A new genus and species of proterochampsid archosauriform has been identified from an almost complete fossilized hindlimb found in southern Brazil.
Artistic representation of a Middle-Late Triassic landscape of southern Brazil depicting two individuals of the proterochampsid archosauriform Retymaijychampsa beckerorum. Image credit: Caio Fantini.
Retymaijychampsa beckerorum roamed our planet during the Late Triassic epoch, some 237 million years ago.
The ancient reptile was a member of Proterochampsidae, a large group of carnivorous archosauriforms that were endemic to South America.
They had dermal armor and long, crocodile-like skull, and most likely filled an ecological niche similar to modern crocodiles.
“The Triassic period witnessed the emergence and extinction of numerous groups of reptiles, including the Proterochampsidae,” said Dr. Rodrigo Müller, a paleontologist with the Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia at the Universidade Federal de Santa Maria.
“Although this clade was previously considered endemic to South America, recent phylogenetic investigations indicate a broader geographical distribution.”
“The oldest known proterochampsids have been found in the Ladinian/lower Carnian deposits of Argentina and Brazil, whereas the most recent records come from the upper Carnian/lower Norian in the same region.”
“Phylogenetic analyses place Proterochampsidae within Proterochampsia, a clade of archosauriforms that is the sister-group to Archosauria.”
“Because of its affinities, the clade is particularly important for understanding the early evolution of archosaurs,” he added.
“In addition, proterochampsids evolved a relatively diverse array of body plans, with some forms exhibiting putative semi-aquatic adaptations, whereas others were adapted to a terrestrial life style.”
The holotype fossil of Retymaijychampsa beckerorum was excavated at the Linha Várzea 2 (Becker) site of the Santa Maria Formation in the municipality of Paraíso do Sul, Rio Grande do Sul, Brazil.
“The specimen consists of an almost complete and articulated hindlimb, making it one of the few specimens with these bones preserved from Brazil,” Dr. Müller said.
The discovery of Retymaijychampsa beckerorum partially fills a long ghost lineage extending from the Middle Triassic to the early Late Triassic.
“Retymaijychampsa beckerorum represents the second proterochampsid from the Pinheiros-Chiniquá Sequence of Brazil and comprises one of the oldest proterochampsids worldwide,” the paleontologist said.
“It has a diagnostic set of hindlimb traits and is phylogenetically close to Proterochampsa, partially filling a ghost lineage of proterochampids more closely related to Proterochampsa than to Rhadinosuchinae.”
“Finally, the co-occurrence of Retymaijychampsa beckerorum and Pinheirochampsa rodriguesi provides further support for the idea of high ecomorphological diversity among proterochampsians in Middle to early Late Triassic environments.”
A paper about the discovery was published online in the journal Acta Palaeontologica Polonica.
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R.T. Müller. 2025. A new proterochampsid archosauriform from the Middle-Upper Triassic of Southern Brazil. Acta Palaeontologica Polonica 70 (1): 7-16; doi: 10.4202/app.01204.2024
