Considerable debate has surrounded the phylogenetic position of the large-bodied theropod Acrocanthosaurus atokensis from the Early Cretaceous Antlers Formation of North America. Many phylogenetic analyses place Acrocanthosaurus as the sister taxon to the smaller- bodied Allosaurus, known from formations in North America and Europe, whereas others recover it as a member of Carcharodontosauridae, a derived group of large-bodied allosauroids that inhabited Gondwana. Re-examination of a well-preserved skull of Acrocanthosaurus (NCSM 14345) has provided new information regarding the morphology of the palatal complex and inner surfaces of the skull and mandible, features that were obscured by a sediment matrix during a previous description. From this revised description, twenty-three new characters were identified and added to a data matrix (164 characters; 17 terminals), the analysis of which recovered a single most parsimonious tree placing Acrocanthosaurus as a derived member of Carcharodontosauridae. This hypothesis is supported by several shared cranial characteristics, including: a sinuous medial groove for the maxillary dental lamina; a small accessory process between the quadratojugal prongs of the jugal; and a dorsal curvature of the jugal ramus of the ectopterygoid. The phylogeny recovered by this analysis fit significantly better with the stratigraphic record than previous hypotheses that place Acrocanthosaurus as more closely related to Allosaurus, a finding supported by visual assessment of phylograms and stratigraphic consistency metrics. An analysis of the paleobiogeography of Allosauroidea found Asia to be the most likely ancestral area for the clade, consistent with previous analyses. Distribution of carcharodontosaurid ancestors likely reached both North America and Gondwana during the Valanginian or Barremian stages, with Europe providing a connection between the two continents.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-06272008-015218 |
| Date | 08 August 2008 |
| Creators | Eddy, Drew Richard |
| Contributors | Julia A. Clarke, Mary H. Schweitzer, Elana L. Leithold |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-06272008-015218/ |
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