonian Stage boundary as determined from molluscan assemblages found in direct association, and both include skull material. The larger of the two also includes pectoral and pelvic elements previously unknown for this taxon. These specimens represent the first records of B. lucasi from the western margin of the Cretaceous Western Interior Seaway; previously recorded specimens were recovered in Kansas and Texas. The Cenomanian through middle Turonian temporal range of B. lucasi, in addition to its geographic range across the seaway, indicates that this taxon suffered few, if any, negative consequences as a result of global scale oceanographic events, including marine extinctions, that transpired during late Cenomanian-early Turonian time.

A leatherback sea turtle from the Eocene of Antarctica: implications for antiquity of gigantothermy in Dermochelyidae

(2003). A leatherback sea turtle from the Eocene of Antarctica: implications for antiquity of gigantothermy in Dermochelyidae. Journal of Vertebrate Paleontology: Vol. 23, No. 4, pp. 945-949.

Stratigraphy, chronology, biogeography, and taxonomy of early Miocene small chalicotheres in North America

Abstract In the late 19th century, rare fossil remains of a small chalicothere were recovered from early Miocene rocks of the John Day Formation of north-central Oregon. Totaling eight isolated teeth and four foot bones, and gathered by various collectors from several localities, these specimens were not at first recognized as chalicotheres, and were originally assigned to a dental species, Lophiodon? oregonensis, and a postcranial species, Moropus distans. All were assigned to the chalicothere genus Moropus by Holland and Peterson in 1914. The lack of precise geographic and stratigraphic data did not permit any definitive assessment of age, origin, or evolutionary stage. We report here newly discovered teeth and foot bones of M. oregonensis found from 1994–1998 at precisely located levels in the John Day Formation. These new discoveries indicate that M. oregonensis occurs in upper John Day units but is absent from the lower part of the formation. One tooth occurs in proximity to a tuff dated at 22.6 ± 0.13 Ma, hence establishes a minimum age for the appearance of the species in North America. New dental and foot elements allow us to synonymize Moropus distans with M. oregonensis, now the type species of the genus Moropus. Additionally, a small chalicothere, probably M. oregonensis, occurs at four Arikareean Gulf Coast sites in north Florida and east Texas. It is suggested that these animals, along with the Oregon chalicotheres, represent relatively primitive populations inhabiting mesic coastal environments of the Pacific margin and southern United States in the early Miocene.

Tail-Drag Marks and Dinosaur Footprints from the Upper Cretaceous Toreva Formation, Northeastern Arizona

Abstract The first Late Cretaceous dinosaur tracksite recorded from Arizona, preserving over 100 footprints, also preserves sinuous grooves here interpreted to be impressions left by the tail of a large vertebrate as it dragged through sediment now assigned to the Toreva Formation. Although no footprints are preserved that can be referred unambiguously to the individual or individuals that produced the tail-drag marks, the dynamic nature of the surface upon which the tracks were made, likely a river or stream shoreline, could have easily resulted in their disturbance or obliteration. As best as can be determined on the basis of a depauperate marine fauna from the lower part of the unit, and on the basis of a substantial hiatus that separates the lower and upper parts, the site is probably middle Coniacian in age. These tracks and drag marks add significantly to the exceptionally rare record of terrestrial vertebrates known from the Toreva Formation.

A gravid fossil turtle from the Upper Cretaceous (Campanian) Kaiparowits Formation, southern Utah

An Adocus turtle collected from the Upper Cretaceous (late Campanian) Kaiparowits Formation in southern Utah contains partial eggs and numerous well-preserved bones beneath the carapace. The bones include the closely associated–articulated elements of the right pectoral girdle, skull and cervical vertebrae. The eggs are about 35 mm in diameter, and the rigid 250–280-μm thick eggshell exhibits needle-like aragonitic crystals that form the narrow, straight shell units. The eggs appear smaller than those within a gravid Adocus from Alberta, and the eggshell is thinner and lacks the feathered structure reported in the Alberta eggs. Differences in the Utah and Alberta Adocus eggs may result from differences in the stage of egg formation or the specimens may represent different Adocus species.

The last fossil primate in North America, new material of the enigmatic Ekgmowechashala from the Arikareean of Oregon.

OBJECTIVE Primates were common in North America through most of the Eocene, but vanished in the Chadronian, about 35 million years ago. In the Arikareean, about 6 million years later, the enigmatic primate Ekgmowechashala appeared in the Great Plains and Oregon. This taxon shows little resemblance to other North American primates and its phylogenetic position has long been debated. New material of this taxon allows a revised assessment of its age and how it is related to other primates. METHODS Recently collected Ekgmowechashala specimens from the Turtle Cove Member of the John Day Formation in Oregon are described. These specimens are compared to previously collected material from South Dakota and Nebraska, as well as other fossil primates from North America and Asia. RESULTS Study of the John Day material allows diagnosis of a new, distinct species. Comparison of Ekgmowechashala to a pair of recently described Asian primates, Muangthanhinius and Bugtilemur, suggests that it is a strepsirrhine adapiform, rather than an omomyid. The well-defined stratigraphy and dated marker beds of the Turtle Cove Member provide a refined age for Ekgmowechashala occurrences in Oregon, during the Oligocene (early Arikareean). CONCLUSIONS The age and morphology of these ekgmowechashaline taxa suggest that the group originated in Asia and dispersed to North America in the Oligocene, after the extinction of other primates in North America. Contemporaneous occurrences of Ekgmowechashala in Oregon and the Great Plains indicate the last non-human primates vanished in North America about 26 million years ago.

An Unexpectedly Derived Odontocete from the Ashley Formation (Upper Rupelian) of South Carolina, U.S.A.

ABSTRACT Fossil whale material from the Oligocene-aged marine beds underlying the region around Charleston, South Carolina, has provided an unparalleled view of post-archaeocete cetacean evolution. Both the Chattian-aged Chandler Bridge Formation and the underlying Rupelian-aged Ashley Formation have yielded dozens of specimens, many yet-to-be described, that document an explosive evolutionary radiation at this time, particularly in odontocetes, but in early mysticetes as well. Specimens include early odontocetes, such as Ashleycetus planicapitis, Xenorophus sloanii, and Agorophius pygmaeus; the earliest baleen-bearing mysticetes, such as Eomysticetus whitmorei and E. carolinensis; and even multiple species of archaeocete-like toothed mysticetes, such as the recently described Coronodon havensteini. Herein, we describe yet another species of odontocete from the Ashley Formation, but one that is surprisingly derived relative to contemporary species noted above that maintain a pronounced intertemporal constriction, with broad exposure of the parietals across the skull roof. In contrast to those taxa, Ediscetus osbornei, gen. et sp. nov., shows an unexpectedly advanced degree of ‘telescoping’ whereby there is no exposure of the parietals across the vertex of the skull and only minimally exposed ‘parietal triangles’ at the lateral margins of the nearly lost intertemporal constriction. Phylogenetic analyses of a supermatrix of morphological and molecular data place E. osbornei slightly outside the odontocete crown group, with the presence of double-rooted teeth and a deep maxillary cleft, among other features, supporting this position. The holotype also has a well-developed articular ridge on the petrosal, typically considered a platanistoid synapomorphy, indicating that this character shows more homoplasy than generally realized.