Trialestes romeri (Bonaparte 1982)= Triassolestes (Reig, 1963/Tillyard, 1918) Carnian, Late Triassic ~235 mya is known from scattered parts. Clark, Sues and Berman (2000) redescribed the known parts and admitted the possibility that this taxon combined dinosaurian and crocodylomorph characters. As it nests here, Trialestes was derived from a sister to Pseudhesperosuchus.This clade phylogenetically preceded Herrerasaurus and the Dinosauria.

Distinct from Pseudhesperosuchus, the skull of Trialestes had a larger antorbital fenestra and a deeper rostrum. The mandibular fenestra was smaller.

The vertebral centra had excavated lateral surfaces, for bird-like air sacs. The radius was longer than the humerus, a character otherwise known only in dinosaurs. The radiale was smaller than the ulnare, matching the radius and ulna. The fingers were tiny.

The pelvis was semi-perforated, as in basal dinosaurs, with a well-developed supraacetabular crest. The dorsal pelvis was straight, as in Gracilisuchus. The femoral head was inturned, suggesting an erect posture. The ankle joint supported that stance had a crocodile normal configuration and a functionally pentadactyl pes.

Juveniile Trialestes (MCZ 4116, MCZ 4118, Brinkman 1981; Middle Triassic) these two specimens have a taller, narrow skull and do not nest with Gracilisuchus in the LRT, but more at a basal node, alongside the very much larger Trialestes (above).

Bonaparte JF 1982. Classification of the Thecodontia. Geobios Mem. Spec. 6, 99-112

Brinkman D 1981. The origin of the crocodiloid tarsi and the interrelationships of thecodontian archosaurs. Breviora 464: 1–23.

Clark JM, Sues H-D and Berman DS 2000. A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs. Journal of Vertebrate Paleontology 20(4):683-704.

deFranca MAG, Bittencourt JdS and Langer MC 2013. Reavaliação taxonomica de Barberenasuchus brasiliensis (Archosauriformes), Ladiniado do Rio Grande do Sul (Zona-Assembleia de Dinodontosaurus). Palaenotogia em Destaque Edição Especial Octubro 2013: 230.

Irmis RB, Nesbitt SJ and Sues H-D 2013. Early Crocodylomorpha. Pp. 275–302 in Nesbitt, Desojo and Irmis (eds). Anatomy, phylogeny and palaeobiology of early archosaurs and their kin. The Geological Society of London. doi:10.1144/SP379.24.

Kischlat EE 2000. Tecodôncios: a aurora dos arcossáurios no Triássico. Pp. 273–316 in Holz and De Ros (eds.). Paleontologia do Rio Grande do Sul. Porto Alegre: CIGO/UFRGS.

Lecuona A, Ezcurra MD and Irmis RB 2016. Revision of the early crocodylomorph Trialestes romeri (Archosauria, Suchia) from the lower Upper Triassic Ischigualasto Formation of Argentina: one of the oldest-known crocodylomorphs. Papers in Palaeontology (advance online publication). DOI: 10.1002/spp2.1056

Reig, OA 1963. La presencia de dinosaurios saurisquios en los “Estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina). Ameghiniana 3: 3-20.

Riff D et al. 2012. Crocodilomorfos: a maior diversidade de répteis fósseis do Brasil. TERRÆ 9: 12-40, 2012.

Zanno LE, Drymala S, Nesbitt SJ and Schneider VP 2015. Early Crocodylomorph increases top tier predator diversity during rise of dinosaurs. Scientific Reports 5:9276 DOI: 10.1038/srep09276.

wiki/Trialestes