Placentation in colugos

Colugo fetus near term from Hubrecht (1919)

Colugos (once known as flying lemurs) are of interest because of their close relationship to primates. Dermoptera (colugos), Scandentia (tree shrews) and Primates group together as Euarchonta.

Dilated maternal blood spaces in a colugo placenta

Hill Collection micrograph courtesy of Allen C. Enders

Their placentation is of interest because it seems to be intermediate between a labyrinthine and villous form. Starck referred to it as a Zwischenform and Wislocki compared it to the trabecular placenta of Neotropical primates. This not withstanding, we still lack a complete description of the term placenta. Mossman (previous post) could not reconcile his own observations with unpublished drawings by Luckett and urged further study. 

Hubrecht (previous post) accumulated 182 uteri of the Sunda colugo (Galeopterus variegatus). His thorough description of early fetal development, published posthumously (Verhandelingen der Koninklijke Akademie van Wetenschappen 1919), stopped at the establishment of the definitive placenta. J. P. Hill collected specimens of the Sunda colugo and the Philippine colugo (Cynocephalus volans) but did not describe them. Nor did Amoroso (previous post) who apparently borrowed most of Hill's slides. The time is ripe for a thorough study of colugo placentation.