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| Sauropia macrorhinus Müller, Roberto-da-Silva, Aurélio & Kerber, 2026 Artwork by Caetano Soares. |
Abstract
The Middle Triassic fossil record of South American parareptiles is scarce, with only a few procolophonoid specimens known. Here, we describe Sauropia macrorhinus gen. et sp. nov., a procolophonoid from the Ladinian (Pinheiros-Chiniquá Sequence of the Santa Maria Supersequence) of southern Brazil. The holotype, a nearly complete skull measuring only 9.5 mm in length, represents the smallest tetrapod known from these deposits. Its unique combination of features includes a proportionally large external naris, slender dorsal ramus of the maxilla, broad interorbital space, and three premaxillary teeth. Phylogenetic analyses consistently recover Sauropia macrorhinus gen. et sp. nov. as an early-diverging procolophonid, although its phylogenetic placement is complicated by its putatively immature ontogenetic stage. Its morphology provides valuable insight into early developmental stages of parareptiles and contributes to the understanding of Middle Triassic terrestrial ecosystems. Based on size and dentition, the new taxon was likely insectivorous or fed on other small invertebrates, possibly being predated upon by small carnivorous organisms. This discovery expands the taxonomic and ecological diversity known for Middle Triassic faunas of South America and enhances our understanding of the structure and complexity of terrestrial food webs in Middle Triassic ecosystems, preceding the Carnian Pluvial Episode and the rise of dinosaurs.
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| Results of the phylogenetic analysis and ordinary linear regressions. (a) Time-calibrated reduced global strict consensus tree depicting the phylogenetic position of Sauropia macrorhinus gen. et sp. nov. Values on the branches represent absolute (left) and GC (right) frequencies from symmetric resampling with no-zero weighting. The temporal bars for each OTU represent the maximum and minimum ages of each geological unit. Geological Time Scale was generated with GIMP version 2.8 (https://www.gimp.org/). Artistic representation of Sauropia macrorhinus gen. et sp. nov. by Caetano Soares. (b) Scatter plots of log-transformed measurements of the skull length and the orbitotemporal length of selected procolophonoids (n = 31). Linear regression line is shown in black, with the 0.95 confidence interval indicated by red dotted lines. |
Systematic paleontology
Parareptilia Oslo, 1947
Procolophonoidea Romer, 1956
cf. Procolophonidae Seeley, 1888
Sauropia macrorhinus gen. et sp. nov.
Holotype CAPPA/UFSM 0510, an almost complete skull with mandible in occlusion.
Diagnosis: Sauropia macrorhinus differs from all other known procolophonoids with comparable material in (*local autapomorphies): Skull nearly as wide as it is long; proportionally large external naris (taller than the orbitotemporal fenestra)*; broad interorbital space in dorsal view; posterior margin of the orbitotemporal fenestra almost reaching the posterior end of the skull; premaxillae bearing three teeth; slender dorsal ramus of the maxilla*; absence of a temporal fenestra bordered anteriorly by the postorbital; U-shaped mandible in ventral view; and anterior maxillary teeth with a circular cross-section (not labiolingually expanded) and lacking a basal constriction.
Etymology: The genus name combines the Greek word “sauros” (= lizard) and the Portuguese word “piá” (= young boy), a regional term from southern Brazil rooted in Gaúcho culture, particularly in the state of Rio Grande do Sul, where it is commonly used to refer to a child. The name alludes to the small size and putative early ontogenetic stage of the holotype. The specific epithet combines the Greek words “makros” (= large) and “rhinos” (= nose or snout), in reference to the proportionally enlarged external naris of the holotype.
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| Artistic representation of Sauropia macrorhinus gen. et sp. nov. Artwork by Caetano Soares. |
Rodrigo T. Müller, Lúcio Roberto-da-Silva, Pedro Lucas Porcela Aurélio and Leonardo Kerber. 2026. The Smallest Tetrapod from the Middle Triassic of South America: A New procolophonoid parareptile from the Ladinian of Southern Brazil. Scientific Reports. 16: 866. DOI: doi.org/10.1038/s41598-026-35114-3 [28 January 2026]