First record of rhynchosaurs ( Archosauromorpha : Rhynchosauria : Hyperodapedontinae ) from the early Late Triassic Santacruzodon Assemblage Zone of the Santa Maria Supersequence, Brazil

Abstract

Rhynchosauria is a group of extinct, exclusively Triassic, terrestrial, and herbivorousarchosauromorphs, characterized by a peculiar maxillary-mandibularapparatus. They reached global distribution during the Carnian, with theHyperodapedontinae clade. The rhynchosaurian record from South America isincluded in the Ladinian-?earliest Carnian Dinodontosaurus AssemblageZone (Pinheiros-Chiniqua Sequence, Brazil) and Tarjadia Assemblage Zone(Chañares Formation, Argentina), and for strictly Carnian HyperodapedonAssemblage Zone (Lower Candelaria Sequence, Brazil) and Ischigualasto Formation(Argentina). Here, we present the first record of Hyperodapedontinaefrom the Brazilian Early Carnian Santacruzodon Assemblage Zone (Santa CruzSequence). The most diagnostic elements belong to a nearly complete left pes,which presents a combination of hyperodapedontine traits. The presence of asecond individual of cf. Hyperodapedontinae is based on a fragmentary, isolatedleft metatarsal IV. An isolated fragment of premaxilla could belong to thesecond specimen (based on preservation mode) or to a third individual. Thisnew report fills a gap within the South American rhynchosaurian distribution,strengthening biostratigraphic correlation with other regions from Gondwana(i.e., Madagascar), where similar and coeval faunas are known. The inclusionof these specimens in a phylogenetic dataset resulted in low resolution results,due to missing data because postcranial characters for rhynchosaurs are stillpoorly explored.