| Cycadeoidea | |
|---|---|
 | |
| Life reconstruction ofCycadeoidea | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Order: | †Bennettitales |
| Family: | †Cycadeoidaceae |
| Genus: | †Cycadeoidea Buckland, 1828 |
| Type species | |
| †Cycadeoidea megalophyllaBuckland | |
| Species | |
See text. | |
| Synonyms[1] | |
| |
Cycadeoidea is anextinctgenus ofbennettitalean plants known from theCretaceous (and possibly the Jurassic) of North America, Europe and Asia.[2] They grew ascycad-like plants with a short trunk topped with a crown of leaves.
William Buckland originally gave the name to two species he described,C. megalophylla andC. microphylla, in 1828, seeing characteristics akin to livingcycads.[3]Robert Brown and Mr. Loddiges ofLoddiges Nursery in Hackney had seen living cycads and urged him to name the fossils after them.[4] The original type specimens of both taxa have not been located, so new type material has been chosen.[4]
Classification of species within the genus is very difficult, as severaltrunks have been described as species, and a further fourteen species are known from detachedleaf remains, but there is no way of telling which leaf remains go with which trunk remains (if any).[4]
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Cycadeoidea stems were "short and barrel-shaped," with a "crown ofpinnate leaves" atop the stem.[5] The trunk was covered in imbricate leaf bases, similar to the trunks of cycads. The exact nature of the leaves that topped the stem is unclear, as the trunks are preserved without the adult leaves. The reproductive structures are bisexual (i.e. having a combined male and female organ), and are deeply sunken into the stem on the axils of the leaves, and they are surrounded by scales and embedded within the persistent leaf bases.[4] The genus may have undergoneself-pollination, although it is also possible thatinsects were involved in the process.[5] The size and shape of the trunk has been used to distinguish species, however forms intermediate between two species suggest the two might be merely different-sized or aged plants can't be excluded.[4]
The following species have been described:
TheIsle of Portland was the site of the first specimens recovered, described by Buckland asC. megalophylla (thetype species) andC. microphylla.[4]
Cycadeoidea gibsoniana is a species collected fromLower Greensand fromLuccombe Chine on theIsle of Wight, notable for the remarkable state of preservation of its plant parts. The original specimen was found byThomas Field Gibson and was extensively broken and sliced to examine its anatomy.[4][7]
Four well preserved cones of a speciesC. maccafferyi were uncovered in theUpper CretaceousHaslam Formation onVancouver andHornby Island inBritish Columbia.[6]
The distribution of the species is primarily Cretaceous in age, though some remains of the genus may date to the Jurassic.[4]