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| Parvosuchus aurelioi Müller, 2024 Artwork by Matheus Fernandes. |
Abstract
Before the rise of dinosaurs and pterosaurs, pseudosuchians—reptiles from the crocodilian lineage—dominated the Triassic land ecosystems. This lineage diversified into several less inclusive clades, resulting in a wide ecomorphological diversity during the Middle and Late Triassic. Some giant pseudosuchians occupied the top of the trophic webs, while others developed extensive bony armor as a defense mechanism, which later evolved as a convergence in the avemetatarsalian lineage. On the other hand, there were groups like the Gracilisuchidae, which was composed of carnivorous forms with lightweight build and less than 1 m in length. The fossil record of gracilisuchids is geographically restricted to China and Argentina, with one ambiguous record from Brazil. In the present study, the first unambiguous gracilisuchid from Brazil is described. Parvosuchus aurelioi gen. et sp. nov. comes from the Dinodontosaurus Assemblage Zone of the Santa Maria Formation, which is associated with the Ladinian-Carnian boundary. Composed of a complete cranium, vertebrae, pelvic girdle and hindlimbs, the new species nests with Gracilisuchus stipanicicorum and Maehary bonapartei in a phylogenetic analysis. Its discovery fills a taxonomic gap in Brazilian pseudosuchian fauna and reveals the smallest known member of this clade from the Dinodontosaurus Assemblage Zone, highlighting the diversity of pseudosuchians during the moment that preceded the dawn of dinosaurs.
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| Skull and lower jaws of Parvosuchus aurelioi gen. et sp. nov. Holotype (CAPPA/UFSM 0412) from the Pinheiros-Chiniquá Sequence (Ladinian-Carnian boundary) of the Santa Maria Supersequence, southern Brazil. |
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| Provenance of Parvosuchus aurelioi gen. et sp. nov. (a) Location and geological context of the Linha Várzea 2 site, Paraíso do Sul, Rio Grande do Sul, Brazil. (b) General view of the Linha Várzea 2 site (taken in January 2023). (c) Hypothetical reconstruction of the skeleton of the Parvosuchus aurelioi gen. et sp. nov. depicting (in orange) the preserved portions of CAPPA/UFSM 0412. Unpreserved portions are based on the skeletal reconstruction of Gracilisuchus stipanicicorum by Jorge González. |
Systematic paleontology
Archosauria Cope, 1869
Pseudosuchia Zittel, 1887–1890
Gracilisuchidae Butler et al., 2014
Parvosuchus aurelioi gen. et sp. nov.
Holotype: CAPPA/UFSM 0412, a partial skeleton, including a skull with lower jaws, 11 dorsal vertebrae, two sacral vertebrae, a complete pelvic girdle, both femora (lacking the distal portion), partial left tibia, partial left fibula, and left calcaneum.
Etymology: The genus name combines the Latin word “parvus” (= small) and the Greek word “suchus” (= crocodile). The specific epithet honors Pedro Lucas Porcela Aurélio for his passion for paleontology and prospecting, as well as for having discovered the fossil material described here.
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| Results of the phylogenetic analysis and diversity of the Dinodontosaurus Assemblage Zone of Brazil. (a) Time-calibrated reduced strict consensus tree depicting the phylogenetic position of Parvosuchus aurelioi gen. et sp. nov. Number on nodes represent Bremer support values higher than 1. The temporal bars for each OTU represent the maximum and minimum ages of each geological unit. Divergence times set as approximately 1 million years. (b) Percentage of taxonomic groups recorded in the Dinodontosaurus Assemblage Zone according to the number of species. (c) Approximate body length of pseudosuchian species from the Dinodontosaurus ZA. |
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| Artistic representation of a Middle-Late Triassic landscape of southern Brazil. (a) A large Prestosuchus chiniquensis feeds on the carcass of a dicynodont while individuals of Parvosuchus aurelioi gen. et sp. nov. compete for scraps. (b) and (c) depict details of individuals of Parvosuchus aurelioi gen. et sp. nov. Artwork by Matheus Fernandes. |
Rodrigo T. Müller. 2024. A New small-sized predatory pseudosuchian Archosaur from the Middle-Late Triassic of Southern Brazil. Scientific Reports. 14, 12706. DOI: 10.1038/s41598-024-63313-3
