part of overlaps start stage end stage urohyal The urohyal is a median dermal bone that ossifies in the membrane between the paired sternohyoideus muscles ventral to the anterior end of copula 1. It is an unpaired ossification of the tendon of the sternohyoideos muscles in basal teleosts, and it is paired in catfishes (Arratia and Schultze, 1990). zebrafish_anatomy ZFA:0000452 TAO:0000452 dermatocranium ventral hyoid arch dermal bone dorsal hypohyal-urohyal joint unknown adult