pectoral fin spine Pectoral-fin lepidotrichium 1 with mostly co-ossified and unsegmented hemitrichia that form a stiff and usually thick shaft and enlarged basal processes that moveably articulate with the pectoral girdle. The pectoral fin spine may also result from the fusion of several lepidotrichia that form a stiff shaft. TAO:0001787 pectoral spine teleost_anatomy pectoral fin lepidotrichium