Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America


Hypotheses of feeding behaviors and community structure are testable with rare direct evidence of trophic interactions in the fossil record (e.g., bite marks). We present evidence of four predation, scavenging, and/or interspecific fighting events involving two large paracrocodylomorphs (=‘rauisuchians’) from the Upper Triassic Chinle Formation (∼220–210 Ma). The larger femur preserves a rare history of interactions with multiple actors prior to and after death of this ∼8–9-m individual. A large embedded tooth crown and punctures, all of which display reaction tissue formed through healing, record evidence of a failed attack on this individual. The second paracrocodylomorph femur exhibits four unhealed bite marks, indicating the animal either did not survive the attack or was scavenged soon after death. The combination of character states observed (e.g., morphology of the embedded tooth, ‘D’-shaped punctures, evidence of bicarination of the marking teeth, spacing of potentially serial marks) indicates that large phytosaurs were actors in both cases. Our analysis of these specimens demonstrates phytosaurs targeted large paracrocodylomorphs in these Late Triassic ecosystems. Previous distinctions between ‘aquatic’ and ‘terrestrial’ Late Triassic trophic structures were overly simplistic and built upon mistaken paleoecological assumptions; we show they were intimately connected at the highest trophic levels. Our data also support that size cannot be the sole factor in determining trophic status. Furthermore, these marks provide an opportunity to start exploring the seemingly unbalanced terrestrial ecosystems from the Late Triassic of North America, in which large carnivores far outnumber herbivores in terms of both abundance and diversity.

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Field Museum of Natural History University of Chicago collections, Chicago, Illinois, U.S.A.


Field Museum of Natural History Fossil Reptile collections, Chicago, Illinois, U.S.A.


Ruth Hall Museum at Ghost Ranch, New Mexico, U.S.A.


Instituto Miguel Lillo, Tucuman, Argentina


Division of Paleontology of the Museo de Ciencias Naturales, Universidad Nacional de San Juan, Argentina


Texas Tech University Museum of Paleontology, Lubbock, Texas, USA


University of California Museum of Paleontology, Berkeley, California, USA


The High-Resolution X-ray Computed Tomography Facility at The University of Texas at Austin, Austin, Texas, U.S.A


Yale Peabody Museum, New Haven, Connecticut, USA


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Financial support for CT scanning was provided to MRS by the Jackson School of Geosciences and the William J. Powers, Jr. Presidential Graduate Fellowship, The University of Texas at Austin. Details related to FMNH PR 1694 were provided by W. Simpson. Information related to GR 264 was confirmed by A. Downs. Initial access to and data on GR 264 at UCMP was provided to SKD by P. Holroyd. Measurement data for some taxa in Table 1 of the Electronic Supplemental Data was provided by J. Desojo and B. Muller. Helpful discussion with C. Sumrall, S. Sheffield, R. Roney, and J. Horton, as well as informative comments from reviewer C. Brown, an anonymous reviewer, and editor S. Thatje, improved the quality of this manuscript.

The research presented in this study complies with all relevant state and federal laws. The authors declare that they have no conflicts of interest.

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Drumheller, S.K., Stocker, M.R. & Nesbitt, S.J. Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America. Naturwissenschaften 101, 975–987 (2014).

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  • Loricata
  • Phytosauria
  • Tooth
  • Computed tomography
  • Apex predator