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Full-Text Articles in Life Sciences
Morphologic And Ontogenetic Patterns In Elasmosaur Neck Length, With Comments On The Taxonomic Utility Of Neck Length Variables, F. Robin O’Keefe, Norton Hiller
Morphologic And Ontogenetic Patterns In Elasmosaur Neck Length, With Comments On The Taxonomic Utility Of Neck Length Variables, F. Robin O’Keefe, Norton Hiller
Biological Sciences Faculty Research
Elasmosaur cervical vertebrae are common fossils, but their taxonomic utility is limited due to a lack of understanding concerning their shape within and among taxa. In this paper, we analyze data from complete elasmosaur necks in an attempt to quantify and understand the variation in centrum dimensions. In accord with previous studies, variation in cervical centrum shape is found to stem from at least three sources: ontogeny, intracolumn variation, and intercolumn or taxonomic variation. Ontogenetic variability seems reminiscent of that seen in Cryptoclidus, with an overall positive allometry in the length of all centra that is accentuated in the mid-cervical …
Neoteny And The Plesiomorphic Condition Of The Plesiosaur Basicranium, F. Robin O’Keefe
Neoteny And The Plesiomorphic Condition Of The Plesiosaur Basicranium, F. Robin O’Keefe
Biological Sciences Faculty Research
The purpose of this paper is to describe the condition of the braincase in stratigraphically early and morphologically primitive plesiosaurs. Information on the braincase of plesiomorphic taxa is important because it establishes the polarity of characters occurring in more derived plesiosaurs. This paper begins with a short review of braincase anatomy in stem-group sauropterygians. Data on braincase morphology of the plesiomorphic plesiosaur genera Thalassiodracon and Eurycleidus are then presented and interpreted via comparison with other plesiosaurs, stemgroup sauropterygians, and stem diapsids (Araeoscelis). Early diapsids are relevant because plesiosaur skulls more closely resemble early diapsids than stem-group sauropterygians in several key …
The Vertebrate Fauna Of The Upper Permian Of Niger. Iv. Nigerpeton Ricqlesi (Temnospondyli: Cochleosauridae), And The Edopoid Colonization Of Gondwana, J. Sebastien Steyer, Ross Damiani, Christian A. Sidor, F. Robin O’Keefe, Hans C.E. Larsson, Abdoulaye Maga, Oumarou Ide
The Vertebrate Fauna Of The Upper Permian Of Niger. Iv. Nigerpeton Ricqlesi (Temnospondyli: Cochleosauridae), And The Edopoid Colonization Of Gondwana, J. Sebastien Steyer, Ross Damiani, Christian A. Sidor, F. Robin O’Keefe, Hans C.E. Larsson, Abdoulaye Maga, Oumarou Ide
Biological Sciences Faculty Research
We describe the edopoid temnospondyl Nigerpeton ricqlesi from the Upper Permian Moradi Formation of northern Niger on the basis of two partial skulls and tentatively associated postcranial material. This crocodile-like taxon displays several edopoid characters states such as a long prenarial region with enlarged premaxillae, elongated vomers, large, posteriorly tapering choanae, and a jugal that broadens anteriorly. Nigerpeton possesses a unique carnivorous dentition. It is autapomorphic in its possession of an extremely elongate snout bearing a maxillary bulge that accommodates three hypertrophied caniniform teeth, inner premaxillary tusks, and anterior paired fenestrae, which pierce the skull roof. In addition, both the …