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bgsu1185914798.pdf (8.74 MB)
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A Phylogenetic Analysis of the Basal Ornithischia (Reptilia, Dinosauria)
Author Info
Spencer, Marc Richard
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1185914798
Abstract Details
Year and Degree
2007, Master of Science (MS), Bowling Green State University, Geology.
Abstract
The placement of
Lesothosaurus diagnosticus
and the Heterodontosauridae within the Ornithischia has been problematic. Historically,
Lesothosaurus
has been regarded as a basal ornithischian dinosaur, the sister taxon to the Genasauria. Recent phylogenetic analyses, however, have placed
Lesothosaurus
as a more derived ornithischian within the Genasauria. The Fabrosauridae, of which
Lesothosaurus
was considered a member, has never been phylogenetically corroborated and has been considered a paraphyletic assemblage. Prior to recent phylogenetic analyses, the problematic Heterodontosauridae was placed within the Ornithopoda as the sister taxon to the Euornithopoda. The heterodontosaurids have also been considered as the basal member of the Cerapoda (Ornithopoda + Marginocephalia), the sister taxon to the Marginocephalia, and as the sister taxon to the Genasauria. To reevaluate the placement of these taxa, along with other basal ornithischians and more derived subclades, a phylogenetic analysis of 19 taxonomic units, including two outgroup taxa, was performed. Analysis of 97 characters and their associated character states culled, modified, and/or rescored from published literature based on published descriptions, produced four most parsimonious trees. Consistency and retention indices were calculated and a bootstrap analysis was performed to determine the relative support for the resultant phylogeny. The Ornithischia was recovered with
Pisanosaurus
as its basalmost member. A monophyletic Genasauria was recovered with two major clades:
Eocursor
+ Cerapoda and Fabrosauridae + Thyreophora.
Lesothosaurus
was recovered within the Fabrosauridae, along with a clade consisting of
Stormbergia
+
Agilisaurus
. The Heterodontosauridae was recovered as the basalmost taxon of the Cerapoda. In the bootstrap analysis, however, several taxa, including the Fabrosauridae, collapse down to form a polytomy at the base of the Genasauria consisting of
Eocursor
,
Lesothosaurus
,
Stormbergia
+
Agilisaurus
, Cerapoda, and Thyreophora. This analysis is the first to recover a weakly-supported Fabrosauridae clade, and lends further support to the placement of the Heterodontosauridae within the Cerapoda, but outside of the Ornithopoda. Additionally, the implication of the phylogenetic relationship of
Eocursor
and the Cerapoda indicates, paleobiogeographically, that they evolved in the southern supercontinent of Gondwana in present-day southern Africa.
Committee
Margaret Yacobucci (Advisor)
Pages
140 p.
Subject Headings
Paleontology
;
Paleozoology
Keywords
Dinosauria
;
Ornithischia
;
phylogenetic systematics
;
basal ornithischians
Recommended Citations
Refworks
EndNote
RIS
Mendeley
Citations
Spencer, M. R. (2007).
A Phylogenetic Analysis of the Basal Ornithischia (Reptilia, Dinosauria)
[Master's thesis, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1185914798
APA Style (7th edition)
Spencer, Marc.
A Phylogenetic Analysis of the Basal Ornithischia (Reptilia, Dinosauria).
2007. Bowling Green State University, Master's thesis.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1185914798.
MLA Style (8th edition)
Spencer, Marc. "A Phylogenetic Analysis of the Basal Ornithischia (Reptilia, Dinosauria)." Master's thesis, Bowling Green State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1185914798
Chicago Manual of Style (17th edition)
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Document number:
bgsu1185914798
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Copyright Info
© 2007, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.