(anatomy) The thickened layer of skin adjoining fingernails and toenails, particularly at the base of the nail.
(zoology, veterinary medicine) The protective capsule that surrounds the hoof of foetuses and neonates of hoofed animals, which disappears soon after birth, but remnants of which remain as part of the permanent hoof.
2014, Kevin T. Corley, Jonna M. Jokisolo, Chapter 172: Evaluation of the Compromised Neonatal Foal, Kim A. Sprayberry, N. Edward Robinson, Robinson's Current Therapy in Equine Medicine, 7th Edition, page 720,
The presence of eponychium (also called “foal slippers”) on the feet (Figure 172-3) is indicative that the foal has not yet stood.