 In one of the earliest phylogenetic analyses of the group , Gardiner ( 1983 ) recognized five characteristics that made Temnospondyli a clade : a bone at the back of the skull , the <unk> , is connected to another bone on the underside of the skull , the pterygoid ; large openings called <unk> vacuities are present between the <unk> ; the stapes ( a bone involved in hearing ) is connected to the <unk> and projects upward ; the <unk> , a bone in the pectoral girdle , is thin ; and part of the vertebra called the <unk> attaches 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 ( uncinate processes ) on the ribs , and a pelvic girdle with each side having a single iliac blade . These shared characteristics are called synapomorphies . 
