UNEXPECTED MORPHOLOGY OF SUPPOSED DINOSAUR PRECURSORS SHEDS LIGHT ON A PHYLOGENETIC ENIGMA. Despite this, the phylogenetic position of lagerpetid

EZCURRA, M. D.; NESBITT, S. J.; BRONZATI, M.; AGNOLIN, F. L.; BENSON, R. B. J.; BRISSÓN EGLI, F.; CABREIRA, S. F.; EVERS, S.; GENTIL, ADRIEL R.; IRMIS, R. B.; MARTINELLI, A.; NOVAS, F. E.; ROBERTO DA SILVA, L.; SMITH, N. D.; STOCKER, MICHELLE R.; TURNER, A. H.; LANGER, M. C.

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2019

Lagerpetids are one of the most enigmatic and poorly known Triassic archosauromorphs, with an anatomical record mostly limited to the braincase, dorsal and sacral vertebrae, pelvic girdle and hindlimb. Despite this, the phylogenetic position of lagerpetids as the sister-taxa of Dinosauriformes has been repeatedly found in quantitative analyses during the last three decades. Here, we report new morphological information provided by lagerpetid specimens from the Carnian˗Norian of Argentina, Brazil, and North America that substantially expands our knowledge of the clade. Lagerpetids show unexpected features, such as an elongated dentary with a pointed and edentulous anterior end, a high tooth count, and tricuspid tooth crowns. These novel data were included in a comprehensive phylogenetic analysis of early archosauromorphs that recovered lagerpetids as the sister-taxon to Pterosauria rather than to Dinosauriformes. The Lagerpetidae+Pterosauria clade possesses high branch supports and more than 20 synapomorphies, including an upper temporal bar level with the orbit mid-height, dorsally inflated endocranial roof, hypertrophied floccular recess, subequal height and width of osseous labyrinth of inner ear (analysed as a 3D morphogeometric character), splenial reduced/absent, dorsoventrally tall pubo-ischiadic plate, hook-shaped femoral head, and fused astragalocalcaneum. Our results shed light on a long standing evolutionary enigma, bridging the morphological gap between pterosaurs and other diapsid groups. The anatomy of lagerpetids informs on the sequence of acquisition of character-states towards the pterosaurian body plan, in which some neuroanatomical and appendicular features were acquired before the origin of Pterosauria and subsequently co-opted in a phenotype capable of active flight.