New rhadinosuchine proterochampsids from the late Middle‐early Late Triassic of southern Brazil enhance the diversity of archosauriforms

Abstract

Proterochampsidae is a clade of non‐archosaurian archosauriforms restricted to the Middle to the Late Triassic of the Ischigualasto‐Villa Unión Basin of Argentina and the Santa Maria Supersequence of Brazil. A reappraisal of proterochampsid specimens from the Brazilian Dinodontosaurus Assemblage Zone (AZ) of the Pinheiros‐Chiniquá Sequence (late Ladinian‐early Carnian) is presented here. One of the specimens was preliminary assigned to Chanaresuchus sp., whose type species comes from the Massetognathus‐Chanaresuchus AZ of the Chañares Formation of Argentina. However, our revision indicates that it differs from Chanaresuchus, being more closely related to the middle‐late Carnian Rhadinosuchus gracilis. We therefore propose the new taxon, Pinheirochampsa rodriguesi, to reallocate this specimen. Additionally, we present a revision of other putative Chanaresuchus occurrences in Brazil, including the only known specimen described for the Santacruzodon AZ (Santa Cruz do Sul Sequence; early Carnian), also proposing it as a new taxon: Kuruxuchampsa dornellesi. Both new species are characterized, among other features, by transverse expansion of the anterior end of the rostrum, similar to the condition present in Rhadinosuchus, but absent in Chanaresuchus, Gualosuchus, Pseudochampsa, and non‐rhadinosuchine proterochampsids. These two new species expand the growing knowledge of the non‐archosaurian archosauriform diversity during the Middle‐Late Triassic in South America and enhance faunal and chronological comparisons between approximately coeval geological units between Argentina and Brazil.

Cranial osteology and paleoneurology of Tarjadia ruthae: An erpetosuchid pseudosuchian from the Triassic Chañares Formation (late Ladinian‐?early Carnian) of Argentina

“…The recognition of two Azs in the lower half of the Chañares Formation based on stratigraphically controlled fossils and datings (Ezcurra et al, 2017Ezcurra, Nesbitt, Fiorelli, & Desojo, 2020) supported the hypothesis that the Dinodontosaurus AZ could bear two subzones (Martinelli et al, 2017). However, outcrop correlations along southern Brazil are far from being clearly understood and most key fossils lack a controlled stratigraphic provenance (Martinelli et al, 2017;Paes Neto et al, 2024). The closely related erpetosuchids Tarjadia from Argentina and Archeopelta from Brazil support the biostratigraphical relationships of the Tarjadia AZ of the Chañares Formation with the Dinodontosaurus AZ sensu lato.…”

“…The Chañares Formation of the Ischigualato-Villa Uni on Basin (Argentina) and the Dinodontosaurus AZ of the Pinheiros-Chiniqu a Sequence, Santa Maria Supersequence (Brazil) have been traditionally considered coeval, around the lastest Middle to earliest Late Triassic span, due to having in common several taxa at specific (e.g., the cynodonts Massetognathus pascuali and Chiniquodon theotonicus), generic (e.g., the kannemeyeriiform Dinodontosaurus), and familiar/subfamiliar level (e.g., probainognathids, stenaulorhynchines, proterochampsids, erpetosuchids, lagerpetids) (Escobar et al, 2021;Ezcurra et al, 2017;Kammerer & Ordoñez, 2021;Langer et al, 2007;Martinelli et al, 2016Martinelli et al, , 2017Müller et al, 2023;Ordoñez et al, 2020;Paes Neto et al, 2024;Schultz et al, 2020). In the last years refinement of taxonomic proposals, stratigraphically controlled fossil collections and radiometric data have been considerably improved the relationships among faunal associations of western Argentina and southern Brazil (e.g., Desojo, Fiorelli, et al, 2020;Ezcurra et al, 2017;Langer et al, 2018;Martinelli et al, 2017;Philipp et al, 2018;Schmitt et al, 2019).…”

The dawn of an Era: New contributions on comparative and functional anatomy of Triassic tetrapods

“…Furthermore, the authors perform a comprehensive phylogenetic analysis, encompassing other chiniquodontids, demonstrating the existence of a lineage within Chiniquodontidae, the Aleodontinae, comprising forms found in both Africa and South America. Concerning late Middle to early Late Triassic archosauriforms, Paes‐Neto et al (2024, this issue) describe two new taxa belonging to the enigmatic proterochampsids. Typically specialized with bizarre morphologies, proterochampsids are a group of archosauriforms hitherto endemic to South America.…”

The redescription of Malerisaurus robinsonae (Archosauromorpha: Allokotosauria) from the Upper Triassic lower Maleri Formation, Pranhita‐Godavari Basin, India

“…In order to reassess the phylogenetic relationships of Malerisaurus robinsonae we merged, into a single dataset, the most recent iterations of the phylogenetic data matrix of the CoArTreeP (the Complete Archosauromorph Tree Project; see Ezcurra, 2016 for the first iteration of this project), which were published by Ezcurra et al (2023), Müller et al (2023), andPaes-Neto et al (2024). This is the most extensive phylogenetic dataset currently available for Permian and Triassic archosauromorphs.…”

“…Scale bars equal 5 mm. ambiguous in Müller et al, 2023), Augustaburiania vatagini as a deeply nested tanystropheid and not as a dinocephalosaurid (but as in Müller et al, 2023), Amotosaurus rotfeldensis as the sister taxon to Raibliania calligarisi and not in more distant positions within Tanystropheidae, the Long Reef proterosuchian as more closely related to the Erythrosuchidae + Eucrocopoda clade than to Proterosuchidae (not included in Müller et al, 2023 andPaes-Neto et al, 2024), and Tawa hallae as an herrerasaurian and not as closer to Neotheropoda than to Herrerasaurus ischigualastensis (but as in Müller et al, 2023).…”