The rosids are members of a large monophyletic clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms.
The clade is divided into 16 to 20 orders, depending upon circumscription and classification. These orders, in turn, together comprise about 140 families. The rosids and the asterids are by far the largest clades in the eudicots .
Fossil rosids are known from the Cretaceous period. Molecular clock estimates indicate that the rosids originated in the Aptian or Albian stages of the Cretaceous, between 125 and 99.6 million years ago.
== The name ==
The name "rosids" is based upon the name "Rosidae", which had usually been understood to be a subclass. In 1967, Armen Takhtajan showed that the correct basis for the name "Rosidae" is a description of a group of plants published in 1830 by Friedrich Gottlieb Bartling. This clade was later renamed "Rosidae" and has been variously delimited by different authors. The name "rosids" is informal, and not assumed to have any particular taxonomic rank like the names authorized by the ICBN. The rosids are monophyletic based upon evidence found by molecular phylogenetic analysis.
Three different definitions of the rosids are currently in use. Some authors include the orders Saxifragales and Vitales in the rosids. Others exclude both of these orders. The circumscription used in this article is that of the APG II classification, which includes Vitales, but excludes Saxifragales.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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