lepidotrichium

(plural lepidotrichia))

a definitive fin ray (including spines), usually dermal bones found in Teleostomi. Each lepidotrich is formed of two hemitrichs closely joined along their length except basally where they diverge to articulate with the pterygiophores. See also actinotrichia, ceratotrichia. Lepidotrichia are thought to have evolved from scales. The pelvic and hypochordal fin membranes of Acanthodii bear rows of scales which correspond to the primitive condition of lepidotrichia. Lepidotrichia form like actinotrichia but become surrounded by bony tissue, develop segments and sometimes branch