| Gondwanax | |
|---|---|
 | |
| Speculativelife restoration | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria (?) |
| Clade: | †Ornithischia (?) |
| Family: | †Silesauridae |
| Clade: | †Sulcimentisauria |
| Genus: | †Gondwanax Müller,2025 |
| Species: | †G. paraisensis |
| Binomial name | |
| †Gondwanax paraisensis Müller, 2025 | |
Gondwanax (meaning "lord ofGondwana") is anextinct genus ofsilesauriddinosauriform from theTriassicPinheiros-Chiniquá Sequence of Brazil. The genus contains asingle species,G. paraisensis, known from a partial skeleton.Gondwanax represents one of the oldest known dinosauromorphs, and, alongside the roughly coevalGamatavus, one of the oldest South American silesaurs. While the possession of two sacral vertebrae characterizes more basal "silesaurid" taxa,Gondwanax has three—the oldest occurrence of this trait in the fossil record.
| range_map_caption =Gondwanaxtype locality inParaíso do Sul municipality, BrazilTheGondwanax fossil material was discovered in 2014 by physician and paleontology enthusiast Pedro L. P. Aurelio at the "Linha Várzea 2" ("Becker") site, belonging to thePinheiros-Chiniquá Sequence of the Santa Maria Supersequence (Formation) inParaíso do Sul municipality ofRio Grande do Sul, Brazil. These layers are representative of theDinodontosaurusAssemblage Zone. He subsequently donated it to a university for study in 2021.[1] Theholotype specimen, CAPPA/UFSM 0417, is a single right femur. Several other partially disarticulated bones were found in association with this specimen. While no overlapping bones suggest the presence of multiple individuals, this possibility has not been ruled out as the bones were not found in perfect articulation. The additional material comprises twocervical, severaldorsal, threesacral, and at least threecaudal vertebrae, and a partialpelvic girdle.<[2]
In 2024, Rodrigo Temp Müller announcedGondwanax paraisensis as a new genus and species of silesaurids based on these fossil remains. Thegeneric name,Gondwanax, combinesGondwana—the name of an ancient 'supercontinent' containing South America—with theAncient Greekἄναξ, meaning "lord" or "king", in reference to the preeminence of dinosauromorphs throughout the Mesozoic Era. Thespecific name,paraisensis, references the municipality of Paraíso do Sul, where the specimens were found. The final version of the publicationdescribingGondwanax paraisensis was published the following year.[2]
Having been found in rocks belonging to theLadinian–Carnian,Gondwanax is notable as it is one of the oldest known dinosauromorphs.Gamatavus, another 'silesaurid' from the same locality, andGondwanax together represent the oldest South American 'silesaurs'.[2]
The fossil material ofGondwanax indicates a body length of about 1 metre (3.3 ft).[1] The basalmost 'silesaurids' are characterized by only two sacral vertebrae. However,Gondwanax is the oldest fossil dinosauromorph that has three sacral vertebrae.[2]
In hisphylogenetic analysis, Müller (2025) recoveredGondwanax as abasal member of theSulcimentisauria. Similar to a number of recent studies, these taxa, along with other "traditional"silesaurids, are treated as aparaphyletic grade of ornithischians.[3][4] These results are displayed in thecladogram below:[2]
Gondwanax was found in the "Linha Várzea 2" site of theDinodontosaurus Assemblage Zone (AZ) of the Santa Maria Formation. ThegracilisuchidParvosuchus was also found in this site.[5] The roughly coeval "Picada do Gama" site has yielded a closely related "silesaurid",Gamatavus. Other localities indicate that these animals likely shared an ecosystem withdicynodonts,cynodonts,[6]pseudosuchians,aphanosaurs,[7]rhynchosaurs,[8] andprocolophonoids.[9][10]
The BrazilianDinodontosaurus Assemblage Zone shares many faunal similarities with the ArgentinianTarjadia Assemblage Zone, the dinosauromorph-bearing units of the TanzanianLifua Member, and the ZambianNtawere Formation, potentially indicating that these units belong to similar temporal ranges.[10]
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