Document Type
Thesis
Abstract
The majority of cryptocleidoid plesiosaurs have been recovered from Upper Jurassic units in the United Kingdom, but Tatenectes laramiensis is one of two cryptocleidoids documented from the Sundance Formation (Wyoming, USA). The purpose of this research is to describe new fossil material of Tatenectes and to reevaluate the phylogenetic position of this genus within the cryptocleidoid lineage based on this new material. The Sundance Formation was deposited in the Sundance Seaway, a shallow isolated epicontinental seaway, which inundated the northern Rocky Mountain states in several pulses during the Jurassic. The fossils were collected during fieldwork in the Bighorn Basin in North-central Wyoming from “Redwater Shale member” sediments, near Shell, Wyoming. This new material includes a partial skull, a humerus missing part of the shaft, and a partial pectoral girdle, among other elements. Nine new phylogenetic characters based on morphological features of the humerus and pectoral girdle were integrated into previously existing character matrices for cryptocleidoids to generate new phylogenetic trees using parsimony criteria. The pectoral girdle is very short anteriorly and most closely resembles that of Tricleidus seeleyi. Two most parsimonious trees were obtained, and the consensus tree solidifies the phylogenetic position of Tatenectes as being most closely related to the Oxford Clay cimoliasaurid Kimmerosaurus. The relationship between the highly derived pliosauromorph Polycotylidae and the cimoliasaurid plesiosaurs is also strengthened.
Date Awarded
2007
Department
Geology
Advisor 1
Rowan Lockwood
Advisor 2
Robin O'Keefe
Recommended Citation
Street, Hallie, "Description and phylogenic analysis of cryptocleidoid pleisosaurs based on new material of Tatenectes laramiensis from the Sundance Formation (Wyoming, USA)" (2007). Geology Senior Theses. William & Mary. Paper 186.
https://scholarworks.wm.edu/geologyseniors/186
