The coracoid bar and its phylogenetic importance for elasmobranchs (Chondrichthyes).

In a seminal study on elasmobranch systematics, Maisey proposed the monophyly of a large lineage of sharks based primarily on the sharing of an orbitostylic jaw suspension. This group was later redefined as the Squalomorphi, which included Squatinidae but not Batoidea. Subsequent morphological analyses, however, rejected Maisey's scheme, which was left aside for nearly two decades until the first molecular phylogenies began to cluster again the orbitostylic sharks into a monophyletic group. In a broad comparative investigation of the anatomy of the appendicular skeleton of cartilaginous fishes, we discovered new evidence supporting the monophyly of squalomorph sharks: the presence of a posterior process at the lateral region of the coracoid bar serving as a origin site for the depressor pectoralis II muscle. This feature would be the first strong morphological evidence in 40 years potentially supporting the monophyly of Squalomorphi. [ABSTRACT FROM AUTHOR]