FORELIMB POSTURE IN CHILESAURUS DIEGOSUAREZI (DINOSAURIA, THEROPODA) AND ITS BEHAVIORAL AND PHYLOGENETIC IMPLICATIONS

CHIMENTO, NICOLÁS; AGNOLIN, FEDERICO; NOVAS, FERNANDO; EZCURRA, MARTÍN; SALGADO, LEONARDO; ISASI, MARCELO; SUÁREZ, MANUEL; DE LA CRUZ, RITA; RUBILAR-ROGERS, DAVID; VARGAS, ALEXANDER

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2017 vol. 54 p. 567 - 575

0002-7014

Many dinosaur skeletons show evidence of behavior, including feeding, predation,40 nesting, and parental care. The resting posture of the forelimbs has been studied in some41 theropod species, in relation to the acquisition of flight in advanced maniraptoran42 theropods. Chilesaurus diegosuarezi is a bizarre tetanuran recently described from the43 Toqui Formation (latest Tithonian) of southern Chile that is represented by multiple44 well-preserved and articulated specimens. The aim of the present work is to analyze the45 forelimb posture of four articulated specimens of Chilesaurus: SNGM-1935 (holotype),46 SNGM-1936, SNGM-1937, SNGM-1938; focusing on its anatomical description, and47 phylogenetic and behavioral implications. All the preserved specimens of Chilesaurus48 show strongly ventrally flexed arms with the hands oriented backwards, an arrangement49 that closely resembles those in dinosaur specimens previously described as preserving50 resting posture, such as Mei long, Sinornithoides youngi, and Albinykus baatar. As a51 result, it seems that individuals of Chilesaurus have been in passive activity (e.g.52 feeding, resting) when they were buried quickly, allowing their fossilization in life53 position and preserving the forelimb resting posture. The arrangement of the forelimb54 bones in Chilesaurus could show the first evidences of the structures linked to the55 muscles that flex the forearms, features related with the acquisition of flying control in56 advanced maniraptorans.