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Bennettitales (the cycadeoids) is an extinct order of seed plants that first appeared in the Triassic period and became extinct in most areas toward the end of the Cretaceous (i.e. they existed around ),〔Speer, Brian R., 2000. ''Introduction to the Bennettitales'' http://www.ucmp.berkeley.edu/seedplants/bennettitales.html (''accessed 13 Oct 2005'').〕 although some Bennettitales appear to have survived into Oligocene times in Tasmania and eastern Australia.〔McLoughlin, S., Carpenter, R.J. & Pott, C., 2011. Ptilophyllum muelleri (Ettingsh.) comb. nov. from the Oligocene of Australia: Last of the Bennettitales? International Journal of Plant Sciences 172, 574–585.〕 Some were characterized by thick trunks and pinnately compound leaves that bore a superficial resemblance to those of cycads, differing primarily in stomatal arrangement.〔Pigg, Kathleen. 2005 ''The Cycads, Cycadeoids (Bennettitales) and Ginkgophytes'' http://lsweb.la.asu.edu/kpigg/CYCAD.html (''accessed 21 Sept 2007'').〕 The taxon comprises two groups, the Cycadeoidaceae, represented by ''Cycadeoidea'' and ''Monanthesia'' which had stout trunks and bisporangiate strobili (cones serving as their reproductive structures), and the Williamsoniaceae including ''Williamsonia'', ''Williamsoniella'', ''Wielandella'' and ''Ischnophyton'' which had slender, branching trunks and either bisporangiate or monosporangiate strobili. Bennettitales have been placed among the anthophytes and for some time were considered to be close relatives of the flowering plants on account of their flower-like reproductive structures (a whorl of microsporangiate structures that surround an inner receptacle).〔 However, more detailed morphological studies have shown the hypothetical anthophytes clade to be polyphyletic, with the Bennettitales more closely related to the cycads, ginkgo and conifers than to the angiosperms. Molecular fossil evidence, however, indicates the possibility that Bennettitales and Angiosperms (along with Gigantopteridales) form a clade, based on the presence of oleanane in fossils of these groups. ==Gallery== Image:Bennettitales_stump_top.JPG|A fossilised Bennettitales, squashed by later compression. Image:Bennettitales_stump_side.JPG|Side view. Note embedded "flowers". Image:Bennettitales_flower.JPG|A flower-like structure. Image:Zamites_mariposana.jpg|Fossil leaf of ''Zamites mariposana'' from the Jurassic. 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「Bennettitales」の詳細全文を読む スポンサード リンク
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