Pterygopodia

from The Collaborative International Dictionary of English v.0.48

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.
   [1913 Webster]