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Apex predators trophic interactions in Late Triassic of western North America



Ben Creisler
bcreisler@gmail.com

A new online paper:

Stephanie K. Drumheller, Michelle R. Stocker & Sterling J. Nesbitt (2014)
Direct evidence of trophic interactions among apex predators in the
Late Triassic of western North America.
Naturwissenschaften (advance online publication)
DOI: 10.1007/s00114-014-1238-3
http://link.springer.com/article/10.1007/s00114-014-1238-3

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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