New rhadinosuchine proterochampsids from the late Middle-early Late Triassic of southern Brazil enhance the diversity of archosauriforms

Abstract

Proterochampsidae is a clade of non-archosaurian archosauriforms restrictedto the Middle to the Late Triassic of the Ischigualasto-Villa Union Basin ofArgentina and the Santa Maria Supersequence of Brazil. A reappraisal of proterochampsidspecimens from the Brazilian Dinodontosaurus AssemblageZone (AZ) of the Pinheiros-Chiniqua Sequence (late Ladinian-early Carnian)is presented here. One of the specimens was preliminary assigned to Chanaresuchussp., whose type species comes from the Massetognathus-ChanaresuchusAZ of the Chañares Formation of Argentina. However, our revisionindicates that it differs from Chanaresuchus, being more closely related to themiddle-late Carnian Rhadinosuchus gracilis. We therefore propose the newtaxon, Pinheirochampsa rodriguesi, to reallocate this specimen. Additionally,we present a revision of other putative Chanaresuchus occurrences in Brazil,including the only known specimen described for the Santacruzodon AZ (SantaCruz do Sul Sequence; early Carnian), also proposing it as a new taxon: Kuruxuchampsadornellesi. Both new species are characterized, among other features, bytransverse expansion of the anterior end of the rostrum, similar to the conditionpresent in Rhadinosuchus, but absent in Chanaresuchus, Gualosuchus, Pseudochampsa,and non-rhadinosuchine proterochampsids. These two new species expand the growing knowledge of the non-archosaurian archosauriform diversityduring the Middle-Late Triassic in South America and enhance faunal and chronologicalcomparisons between approximately coeval geological units betweenArgentina and Brazil.