PT  - JOURNAL ARTICLE
AU  - Felipe C. Montefeltro
AU  - Stephan Lautenschlager
AU  - Pedro L. Godoy
AU  - Gabriel S. Ferreira
AU  - Richard J. Butler
TI  - A unique predator in a unique ecosystem: modelling the apex predator from the Late Cretaceous crocodyliform-dominated fauna in Brazil
AID  - 10.1101/843334
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 843334
4099  - http://biorxiv.org/content/early/2019/11/15/843334.short
4100  - http://biorxiv.org/content/early/2019/11/15/843334.full
AB  - Theropod dinosaurs were relatively scarce in the Late Cretaceous ecosystems of southeast Brazil. Instead, the abundant hypercarnivore crocodyliforms known as baurusuchids were probably playing the ecological role as apex predators. Baurusuchids exhibited a series of morphological adaptations associated to this ecological role, but quantitative biomechanical assessments to support this were lacking to date. Here, we employ a biomechanical modelling approach, using finite element analysis (FEA) on skull and mandible models of a baurusuchid specimen, allowing us to characterise the craniomandibular apparatus of baurusuchids, as well as to test the hypothesis that their functional morphology allowed them to outcompete other carnivores, such as theropods. Our results demonstrate, for the first time, the ecological role of this group as specialised apex predators in the continental Late Cretaceous ecosystems of South America. With a with a relatively weak bite force (~600 N), baurusuchids preying strategies probably relied on other morphological specializations, such as ziphodont dentition and strong cervical musculature. Consistently, comparative assessments of the stress distribution and magnitude of scaled models of other predators (the theropod Allosaurus fragilis and the living crocodylian Alligator mississippiensis) show discrepant responses to loadings under the same functional scenarios, further suggesting considerably distinct predatory behaviors for these animals. The unique selective pressures from the arid to semi-arid Late Cretaceous palaeoecosystems of southeast Brazil, which were dominated by crocodyliforms, possibly drove the emergence and evolution of such exclusive set of biomechanical features seen in baurusuchids, which had not been previously reported for any other predatory taxon.