Two cases of asymmetrical conjoined twins in wild mammals from the Netherlands

Case reports of conjoined twins (‘Siamese twins’) in wild mammals are very scarce. Most published reports of conjoined twinning concern cases in man or in domestic mammals. In this article two cases of asymmetrical conjoined twinning in wild mammals are described: an omphalopagus parasiticus in a black rat Rattus rattus and a pygopagus parasiticus in a European hedgehog Erinaceus europaeus. The omphalopagus and pygopagus are the first published cases of parasitic conjoined twinning in wild mammals.