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A Production of

Saurosuchus galileiFossil, Fossil Pseudosuchid
Dr. Oscar Alcober - Museo de Ciencias Naturales, San Juan, Argentina
Saurosuchus galilei
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skull
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Museo de Ciencias Naturales, Universidad Nacional de San Juan, Argentina (PVSJ 32)

Image processing: Ms. Farrah Welch
Image processing: Dr. Ted Macrini
Publication Date: 15 Jan 2001

ITIS TNS Google MSN

Saurosuchus is a rauisuchian archosaur, distantly related to crocodylians. There are at least seven other specimens of Saurosuchus known, all collected in the Triassic Ischigualasto Formation. Only three include cranial material. All the specimens collected during the late 1950's and early 1960's by Alfred Romer and his team are housed in the collection at the University of Tucumán in northern Argentina. The remaining specimens are in the collection of the Museum of Natural Sciences in San Juan, Argentina.

About the Species

The specimen used for CT scanning is PVSJ 32 (Paleontología de Vertebrados del Museo de San Juan). It was collected in the base of the Ischigualasto Formation, in the northwest region of the San Juan Province in Argentina, about 15 meters above a tuff layer dated at 228 MY (Rogers et al, 1993). The specimen was found mostly articulated in a silty abandoned channel deposit. The skull is almost complete, but unfortunately erosion has destroyed the anteroposterior rami of the quadratojugal, both ventral articular surfaces of the quadrates, almost all of the left paraoccipital process, the anterior most portion of the palate, and the posterior part of both mandibular rami. Most of the maxillary and mandibular teeth have also been lost to erosion. This new skull of Saurosuchus preserves the entire posterior region of the braincase, revealing anatomical features not present in the holotype PVL 2062 (Sill, 1974). This new information includes details of virtually the entire palate, a nearly complete braincase, and the anterior portion of both mandibular rami. The preservation of the skull is generally very good, except in the most superficial layer of the external aspect of the premaxilla and maxilla, which are covered by a dense coating of hematite. This was removed using mechanical methods, aided by a small amount of acetic acid. There is an observable amount of deformation in this specimen because of lateral shear and compression. One can see that elements of the right side of the cranium have been displaced dorsally with respect to their counterparts on the left. This displacement has the effect of disarticulating the braincase, closing the medial aperture between the palatines and the pterygoid.


Working a site at the base of the Upper Triassic Ischigualasto Formation in the Ischigualasto Provincial Park, San Juan, Argentina. The gray layers are sandy paleochannels, the green layers are levee deposits, and the reddish-purple layers are paleosols. Lunchtime at the outcrop. No trees, no shade. Having fun to forget about the killer sun and the nearly 110 degree (F) temperatures.



About this Specimen

The skull of Saurosuchus was scanned by Richard Ketcham and Matthew Colbert on 09 November 1999, using the Pantak X-ray source and a translate-rotate scan protocol with the P250D detector system. The specimen was wedged in air. Parameters were 420 kV (energy potential) and 4.7 mA filament setting. Two brass filters were used to reduce beam-hardening artifacts. The source-object distance (S.O.D.) was 661 mm, 2 views, 1 ray per view, 2 samples per view, field of reconstruction 400 mm, reconstruction offset 500, and reconstruction scale 150. The specimen was scanned in the coronal plane, the slice thickness at 2.0 mm and an interslice spacing of 1.8 mm.

The 16-bit coronal slices were adjusted for tonal contrasts and dropped to 8-bit for further image processing. The slices were digitally stacked and resliced orthogonally in the sagittal and horizontal  planes using National Institute of Health Image software (NIH Image version 1.62b17_ppc).

The final processed data include anatomical labels on every fifth slice in all three planes for the skull. Additionally, anatomical structures visible in the slices of the braincase were labeled in all three slice planes (the braincase of Saurosuchus was removed from the skull and scanned separately). The digital information, accompanied by the written description of the internal anatomy, will be published on CD-ROM and distributed as a supplement in a regular scientific journal. This data set will add to the growing digital library of vertebrate morphology generated at the University of Texas at Austin.

Sample slices from the Saurosuchus CD-ROM:

Saurosuchus coronal slice 165 Saurosuchus coronal slice 165 labelled Saurosuchus coronal slice 165 labels and sutures

Unlabeled coronal slice 165. Click on the thumbnail for an unreduced version.

Labeled coronal slice 165. Click on the thumbnail for an unreduced version.

Labeled coronal slice 165 with sutures between bones outlined. Click on the thumbnail for an unreduced version.

About the
Scan

Literature

Alcober, O. 1996. Revisión de los Crurotarsis, Estratigrafía y Tafonomía de la Formacíon Ischigualasto. Unpublished Ph.D. Thesis, Universidad Nacional de San Juan.

______, and J. M. Parrish. 1997. A new poposaurid from the Upper Triassic of Argentina. Journal of Vertebrate Paleontology 17(Supplement to 3):548-556.

Azevedo, S. 1991. Prestosuchus chiniquensis Huene 1942 (Reptilia, Archosauria, Thecodontia, Proterosuchia, Rauisuchidae), da Formacao Santa Maria, Triassico do Estado do Rio Grande do Sul, Brasil. Tesis Doctoral, Universidade Federal do Rio Grande do Sul.

Barberena, M. C. 1978. A huge thecodont skull from the Triassic of Brazil. Pesquisas 7:111-129.

Benton, M. J. 1984. Rauisuchians and the success of dinosaurs. Nature 310:101.

______.1986. The late Triassic reptile Teratosaurus, a rauisuchian, not a dinosaur. Paleontology 29:293-301.

______, and J. M. Clark. 1988. Archosaur phylogeny and the relationships of the Crocodylia. Pp. 295-338 in: Phylogeny and Classification of the Tetrapods (M. J. Benton, ed.). Clarendon Press, Oxford.

Bonaparte, J. F. 1972. Los Tetrápodos del sector Superior de la Formación Los Colorados (Triásico Superior). 1 Parte. Opera Lilloana 22:1-183.

______. 1981. Descripción de Fasolasuchus tenax y su significado el la sistemática y evolución de los Thecodontia. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" 3:55-101.

______. 1982. Classification of the Thecodontia. Geóbios, Mémoire Spéciale 6:99-112.

Charig, A. J. 1957. New Triassic archosaurs from Tanganyika, including Mandasuchus and Teleocrater. Dissertation Abstracts, Cambridge University.

Chatterjee, S. 1985. Postosuchus, a new thecodontian reptile from the Triassic of Texas and the origin of tyrannosaurs. Philosophical Transactions of the Royal Society of London B 309:395-460.

______, and Majumdar P. K. 1987. Tikisuchus romeri, a new rauisuchid reptile from the late Triassic of India. Journal of Paleontology 61:787-793.

Dawley, R. M., J. M. Zawiskie, and J. W. Cosgriff. 1979. A rauisuchid thecodont from the Popo Agie Formation of Wyoming. Journal of Paleontology 53:1428-1431.

Gauthier, J. A. 1986. Saurischian monophyly and the origin of birds. Memoirs, California Academy of Sciences 8:1-55.

Gower, D. J., and A. G. Sennikov. 1996. Morphology and phylogenetic informativenness of early archosaur braincases. Palaeontology 39:883-906.

Huene, F. V. 1936. The constitution of the Thecodontia. American Journal of Science 5:207-217.

______. 1942. Die fossilen Reptilien des Südamerikanishen Gondwanalandes. Ergebnisse der Sauriergrabungen in Südbrasilien, 1928/1929. München: C. H. Beckshe.

______. 1956. Paläontologie und Phylogenie der neideren Tetrapoden. G. Fisher, editor. Jena.

Juul, L. 1994. The Phylogeny of basal archosaurs. Palaentologia Africana 31:1-38.

Krebs, B. 1965. Ticinosuchus ferox nov. gen. nov. sp. Ein neuer Pseudosuchier aus der Trias des Monte San Giorgio. Schweizerische Palaontologische Abhandlungen 81:1-140.

Long, R. A., and P. A. Murry. 1995. Late Triassic (Carnian and Norian) Tetrapods from the Southern United States. Bulletin of the New Mexico Museum of Natural History and Science.

Parrish, J.M. 1993. Phylogeny of the Crocodylotarsy, with reference to Archosaurian and Crurotarsan Monophyly. Journal of Vertebrate Paleontology 13 (Supplement to3):287-308.

Reig, O. A. 1959. Primeros datos descriptivos sobre nuevos reptiles arcosaurios del Triásico de Ischigualasto (San Juan, Argentina). Revista de la Asociación Argentina de Geología 13: 257-270.

Reig, O. A. 1961. Acerca de la posición sistemática de la familia Rauisuchidae y del género Saurosuchus (Reptilia -Thecodontia). Publicaciones del Museo Municipal de Ciencias Naturales y Tradicionales de Mar del Plata 3:73-114.

Romer, A. S. 1966. Vertebrate Paleontology. University of Chicago Press. 468 pp.

______. 1971. The Chañares (Argentina) Triassic reptile fauna. VIII. A fragmentary skull of a large thecodont, Luperosuchus fractus. Breviora 373:1-8.

______. 1972. The Chañares (Argentina) Triassic reptile fauna. XIII. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum gen. et sp. nov. Breviora 390:1-13.

Rogers, R. R., C. C. Swisheri, P. C. Sereno, A. M. Monetta, C. A. Forster, and R. N. Martinez. 1993. The Ischigualasto tetrapod assemblage (Late Triassic, Argentina) and argon-40/argon-39 dating of dinosaur origins. Science 260:794-797.

Sereno, P. C. 1991. Basal archosaurs: phylogenetic relationships and functional implications. Society of Vertebrate Paleontology Memoir 2:1-53.

______, and A. B. Arcucci. 1990. The Monophyly of crurotarsal archosaurs and the origin of bird and crocodile ankle joints. Neues Jahrbuch für Geologie und Palaontologie, Abhandlungen 180:21-52.

Sill, W. D. 1974. The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts. Bulletin of the Museum of Comparative Zoology 146: 317-362.

Walker, A. D. 1961. Triassic reptiles from the Elgin area: Stagonolepis, Dasygnathus and their allies. Philosophical Transactions of the Royal Society B 244:103-204.

Links

Other archosaurs from the Ischigualasto Formation scanned at UTCT:

The skull of Herrerasaurus ischigualastensis

The skull of Eoraptor lunensis

Literature
& Links

None available.

Additional
Imagery

To cite this page: Dr. Oscar Alcober, 2001, "Saurosuchus galilei" (On-line), Digital Morphology. Accessed October 21, 2014 at http://digimorph.org/specimens/Saurosuchus_galilei/.

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