# The smallest tetrapod from the Middle Triassic of South America: a new procolophonoid parareptile from the Ladinian of Southern Brazil

## TL;DR

A new tiny reptile species from the Middle Triassic of Brazil expands our understanding of ancient ecosystems and reptile diversity.

## Contribution

The discovery of the smallest known tetrapod from the Middle Triassic of South America, Sauropia macrorhinus.

## Key findings

- Sauropia macrorhinus is the smallest tetrapod known from the Middle Triassic of South America.
- The species exhibits unique morphological features and likely occupied a niche as an insectivore in early food webs.
- The find enhances understanding of Middle Triassic terrestrial ecosystems before the rise of dinosaurs.

## 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.

The online version contains supplementary material available at 10.1038/s41598-026-35114-3.