THE POSTURE OF THE FORELIMBS IN CHILESAURUS DIEGOSUAREZI (DINOSAURIA, THEROPODA) AND ITS BEHAVIORAL AND PHYLOGENETIC IMPLICATIONS

AGNOLÍN, FEDERICO L.; SALGADO, LEONARDO; DE LA CRUZ, RITA; NOVAS, FERNANDO E.; ISASI, MARCELO P.; RUBILAR-ROGERS, DAVID; CHIMENTO, NICOLÁS R.; EZCURRA, MARTÍN D.; SUÁREZ, MANUEL; VARGAS, ALEXANDER O.

Buenos Aires

Jornada; XXX Jornadas Argentinas de Paleontología de Vertebrados; 2016

Museo Argentino de Ciencias Naturales

Many dinosaur skeletons show evidence of behavior, including feeding, predation, nesting and parental care. However, many aspects of dinosaur habits are still uncertain or remain poorly known. The resting posture of the forelimbs has been studied in theropods species, in regards with the acquisition of flight in advanced maniraptoran theropods. Chilesaurus diegosuarezi is a bizarre tetanuran recently described for the Toqui Formation (latest Tithonian) of southern Chile. In the present work we study and analize the posture of four articulated specimens of Chilesaurus diegosuarezi: SNGM-1935 (holotype), SNGM-1936, SNGM-1937, SNGM-1938 (Servicio Nacional de Geología y Minería, Chile). All the specimens of Chilesaurus showed a similar position and interrelations of the forelimbs bones. In concordance with resting posture, the four specimens here described of Chilesaurus have the forelimbs ventrally flexed and with the hands oriented backwards. The position of the forelimbs elements of Chilesaurus is concordant with previous descriptions for resting posture in some derived theropods as Mei long, Sinornithoides youngi and Albinykus baatar. It is possible, that individuals of Chilesaurus have been in passive activity (feeding, resting, etc.) when were buried quickly, allowing a fossilization almost in life position. The position of the forelimb bones in Chilesaurus could show the first evidences of the structures linked to the muscles that flex the forearms (e.g., three-fingered hand with partial laterally folding capability), features related with the acquisition of flying control.