Body mass estimates of phytosaurs (Archosauria: Parasuchidae) from the Petrified Forest Formation (Chinle Group: Revueltian) based on skull and limb bone measurements.

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Andrew B. Heckert Ph.D., Assistant Professor of Geology (Creator)
Institution
Appalachian State University (ASU )
Web Site: http://www.library.appstate.edu/

Abstract: Phytosaurs were the largest and most common semi-aquatic predators of the Late Triassic. Although their skulls are relatively common in the fossil record, articulated, or even associated skeletons are extremely rare, so it has always been difficult to gauge just how large (mass or length) an individual phytosaur may have been. Body mass in particular is an important physiological variable, often used for the scaling of organs, biomass determination, biomechanics, and locomotion. We take advantage of phytosaurs’ general similarity to extant crocodilians to attempt to reconstruct body mass and length based on measurements of the skulls and limbs of phytosaurs from the Upper Triassic Snyder and Canjilon quarries in north-central New Mexico. These quarries, in the Painted Desert Member of the Petrified Forest Formation (Revueltian: early-mid Norian) preserve catastrophic death assemblages that appear to well-represent discrete populations of phytosaurs. We also utilize a snout-vent measurement based on an articulated skeleton from the Canjilon quarry to compare the accuracy of different equations based on discrete limb elements. Body mass estimates for Snyder quarry phytosaurs range between 25 and 500 kg, with most specimens yielding estimates of approximately 200-350 kg. The Canjilon quarry sample encompasses fewer juveniles and more robust adults, including one individual that may have weighed as much as 535 kg. From equations based on nine extant crocodilian genera, these Revueltian phytosaurs appear to have approached 4.5 m total body length for a ~ 400 kg phytosaur. The prevalence of subadult to adult phytosaurs in both quarries based on body mass estimates corroborates qualitative estimates of the population structure based on skull sizes alone, thereby reinforcing the hypothesis that both quarries are catastrophic assemblages.

Additional Information

Publication
Hurlburt, G.R., Heckert, A.B., and Farlow, J.O., (2003) Body mass estimates of phytosaurs (Archosauria: Parasuchidae) from the Petrified Forest Formation (Chinle Group: Revueltian) based on skull and limb bone measurements. New Mexico Museum of Natural History and Science Bulletin 24 (Paleontology and Geology of the Upper Triassic (Revueltian) Snyder Quarry, New Mexico) p. 105-113. (ISSN 1524-4156) Archived in NC DOCKS with permission of the editor. The version of record is available at: http://econtent.unm.edu/
Language: English
Date: 2003