Monday, March 1, 2021

[Paleontology • 2021] Oryporan insolitus • An Early‐diverging Procolophonid from the lowermost Triassic of South America and the Origins of Herbivory in Procolophonoidea

Oryporan insolitus 
Pinheiro, Silva‐Neves & Da‐Rosa, 2021

Illustration: Márcio L. Castro. 

Procolophonoidea was the only parareptile clade to survive the end‐Permian mass extinction, and they experienced a major adaptive radiation during the Triassic. The flourishing of procolophonoid lineages in highly stressful post‐extinction environments may be, at least in part, a result of their early adaptations to herbivory, which would eventually become the most common feeding strategy in later representatives of the group. Although procolophonoids are comparatively diverse in the South African Lystrosaurus declivis Assemblage Zone, only the Gondwanan widespread taxon Procolophon trigoniceps has been thus far reported in South American deposits of similar age. Here, we present a new procolophonid genus and species from the Lower Triassic Sanga do Cabral Formation of Brazil. Oryporan insolitus gen. et sp. nov. combines typical adaptations suggestive of herbivory with primitive character states that are peculiar to early procolophonoids. Accordingly, phylogenetic analysis places the new species as an early‐diverging procolophonid, thus far the phylogenetically earliest to develop apparent adaptations for herbivory. Character optimization shows that the bulbous, labiolingually expanded molariforms of most procolophonids (usually interpreted as indicative of high‐fibre herbivory) were co‐opted from an insectivorous dentition. The new taxon also highlights the diversity of feeding habits displayed by Early Triassic procolophonoids, which was probably crucial for the survival of the clade in post‐extinction disaster communities.

Keywords: Gondwana, Parareptilia, Lower Triassic, feeding ecology, phylogeny


Genus ORYPORAN nov.
Type and only known species: Oryporan insolitus gen. et sp. nov.

Derivation of name: In the indigenous Guaraní Language (Mbyá dialect), the epithet Oryporan can be translated as beautiful (porã) smile (ory), in reference to the well‐preserved, smile‐like tooth series of the holotype. Pronounced ‘Oh‐ree-pow‐ran’.

Oryporan insolitus sp. nov.
Derivation of name: Latin. Insolitus, meaning rare, unusual.

Holotype: UFSM 11443 (Figs 2, 3), an incomplete skull with the mandible still in occlusion.

Type locality: Bica São Tomé locality (Da‐Rosa et al. 2009), São Francisco de Assis municipality, Rio Grande do Sul State, Brazil.

Type horizon: The Bica São Tomé fossil site is probably the most prolific outcrop thus far known from the Sanga do Cabral Formation. This sedimentary unit is considered to be Induan or Olenekian (Lower Triassic) mainly based on the abundant occurrences of the Gondwanan widespread procolophonid Procolophon trigoniceps. As such, the Sanga do Cabral Formation is probably correlated to the upper Katberg Formation of the Karoo Basin (Lystrosaurus declivis Assemblage Zone, South Africa) (Botha & Smith 2006; Dias‐da‐Silva et al. 2006, 2017). The outcrop is characterized by fine sandstone red beds, intercalated with coarse sandstones and intraformational conglomerates. Besides P. trigoniceps and Oryporan insolitus gen. et sp. nov., the Bica São Tomé site has already yielded the archosauromorphs Teyujagua paradoxa and Elessaurus gondwanoccidens (Pinheiro et al. 2016, 2020; De‐Oliveira et al. 2020), the capitosauroid temnospondyl Tomeia witecki (Eltink et al. 2016), and several as yet unpublished specimens. For a thorough description of the Sanga do Cabral Formation and Bica São Tomé geology and deposition environment, see Da‐Rosa et al. (2009) and Dias‐Da‐Silva et al. (2017).

Diagnosis: Oryporan insolitus gen. et sp. nov. can be distinguished from all other known procolophonids based on the following combination of characters (autapomorphies are designated with an asterisk(*)): at least 12 maxillary teeth; 12 dentary teeth; dentition is not inset from the maxillary surface; anterior maxillary teeth are D‐shaped in cross‐section*; maxillary and dentary molariforms are bulbous, labiolingually expanded and bicuspid, lacking labiolingual ridges; anterior dentary teeth are blunt and well‐spaced from each other*; maxillary molariform labial cusps are higher than their lingual counterparts; dentary molariform lingual cusps are higher than their labial counterparts*.

Felipe L. Pinheiro, Eduardo Silva‐Neves and Átila A. S. Da‐Rosa. 2021. An Early‐diverging Procolophonid from the lowermost Triassic of South America and the Origins of Herbivory in Procolophonoidea. Papers in Palaeontology. DOI: 10.1002/spp2.1355