|
The bird order Casuariiformes has four surviving members: the three species of cassowary, and the only remaining species of emu. The emus are classified in the family, Dromaiidae, while the cassowaries are all located within the Casuariidae family. All four members of the order are very large flightless birds native to Australia-New Guinea.〔Clements, J (2007)〕 The characteristics of the family are those of its members. ==Systematics and evolution== The emus form a distinct family, characterized by legs adapted for running. As with all ratites, there are several contested theories concerning their evolution and relationships. As regards this order, it is especially interesting whether emus or cassowaries are the more primitive form: the latter are generally assumed to retain more plesiomorphic features, but this does not need to be true at all; the fossil record is also ambiguous, and the present state of genomics does not allow for sufficiently comprehensive analyses. A combination of all these approaches with considerations of plate tectonics at least is necessary for resolving this issue. The total number of cassowary species described, based on minor differences in casque shape and color variations, formerly reached nine. Now, however, only 3 species are recognized, and most authorities only acknowledge few subspecies or none at all. The fossil record of casuariforms is interesting, but not very extensive. Regarding fossil species of ''Dromaius'' and ''Casuarius'', see their genus pages. Some Australian fossils initially believed to be from emus were recognized to represent a distinct genus, ''Emuarius'',〔From "Emu" + "''Casuarius''". Describer W. E. Boles commonly refers to the genus as "emuwaries" or "cassomus".〕 which had a cassowary-like skull and femur and an emu-like lower leg and foot. In addition, the first fossils of mihirungs were initially believed to be from giant emus,〔The vernacular name "mihirung" is derived from ''mihirung paringmal'', which means "giant emu" in the Chaap Wuurong language〕 but these birds were completely unrelated. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Casuariiformes」の詳細全文を読む スポンサード リンク
|