The posterior margin of the squamosal, quadrate and quadratojugal slope strongly posteroventrally, a condition different from the subvertical orientation present in “protosuchians” and notosuchians 17, 18 (Fig. The new taxon helps fill the morphological gap between “protosuchian” grade and early branching mesoeucrocodylian crocodyliforms.īurkesuchus exhibits a dorsoventrally compressed braincase and cranium that is transversely wide at the posterior margin. The aim of the present contribution is to provide a preliminary description of Burkesuchus, emphasizing the particular combination of both derived and plesiomorphic characters. The paucity of the Jurassic crocodyliform fossil record of non-pelagic forms is one of the main reasons for uncertainties on the morphological changes that occurred between basal “protosuchians” and more derived mesoeucrocodylians. In the case of South America, Jurassic non-thalattosuchian crocodyliforms are solely represented by the putative paralligatorid Batrachomimus from the Upper Jurassic of Brazil 10. Jurassic non-pelagic crocodyliforms are represented by protosuchian-grade taxa and, on the other hand, by modern aspect neosuchians such as Goniopholididae, Atoposauridae and Pholidosauridae 1, 5– 9. Much less is known about non-pelagic crocodyliforms from this time span, complicating our understanding of diversification patterns and the origin of eusuchians and the line to modern crocodylians 2– 4. In contrast to the Cretaceous Period and Cenozoic Era, crocodyliforms from the Jurassic Period are predominantly known from marine forms (e.g., thalattosuchians) 1. This new discovery expands the meagre record of non-pelagic representatives of this clade for the Jurassic Period, and together with Batrachomimus, from Upper Jurassic beds of Brazil, supports the idea that South America represented a cradle for the evolution of derived crocodyliforms during the Late Jurassic. Phylogenetic analysis supports Burkesuchus as a basal member of Mesoeucrocodylia. A well-defined longitudinal groove runs along the lateral edge of the postorbital and squamosal, indicative of a anteroposteriorly extensive upper earlid.
Burkesuchus was a small-sized crocodyliform (estimated length 70 cm), with a cranium that is dorsoventrally depressed and transversely wide posteriorly and distinguished by a posteroventrally flexed wing-like squamosal.
Burkesuchus was found on the same levels that yielded titanosauriform and diplodocoid sauropods and the herbivore theropod Chilesaurus diegosuarezi, thus expanding the taxonomic composition of currently poorly known Jurassic reptilian faunas from Patagonia. The new taxon constitutes one of the few records of non-pelagic Jurassic crocodyliforms for the entire South American continent. , from the Upper Jurassic (Tithonian) Toqui Formation of southern Chile. We describe the basal mesoeucrocodylian Burkesuchus mallingrandensis nov.
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