Gnathovorax cabreirai: a new early dinosaur and the origin and initial radiation of predatory dinosaurs

Abstract

Predatory dinosaurs were an important ecological component of terrestrial Mesozoic ecosystems. Though theropod dinosaurs carried this role during the Jurassic and Cretaceous Periods (and probably the post-Carnian portion of the Triassic), it is difficult to depict the Carnian scenario, due to the scarcity of fossils. Until now, knowledge on the earliest predatory dinosaurs mostly relies on herrerasaurids recorded in Carnian strata of South America. Phylogenetic investigations recovered the clade in different positions within Dinosauria, whereas fewer studies challenged its monophyly. Although herrerasaurid fossils are much better recorded in present-day Argentina than in Brazil, Argentinean strata so far yielded no fairly complete skeleton representing a single individual. Here, we describe Gnathovorax cabreirai, a new herrerasaurid based on an exquisite specimen found as part of a multitaxic association form southern Brazil. The type specimen comprises a complete and well-preserved articulated skeleton, preserved in close association (side by side) with rhynchosaur and cynodont remains. Given its superb state of preservation and completeness, the new specimen sheds light into poorly understood aspects of the herrerasaurid anatomy, including endocranial soft tissues. The specimen also reinforces the monophyletic status of the group, and provides clues on the ecomorphology of the early carnivorous dinosaurs. Indeed, an ecomorphological analysis employing dental traits indicates that herrerasaurids occupy a particular area in the morphospace of faunivorous dinosaurs, which partially overlaps the area occupied by post-Carnian theropods. This indicates that herrerasaurid dinosaurs preceded the ecological role that later would be occupied by large to medium-sized theropods.

The endocranial anatomy of Buriolestes schultzi (Dinosauria: Saurischia) and the early evolution of brain tissues in sauropodomorph dinosaurs

“…Time‐calibrated simplified phylogenetic tree of early dinosaurs (composite from Langer et al, 2014; Müller, 2019; Pacheco et al, 2019) and comparison of selected cranial endocasts in dorsal and left lateral views. Megapnosaurus from Raath (1977); Zupaysaurus from Paulina‐Carabajal et al (2019); Sinosaurus from Xing et al (2014); Allosaurus from Rogers (1998); Plateosaurus from Bronzati et al (2017); Ngwevu from Sereno et al (2007); Spinophorosaurus from Knoll et al (2012).…”

Osteological redescription of the Late Triassic sauropodomorph dinosaur Thecodontosaurus antiquus based on new material from Tytherington, southwestern England

“…On the medial side and slightly distal to this scar, a medial pitted ridge is present (Fig. 11F), which is less pronounced and proximodistally elongated than that in Buriolestes (Müller et al, 2018c) and Gnathovorax (Pacheco et al, 2019). The distal end of the fibula is anteroposteriorly expanded and oval in distal view.…”

“…7A, B) and represent the insertion of M. triceps brachii. The apex of the olecranon process is abraded in most of the specimens, but in those that preserve it, it is less prominent than in Saturnalia (Langer et al, 2007) and Chromogisaurus (Ezcurra, 2010) and some early saurischians such as Eodromaeus (Martínez et al, 2011) and Gnathovorax (Pacheco et al, 2019).…”

Peer Review #1 of "Testing pterosaur ingroup relationships through broader sampling of avemetatarsalian taxa and characters and a range of phylogenetic analysis techniques (v0.1)"

“…However, H. ischigualastensis is not necessarily the best representative of the 'basal' dinosaurian condition, being a very large predator that is quite distinct in terms of its anatomy to many, if not most, of the earliest dinosaurs (see, Brusatte et al, 2010;Baron, Norman and Barrett, 2017a). In fact, the position of this taxon has proved to be highly unstable in recent times (see, Baron, Norman and Barrett, 2017b;Langer et al, 2017;Lee et al, 2019;Pacheco et al, 2019) Manuscript to be reviewed 2018). Moreover, in the analyses by Britt et al (2018) and Dalla Vecchia (2019), H. ischigualastensis is recovered as the sister taxon to the rauisuchid paracrocodylomorph Postosuchus kirkpatricki, which might suggest that character optimisation outside of the pterosaurian lineage is somewhat confused and misleading.…”