The Collaborative International Dictionary
Pterygopodium
Pterygopodium \Pter`y*go*po"di*um\, n.; pl. Pterygopodia. [NL., fr. Gr. ?, ?, a fin + ?, dim. of ?, ?, a foot.] (Anat.) A specially modified part of the ventral fin in male elasmobranchs, which serves as a copulatory organ, or clasper.
Wiktionary
pterygopodium
n. (context anatomy English) A modified part of the ventral fin in male elasmobranchs, which serves as a copulatory organ, or clasper.