caudal principal ray
caudal principal ray
"Caudal fin lepidotrichium that is adjacent to a branched ray. Caudal principal rays may be segmented but unbranched and the main element forming the dorsal or ventral leading margin of the caudal fin or a ray that may be only segmented-and-branched and forms part of the middle-posterior region of the fin. A caudal principal ray is an unpaired median bone."