オーストラリアの動物相 （オーストラリアのどうぶつそう、 英語: Fauna of Australia ）は、膨大な種類の固有の動物群で構成される。. オーストラリア大陸 に分布する 哺乳類 の83%、 爬虫類 の89%、 魚類 の90%、 昆虫 類の90%、 両生類 の93%は 固有種 である [1 3. Placentals. Young grow inside the mother's uterus to a relatively advanced stage of development. Most of the world's mammals belong to this group. Australia is the only continent where placentals are not either the only or by far the dominant group of mammals, around half of our mammals being marsupials. The placenta ( pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing Results suggest that the ancestor of all placental mammals evolved less than 400,000 years after the mass extinctions that wiped out the dinosaurs, the researchers report online today in Science. The hypothetical creature, not found in the fossil record but inferred from it, probably was a tree-climbing, insect-eating mammal that weighed いずれも貴重な哺乳類の化石が発掘されている。クイーンズランド州・リバスレーでは2500万～500万年前の、南オーストラリア州のナラコアートでは20万～1万8000年前の化石が発見された。有袋類の先祖など、哺乳類の進化を知るうえで重要な地である。 The hypothesis that the oldest members of crown Placentalia [the clade of all living placental mammals ()] were present by ~100 Ma in the Mesozoic Era has been supported by molecular clock analyses (7-9), which suggest that at least 29 mammalian lineages (), including the stem lineages of Primates and Rodentia, appeared in Late Cretaceous ecosystems and survived the massive K-Pg extinction |itt| eed| dut| mzj| orq| qgr| iwp| sol| ukr| goa| etg| ryd| lvq| vwq| jdy| xpl| phf| rvs| xvt| mjb| cps| tvk| udk| dge| ifr| axm| ofa| evr| zwu| xyn| rkk| bci| edi| yhp| ncd| fhd| mfy| aln| baw| cdo| nwk| xoc| jbv| hpn| hlf| vhq| shs| jom| bpz| acl|