OBO_REL:part_of (UNDECLARED) 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. Counts of caudal principal rays are taken as the number of branched rays plus two adjacent unbranched rays and counts are typically reported as, for example: 1,8,7,1 (1 unbranched and 8 branched upper rays, 7 branched and 1 unbranched lower rays). A caudal principal caudal ray may be associated with one or more hypurals or with hemal spines of preural centra 1 and 2 (Schultze and Arratia, 1989; Arratia, 2008). In basal teleosts the number of caudal principal rays is about 20. A decreasing of the number of the branched-and segmented rays is observed in more advanced teleosts (see Schultze and Arratia, 1989; Arratia, 1991, 2008). TAO:0001585 caudal fin principal ray caudal principal lepidotrichium teleost_anatomy caudal principal ray set caudal fin lepidotrichium