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.

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.

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.

Literature

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Links

Other archosaurs from the Ischigualasto Formation scanned at UTCT:

The skull of Herrerasaurus ischigualastensis

The skull of Eoraptor lunensis

None available.