urohyal

from The Century Dictionary.

• noun In ichthyology, a median bone of fishes between the hypohyals and extending back under the gills.
• Of or pertaining to the urohyal.
• noun In ornithology, the tail-piece of the composite hyoid bone; the median azygous backward-projecting element of that bone, borne upon the basihyal; the basibranchial element, or base of the first branchial arch.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat.) Of or pertaining to one or more median and posterior elements in the hyoidean arch of fishes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Of or pertaining to one or more median and posterior elements in the hyoidean arch of fishes.
• noun anatomy A urohyal bone or cartilage.