|
Holozoa is a group of organisms that includes animals and their closest single-celled relatives, but excludes fungi. ''Holozoa'' is also an old name for the tunicate genus ''Distaplia''.''〔 〕 Because Holozoa is a clade including all organisms more closely related to animals than to fungi, some authors prefer it to recognizing paraphyletic groups such as Choanozoa, which mostly consists of Holozoa minus animals.〔 〕 Perhaps the best-known holozoans, apart from animals, are the choanoflagellates, which strongly resemble the collar cells of sponges, and so were theorized to be related to sponges even in the 19th century. ''Proterospongia'' is an example of a colonial choanoflagellate that may shed light on the origin of sponges. The affinities of the other single-celled holozoans only began to be recognized in the 1990s.〔 〕 A group of mostly parasitic species called Icthyosporea or Mesomycetozoea is sometimes grouped with other species in Mesomycetozoa (note the difference in the ending). The amoeboid genera ''Ministeria'' and ''Capsaspora'' may be united in a group called Filasterea by the structure of their thread-like pseudopods. Along with choanoflagellates, filastereans may be closely related to animals, and one analysis grouped them together as the clade Filozoa.〔 ==Fossil record== The oldest fossils of holozoans are animals, which date back to the Ediacaran period, about 600 million years ago.〔 〕 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「Holozoa」の詳細全文を読む スポンサード リンク
|