Itaguyra

Itaguyra Temporal range: Upper Triassic, Carnian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria (?)
Clade:	† Ornithischia (?)
Family:	† Silesauridae
Genus:	† Itaguyra Paes Neto et al., 2025
Species:	†I. occulta
Binomial name
†Itaguyra occulta Paes Neto et al., 2025

Itaguyra (meaning "stone bird") is an extinct genus of dinosauromorphs allied with taxa traditionally regarded as "silesaurids" (possibly the earliest ornithischian dinosaurs). It is known from the Late Triassic (Carnian age) Santa Cruz Sequence of the Santa Maria Supersequence of Brazil. The genus contains a single species, Itaguyra occulta, known from two isolated pelvic bones.

Discovery and naming

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Itaguyra type locality in Rio Grande do Sul, Brazil

The Itaguyra fossil material, two partial pelvic bones, was found in the 'Schoenstatt Sanctuary fossil site', representing outcrops of the Santacruzodon Assemblage Zone of the Santa Cruz Sequence of the Santa Maria Supersequence in Rio Grande do Sul, Brazil. The bones were found and collected mixed with the remains of cynodont therapsids. ^[1] In a 2024 publication, Battista et al. reported this specimen as a new indeterminate archosauriform. ^[2]

In 2025, Paes Neto and colleagues recognized the "silesaurid" affinities of the specimens and described them as a belonging to a new genus and species. They established UFRGS-PV-1365(a)-T, is a partial left ilium, as the holotype specimen. An associated partial ischium, UFRGS-PV-1365(b)-T, was referred as a paratype. The generic name, Itaguyra, combines the Tupi words ita, meaning "stone", and guyra, meaning "bird", referring to its avemetatarsalian (lit. 'bird feet' ^[3] ) classification. The specific name, occulta, is Latin for "hidden", referring to the specimens' discovery alongside bones of cynodonts. ^[1]

Classification

In their phylogenetic analysis, Paes Neto et al. (2025) found Itaguyra to be a basal, non-prionodontian, member of the Ornithischia. Similar to a number of recent studies, these taxa, along with other "traditional silesaurids", were recovered as a paraphyletic grade of ornithischians. ^{[4] [5] [6]} These results are displayed in the cladogram below: ^[1]

Dinosauria	Saurischia Ornithischia Saltopus Lewisuchus "silesaurids" Itaguyra Asilisaurus Sulcimentisauria Gamatavus Gondwanax Amanasaurus Diodorus Technosaurus Parapredentata Ignotosaurus Silesaurus Sacisaurus Lutungutali Kwanasaurus Eucoelophysis Pisanosaurus Laquintasaura Prionodontia

Paleoenvironment

Itaguyra was found in sediments likely belonging to the Santacruzodon Assemblage Zone of the Santa Maria Supersequence. Other fauna from this assemblage include dicynodonts, different groups of cynodonts, paracrocodylomorphs, proterochampsids, rhynchosaurs, and procolophonoids. ^{[1] [2]}

References

1. Paes Neto, V. D.; Pretto, F. A.; Martinelli, A. G.; Battista, F.; Garcia, M.; Müller, R. T.; Schmitt, M. R.; Melo, T. P.; Francischini, H.; Schultz, C. L.; Pinheiro, F.; Soares, M. B.; Kellner, A. W. (2025). "Continuous presence of dinosauromorphs in South America throughout the Middle to the Late Triassic". Scientific Reports. 15. 18498. doi: 10.1038/s41598-025-99362-5 . PMC   12125330 .
2. Battista, Francesco; Ribeiro, Ana Maria; Melo, Tomaz P.; Schultz, Cesar L. (April 2024). "A reinterpretation of taphonomy and palaeoecology of the early Carnian Santacruzodon Assemblage Zone type-locality from the Santa Maria Supersequence, Brazil". Palaeogeography, Palaeoclimatology, Palaeoecology. 639: 112080. Bibcode:2024PPP...63912080B. doi: 10.1016/j.palaeo.2024.112080 .
3. Benton, Michael J. (1999-08-29). "Scleromochlus taylori and the origin of dinosaurs and pterosaurs". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences. 354 (1388): 1423–1446. doi:10.1098/rstb.1999.0489. ISSN   0962-8436. PMC   1692658 .
4. Norman DB, Baron MG, Garcia MS, Müller RT (2022). "Taxonomic, palaeobiological and evolutionary implications of a phylogenetic hypothesis for Ornithischia (Archosauria: Dinosauria)". Zoological Journal of the Linnean Society. 196 (4): 1273–1309. doi: 10.1093/zoolinnean/zlac062 .
5. Fonseca, A. O.; Reid, I. J.; Venner, A.; Duncan, R. J.; Garcia, M. S.; Müller, R. T. (2024). "A comprehensive phylogenetic analysis on early ornithischian evolution". Journal of Systematic Palaeontology. 22 (1). 2346577. Bibcode:2024JSPal..2246577F. doi:10.1080/14772019.2024.2346577.
6. Temp Müller, Rodrigo (January 2025). "A new "silesaurid" from the oldest dinosauromorph-bearing beds of South America provides insights into the early evolution of bird-line archosaurs" . Gondwana Research . 137 (in press): 13–28. Bibcode:2025GondR.137...13M. doi:10.1016/j.gr.2024.09.007.