Brent H. Breithaupt

An Integrated Approach to Three-Dimensional Data Collection at Dinosaur Tracksites in the Rocky Mountain West

Public lands in the Rocky Mountain West are home to an abundance of vertebrate paleontological resources. These fossils typically are found in badlands terrain and at some distance from convenient transportation. These and other factors often make conventional surveying and mapping techniques time-consuming and problematic. Even obtaining quality images, at useful scales with limited distortions, can be difficult. In order to preserve the value of these unique paleontological resources, an integrated approach to close-range photogrammetry and high-accuracy ground-control surveying was developed in northern Wyoming for the documentation of tracks at the Red Gulch Dinosaur Tracksite. At this site, several methods for taking high-resolution, low-distortion photographs of localities were investigated. These methods included using tripods of various heights, remote-controlled airplanes, and an Aerial Camera Blimp System. In addition, the use of a variety of ground-control collection methods, including high accuracy GPS and Light Detection and Ranging, have also been investigated. These various field data collection methods were successfully integrated using soft copy photogrammetry to produce digital terrain models, which can represent the surface to a precision of 1 cm or less. The three-dimensional data were brought into GIS software where they are displayed, combined with photographs, and rotated for viewing from different perspectives. As a result of the success of these technologies in Wyoming, studies of other dinosaur tracksites in Colorado, Utah, and Wyoming (as well as bonebeds) have utilized these methods. The information gained from these sites is aiding in our understanding of community dynamics and preservational history of dinosaur populations in the Rocky Mountain West.

A nearly complete skeleton of an early juvenile diplodocid (Dinosauria: Sauropoda) from the Lower Morrison Formation (Late Jurassic) of north central Wyoming and its implications for early ontogeny and pneumaticity in sauropods

A nearly complete skeleton of a juvenile sauropod from the Lower Morrison Formation (Late Jurassic, Kimmeridgian) of the Howe Ranch in Bighorn County, Wyoming is described. The specimen consists of articulated mid-cervical to mid-caudal vertebrae and most appendicular bones, but cranial and mandibular elements are missing. The shoulder height is approximately 67 cm, and the total body length is estimated to be less than 200 cm. Besides the body size, the following morphological features indicate that this specimen is an early juvenile; (1) unfused centra and neural arches in presacral, sacral and first to ninth caudal vertebrae, (2) unfused coracoid and scapula, (3) open coracoid foramen, and (4) relatively smooth articular surfaces on the limb, wrist, and ankle bones. A large scapula, short neck and tail and elongate forelimb bones relative to overall body size demonstrate relative growth. A thin-section of the mid-shaft of a femur shows a lack of annual growth lines, indicating an early juvenile individual possibly younger than a few years old. Pneumatic structures in the vertebral column of the specimen SMA 0009 show that pneumatisation of the postcranial skeleton had already started in this individual, giving new insights in the early ontogenetic development of vertebral pneumaticity in sauropods. The specimen exhibits a number of diplodocid features (e.g., very elongate slender scapular blade with a gradually dorsoventrally expanded distal end, a total of nine dorsal vertebrae, presence of the posterior centroparapophyseal lamina in the posterior dorsal vertebrae). Although a few diplodocid taxa, Diplodocus, cf. Apatosaurus, and cf. Barosaurus, are known from several fossil sites near the Howe Ranch, identification of this specimen, even at a generic level, is difficult due to a large degree of ontogenetic variation.

Bird tracks from the Upper Cretaceous Cantwell Formation of Denali National Park, Alaska, USA: a new perspective on ancient northern polar vertebrate biodiversity

The Upper Cretaceous Cantwell Formation in Denali National Park and Preserve (DENA), Alaska, contains an unparalleled fossil avian biodiversity. The Cantwell Formation, thousands of metres thick, was deposited near its current latitude and is exposed throughout much of DENA and elsewhere in the central Alaska Range. The Formation comprises a lower, dominantly fluvial sedimentary unit and an upper, mostly volcanic unit. Sedimentation of the lower unit was mainly in alluvial fan, braided and meandering stream, and lacustrine environments, with possible marginal-marine influence at times. Pollen data suggest that these sedimentary rocks are late Campanian or early Maastrichtian in age; thus the Cantwell Formation is correlative with other well-known dinosaur localities in Alaska. Bird tracks are preserved in multiple locations along a 40-km transect in DENA in fluvial and lacustrine deposits. Some bird tracks are found in association with dinosaur tracks and others are found on beds interbedded with dinosaur track-bearing layers. The approximate body sizes of the birds based on tracks show a range from sparrow- to heron-sized birds (∼25–30% larger than the modern Sandhill Crane Grus canadensis). The Cantwell Formation contains footprints assigned to several ichnotaxa found in either Asia or North America based on such morphological criteria as the presence or absence of a hallux, print size and shape, and angle of divarication: Aquatilavipes swiboldae, Ignotornis mcconnelli, Magnoavipes denaliensis sp. nov., Gruipeda vegrandiunus sp. nov. and Uhangrichnus chuni. The presence of a mixed Asian and North American ichnofauna suggests that at least some birds used Alaska as a bridge between Asia and North America. This diverse assemblage of avian traces, combined with the known fossil bone record and invertebrate trace fossil record, demonstrates that the northern Late Cretaceous polar region contained significant biodiversity.

Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs

Relationships between non-avian theropod dinosaurs and extant and fossil birds are a major focus of current paleobiological research. Despite extensive phylogenetic and morphological support, behavioural evidence is mostly ambiguous and does not usually fossilize. Thus, inferences that dinosaurs, especially theropods displayed behaviour analogous to modern birds are intriguing but speculative. Here we present extensive and geographically widespread physical evidence of substrate scraping behavior by large theropods considered as compelling evidence of “display arenas” or leks, and consistent with “nest scrape display” behaviour among many extant ground-nesting birds. Large scrapes, up to 2 m in diameter, occur abundantly at several Cretaceous sites in Colorado. They constitute a previously unknown category of large dinosaurian trace fossil, inferred to fill gaps in our understanding of early phases in the breeding cycle of theropods. The trace makers were probably lekking species that were seasonally active at large display arena sites. Such scrapes indicate stereotypical avian behaviour hitherto unknown among Cretaceous theropods, and most likely associated with terrirorial activity in the breeding season. The scrapes most probably occur near nesting colonies, as yet unknown or no longer preserved in the immediate study areas. Thus, they provide clues to paleoenvironments where such nesting sites occurred.

Latest Cretaceous occurrence of nodosaurid ankylosaurs (Dinosauria, Ornithischia) in Western North America and the gradual extinction of the dinosaurs

ABSTRACT The presence of nodosaurid ankylosaurs in the Lance, Hell Creek, and Laramie formations of western North America is confirmed, thereby extending the geochronological range of this family into the Maastrichtian (Lancian). The material includes a cervical spine and a skull referable to Edmontonia sp., and numerous teeth, plates and a basioccipital, which are questionably assigned to Edmontonia sp. Comparison of the amount of nodosaurid material known from the Judith River Formation (Campanian) with that from the Lancian deposits indicates a substantial decrease in the relative abundance of nodosaurids in the Maastrichtian. Furthermore, the stratigraphic distribution of these nodosaurs is apparently limited to the lower part of the Lancian deposits, suggesting that they became extinct before the end of the Cretaceous. If true, this would support the hypothesis that the dinosaur extinction at the end of the Maastrichtian was gradual, not catastrophic.

Vertebrate Ichnopathology: Pathologies Inferred from Dinosaur Tracks and Trackways from the Mesozoic

Literature concerning dinosaur footprints or trackways exhibiting abnormal gait or morphology reflecting pathology (ichnopathology) is rare. We report on a number of Jurassic and Cretaceous occurrences of theropod footprints from western North America with unusual morphologies interpreted herein as examples of inferred pathologies, or ichnopathologies. The majority of ichnopathologies are primarily manifested in the digit impressions and include examples of swelling, extreme curvature, dislocation or fracture, and amputation. A number of occurrences are single tracks on ex situ blocks with substantial deformation (inferred dislocation or fracture), or absence of a single digit impression. Two occurrences are from in situ natural mould trackways, one of which is a lengthy trackway of a presumed allosauroid with no noticeable deformation of the digits or feet but with strong inward rotation of the left footprint toward the midline and a pronounced, waddling limp. The other is a tyrannosaurid trackway consisting of three footprints (one right, two left) with the two left prints exhibiting repetitive ichnopathology of a partially missing Digit II impression.

Latest Cretaceous Multituberculates of the Black Butte Station Local Fauna (Lance Formation, Southwestern Wyoming), with Implications for Compositional Differences Among Mammalian Local Faunas of the Western Interior

ABSTRACT Latest Cretaceous (Lancian) mammalian faunas of the Western Interior of North America are mostly known from the northern Great Plains and coastal lowland paleoenvironments. Here, we describe a sample of 143 multituberculate mammal teeth from the Lance Formation of southwestern Wyoming. The specimens, which are from two independent collections made in the 1970s by the University of California Museum of Paleontology and the University of Wyoming Geological Museum, are part of the best-sampled local fauna from the central part of the Western Interior. Deposits of the Lance Formation in this region are on the eastern flank of the Rock Springs Uplift near Black Butte Station. The Black Butte Station local fauna was farther west and possibly paleoenvironmentally distinct from most other Lancian local faunas known. The fossil assemblage preserves eight genera and 11 species of multituberculates. There are many common Lancian taxa, a high relative abundance of Cimexomys, the second published occurrences of Parikimys and Paressonodon, and a new species of Cimolodon. Cluster and ordination analyses of multituberculate abundance data from well-sampled Western Interior local faunas show that the Black Butte Station local fauna is distinct from all other local faunas and that variation among mammalian local faunas in composition is correlated with latitude, though paleoenvironmental, temporal, and taphonomic differences may also be factors. Results highlight that explorations in undersampled regions and paleoenvironments are critical to a more complete understanding of the Cretaceous-Paleogene transition. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP