Menadon besairiei: a Gomphodontosuchinae Traversodont Previously Only Found in Madagascar now Found in Middle-Upper Triassic Brazil

The Malagasy cynodont Menadon besairiei (Cynodontia; Traversodontidae) in the Middle–Upper Triassic of Brazil

Authors:

Melo et al

Abstract:

The traversodontid cynodont Menadon besairiei, previously known from the ‘Isalo II’ group of Madagascar, is reported for the first time from the Triassic of southern Brazil. New material referable to M. besairiei was collected in the Schoenstatt outcrop (Santa Cruz do Sul municipality), which belongs to the Santacruzodon Assemblage Zone (Carnian) in the Santa Maria Supersequence. Their attribution to the Malagasy taxon is based on the presence of a deep snout; four upper incisors, with procumbent first and second incisors, and three lower, procumbent incisors; five upper postcanines, the first one ‘peg-like’; six lower postcanines, the two most anterior and the most posterior being reduced; the quadrangular form of the postcanines; a pterygoid reaching the jugal and excluding the maxilla from the suborbital fenestra; a mandible with a tall coronoid process covering the last lower postcanine laterally; and a posteriorly projected angular process. A cladistic analysis of traversodontid cynodonts was performed based on a matrix composed of 30 taxa and 78 characters. In the resulting trees, M. besairiei nested within the clade Gomphodontosuchinae, the only traversodontid subclade reasonably well supported. Thus, the presence of M. besairiei is established in the Santa Cruz do Sul fauna, constituting the first record for South America and confirming the previously proposed biostratigraphic correlation between the ‘Isalo II’ and the Santacruzodon Assemblage Zone.