Master's Theses

Date of Award

Fall 2004

Degree Name

Master of Science (MS)

Department

Geosciences

Advisor

Richard Zawerksi

Abstract

Two large skeletons of Camarasaurus (Dinosauria. Sauropoda) were excavated from single quarry near Thermopolis, central Wyoming from the Upper Morrison Formation (Kimmeridgian, Late Jurassic). Shed theropod teeth and abundant fossil plants and lignite were also found at the quarry. A complicated stratigraphic sequence based on random patterns and thickness of dark gray mudstone, light gray mudstone, thin sandstone, and carbonate nodule layers suggests that the carcasses of the sauropods were buried under an anastomosing river environment. The two partial skeletons include two partial crania, 15 cervical vertebrae, 14 dorsal vertebrae, two sacra, 51 caudal vertebrae, three scapulocoracoids, two sternal pIates, three humeri, two ulnae, two radii, a partial manus, four ilia, four pubes, four Ischia, four femora, a tibia, a fibula, and many rib and chevron fragments. These bones provide new information on the anatomy of Camarasaurus; particularly, the transit ion from the posterior cervicals to anterior dorsal vertebrae that are significant for the taxonomy and morphological variation in the genus. Moreover, the first chevron is also preserved, which has not been previously described well in any sauropod taxa. An unusual pathology is also found in one of the thoracic ribs. The two Camarasaurus are fully grown individuals based on the completely fused centra and neural arches of all the vertebrae, the closed suture between the scapulocoracoids, and the very rugose articulated surfaces on the limb and girdle bones. The massive short neural arches in the anterior and mid-dorsal vertebrae indicate that the specimens represent C. lentis rather than C. grandis. In addition, gradually expanded neural spines on the anterior caudal vertebrae distinguish C. lentus from C. Supremus and C. grandis, both of which have T-shaped neural spines. Thus, the two Wyoming specimens clarify taxonomic problems in the genus to some degree. One of the individuals is about the same body size as the largest known C. lentus and about 80-85% smaller than C. supremus. In addition, the smaller Camarasaurus from Thermopolis exhibits entheses (ossified tendon) on the neural spines of the posterior dorsal and sacral vertebrae. [More]

Rights

Copyright 2004 Takehito Ikejiri

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