cotyledon

noun2

1. •
   The leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling.
2. •
   Each of the patches of villi on the foetal chorion in the placenta of ruminants and some other mammals.

   • Forced to apply animal findings to humans, his human womb also had cotyledons like a dog's. — 1997