Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians

<div><p>We describe two new cynodonts from the early Late Triassic of southern Brazil. One taxon, <i>Bonacynodon schultzi</i> gen. et sp. nov., comes from the lower Carnian <i>Dinodontosaurus</i> AZ, being correlated with the faunal association at the upper half of the lower member of the Chañares Formation (Ischigualasto-Villa Unión Basin, Argentina). Phylogenetically, <i>Bonacynodon</i> is a closer relative to <i>Probainognathus jenseni</i> than to any other probainognathian, bearing conspicuous canines with a denticulate distal margin. The other new taxon is <i>Santacruzgnathus abdalai</i> gen. et sp. nov. from the Carnian <i>Santacruzodon</i> AZ. Although based exclusively on a partial lower jaw, it represents a probainognathian close to <i>Prozostrodon</i> from the <i>Hyperodapedon</i> AZ and to <i>Brasilodon</i>, <i>Brasilitherium</i> and <i>Botucaraitherium</i> from the <i>Riograndia</i> AZ. The two new cynodonts and the phylogenetic hypothesis presented herein indicate the degree to which our knowledge on probainognathian cynodonts is incomplete and also the relevance of the South American fossil record for understanding their evolutionary significance. The taxonomic diversity and abundance of probainognathians from Brazil and Argentina will form the basis of deep and complex studies to address the evolutionary transformations of cynodonts leading to mammals.</p></div