An early‐diverging procolophonid from the lowermost Triassic of South America and the origins of herbivory in Procolophonoidea

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Teyujagua paradoxa is a remarkable early archosauromorph from the Lower Triassic Sanga do Cabral Formation, Brazil. The species was originally described from an almost complete skull and a few associated cervical vertebrae, and no further postcranial elements were known at that time. Additional fieldwork in the Sanga do Cabral Formation, however, was successful in recovering a fairly complete postcranial skeleton attributable to the holotype. Here, we describe this new postcranial material, which is composed of cervical, dorsal, sacral and caudal vertebrae, limbs, pectoral and pelvic girdles, ribs, and gastralia. The description of its postcranial skeleton makes T. paradoxa one of the best‐known early‐diverging archosauromorphs. The cladistic analysis performed after the scoring of postcranial data recovered T. paradoxa in the same position initially described, close to the node that defines the Archosauriformes. Teyujagua paradoxa shares morphological features with representatives of early‐diverging archosauromorphs and archosauriforms, with certain traits demonstrating a mosaic of plesiomorphic and apomorphic character states. We also performed partitioned morphospace and disparity analysis to elucidate the morphological disparity and evolutionary patterns among archosauromorphs. Teyujagua paradoxa occupies a notable position, suggesting an intermediate morphology between early archosauromorphs and proterosuchids. Disparity estimates highlighted Pseudosuchia and Avemetatarsalia as having the highest median disparity, reflecting their diverse cranial and postcranial morphologies, respectively. These findings offer valuable insights into archosauromorph macroevolution and adaptation.

“…Result of the Parsimony phylogenetic analysis of Teyujagua paradoxa (UNIPAMPA 653) in the matrix of Pinheiro et al (2020). …”

Section: Resultsmentioning

confidence: 99%

The postcranial skeleton of Teyujagua paradoxa (Reptilia: Archosauromorpha) from the early Triassic of South America

De‐Oliveira,

Da Silva,

Kerber

et al. 2024

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Section: Phylogenetic Methodsmentioning

confidence: 99%

“…To determine the relationships of Libognathus sheddi among procolophonids, we conducted a phylogenetic analysis using the latest renditions of the Cisneros (2008a) analysis of procolophonid relationships, that of Hamley et al (2021), Pinheiro et al (2021), andButler et al (2024). We merged these three matrices, adding the scorings of Oryporan insolitus by Pinheiro et al (2021), and Hwiccewyrm (Butler et al, 2024) into the more unified matrix of Hamley et al (2021). We replaced the taxon "Owenettidae" with three separate owenettid taxa: Saurodektes kitchingorum, based on personal observation of the holotype BP/1/4195; Barasaurus besairei, based on the descriptions of Meckert (1995); and Candelaria barbouri based on the descriptions of Cisneros et al (2004) and Müller (2021).…”

Section: Phylogenetic Methodsmentioning

confidence: 99%

Cranial anatomy of Libognathus sheddiSmall, 1997 (Parareptilia, Procolophonidae) from the Upper Triassic Dockum Group of West Texas, USA

Mueller,

Small,

Jenkins

et al. 2023

Libognathus sheddi, a leptopleuronine procolophonid from the Upper Triassic Cooper Canyon Formation, Dockum Group, West Texas, was based on an isolated left dentary and partial coronoid. New material referable to Libognathus sheddi, from the Cooper Canyon Formation, provides new information on the cranial anatomy. This new cranial material includes the antorbital portion of a skull, a left maxilla and premaxilla, quadratojugals, and dentaries, including intact tooth rows in the upper and lower jaws. Libognathus shows autapomorphies including; dentary deep with ventral margin oblique to tooth row immediately from the symphysis at ≥23°; anterior projecting coronoid contacting the lingual surface of the dentary underlying the last two dentary teeth; reduced contact between the lacrimal and the nasal; suborbital foramen formed by the maxilla and ectopterygoid, excluding the palatine; a posterior supralabial foramen shared by the maxilla and jugal; a Y‐shaped antorbital pillar formed by the palatine, and massive orbitonasale and facial foramina (shared with unnamed southwest USA leptopleuronines). Phylogenetic analysis indicates that Libognathus is a highly derived leptopleuronine procolophonid, closely related to Hypsognathus fenneri and other southwest USA Revueltian leptopleuronines, which fall out as sister taxa to Hypsognathus, a relationship supported by a maxillary dentition restricted anterior to the orbital margin, a possibly synapomorphic orbitonasale septum in the form of an “antorbital pillar” created by the palatine, an anteroventral process of the jugal, and the presence of a small diastema between the first dentary tooth and the more posterior dentition. Libognathus exhibits a possible ankylosed protothecodont tooth implantation with frequent replacement, differing from some other proposed procolophonid implantation and replacement models. Chinle Formation and Dockum Group leptopleuronines are restricted to the Revueltian teilzone/holochronozone, making them possible Revueltian index taxa.

“…Procolophonids were a successful and widespread group of small-bodied parareptiles that originated in the late Permian, appear to have been unaffected by the end-Permian mass extinction event, and subsequently underwent an evolutionary radiation in the Triassic (Cisneros, 2008;Cisneros & Ruta, 2010;MacDougall et al, 2019;Modesto et al, 2001;Ruta et al, 2011;Tsuji & Müller, 2009). Triassic fossils of the group are known from localities worldwide, including Western Europe (Säilä, 2010;Skinner et al, 2020;Spencer, 2000;Spencer & Storrs, 2002;Sues & Reisz, 2008;Zaher et al, 2019), Russia (Ivakhnenko, 1979;Spencer & Benton, 2000), China (Li, 1983(Li, , 1989, southern Africa (Carroll & Lindsay, 1985;deBraga, 2003;Falconnet et al, 2012;Modesto et al, 2001;Modesto et al, 2010;Modesto & Damiani, 2003;Tsuji, 2018), North America (Sues et al, 2000;Sues & Baird, 1998), South America (Cisneros & Schultz, 2003;Piñeiro et al, 2004;Pinheiro et al, 2021;Silva-Neves et al, 2020), and Australia (Hamley et al, 2021). The group was most widespread and abundant during the Early Triassic and the early Middle Triassic (Anisian) but is relatively scarce in post-Anisian assemblages (Cisneros, 2008).…”

mentioning

confidence: 99%

Hwiccewyrm trispiculum gen. et sp. nov., a new leptopleuronine procolophonid from the Late Triassic of southwest England

Butler,

Meade,

Cleary

et al. 2023

The fissure fill localities of southwest England and South Wales are well‐known for preserving rich assemblages of predominantly small‐bodied Late Triassic to Early Jurassic tetrapods, but many aspects of these assemblages remain contentious. The age of the Late Triassic fissures is disputed, with some lines of argument suggesting a latest Triassic (Rhaetian) age, whereas other evidence suggests they may be as old as Carnian. The fissures have been hypothesized by some workers to have formed on an archipelago, with island effects invoked to explain aspects of the assemblages such as the abundance of small‐bodied species. Procolophonids were a successful group of Triassic parareptiles, best known from Early to early Late Triassic assemblages, but have only recently been described from one of the fissure fill sites (Ruthin) based upon fragmentary remains. Here, we describe new procolophonid specimens from another fissure (Cromhall) that represent at least six individuals of different sizes, with much of the skeleton represented including well‐preserved skull material. The Cromhall procolophonid shows strong similarities to Late Triassic procolophonids from Scotland, Brazil and North America, but both autapomorphies and a unique character combination demonstrate that it represents a new species, which we name as Hwiccewyrm trispiculum gen. et sp. nov. Phylogenetic analysis places Hwiccewyrm in a derived clade within Leptopleuroninae, together with Leptopleuron, Hypsognathus, and Soturnia. The largest specimens of Hwiccewyrm demonstrate a body size that is similar to Leptopleuron and Hypsognathus, supporting other recent work that has questioned the insular dwarfism hypothesis for the fissure fill assemblages.