Osteostracans have extremely anterior pharyngeal arches: the most anterior gill pouch (probably lying between the mandibular ... Compared to a living gnathostome the most distinctive features are the broad suborbital shelves that form a floor for the eye ... Phylogenetic relationships among Vertebrata with Placodermi resolved as a paraphyletic segment of the gnathostome stem group ( ... The angle between the anterior and posterior bulges is about 70°. Between the anterior and posterior bulges, the floor of the ...