- Evidence of H beta 58, a gene involved in mammalian placental development, in the three-toed skink, Chalcides chalcides (Squamata: Scincidae), a viviparous placentotrophic reptile. Paulesu, L., Cateni, C., Romagnoli, R., Chellini, F., Angelini, F., Guarino, F.M., Rider, V., Imakawa, K., Bigliardi, E. Placenta (2001)