Forelimb Posture in Chilesaurus diegosuarezi (Dinosauria, Theropoda) and Its Behavioral and Phylogenetic Implications

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

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, nesting, and parental care. The resting postureof the forelimbs has been studied in some theropod species, in relation to the acquisition of flight in advanced maniraptoran theropods. Chilesaurusdiegosuarezi is a bizarre tetanuran recently described from the Toqui Formation (latest Tithonian) of southern Chile that is representedby multiple well-preserved and articulated specimens. The aim of the present work is to analyze the forelimb posture of four articulatedspecimens of Chilesaurus diegosuarezi, focusing on its anatomical description, and phylogenetic and behavioral implications. All the preservedspecimens show strongly ventrally flexed arms with the hands oriented backwards, an arrangement that closely resembles those in dinosaurspecimens previously described as preserving resting posture, such as Mei long, Sinornithoides youngi and Albinykus baatar. As a result, it seemsthat individuals of Chilesaurus diegosuarezi have been in passive activity (e.g. feeding, resting) when they were buried quickly, allowing theirfossilization in life position and preserving the forelimb resting posture. The arrangement of the forelimb bones in Chilesaurus could show thefirst evidences of the structures linked to the muscles that flex the forearms, features related with the acquisition of flying control in advancedmaniraptorans.