EN
Of the family Pteropodidae (Megachiroptera), only the placentae of Rousettus and Pteropus have been examined ultrastructurally. Recently, the interhemal membrane characteristics of some members of this family have been questioned. We report here on the fine structure of the interhemal membrane of Rousettus leschenaulti and Cynopterus sphinx gangeticus. Contrary to earlier reports of a consistent endotheliochorial nature of the membrane until mid-gestation in Rousettus, such a condition is found to be restricted to the trilaminar blastocyst stage. Thereafter, the placental membrane was hemodichorial. We also document how the trophoblast surface has been modified to create honeycombed intrasyncytial desmosomes in Rousettus. The intrasyncytial lamina and maternal endothelium are lacking in the hemodichorial interhemal membrane of Cynopterus.