Fossil rosids are known from theCretaceous period.Molecular clock estimates indicate that the rosids may have originated in theAptian orAlbian stages of theCretaceous, between 125 and 99.6 million years ago.[5][6]
Today's broadleaved forests are dominated by rosid species, which in turn help with diversification in many other living lineages. Additionally, rosid herbs and shrubs are a significant part of arctic/alpine and temperate floras. The clade also includes some aquatic, desert and parasitic plants.[7]
The name 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 agroup of plants published in 1830 byFriedrich Gottlieb Bartling.[8] The clade was later renamed "Rosidae" and has been variouslydelimited by different authors. The name "rosids" is informal and not assumed to have any particulartaxonomic rank like the names authorized by theICBN. The rosids aremonophyletic based upon evidence found bymolecular phylogenetic analysis.[citation needed]
Three differentdefinitions of the rosids were used. Some authors included the ordersSaxifragales andVitales in the rosids.[9] Others excluded both of these orders.[10] The circumscription used in this article is that of theAPG IV classification, which includes Vitales, but excludes Saxifragales.
The rosids consist of two groups: the order Vitales and the eurosids (true rosids).The eurosids, in turn, are divided into two groups: fabids (Fabidae, eurosids I) and malvids (Malvidae, eurosids II).[10]
The rosids consist of 17 orders. In addition to Vitales, there are eight orders in fabids and eight orders in malvids. Some of the orders have only recently been recognized.[10] These are Vitales,[12] Zygophyllales,[13] Crossosomatales,[14] Picramniales,[15] and Huerteales.[16]
Thenitrogen-fixing clade contains a high number ofactinorhizal plants (which have root nodules containingnitrogen fixing bacteria, helping the plant grow in poor soils). Not all plants in this clade are actinorhizal, however.[17]
^Scotland, Robert W.; Wortley, Alexandra H. (2003), "How many species of seed plants are there?",Taxon,52 (1):101–4,doi:10.2307/3647306,JSTOR3647306
^Soltis, Douglas E.; Soltis, Pamela S.; Peter K. Endress;Mark W. Chase (2005),Phylogeny and Evolution of the Angiosperms, Sunderland, Massachusetts, US: Sinauer,ISBN978-0-87893-817-9
^Chalk, L. (1983), "Wood structure", in Metcalfe, C.R.; Chalk, L. (eds.),Wood Structure and Conclusion of the General Introduction, Anatomy of the Dicotyledons, vol. II (2nd ed.), Clarendon Press, pp. 1-51 [1-2 by C. R. Melcalfe],ISBN978-0-19-854559-0
^Hutchinson, John (1979) [1973],The Families of Flowering Plants (3rd ed.), Oxford University Press,ISBN9783874291606
^Worberg, Andreas; Alford, Mac H.; Quandt, Dietmar; Borsch, Thomas (2009), "Huerteales sister to Brassicales plus Malvales, and newly circumscribed to include Dipentodon, Gerrardina, Huertea, Perrottetia, and Tapiscia",Taxon,58 (2):468–478,doi:10.1002/tax.582012
