| Gamatavus Temporal range: Middle Triassic, (Ladinian–early Carnian) PreꞒ Ꞓ O S D C P T J K Pg N | |
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria (?) |
| Clade: | †Ornithischia (?) |
| Family: | †Silesauridae |
| Genus: | †Gamatavus Pretto et al., 2022 |
| Species: | †G. antiquus |
| Binomial name | |
| †Gamatavus antiquus Pretto et al., 2022 | |
 
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| Gamatavus type locality in Dilermando de Aguiar Municipality, Brazil | |
Gamatavus (meaning "Picada do Gama great-grandfather") is a genus of silesaurid dinosauriform from the Middle Triassic Santa Maria Formation of Dilermando de Aguiar Municipality, Brazil. The genus contains a single species, G. antiquus, known from a partial ilium. Gamatavus represents one of the oldest silesaurids known from South America, alongside the roughly coeval Gondwanax.
Discovery and naming
The Gamatavus holotype specimen, UFSM 11348a, was discovered in the Dinodontosaurus Assemblage Zone of the Santa Maria Formation (‘Picada do Gama’ site), dated to the Ladinian–early Carnian stages of the Middle Triassic. It consists of a partial right ilium. A partial left femur and four incomplete vertebrae were found in association with the holotype, but they were not assigned to Gamatavus.
In 2022, Pretto et al. described Gamatavus antiquus as a new genus and species of silesaurid based on these remains. The generic name, "Gamatavus", combines a reference to the type locality (Picada do Gama site) with the Latin word "atavus", meaning "great-grandfather". The specific name, "antiquus", is derived from a Latin word meaning "ancient".
Classification
Pretto et al. (2022) tested the phylogenetic relationships of Gamatavus in the datasets of Ezcurra et al. (2020) and Müller and Garcia (2020), both of which show alternate positions for silesaurids — the former as non-dinosaurian dinosauromorphs, and the latter as early ornithischian dinosaurs. Their results are shown in the cladograms below.
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Topology 1: Ezcurra et al. (2020) dataset
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Topology 2: Müller and Garcia (2020) dataset
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Paleoenvironment
The Gamatavus holotype was found in the Dinodontosaurus Assemblage Zone of the Santa Maria Formation. It coexisted with dicynodonts, cynognathians, probainognathians, pseudosuchians, aphanosaurs, rhynchosaurs, and procolophonoids. The Brazilian Dinodontosaurus Assemblage Zone shares many faunal similarities with the Argentinian Tarjadia Assemblage Zone, the dinosauromorph-bearing units of the Tanzanian Lifua Member, and the Zambian Ntawere Formation, potentially indicating that these units belong to the same temporal range.
References
- ^ Pretto, Flávio Augusto; Müller, Rodrigo Temp; Moro, Debora; Garcia, Maurício Silva; Paes Neto, Voltaire Dutra; da Rosa, Átila Augusto Stock (2022-09-28). "The oldest South American silesaurid: New remains from the Middle Triassic (Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage Zone) increase the time range of silesaurid fossil record in southern Brazil". Journal of South American Earth Sciences. 120: 104039. doi:10.1016/j.jsames.2022.104039. ISSN 0895-9811. S2CID 252609210.
- Temp Müller, Rodrigo (2024). "A new "silesaurid" from the oldest dinosauromorph-bearing beds of South America provides insights into the early evolution of bird-line archosaurs". Gondwana Research (in press). doi:10.1016/j.gr.2024.09.007.
