Allantois wani membrane ne wanda ke samuwa a lokacin ci gaban amfrayo a cikin dabbobi masu shayarwa da wasu kasusuwa. Yana daya daga cikin membranes na extraembryonic, wanda ke nufin yana tasowa a wajen tayin kanta. Allantois yana taka muhimmiyar rawa wajen musayar iskar gas da kayan sharar gida tsakanin tayin da ke tasowa da kuma zagayen mahaifa. Yana kuma taimakawa wajen samuwar igiyar cibiya da mahaifa.