Tainrakuasuchus
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This article was last edited by Junsik1223 (talk | contribs) 0 seconds ago. (Update timer)| Tainrakuasuchus | |
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| Scientific classification Edit this classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Clade: | Pseudosuchia |
| Clade: | †Poposauroidea |
| Genus: | †Tainrakuasuchus Müller et al., 2025 |
| Species: | †T. bellator
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| Binomial name | |
| †Tainrakuasuchus bellator Müller et al., 2025
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Tainrakuasuchus is an extinct genus of poposauroid pseudosuchians known from the Middle Triassic Dinodontosaurus Assemblage Zone, part of the Santa Maria Supersequence of Brazil. The genus contains a single species, Tainrakuasuchus bellator, known from part of the lower jaw, five vertebrae, and a partial pelvic girdle.
History and naming
[edit ]Tainrakuasuchus was described based on fossil material discovered at the Posto site of the Ladinian Pinheiros-Chiniquá Sequence, Santa Maria Supersequence, in Rio Grande do Sul, Brazil. The holotype and only known specimen, CAPPA/UFSM 0506, consists of a partial lower jaw, five vertebrae and a partial hip.[1]
The first part of the name Tainrakuasuchus derives from a combination of the Guarani words "tain" and "rakua", meaning "tooth" and "pointed" respectively, meant to invoke the pointed teeth of the lower jaw. The second part of the name derives from the Greek "suchus" meaning "crocodile". The species name "bellator" is of Latin origin and translates to "warrior" or "fighter". Müller and colleagues explain the species name as a tribute to the people of Rio Grande do Sul, citing their "historical resilience and enduring spirit" and highlighting the at the time recent struggles with floodings in the state.[1]
Description
[edit ]The dentary bone of Tainrakuasuchus is described as slender, with a height to length ratio of 0.1, which resembles the closely related Mandasuchus from Africa while setting it appart from the tall dentaries seen in the ornithosuchid Dynamosuchus . The lateral face of the dentary prominently features a groove that begins about two thirds down the bones length and runs just below the toothrow until the elevated posterodorsal process. Similar structures have been identified in other early poposauroids, namely Mambawakale , while a series of foramina occupies the same position in Mandasuchus. Towards the back of the element the dentary forms a posterodorsal process that rises above the toothrow and is split into a distinct upper and lower surface by a notch. The dentary is the only bone to participate in forming the mandibular symphysis, the part of the mandible where the two halves are sutured to each other, excluding the splenial as in most other poposauroids. The symphysis itself is short and only occupies the front-most part of the dentary, which contrasts with Mambawakale and ornithosuchids which have a more substantially elongated symphysis.[1]
In contrast to the lateral surface of the dentary, the medial face of the splenial is generally described as plain, lacking foramina or grooves. The splenial begins anteriorly as a slender bone, but grows taller further back in the lower jaw. Like the dentary the splenial forms a posterodorsal and ventrolateral process, the latter of which extending further back than the former. Here the splenial does bear a ridge and accompanying groove.[1]
While only four actual teeth are preserved in the holotype specimen of Tainrakuasuchus, the dentary bone bears 17 dental alveoli, a count that is comparable to Mambawakale. Some more derived poposauroids bear fewer teeth or lost them altogether in the case of shuvosaurids. The preserved teeth show a blade-like morphology, being lateromedially compressed and recurved. While the teeth bear some features indicative of ziphodonty, the actual presence of serrations that defines this tooth morphology cannot be determined due to the holotypes poor preservation.[1]
Classification
[edit ]In their 2025 phylogenetic analysis, Müller and colleagues recovered Tainrakuasuchus as a member of the paracrocodylomorph clade Poposauroidea, as the sister taxon to Mandasuchus , known from rocks of approximately the same age in Tanzania. These results are displayed in the cladogram below:[1]
Paleobiology
[edit ]
The sediments of the Dinodontosaurus Assemblage Zone are known to preserve a both taxonomically and ecologically diverse pseudosuchian fauna with between 6 and 8 recognized species. The smallest among them was Parvosuchus, which with a length of only around 1 m (3 ft 3 in) was likely restricted to small prey items. On the opposite side of the spectrum sits Prestosuchus, likely the apex predator of the fauna and the largest of the local pseudosuchians. With a range between 2–4 m (6 ft 7 in – 13 ft 1 in) erpetosuchids like Archeopelta and Pagosvenator and poposauroids like Schultzsuchus and Tainrakuasuchus represent medium-sized predators. While falling into a similar size range, early poposauroids like Tainrakuasuchus would have likely been distinct in their ecology from erpetosuchids due to differences in their skulls and dentition. Basal poposauroids possess teeth throughout the maxilla, whereas in erpetosuchids the teeth of the upper jaw are concentrated closer to the tip, suggesting that these animals captured prey in different manners or fed on different prey altogether.[1]
While the holotype of Tainrakuasuchus suggests a moderate size of up to 3 m (9.8 ft), isolated remains form the Posto locality could indicate the presence of even larger individuals. However, even at a greater size Tainrakuasuchus would have been ecologically distinct from the other large predator of the fauna, as poposauroid neck vertebrae are longer and shallower and therefore not built to deal with the same stresses as those likely dealt with by "rauisuchians" such as Prestosuchus.[1]
References
[edit ]- ^ a b c d e f g h Müller, Rodrigo Temp; Garcia, Mauricio Silva; Damke, Lísie Vitória Soares; Prestes de Bem, Fabiula; Fonseca, André de Oliveira; Doering, Mariana; Schiefelbein, Jeung Hee; Laste, Vitória Zanchett Dalle (2025年12月31日). "Osteology, taxonomy and phylogenetic affinities of a new pseudosuchian archosaur from the Middle Triassic of southern Brazil". Journal of Systematic Palaeontology. 23 (1): 2573750. doi:10.1080/14772019.2025.2573750. ISSN 1477-2019.
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