Skip to main content
    • Aa
    • Aa

Cranial anatomy of the Late Triassic phytosaur Machaeroprosopus, with the description of a new species from West Texas

  • Axel Hungerbühler (a1), Bill Mueller (a2), Sankar Chatterjee (a2) and Douglas P. Cunningham (a2)

The skull anatomy of a new species of the phytosaur Machaeroprosopus is described for the first time on the basis of two specimens from the Upper Triassic Cooper Canyon Formation of Texas. Additional information is provided by a third specimen referred to Machaeroprosopus sp. A paranasal bone, an additional paired element of the narial region, is identified. Important new data are presented for the braincase, including the morphology of the epipterygoid and presphenoid, an anterior process of the prootic, an anteroventral process of the laterosphenoid, and a parasphenoid process. Machaeroprosopus lottorum n. sp. is characterised by four apomorphies: a supratemporal fenestra closed on the skull roof with bevelled anterior rim, a comparatively short squamosal, a flat and rugose narial rim, and medially extended palatines that come close to form an ossified secondary palate. With respect to the supratemporal fenestra, the supraoccipital–parietal complex and several features of the squamosal, Machaeroprosopus lottorum n. sp. bridges the morphological gap between species previously referred to the genera Pseudopalatus and Redondasaurus. A parsimony analysis of known species of Machaeroprosopus supports the hypothesis that the development of the rostral crest in Machaeroprosopus is a sexually dimorphic feature, and questions the validity of the genus Redondasaurus. Consequently, Redondasaurus is here considered a junior synonym of Machaeroprosopus.

Linked references
Hide All

This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

H. T. Anderson 1936. The jaw musculature of the phytosaur, Machaeroprosopus. Journal of Morphology 59, 549–74.

S. Chatterjee 1985. Postosuchus, a new thecodontian reptile from the Triassic of Texas and the origin of tyrannosaurs. Philosophical Transactions of the Royal Society, London B 309, 395460.

J. M. Clark , J. Welman , J. A. Gauthier & J. M. Parrish 1993. The laterosphenoid bone of early archosauriforms. Journal of Vertebrate Palaeontology 13, 4857.

P. J. Currie 1985. Cranial anatomy of Stenonychosaurus inequivalis (Saurischia, Theropoda) and its bearings on the origin of birds. Canadian Journal of Earth Sciences 22, 1643–58.

P. J. Currie & X.-J. Zhao 1993. A new carnosaur (Dinosauria, Theropoda) from the Jurassic of Xinjang, People's Republic of China. Canadian Journal of Earth Sciences 30, 2037–81.

K. D. Doyle & H.-D. Sues 1995. Phytosaurs (Reptilia: Archosauria) from the Upper Triassic New Oxford Formation of York County, Pennsylvania. Journal of Vertebrate Paleontology 15, 545–53.

J. A. Gauthier , A. G. Kluge & T. Rowe 1988. Amniote phylogeny and the importance of fossils. Cladistics 4, 105209.

D. J. Gower 1997. The braincase of the early archosaurian reptile Erythrosuchus africanus. Journal of Zoology 242, 557–76.

D. J. Gower 2002. Braincase evolution in suchian archosaurs (Reptilia: Diapsida): evidence from the rauisuchian Batrachotomus kupferzellensis. Zoological Journal of the Linnean Society 136, 4976.

D. J. Gower & A. D. Walker 2002. New data on the braincase of the aetosaurian archosaur (Reptilia: Diapsida) Stagonolepis robertsoni Agassiz. Zoological Journal of the Linnean Society 136, 723.

J. T. Gregory 1962. The genera of phytosaurs. American Journal of Science 260, 652–90.

A. Hungerbühler 2000. Heterodonty in the European phytosaur Nicrosaurus kapffi and its implications for the taxonomic utility and functional morphology of phytosaur dentitions. Journal of Vertebrate Paleontology 20, 3148.

A. Hungerbühler 2002. The Late Triassic phytosaur Mystriosuchus westphali, with a revision of the genus. Paleontology 45, 377418.

G. F. Jaeger 1828. Über die fossilen Reptilien, welche in Würtemberg aufgefunden worden sind. Stuttgart, Germany: Metzler. 48 pp.

W. Janensch 1936. Über Bahnen von Hirnvenen bei Saurischiern und Ornithischiern, sowie einigen anderen fossilen und rezenten Reptilien. Palaeontologische Zeitschrift 18, 181–98.

W. Langston Jr. 1949. A new species of Paleorhinus from the Triassic of Texas. American Journal of Science 247, 324–41.

J. H. Lees 1907. The skull of Paleorhinus. Journal of Geology 15, 121–51.

T. M. Lehman & S. Chatterjee 2005. Depositional setting and vertebrate biostratigraphy of the Triassic Dockum Group of Texas. Journal of Earth System Sciences 114, 325–51.

M. G. Mehl 1922. A new phytosaur from the Trias of Arizona. Journal of Geology 30, 44157.

S. J. Nesbitt 2011. The early evolution of archosaurs: Relationships and origin of major clades. Bulletin of the American Museum of Natural History 352. 292 pp.

W. G. Parker & J. W Martz , 2011. The Late Triassic (Norian) Adamanian–Revueltian tetrapod faunal transition in the Chinle Formation of Petrified Forest National Park, Arizona. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 101 (for 2010), 231–60.

J. M. Parrish 1994. Cranial osteology of Longosuchus meadei and the phylogeny and distribution of the Aetosauria. Journal of Vertebrate Paleontology 14, 196209.

O. Rieppel 1993. Studies on the skeleton formation in reptiles. V. Patterns of ossification in the skeleton of Alligator mississippiensis DAUDIN (Reptilia, Crocodylia). Zoological Journal of the Linnean Society 109, 301–25.

P. Senter 2002. Lack of a pheromonal sense in phytosaurs and other archosaurs, and its implications for reproductive communication. Paleobiology 28, 544–50.

P. C. Sereno 1991. Basal archosaurs: phylogenetic relationships and functional implications. Society of Vertebrate Paleontology Memoir 2. 53 pp.

B. J. Small 2002. Cranial anatomy of Desmatosuchus haplocerus (Reptilia: Archosauria: Stagonolepididae). Zoological Journal of the Linnean Society 136, 97111.

J. B. Smith & P. Dodson 2003. A proposal for a standard terminology of anatomical notation and orientation in fossil vertebrate dentitions. Journal of Vertebrate Paleontology 23, 112.

M. R. Stocker 2010. A new taxon of phytosaur (Archosauria: Pseudosuchia) from the Norian (Late Triassic) Sonsela Member (Chinle Formation) in Arizona, and a critical re-evaluation of Leptosuchus Case, 1922. Palaeontology 53, 9971022.

A. D. Walker 1990. A revision of Sphenosuchus acutus Haughton, a crocodylomorph reptile from the Elliot Formation (late Triassic or early Jurassic) of South Africa. Philosophical Transactions of the Royal Society, London, Series B 330, 1120.

J. R. Wible , D. Miao & J. A. Hopson 1990. The septomaxilla of fossil and recent synapsids and the problem of the septomaxilla of monotremes and armadillos. Zoological Journal of the Linnean Society 98, 203–28.

M. Wilkinson 1995. A comparison of two methods of character construction. Cladistics 11, 297308.

M. Wilkinson & M. J. Benton 1996. Sphenodontid phylogeny and the problem of multiple trees. Philosophical Transactions of the Royal Society, London Series B 351, 116.

L. M. Witmer 1997. The evolution of the antorbital cavity in archosaurs: A study in soft-tissue reconstruction in the fossil record with analysis of the function of pneumaticity. Society of Vertebrate Paleontology Memoir 3. 73 pp.

K. E. Zeigler , S. G. Lucas & A. B. Heckert 2003b. Variation in the Late Triassic Canjilon quarry (Upper Chinle Group, New Mexico) phytosaur skulls: a case for sexual dimorphism. Paläontologische Zeitschrift 77, 341–51.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Earth and Environmental Science Transactions of The Royal Society of Edinburgh
  • ISSN: 1755-6910
  • EISSN: 1755-6929
  • URL: /core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh
Please enter your name
Please enter a valid email address
Who would you like to send this to? *



Altmetric attention score

Full text views

Total number of HTML views: 3
Total number of PDF views: 17 *
Loading metrics...

Abstract views

Total abstract views: 463 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 21st September 2017. This data will be updated every 24 hours.