New cranial and postcranial elements of Mourasuchus (Alligatoroidea: Caimaninae) from the late Miocene of Venezuela and their palaeobiological implications

ABSTRACT

A partial skeleton of Mourasuchus, one of the most peculiar crocodylians of all time, that includes cranial and postcranial elements recovered from the late Miocene bone-beds of the Urumaco Formation (northwestern Venezuela) is herein described. Based on the presence of tall squamosal eminences, we assigned it to Mourasuchus arendsi. To provide an empirical assessment of the palaeobiological affinities of Mourasuchus, we performed estimations of the body mass and body length based on several Mourasuchus skull measurements, and an analysis of death roll capability. Our results indicate that Mourasuchus was indeed a large crocodylian, with a body length bigger than 9 m and weighed more than 4 tons. We find that Mourasuchus arendsi was incapable of executing the ‘death roll’ as a feeding behaviour and as such was unable to predate giant mammals, which are relatively common in the Urumaco Formation. Finally, the specimen includes a slender humerus, which may indicate that Mourasuchus had weak forelimbs and would spend more time in the water.

KEYWORDS:

• Mourasuchus
• Mourasuchus arendsi
• ‘death roll’
• Urumaco Formation
• palaeobiology
• palaeoecology

Acknowledgments

The Instituto del Patrimonio Cultural (Venezuela) provided permission for the collection of the fossil material. We thank D. Ruiz, M. Nuñez, L. Sánchez and C. Cáceres for their work and camaraderie during salvage excavations in the field. We are very grateful to G. Ojeda and J. Reyes for providing us access to the holotype specimen of M. arendsi at CIAAP, UNEFM, Coro, Venezuela. We thank Lucy Souza for comments and discussions on postcranial anatomy. We are indebted to Alexander K. Hastings and two anonymous reviewers for criticism and suggestions that greatly improved the manuscript.

Disclosure statement

The authors declare they have no conflicts of interest in the publication of this paper.

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Additional information

Funding

This work was supported by the [Instituto Venezolano de Investigaciones Científicas – IVIC] under Grant [1096] to ADR; [Fundação de Amparo à Pesquisa do Estado de São Paulo –FAPESP] under Grant [2013/04516-1] to GMC; [Conselho de Desenvolvimento Científico e Tecnológico – CNPq] under Grant [40808/2016-7] to GMC; [Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil – CAPES] under Grant [Finance Code 001] to GMC; and [Conicyt–PCHA] under grant [Doctorado Nacional/2018–21180471] to AS; Consejo Nacional de Innovación, Ciencia y Tecnología [Doctorado Nacional/2018–21180471]; Conselho Nacional de Desenvolvimento Científico e Tecnológico [40808/2016-7]; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior [Finance Code 001]; Fundação de Amparo à Pesquisa do Estado de São Paulo [2013/04516-1]; Instituto Venezolano de Investigaciones Científicas [1096].