Identification of syncytin-car-1, an endogenous retroviral envelope gene involved in placentation and conserved in Carnivora: a syncytin in a new superorder of placental mammals by Heidmann Thierry, Mulot Baptiste, Dupressoír Anne, Reynaud Karine, Véron Géraldine, Bernard-Stoecklin Sybille, Heidmann Odile, Cornells Guillaume