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J. Willis Stovall

Bio: J. Willis Stovall is an academic researcher. The author has contributed to research in topics: Phytosaur & Muscle hypertrophy. The author has an hindex of 5, co-authored 12 publications receiving 162 citations.

Papers
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Journal ArticleDOI
TL;DR: The relationships of Acrocanthosaurus and Altispinax are studied to establish a cladistic relationship between these dinosaurs and their relatives, the Tournaisian dinosaurs.
Abstract: 696 Introduction -697 Type -699 Paratype -699 Generic diagnosis -699 Description of the skeleton -700 Skull -700 Frontals -701 Parietals -701 Prootic -702 Jugal -702 Lachrymal -702 Postorbital complex -703 Squamosal -703 Basioccipital -----703 Exoccipitals and paroccipitals 703 Supraoccipitals -704 Alisphenoids -----------704 Orbitosphenoids and ethmoids 704 Basisphenoids .-.--------------704 Ectopterygoid ---------------705 Lower jaw -705 Measurements of the skull 705 Vertebral column -706 Cervical vertebrae -706 Measurements of the cervical vertebrae -709 Dorsal vertebrae ---709 Measurements of the dorsal vertebrae -711 Caudal vertebrae 711 Measurements of the caudal vertebrae 714 Discussion of the vertebral spines 714 Chevrons 715 Ribs -716 Gastralia -716 Pectoral girdle -716 Coracoid -716 Pelvic girdle -717 Pubis -717 Ischium 717 Hind limb7J!9 Femur -718 Tibia -718 Fibula -719 Pes -719 Measurements of the hind limb and foot -720 Observations on the taxonomy of Altispinax -721 The relationships of Acrocanthosaurus 722 Conclusions 723 Acknowledgments -724 References 724

110 citations

Journal ArticleDOI
TL;DR: It is concluded that all 3 of the terrace deposits were laid down during the Wisconsin stage of the Pleistocene and suggested that Trinity Terrace is the up-stream equivalent of the Lissie formation; that the Trinidad Terrace may be equivalent to the Beaumont formation; and that the present flood plain represents practically all of the Recent time.
Abstract: An attempt is made to correlate the various stratigraphic units of the Pleistocene in Henderson and adjoining counties to related up-dip terrace deposits with the equivalent formations of the Gulf Coastal Plain and to determine the age of these terraces as compared with the glacial deposits in the glaciated states. The highest of a series of 3 alluvial terraces associated with the present Trinity River in the area under consideration in east-central Texas is especially well-developed and offers the possibility of serving as a standard unit for correlation of other stream deposits in the Texas coastal plain. The 3 terraces are herein designated, from highest to lowest, as Trinity Terrace, Trinidad Terrace, and Power Plant Terrace. An interesting assemblage of vertebrate fossils containing 17 genera, including a new species of Megalonyx, collected from numerous sand and gravel pits located on the highest terrace, is described. On the basis of paleontologic and stratigraphic evidence it is concluded that all 3 of the terrace deposits were laid down during the Wisconsin stage of the Pleistocene. It is suggested that Trinity Terrace is the up-stream equivalent of the Lissie formation; that the Trinidad Terrace may be equivalent to the Beaumont formation; and that the present flood plain represents practically all of the Recent time.

12 citations

Journal ArticleDOI
TL;DR: The discovery of Morrison dinosaur bones in Cimarron County, Oklahoma, led to a study of the geology of the area as mentioned in this paper, which brought to light six deposits containing remains of these animals of which four genera have been identified.
Abstract: The discovery of Morrison dinosaur bones in Cimarron County, Oklahoma, led to a study of the geology of the area. This investigation brought to light six deposits containing remains of these animals, of which four genera have been identified. The study showed that the Morrison extends down the Cimarron River, beyond Highway 38, north of Boise City. At Robbers' Roost, 4 miles east of the New Mexico state line, the Morrison is unusually thick but thins rapidly toward the east, owing to erosion of a post-Morrison dome. For this reason, and because the Morrison has only a few feet of sediment between it and the Triassic, and because it is overlain by Lower Cretaceous sediments, it seems best assigned to the Jurassic.

10 citations

Journal ArticleDOI
TL;DR: The phylogenetic relationships of the Phytosauria are discussed, and a new species of Angistorhinus is described from Big Spring, Texas.
Abstract: The phylogenetic relationships of the Phytosauria are discussed, and a new species of Angistorhinus is described from Big Spring, Texas.

9 citations

Journal ArticleDOI
TL;DR: A skull of the phytosaur Machaeroprosopus, discovered in the Sloan Canyon formation, confirms the Triassic age of the rocks lying beneath the Exeter (Jurassic) in the valley of the dry Cimarron River of Union County, New Mexico andCimarron County, Oklahoma as mentioned in this paper.
Abstract: A skull of the phytosaur Machaeroprosopus, discovered in the Sloan Canyon formation, confirms the Triassic age of the rocks lying beneath the Exeter (Jurassic) in the valley of the dry Cimarron River of Union County, New Mexico, and Cimarron County, Oklahoma. The underlying red beds, the Sloan Canyon formation, and the Sheep Pen Canyon formation form a continuous and conformable succession of strata in this region, and the conclusion is drawn that these three units should be included in the Dockum group.

9 citations


Cited by
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Journal ArticleDOI
TL;DR: Resolution of the antorbital cavity is correctly viewed as a “soft-tissue problem,” and is addressed within the context of the extant phylogenetic bracket (EPB) approach for reconstructing the unpreserved features of fossil organisms.
Abstract: The most commonly cited apomorphy of Archosauriformes is an opening in the snout known as the antorbital cavity. Despite the ubiquity and prominence of the antorbital cavity, its function and importance in craniofacial evolution have been problematic. Discovering the significance of the antorbital cavity is a two step process: first, establishing the function of the bony cavity (that is, its soft-tissue relations), and second, determining the biological role of the enclosed structure. The first step is the most fundamental, and hence is examined at length. Three hypotheses for the function of the antorbital cavity have been advanced, suggesting that it housed (1) a gland, (2) a muscle, or (3) a paranasal air sinus. Thus, resolution is correctly viewed as a “soft-tissue problem,” and is addressed within the context of the extant phylogenetic bracket (EPB) approach for reconstructing the unpreserved features of fossil organisms. The soft-anatomical relations of the antorbital cavity (or any bony st...

497 citations

01 Jan 1976
TL;DR: In this article, the authors propose a method to solve the problem of "uniformity" of the problem: this article ] and "unweighting" the problem with respect to
Abstract: ...................................

483 citations

Journal ArticleDOI
TL;DR: High-resolution x-ray computed tomographic analysis of the skull reveals internal details not previously observed, raising several possibilities, including the complete absence of a bony sternum in tyrannosaurids.
Abstract: A detailed osteological description of Tyrannosaurus rex Osborn, 1905 is presented, based primarily on the most complete specimen yet collected of this taxon (FMNH PR2081, popularly known as “Sue”) but also including observations from other specimens. Skull morphology of FMNH PR2081 is largely congruent with that described for previous specimens, but new details are added. Palatal morphology of FMNH PR2081 differs slightly from that of previously-described specimens—the internal choanae are slightly larger relative to skull size, and the anterior expansion of the fused vomers is elongate. Posteriorly, the vomers pass medially for nearly the entire length of the pterygoids. High-resolution x-ray computed tomographic (CT) analysis of the skull reveals internal details not previously observed. Complex recess systems can be traced in the jugal, lacrymal, ectopterygoid, quadrate, exoccipital, supraoccipital, prootic, and basioccipital. The exoccipital recess was perforated by a small foramen on the po...

400 citations

Journal ArticleDOI
17 May 1996-Science
TL;DR: Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation.
Abstract: Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.

379 citations

Journal ArticleDOI
TL;DR: The phylogenetic history of ornithischian and saurischian dinosaurs reveals evolutionary trends such as increasing body size and Adaptations to herbivory in dinosaurs were not tightly correlated with marked floral replacements.
Abstract: ▪ Abstract Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the emergence of functionally modern birds. The dinosaurian radiation began in the Middle Triassic, significantly predating the global dominance of dinosaurs by the end of the period. The phylogenetic history of ornithischian and saurischian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory in dinosaurs were not tightly correlated with marked floral replacements. Dinosaurian biogeography during the era of continental breakup principally involved dispersal and regional extinction.

362 citations