Placental ontogeny in Tasmanian snow skinks (genus Niveoscincus) (Lacertilia: Scincidae)
Article first published online: 23 DEC 2008
Copyright © 2008 Wiley-Liss, Inc.
Journal of Morphology
Volume 270, Issue 4, pages 485–516, April 2009
How to Cite
Stewart, J. R. and Thompson, M. B. (2009), Placental ontogeny in Tasmanian snow skinks (genus Niveoscincus) (Lacertilia: Scincidae). J. Morphol., 270: 485–516. doi: 10.1002/jmor.10704
- Issue published online: 6 MAR 2009
- Article first published online: 23 DEC 2008
- Australian Research Council Large
- Australian Research Council Large and Discovery
Lizards of the viviparous genus Niveoscincus contributed importantly to a classic model for the evolution of placentation of squamate reptiles. This model predicts that: (1) placental function is correlated with placental structural complexity and (2) the type of chorioallantoic placenta attributed to three species of Niveoscincus (N. metallicus, N. ocellatus, N. pretiosus) is intermediate in complexity to a highly placentotrophic type of placenta. Recent studies of two of these species (N. metallicus, N. ocellatus) revealed additional variation in placental structure, as well as variation in the level of placentotrophy; N. metallicus is predominantly lecithotrophic, while N. ocellatus is highly placentotrophic. We used light microscopy to study placental ontogeny in two biennially reproducing species of Niveoscincus (N. greeni, N. microlepidotus) and placental morphology in late stage embryos of N. pretiosus. These data, in combination with prior studies, provide descriptions of placental structure for six of the eight species assigned to this lineage. The genus Niveoscincus has greater variation in placental structure than any other squamate lineage. We recognize four distinct groupings among these six species based on placental structure. The most highly placentotrophic species, N. ocellatus, has a complex placental morphology, yet shares these structures with a predominantly lecithotrophic species, N. microlepidotus. Thus, among species of Niveoscincus, placental structural complexity is not an infallible predictor of overall placental function. J. Morphol. 2009. © 2008 Wiley-Liss, Inc.