 In one of the earliest phylogenetic analyses of the group , <unk> ( 1983 ) recognized five characteristics that made <unk> a clade : a bone at the back of the skull , the <unk> , is connected to another bone on the underside of the skull , the <unk> ; large openings called <unk> <unk> are present between the <unk> ; the <unk> ( a bone involved in hearing ) is connected to the <unk> and projects upward ; the <unk> , a bone in the pectoral <unk> , is thin ; and part of the <unk> called the <unk> <unk> to the neural arch . Additional features were given by Godfrey et al . ( 1987 ) , including the contact between the <unk> and <unk> at the back of the skull , small projections ( <unk> processes ) on the ribs , and a pelvic <unk> with each side having a single <unk> blade . These shared characteristics are called <unk> . 
