Research Library | Digital Repository

Braincase of the Upper Devonian shark Cladodoides wildungensis (Chondrichthyes, Elasmobranchii), with observations on the braincase in early chondrichthyans. Bulletin of the AMNH ; no. 288

Show simple item record

dc.contributor.author Maisey, John G. en_US
dc.date.accessioned 2005-10-06T14:15:25Z
dc.date.available 2005-10-06T14:15:25Z
dc.date.issued 2005 en_US
dc.identifier.uri http://hdl.handle.net/2246/456
dc.description 103 p. : ill. ; 26 cm. en_US
dc.description Includes bibliographical references (p. 98-103). en_US
dc.description.abstract "The braincase of an Upper Devonian shark (Cladodoides wildungensis) is investigated using high-resolution CT scanning, and its internal and external morphology is described from three-dimensional digital reconstructions. Many features are shared with modern elasmobranchs (neoselachians); these mostly represent conserved elasmobranch, chondrichthyan, or gnathostome characters. C. wildungensis resembles neoselachians in having a closed metotic fissure defining a glossopharyngeal canal, unlike some early chondrichthyans (e.g., Pucapampella, Orthacanthus) in which an open metotic fissure extends a considerable distance beneath the otic capsule. However, the glossopharyngeal canal in C. wildungensis is connected to a persistent dorsal fissure between the occipital arch and otic capsules, whereas this fissure becomes closed during neoselachian ontogeny. The embryonic polar cartilage apparently made a much greater contribution to the basicranium than in neoselachians and gnathostomes generally. This has affected the position of the efferent pseudobranchial foramen and the location of the orbital articulation in Cladodoides (both of which are located anteriorly in the orbit), as well as the size and extent of the dorsum sellae and the hypophyseal chamber inside the braincase. Another unusual feature in Cladodoides is the postorbital position of its trigeminal and facial nerves; instead of being situated in a trigemino-facial fossa of the orbit as in neoselachians, their foramina are located behind the postorbital process, although the pituitary vein and the origin of the external rectus eye muscle (located within the trigemino-facial fossa in neoselachians) both lie in the posterior part of the orbit. The oblique orientation of the postorbital arcade (derived from the embryonic lateral commissure) may be related to the exclusion of the trigeminal and facial nerves from the orbit. A laterally oriented canal through the process probably contained the trigeminal maxillary ramus (perhaps accompanied by the buccal ramus of the anterodorsal lateral line nerve). By contrast, in neoselachians these rami pass directly into the orbit (sometimes forming a buccal-maxillary complex), but they do not pass through the postorbital process. The Cladodoides braincase probably represents a juvenile or submature individual and shows indications of incomplete development (e.g., presence of a wide buccohypophyseal fenestra and absence of a precarotid commissure; incomplete enclosure of the internal carotids and orbital arteries by basicranial cartilage; incomplete closure of the braincase roof along the dorsal midline). The braincase also lacks multiple-layered prismatic calcification, possibly representing another juvenile feature. The phylogenetic relationship of Cladodoides wildungensis is discussed. Dental, postcranial, and cranial features lend some support to the old hypothesis that cladodont sharks form a monophyletic group. While such a view is at variance with several recently published phylogenetic analyses, many of the characters noted in the present work have yet to be tested within a rigorous cladistic framework, and their phylogenetic significance is uncertain"--P. 3. en_US
dc.format.extent 5084685 bytes
dc.format.mimetype application/pdf
dc.language eng en_US
dc.language.iso en_US
dc.publisher New York, NY : American Museum of Natural History en_US
dc.relation.ispartofseries Bulletin of the American Museum of Natural History ; no. 288 en_US
dc.subject.lcc QH1 .A4 no.288, 2005 en_US
dc.subject.lcsh Cladodoides wildungensis. en_US
dc.subject.lcsh Skull -- Anatomy. en_US
dc.subject.lcsh Paleontology -- Devonian. en_US
dc.subject.lcsh Sharks, Fossil. en_US
dc.subject.lcsh Chondrichthyes, Fossil. en_US
dc.subject.lcsh Sharks -- Phylogeny. en_US
dc.title Braincase of the Upper Devonian shark Cladodoides wildungensis (Chondrichthyes, Elasmobranchii), with observations on the braincase in early chondrichthyans. Bulletin of the AMNH ; no. 288 en_US
dc.title.alternative Cranial morphology of Cladodoides en_US
dc.type text en_US


Files in this item

This item appears in the following Collection(s)

  • Bulletin of the American Museum of Natural History
    The Bulletin, published continuously since 1881, consists of longer monographic volumes in the field of natural sciences relating to zoology, paleontology, and geology. Current numbers are published at irregular intervals. The Bulletin was originally a place to publish short papers, while longer works appeared in the Memoirs. However, in the 1920s, the Memoirs ceased and the Bulletin series began publishing longer papers. A new series, the Novitates , published short papers describing new forms.

Show simple item record

Search Entire Repository

Advanced Search

Browse

My Account