Tralkasaurus
| Tralkasaurus Temporal range:
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|---|---|
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Abelisauridae |
| Genus: | †Tralkasaurus Cerroni et al., 2020 |
| Type species | |
| †Tralkasaurus cuyi Cerroni et al., 2020
| |
Tralkasaurus (meaning "thunder lizard") is a
Discovery and naming
The Violante Farm fossil site in
The specimens discovered included an incomplete skeleton of an
Description
Tralkasaurus was described by Cerroni and colleagues as a "medium-sized abelisaurid" based on the available material. Its maxilla has a length of 22 centimetres (8.7 in), smaller than that of the similarly "medium-sized" Skorpiovenator (at 32 centimetres (13 in), with the whole animal measuring 6 metres (20 ft) long).[4] It is most comparable to the smallest-known abelisaurid, MMCh-PV 69, from the Candeleros Formation, with Tralkasaurus' pubis measuring 35 centimetres (14 in) long and MMCh-PV 69's pubis measuring 41 centimetres (16 in) long.[1][5]
The maxilla of Tralkasaurus is a subtriangular bone covered in neurovascular foramina (pits formed by innervation) and rugosities (roughened areas). It encloses the antorbital fenestra from the front; Tralkasaurus is unique among abelisaurids in that front margin of the antorbital fenestra slopes forwards and upwards, instead of being vertical or sloping backwards. The antorbital fenestra creates fossae on both the upward-projecting process of the maxilla and (atypically among abelisaurids) the inner surface of the bone; this condition is more similar to basal abelisauroids like Noasaurus and Masiakasaurus, as well as the Averostra. Deep neurovascular grooves extend downward from the bottom rim of the antorbital fenestra, which is unlike Carnotaurus, Ekrixinatosaurus, Majungasaurus, and Skorpiovenator but similar to Rugops. More typically, the ascending process tapers and becomes laminar (sheet-like) at the top, like Skorpiovenator, Carnotaurus, and Majungasaurus. The maxilla also bears eleven sockets with four preserved teeth, which are typical of abelisaurids. Like Majungasaurus but unlike Skorpiovenator, the serrations on both edges of the teeth are the same size.[1]
Based on comparisons with Carnotaurus and Majungasaurus, the dorsal vertebrae of Tralkasaurus originated from the mid-to-rear back. The transverse processes that extend out and upward are subtriangular like those of Dahalokely, Viavenator, Majungasaurus, and Masiakasaurus, but unlike the subrectangular processes of Carnotaurus. the parapophyses that project out and downward are distinctive among abelisaurids in their unusual narrowness and shortness; even in abelisaurids like Majungasaurus and MCF-PVPH-237, where the parapophyses are relatively narrow, they are not as rod-like as in Tralkasaurus. A ridge between them, the dorsal paradiapophyseal lamina, is also shallow and relatively low, unlike the strongly-developed ridges in Carnotaurus, Majungasaurus, and Ilokelesia. Another ridge, the posterior paradiapophyseal lamina, is robust and cross-cuts a fossa below the transverse process (the infradiapophyseal fossa), like Dahalokely.[1]
The large transverse processes of the caudal vertebrae, which originated from the front of the tail, are typically abelisaurid, projecting strongly out and upward like Carnotaurus, Skorpiovenator,
Classification
Cerroni and colleagues conducted a
Within the Abelisauridae, the position of Tralkasaurus was more poorly resolved. In particular, it exhibits a conflicting blend of characteristics: the projections on the caudal transverse processes are typical of the Brachyrostra, but the presence of extensive antorbital fossae on the maxilla is plesiomorphic (i.e. characteristic of basal abelisauroids, and unlike other abelisaurids). The phylogenetic analysis accordingly placed Tralkasaurus among basal abelisaurids, but was unable to resolve its affinities beyond a polytomy (collapsed tree). The resulting phylogenetic tree is partially reproduced below.[1]
Palaeoecology
Numerous theropods are known from the Violante Farm fossil site of the Huincul Formation, including Gualicho[2] and Aoniraptor (which may or may not represent the same megaraptoran), the carcharodontosaurid Taurovenator,[6] a coelurosaur (identified by Cerroni and colleagues as an unenlagiine) and another carcharodontosaurid that remain unnamed, but are likely distinct species, and another indeterminate megaraptoran.[1] Other dinosaurs also include a titanosaurian sauropod and an ornithopod. Additional vertebrates from the Violante Farm site include the eilenodontid rhynchocephalian Patagosphenos;[7] a crocodyliform, possibly belonging to the Neosuchia; a squamate; a chelid turtle; and a fish referred to Lepidotes.[3]
Dinosaurs named from other localities in the Huincul Formation include titanosaurs (Argentinosaurus, Choconsaurus, and Chucarosaurus),[8] rebbachisaurids (Cathartesaura and Limaysaurus),[9] carcharodontosaurids (Mapusaurus and Meraxes),[10] abelisaurids (Skorpiovenator and Ilokelesia), an elaphrosaurine (Huinculsaurus),[11] and a paravian (Overoraptor).[12]
See also
References
- ^ S2CID 213781725.
- ^ PMID 27410683.
- ^ ISSN 2469-0228.
- .
- .
- ^ Motta, M.J.; Aranciaga Rolando, A.M.; Rozadilla, S.; Agnolín, F.E.; Chimento, N.R.; Brissón Egli, F.; Novas, F.E. (2016). "New theropod fauna from the Upper Cretaceous (Huincul Formation) of northwestern Patagonia, Argentina". New Mexico Museum of Natural History and Science Bulletin. 71: 231–253 – via ResearchGate.
- S2CID 135429146.
- ISSN 0195-6671.
- ^ Calvo, Jorge O.; Salgado, Leonardo (1995). "Rebbachisaurus tessonei sp. nov. a new Sauropoda from the Albian-Cenomanian of Argentina; new evidence on the origin of the Diplodocidae" (PDF). Gaia. 11: 13–33. Archived from the original (PDF) on 23 September 2021.
- S2CID 250343124.
- S2CID 214118853.
- S2CID 218913199.