Term: pectoral fin fin fold actinotrichium
Name: pectoral fin
Synonyms: forefin, pectoral fins
Definition: Paired fin that is located in the thoracic region of the body.
Ontology: Anatomy Ontology [ZFA:0001161]

Name: fin fold actinotrichium
Synonyms: fin fold actinotrichia, median fin fold actinotrichium
Definition: Portion of tissue which is a slender, horny, flexible, unsegmented fibril, which strengthens the embryonic fin fold. Actinotrichia are translucent, exhibit birefringence (double refraction) and are composed of the scleroprotein elastoidine.
Ontology: Anatomy Ontology [ZFA:0000089]