The Collaborative International Dictionary of English v.0.48:

Syndactyl \Syn*dac"tyl\, Syndactyle \Syn*dac"tyle\, a. [Syn- +
   Gr. ? finger, toe.] (Zool. & Med.)
   Having two or more digits wholly or partly united. See
   Syndactylism.
   [Webster 1913 Suppl.]