Morphology of the braincase in the Cretaceous hybodont shark Tribodus limae (Chondrichthyes, Elasmobranchii), based on CT scanning. (American Museum novitates, no. 3681)

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dc.contributor.author Lane, Jennifer A.
dc.date.accessioned 2010-03-09T19:58:49Z
dc.date.available 2010-03-09T19:58:49Z
dc.date.issued 2010
dc.identifier.uri http://hdl.handle.net/2246/6044
dc.description 70 p. : ill. (some col.) ; 26 cm. "March 4, 2010." Includes bibliographical references (p. 67-70). en
dc.description.abstract The braincase of the Lower Cretaceous hybodont shark Tribodus limae is examined using high-resolution CT scanning, and its internal and external morphology is described based on three-dimensional digital reconstructions. This study represents the first in-depth examination of a hybodont braincase using CT scanning and digital imaging technology. The braincase of an additional Lower Cretaceous hybodont, Egertonodus basanus, is also digitally reconstructed and compared to Tribodus. A reconstruction of cranial nerves and blood vessels in Tribodus is presented on the basis of preserved foramina. The braincase of Tribodus shares many features with those of Egertonodus and neoselachians, providing further support for the sister-group relationship between hybodonts and extant elasmobranchs. CT scans confirm that in both Tribodus and Egertonodus the glossopharyngeal and vagus canals converge and exit from a common foramen (also found in Chlamydoselachus). In both of the hybodonts examined, the trochlear nerve exits the braincase anterior to the optic nerve, a possible hybodont synapomorphy. Separate foramina for the two rami of the octaval nerve are present in both Tribodus and Egertonodus, and may represent an additional hybodont synapomorphy. Also, both taxa have three separate foramina for the trigeminal, facial, and anterodorsal lateral line nerves, apparently including an individual foramen for the superficial ophthalmic complex. However, the basicranial arterial system in Tribodus differs considerably from that of Egertonodus in that in the former the internal carotid arteries enter the braincase much farther posteriorly and through paired foramina rather than a single median foramen. The median ventral basicranial process in Tribodus is similar in structure and position to median ventral processes seen in some extant neoselachians (e.g., Etmopterus) and in embryonic Torpedo (although in the latter this structure disappears during development), and thus may have had a similar ontogenetic origin. en
dc.format.extent 33035632 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher New York, NY : American Museum of Natural History. en
dc.relation.ispartofseries American Museum novitates, no. 3681. en
dc.subject Tribodus limae. en
dc.subject Egertonodus basanus. en
dc.subject Sharks, Fossil. en
dc.subject Brazil. en
dc.subject Cretaceous. en
dc.title Morphology of the braincase in the Cretaceous hybodont shark Tribodus limae (Chondrichthyes, Elasmobranchii), based on CT scanning. (American Museum novitates, no. 3681) en
dc.title.alternative Braincase in the shark Tribodus limae. en

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  • American Museum Novitates
    Novitates (Latin for "new acquaintances"), published continuously and numbered consecutively since 1921, are short papers that contain descriptions of new forms and reports in zoology, paleontology, and geology. New numbers are published at irregular intervals.

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