Placental ontogeny of the Australian scincid lizardsNiveoscincus coventryiandPseudemoia spenceri

Placentation in the Mexican scincid lizard Plestiodon brevirostris (Squamata: Scincidae)

“…It is evident that the chorioallantoic placenta is a simple structure, but as development progresses, there is an increase in the vascularization of the maternal and embryonic tissues that form it. The time of formation of this placental type coincides with that of other species of scincids of the genus Niveoscincus , for example: N. ocellatus during Stage 29 (Stewart & Thompson, 2004), N. coventryi during Stage 30 (Stewart & Thompson, 1998), and N. greeni and N. microlepidotus during Stage 31 (Stewart & Thompson, 2009). Additionally, in the Australian skink, Eulamprus tympanum , as gestation progresses through Stage 29, the uterine region of the chorioallantoic placenta forms ridges (Adams et al (2007).…”

“…During development in the non‐vascularized mesoderm, a site of angiogenesis integrates to form a vascularized area. In this way, the vascularized trilaminar omphalopleure, when in contact with the uterine wall, forms the choriovitelline placenta, which has been observed in some species of the Scincidae ( Chalcides chalcides , Blackburn & Callard, 1997; Niveoscincus coventryi and Pseudemoia spenceri, N. greeni, N. microlepidotus , Stewart & Thompson, 1994, 1998, 2009; Mabuya mabouya , Jerez & Ramírez‐Pinilla, 2003; Lacerta vivipara, N. ocellatus , Stewart et al, 2004); in Anguidae, Elgaria coerulea [ Gerrhonotus coeruleus ], Stewart, 1985; Mesaspis viridiflava , Stewart & Mendez de la Cruz, 2018; in Liolaemidae, Liolaemus gravenhorsti , Lemus & Badinez, 1967; L. robustus and L. walkeri , Aguilar et al, 2015; and in Phrynosomatidae, Sceloporus bicanthalis , Guillette & Jones, 1985; Sceloporus mucronatus , Villagrán et al, 2005; S. grammicus , Villagrán Santa Cruz, 1989). In Plestiodon brevirostris , these placental types (chorioplacenta and choriovitelline placenta) are still visible during Stage 29, but are already restricted to a small portion of the embryonic hemisphere of the embryonic chamber.…”

“…In P. brevirostris , the structure of the omphaloplacenta and the time of embryonic development coincide with that described for other species of scincids, such as P. entrecasteauxii (during Stage 30; Stewart & Thompson, 1996). Additionally, in N. coventryi (Stewart & Thompson, 1998), an incomplete omphaloplacenta is described in Stage 30; while in N. ocellatus , the omphaloplacenta is observed from Stage 29 (Stewart & Thompson, 2004), has a cuboidal chorionic epithelium and the endoderm is made up of squamous cells. Likewise, the omphaloplacenta has also been described for N. greeni and N. microlepidotus (Stage 31) and N. pretiosus (Stage 37; Stewart & Thompson, 2009).…”

“…Therefore, these tissues contribute to the formation of the omphaloplacenta (a unique placental type for Squamata), and Thompson, 1996). Additionally, in N. coventryi (Stewart & Thompson, 1998), an incomplete omphaloplacenta is described in Stage 30; while in N. ocellatus, the omphaloplacenta is observed from Stage 29 (Stewart & Thompson, 2004), has a cuboidal chorionic epithelium and the endoderm is made up of squamous cells. Likewise, the omphaloplacenta has also been described for N.…”

Phylogenetic relationships in the Eugongylini (Squamata: Scincidae): generic limits and biogeography

“…Greer later (1989) treated coventryi as congeneric with Harrisoniascincus zia , presumably following the earlier suggestion of Ingram and Ehmann (1981), which was largely based on colouration and ecological similarities. Stewart and Thompson (1998) found that the species did not possess the unique placental morphology of the species now assigned to Carinascincus , and this difference in placental morphology is mirrored by differences in placental physiology between coventryi and these taxa (Thompson et al . 2001).…”