Anterior caudal transverse processes in sauropod dinosaurs: morphological, phylogenetic and functional aspects

PABLO A. GALLINA AND ALEJANDRO OTERO

AMEGHINIANA

Lugar: Buenos Aires; Año: 2008

0002-7014

ABSTRACT- A great amount of sauropod record is based on caudal vertebrae. Morphological analyses of tail bones were essentially focused on centrum shape, being poorly studied other anatomical features. A particular description on anterior caudal transverse processes (ACTP) is realized in order to improve the scarce knowledge of this tail part. Within Sauropoda there are two different ACTP architecture; simple (single element projected on the vertebral side) and complex (lateral bony laminar plates supported by bony bars). The identity of the ACTP elements includes a rib, a synapophysis and laminar components, for this reason the ACTP laminae are renamed. The ventral laminae include the acpl and the pcdl, whereas the dorsal ones are the prdl and the podl when present. The ACTP morphology is not informative at higher-level phylogeny, but at lower-level the in-group relationships of Diplodocoidea can be improved by means of analyzing these structures. The ACTP morphological variation between the firsts and consecutive caudal vertebrae should presumably be interpreted as a consequence of the relative development of the M. caudofemoralis brevis. The “sacralization” of the ACTP is related to the attachment of the soft tissues associated to the tail. In this sense the Mm. caudofemorales should be the most important muscle group.