 |
| Itaguyra occulta Neto, Pretto, Martinelli, Battista, Garcia, Müller, Schmitt, Melo, Francischini, Schultz, Pinheiro, Soares & Kellner, 2025 |
Abstract
The dawn of dinosaurs is marked by the appearance of the saurischian lineages in the Late Triassic fossil record, around 230 million years ago. This early burst of diversification of the group is majoritarily represented by sauropodomorphs and herrerasaurids in late Carnian to early Norian of Brazil, Argentina, India, and Zimbabwe. However, “silesaurids”, an older and enigmatic group of quadrupedal dinosauromorphs, were recently found, in some works, as stem ornithischians. In this scenario, dinosaurs would have originated far earlier than the end of the Ladinian, a time in which “silesaurids” are already spread through Gondwana. Despite being also recorded in more recent dinosaur-bearing beds in Brazil, “silesaurids” are absent in strata from the early Carnian, an important time frame for dinosaur evolution. Here we present a new “silesaurid”, Itaguyra occulta gen. et sp. nov., that fills up the remaining gap of occurrence of these dinosauromorphs and provides new clues to the success of these putative early ornithischians.
ARCHOSAURIA Cope, 1869 (sensu Gauthier and Padian, 1985).
AVEMETATARSALIA Gauthier, 1986 (sensu Sereno, 1991).
DINOSAUROMORPHA Benton, 1985 (sensu Ezcurra et al. 2020).
Itaguyra occulta gen. nov. et sp. nov.
Etymology: The genus name combines the native Tupi words Ita- (= stone) and -guyra (= bird), referring to the avemetatarsalian nature of the specimen. The specific epithet, derived from Latin, means hidden and refers to the fact that the remains were initially identified as being “mixed up” with other indeterminate cynodont fragments with which they had been collected.
 |
| The new “silesaurid” Itaguyra occulta gen. et sp. nov. (A) Holotype UFRGS-PV-1365-T. (B) Placement of Rio Grande do Sul State (RS) in Brazil. (C) Exposure of the Santa Maria Supersequence in RS. (D) Locality of the type material (red star) and other correlated localities (pink stars). (E) Restoration of the skeleton (artwork by Maurício Garcia) with known elements in pink. |
Holotype: UFRGS-PV-1365(a)-T, a left ilium (Fig. 1A).
Paratype: UFRGS-PV-1365(b)-T, associated ischium (Fig. 1A).
Type and referred locality: The type-materials were collected in the Schoenstatt Sanctuary fossil site (52°27′0.5″ W; 29°44′26.2″ S), in the Santa Cruz do Sul municipality (Fig. 1D), Rio Grande do Sul State, Brazil.
Diagnosis: Itaguyra occulta differs from all other known “silesaurids” with comparable material in (*local autapomorphy): having a faint crest connecting the preacetabular process and the supracetabular crest of the ilium, unlike the prominent ridge of most “silesaurids”*; height of the postacetabular process sub-equal to the height of the acetabulum (shared with Silesaurus opolensis and Kwanasaurus williamparkeri), differing from Lutungutali sitwensis and Gamatavus antiquus (see Discussion); supracetabular crest rounded (shared with Asilisaurus kongwe, Lewisuchus admixtus, Lutungutali sitwensis, and Gamatavus antiquus), unlike the straight outline of Ignotosaurus fragilis, and Kwanasaurus williamparkeri; brevis fossa almost entire visible in lateral view (shared with Silesaurus opolensis Kwanasaurus williamparkeri), being different from Lewisuchus admixtus and Asilisaurus kongwe which are more ventrally oriented; presence of a triangular process continuous to the posterior margin of the brevis fossa (absent in Gamatavus antiquus); triangular ventral margin of the medial wall of the iliac acetabulum (shared with Asilisaurus kongwe, Lutungutali sitwensis, Ignotosaurus fragilis and probably Gamatavus antiquus, but not with Silesaurus opolensis and Kwanasaurus williamparkeri); and, tall shaft of the ischium* (see Discussion).
 |
| Worldwide record of “silesaurids” through the Triassic. Paleogeographic maps of the world during the Anisan to Norian, showing the occurrences of ‘silesaurids’. Silhouettes not to scale, redrawn from different sources. Silhouettes based on the artwork of Matheus Fernandes Gadelha, Maurício Garcia and Voltaire D. Paes Neto. |
Voltaire D. Paes Neto, Flávio A. Pretto, Agustín G. Martinelli, Francesco Battista, Maurício Garcia, Rodrigo T. Müller, Mauricio R. Schmitt, Tomaz P. Melo, Heitor Francischini, Cesar L. Schultz, Felipe Pinheiro, Marina B. Soares and Alexander W. Kellner. 2025. Continuous presence of dinosauromorphs in South America throughout the Middle to the Late Triassic. Scientific Reports. 15, 18498. DOI: doi.org/10.1038/s41598-025-99362-5 [30 May 2025]
