The development of the chorio‐allantoic placenta of the African scaly‐tailed squirrels (family Anomaluridae)

Abstract

The affinities of the isolated rodent family Anomaluridae are unknown. Both sciuromorphous and specialized features characterize its placental morphology. A shallow preplacenta consists of inner cytotrophoblastic and outer syncytiotrophoblastic layers. The early chorio-allantoic placenta consists of the following zones: a hemochorial zone of interconnected trabeculae, lined with outer syncytiotrophoblastic and inner cytotrophoblastic layers; anchoring trabeculae attached to a zone of decidual giant cells, with the giant cells gradually disappearing in later stages; a zone of acidophilic, PAS-positive necrotic material underlying the giant cells; and a zone of decidua basalis underlying the necrotic zone and probably contributing to it. An allantoic vesicle lies on the surface of the early placenta; it is reduced in later stages. The bilaminar omphalopleure persists, and it is attached to the margins of the placental disc. The fetal membranes of Anomahwus are most similar to those of sciuromorphs, Pedetes and Ctenodactylus; this may be the result of primitive retentions.

The chromosomes of the hystricomorphous family Ctenodactylidae (Rodentia: ?Sciuromorpha) and their bearing on the relationships of the four living genera

“…Whatever opinions there are about the relationships of the Ctenodactylidae, they are based on morphological criteria, mainly on the structure of the teeth, skull and embryonic membranes (Tullberg, 1899;Lange, 1938;Ellerman, 1940;Landry, 1957;Luckett, 1971).…”

Major Patterns in Vertebrate Evolution

“…This concept of a monophyletic clustering of the South American and African hystricognathous rodents as an order Hystricognathi is also supported by numerous similarities in features of their soft and hard anatomy, although most of these characters have not been evaluated cladistically as yet. In contrast, the Afro-Asian hystricomorphous (but not hystricognathous) families Anomaluridae, Pedetidae, and Ctenodactylidae do not share this suite of unique and derived fetal membrane characters (Luckett, 1971), and this supports the concept that these taxa are not closely related phyletically to the Hystricognathi.…”

“…The conservative nature of the fetal membranes permits generalizations about their relationships within families and super~amilies to be based on developmental data from relatively few species, since significant differences are rarely found within families . A reconstruction of the morphotype of primate fetal membranes has been presented elsewhere (Luckett, 1974, and the primitive and derived character states of rodent fetal membranes have been discussed by and Luckett (1971). The data utilized in the morphotype reconstruction can be summarized within four general categories: (1) Implantation and amniogenesis.…”

Reproduction in female gundis(Rodentia: Ctenodactylidae)

“…Ctenodactylids have superficial implantation (Lange, 1938) like some sciuromorphs and Pedetes (Luckett, 1971) in contrast to the specialised type of interstitial implantation found in caviomorphs (Roberts & Perry, 1974). In the ctenodactylids, amniogenesis is by a specialised type of folding (Luckett, 1971) like that ili Pedetes, anomalurids and geomyids and quite distinct from cavitation amniogenesis characteristic of caviomorphs. The ctenodactylid placenta bears a striking resemblance to that of Pedetes (Fischer & Mossmann, 1969) and is different from that of all other rodents.…”