A new prozostrodontian cynodont (Therapsida) from the Late Triassic Riograndia Assemblage Zone (Santa Maria Supersequence) of Southern Brazil

Abstract

We report here on a new prozostrodontian cynodont, Botucaraitherium belarminoi gen. et sp. nov., from the Late Triassic Riograndia Assemblage Zone (AZ) of the Candelária Sequence (Santa Maria Supersequence), collected in the Botucaraí Hill Site, Candelária Municipality, state of Rio Grande do Sul, Brazil. The new taxon is based on a single specimen (holotype MMACR-PV-003-T) which includes the left lower jaw, without postdentary bones, bearing the root of the last incisor, canine and four postcanines plus one partial crown inside the dentary, not erupted, and two maxillary fragments, one with a broken canine and another with one postcanine. The features of the lower jaw and lower/upper postcanines resemble those of the prozostrodontians Prozostrodon brasiliensis from the older Hyperodapedon AZ and Brasilodon quadrangularis and Brasilitherium riograndensis from the same Riograndia AZ. The inclusion of Botucaraitherium within a broad phylogenetic analysis, positioned it as a more derived taxon than tritylodontids, being the sister-taxon of Brasilodon, Brasilitherium plus Mammaliaformes. Although the new taxon is based on few cranial elements, it represents a additional faunal component of the Triassic Riograndia AZ of southern Brazil, in which small-sized derived non-mammaliaform cynodonts, closely related to the origin of mammaliaforms, were ecologically well succeed and taxonomically diverse.

A new cynodont from the Santa Maria formation, south Brazil, improves Late Triassic probainognathian diversity

“…, , , ; Soares et al . ). The lower postcanine teeth of these forms bear a strong resemblance to those of Alemoatherium huebneri , mainly on the distribution and relative size of the cusps (Fig.…”

“…) within the clade Prozostrodontia (Liu & Olsen ; Soares et al . ; Martinelli et al . ) as supported by several apomorphic traits such as a slender zygomatic arch, no prefrontal and postorbital bones, a posteriorly extensive secondary palate, and constricted root on postcanine teeth (Bonaparte & Barberena ).…”

“…Prozostrodon brasiliensis , UFRGS‐PV‐248‐T, Bonaparte & Barberena ; Botucaraitherium belarminoi , MMACR‐PV‐003‐T, Soares et al . ). The crown is low, with slightly convex mesial and almost straight distal edges, lacking any kind of serrations.…”

“…; Soares et al . , ; Martinelli & Soares ) and Argentina (Romer , ; Bonaparte ; Bonaparte & Crompton ; Martínez & Forster ; Martínez et al . ; Martinelli & Rougier ) providing unique insights in the study of the major skeletal transformations prior to the mammalian condition (e.g.…”

A juvenile sauropodomorph tibia from the 'Botucaraí Hill', Late Triassic of Southern Brazil

“…The section shows occasional rithmic intervals with millimetric mudstone layers, as well as occasional mud intraclasts. The fossil record of the locality includes the dicynodont Jachaleria candelariensis Araújo & Gonzaga, 1980, the prozostrodontian cynodont Botucaraitherium belarminoi Soares, Martinelli & Oliveira, 2014, as well as an indeterminate phytosaur, a stereospondyl amphibian, and several isolated archosaur teeth (Araújo & Gonzaga, 1980;Dornelles, 1990;Kischlat & Lucas, 2003;Dias-da-Silva et al, 2009;Soares et al, 2014). An isolated tooth referred to Riograndia guaibensis was also reported by Soares et al (2011) from the upper portions of the outcrop.…”