Procolophon Research Articles

Temporal fenestration in a Procolophon trigoniceps specimen (Procolophonoidea) from the Lower Triassic of Brazil.

The parareptiles diversified widely during the Permian and persisted in Pangean ecosystems until the end of the Triassic. However, most parareptiles succumbed to the Permian-Triassic extinction, leading to the exclusive survival of procolophonoids. Procolophonoidea stands out as one of the most diverse parareptile clades, with about 40 species across Pangean land masses. The Early Triassic species Procolophon trigoniceps is known from South Africa, Antarctica, and Brazil. The majority of cranial materials of this procolophonoid are described as anapsid in temporal morphology, however, some skulls discovered in South Africa were found to exhibit temporal fenestration. Once thought to have systematic significance for the genus Procolophon, temporal fenestration was lately proposed to be an anomalous or pathological feature in P. trigoniceps. In this study, we describe new cranial material of P. trigoniceps from the Sanga do Cabral Formation of Brazil that clearly displays temporal fenestration. Aside from the fenestra, the specimen closely resembles more complete Brazilian P. trigoniceps skulls. The recurrent presence of the feature and the varying morphologies exhibited by the temporal fenestrae of P. trigoniceps may substantiate its characterization as an anomalous trait within the species. Furthermore, the occurrence of temporal fenestration in P. trigoniceps specimens from both South America and South Africa underscores parallels between these two Early Triassic ecosystems.

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

AbstractProcolophonoidea was the only parareptile clade to survive the end‐Permian mass extinction, and they experienced a major adaptive radiation during the Triassic. The flourishing of procolophonoid lineages in highly stressful post‐extinction environments may be, at least in part, a result of their early adaptations to herbivory, which would eventually become the most common feeding strategy in later representatives of the group. Although procolophonoids are comparatively diverse in the South African Lystrosaurus declivis Assemblage Zone, only the Gondwanan widespread taxon Procolophon trigoniceps has been thus far reported in South American deposits of similar age. Here, we present a new procolophonid genus and species from the Lower Triassic Sanga do Cabral Formation of Brazil. Oryporan insolitus gen. et sp. nov. combines typical adaptations suggestive of herbivory with primitive character states that are peculiar to early procolophonoids. Accordingly, phylogenetic analysis places the new species as an early‐diverging procolophonid, thus far the phylogenetically earliest to develop apparent adaptations for herbivory. Character optimization shows that the bulbous, labiolingually expanded molariforms of most procolophonids (usually interpreted as indicative of high‐fibre herbivory) were co‐opted from an insectivorous dentition. The new taxon also highlights the diversity of feeding habits displayed by Early Triassic procolophonoids, which was probably crucial for the survival of the clade in post‐extinction disaster communities.

A new, nearly complete skull of Procolophon trigoniceps Owen, 1876 from the Sanga do Cabral Supersequence, Lower Triassic of Southern Brazil, with phylogenetic remarks

ABSTRACTThe Sanga do Cabral Supersequence comprises the Sanga do Cabral and the Buena Vista formations from Brazil and Uruguay respectivelly. The Brazilian unit yields an abundant record of the procolophonid Procolophon trigoniceps, a biostratigraphic marker for the Lower Triassic, which allows correlation with the Katberg Formation, South Africa. P. trigoniceps, has a wide territorial extension, so this is one of the most successful groups after the greatest extinction event, the Permo-Triassic Extinction. We describe a new skull ascribed to Procolophon trigoniceps, which so far represents the most complete and best preserved specimen collected at the Lower Triassic Sanga do Cabral Supersequence, Southern Brazil, and assess its phylogenetic relationships. We also use CT scan techniques to assess hidden structures covered by a hard layer of rock matrix as a non-invasive method, which allowed the visualization of the palatal dentition of this new specimen. The actual diversity of procolophonians at the Sanga do Cabral Supersequence is still unknown because most specimens are fragmentary and poorly preserved, so this new, nearly complete skull fills an important gap in the knowledge of South American P. trigoniceps, given that previously described specimens of this taxon from this region of Gondwana are quite incomplete in comparison.

Biostratigraphic reappraisal of the Lower Triassic Sanga do Cabral Supersequence from South America, with a description of new material attributable to the parareptile genus Procolophon

The Sanga do Cabral Supersequence (SCS), comprises the Brazilian Sanga do Cabral Formation (SCF) and the Uruguayan Buena Vista Formation (BVF). So far, the SCS has yielded temnospondyls, parareptiles, archosauromorphs, putative synapsids, and a number of indeterminate specimens. In the absence of absolute dates for these rocks, a biostratigraphic approach is necessary to establish the ages of the SCF and the BVF. It is well established that the SCF is Early Triassic mainly due to the presence of the widespread Gondwanan reptile Procolophon trigoniceps. Conversely, the age of the BVF is subject of great controversy, being regarded alternatively as Permian, Permo-Triassic, and Early Triassic. The BVF has yielded the definite procolophonid Pintosaurus magnidentis. Procolophonoidea is one of the most diverse and conspicuous terrestrial tetrapod groups of the Lower Triassic Lystrosaurus Assemblage Zone in the Karoo Basin of South Africa, which preserves tetrapods from the aftermath of the end-Permian extinction event. Based on a previous interpretation that the fauna of the BVF is Permian, and in the reinterpretation of disarticulated vertebrae from SCF with ‘swollen’ neural arches as belonging to either seymouriamorphs or diadectomorphs, it was recently suggested that at least part of the SCF is Permian in age, which prompted this comprehensive reevaluation of both SCS's faunal content and geology. Moreoever, new, strikingly large procolophonid specimens (skull, vertebra, and a mandibular fragment) from the SCF are described and referred to the genus Procolophon. The large procolophonid vertebra described here contradicts the recent hypothesis that similar specimens from the SCF belong to seymouriamorphs or diadectomorphs, because its morphology is consistent with that found in Procolophon. There is not a single diagnostic specimen that supports the inference of Permian levels in the SCS. Accordingly, because all diagnostic and biostratigraphically informative fossils from the SCF and the BVF are either Early Triassic or restricted to the Triassic, we conclude that the available biostratigraphic data reinforce an Early Triassic age assignment to the SCS.

Reassessing the affinities of vertebral remains from Permo-Triassic beds of Gondwana

The Sanga do Cabral Formation of southern Brazil has a rich fossil tetrapod assemblage and is suggested to have an Early Triassic age mainly based on the presence of the parareptile Procolophon trigoniceps. However, a Permo-Triassic age can be also suggested for this unit taking into account the presence of putative Permian taxa and some previous stratigraphic assessments. We describe here several large vertebrae from the Sanga do Cabral Formation that display a distinctive morphology that includes the presence of a transverse distance across postzygapophyses more than twice the transverse width of the centrum, and accessory articulation structures in the neural arch that remind the hyposphene and hypantrum present in some basal parareptiles and diadectomorphs. Vertebrae with a similar large size and morphology had been previously reported from the same locality as belonging to the genus Procolophon based on their parareptile appearance (mainly the presence of a swollen neural arch) and the fact that the vertebrae were collected at the same locality where a large fragmentary skull assigned to this taxon was found. However, these vertebrae lack a comparable consistent morphology with those of Procolophon and basic statistical analyses demonstrate that these vertebrae are significantly larger than those expected in the largest known Procolophon skulls of South Africa. The morphology of these vertebra is consistent with that present in seymouriamorphs, pareiasaurs and diadectomorphs, but the absence of exclusive diagnostic characters precludes an assure assignation to either of these taxa. According to their current stratigraphic range, seymouriamorphs are the most plausible postulation, as their younger representatives are known from Late Permian deposits of Russia, but the other candidates cannot be excluded. The presence of any representative of those groups in the Sanga do Cabral Formation would be important because: (1) they would represent the first and only known record of seymouriamorphs or diadectomorphs in Gondwana, regarding the characters that the described vertebrae share with these groups; (2) they would suggest a survivorship for pareisaurs up to the Latest Permian or through the Permian-Triassic boundary, according to geochronological data currently available for this unit; (3) they might also suggest a Late Permian age for at least part of the Sanga do Cabral Formation if the intraformational conglomerates that yielded the vertebrae resulted from the rejuvenation of older levels of the same unit, and they do not include reworking of stratigraphically older strata.

Palaeobiology of Triassic procolophonids, inferred from bone microstructure

Procolophonoidea represent the most successful radiation of Parareptilia that lived during the Permo-Triassic. They are one of the few vertebrate groups that survived the end-Permian extinction and are thus important for studying the recovery of the post-extinction terrestrial ecosystem. Here, we investigate the palaeobiology of three Triassic procolophonid parareptiles, namely Sauropareion anoplus, Procolophon trigoniceps and Teratophon spinigenis, from the Karoo Basin of South Africa, inferred from histological analyses of their limb bones. Results reveal that all three taxa exhibit parallel-fibered bone tissue. Growth rings are absent in the Early Triassic Sauropareion and Procolophon whereas annuli are present in the Middle Triassic Teratophon, even during early ontogeny, suggesting a difference in life histories. Morphology and bone histology imply fossorial lifestyles for all three taxa, suggesting that burrowing may have played an important role in their survival during the harsh post-extinction Triassic environment.

New information on the skull of the Early Triassic parareptile Sauropareion anoplus, with a discussion of tooth attachment and replacement in procolophonids

ABSTRACT A partial reptile skull collected from the Lower Triassic (Induan) Barendskraal locality of South Africa is referable to the procolophonid parareptile Sauropareion anoplus. The specimen comprises the left side of the skull roof, palate, and mandible, and preserves areas not preserved or accessible in the skulls of previously published specimens, including fragmentary remains of the premaxilla, the anterior end of the maxilla, and the anterior end and lingual aspect of the mandible. The maxilla exhibits a maxillary depression that is similar in both shape and relative size to that seen in Procolophon trigoniceps, an anterolateral maxillary foramen that is indistinguishable from those seen in other procolophonoids, and 11 conical teeth. The suborbital foramen is formed ventrally by the palatine and the ectopterygoid. The dentary and the coronoid are fused together indistinguishably in lateral aspect. The marginal teeth appear to be anchored to the jaws by bone of attachment. The dentary teeth are exposed in lingual aspect and appear to be ankylosed to the summit of the bone, suggesting acrodont tooth implantation. Tooth replacement is seen in these teeth, where the lingual surface of a single tooth crown base in the middle of the dentary series is excavated for the apex of a replacement tooth crown, but the excavation does not extend ventrally onto the lingual surface of the bone. Considering that no extant reptiles with acrodont tooth implantation exhibit tooth replacement or bone of attachment, we tentatively regard protothecodonty to be present in S. anoplus.

New basal procolophonid reptile from the Katberg formation (Lower Triassic) of the South African Karoo

A new procolophonid reptile, Kitchingnathus untabeni n. gen. et n. sp., is described from the uppermost strata of the Lystrosaurus Assemblage Zone of the Karoo Basin, South Africa. The new taxon co-occurs with the well-known Procolophon trigoniceps. The most distinctive feature of the new taxon is the presence of numerous small bicuspid molariforms in both the maxilla and the dentary. A phylogenetic analysis indicates that Kitchingnathus occupies a basal position among procolophonids. Character optimisation suggests that bicuspid teeth were acquired independently by the new taxon, and originated twice in procolophonid evolution.

The postcranial skeleton, phylogenetic position, and probable lifestyle of the Early Triassic reptile Procolophon trigoniceps

A morphological study of the postcranial skeleton of Procolophon trigoniceps from the Lower Triassic of South Africa and Antarctica is undertaken. Procolophon shares a sister-group relationship with the procolophonid Tichvinskia from the Lower Triassic of Russia and is a basal member of Procolophonidae. This clade also includes the enigmatic taxon Sclerosaurus, believed most recently to be a pareiasaur relative. Owenettids form a separate lineage from Procolophonidae and are predominantly restricted to the Permian of both South Africa and Madagascar. A phylogenetically based assessment is considered, in which specialized modern taxa (sand lizards) are compared to their nonfossorial sister clade, allowing for "key innovations" to be identified. A similar comparison between owenettids and procolophonids reveals a number of apparent "key innovations" within procolophonids that are suggestive of a burrowing lifestyle for Procolophon.