PHYLOGENETIC INTERPRETATION OF THE EARLY DEVELOPMENT OF THE EUTHERIANBLASTOCYST

The evolutionary innovations in Eutheria (Placentalia) are: loss of yo lk, formation of outer trophoblast and attachment of maternal and embr yonic tissues and circulation systems. Notogenesis and morphogenesis a re running the programme common for Amniota, but the early development of the blastocyst and of extraembryonic membranes differs among the s pecies. Therefore we can assume that the first placentals were not a h omogenous,coup; if they were, they would have responded to innovations in the same way. To serve this issue the characters of fourteen pairs of early ontogenetic events were used for cladistic analysis. In each pair the event exists both in its primitive and derived state. The pa irs 1 to 6 refer to the blastocyst, the pairs 7 to 14 refer to embryon ic nutrition. The placental mammals under study branch into two groups ; decisive for the division is the speed of attachment of the blastocy st to the endometrium, on which the course of the other events is depe ndent. The first group includes: Pholidota, Carnivora, Artiodactyla, C etacea, Perissodactyla, Proboscidea, Hyracoidea, Sirenia and Scandenti a. The second group includes: Macroscelidea, Dermoptera, Chiroptera, R odentia (incl. Lagomorpha) and Edentata. The orders Insectivora and Pr imates appear as diphyletic. From the order Insectivora, the superfami lies Soricoidea and Chrysochloroidea belong to the first group, the su perfamilies Tenrecoidea and Erinacoidea belong to the second group. Fr om the order Primates, the first group includes tribus Strepsirhini (i .e. prosimian superfamilies Lorisoidea and Lemuroidea). Tribus Haplorh ini (prosimians of the superfamily Tarsoidea and suborder Anthropoidea ), belongs to the second group.