No implantation in an extra-uterine pregnancy of a placentotrophic reptile

Placentation is a common feature of live-bearing reptiles and mammals. Placentae are variable between species and can be classified by the extent that embryonic tissue breaches (invades) the uterus. Noninvasive placentation in eutherians is maternally imposed as extra-uterine embryos of species with epitheliochorial placentation will readily invade non-uterine tissues. This study documents the first observation of an extra-uterine pregnancy in a reptile; Pseudemoia entrecasteauxii, which in-utero exhibits non-invasive epitheliochorial placentation. The extra-uterine embryo did not invade maternal tissue suggesting fundamental differences between the nature and evolution of placentation in P. entrecasteauxii and eutherian mammals. (C) 2013 Elsevier Ltd. All rights reserved.