''Cycadeoidea'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of bennettitalean plants known from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

(and possibly the Jurassic) of North America, Europe and Asia. They grew as

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...

-like plants with a short trunk topped with a crown of leaves.

Taxonomy

William Buckland William Buckland Doctor of Divinity, DD, Royal Society, FRS (12 March 1784 – 14 August 1856) was an English theologian, geologist and paleontology, palaeontologist. His work in the early 1820s proved that Kirkdale Cave in North Yorkshire h ...

originally gave the name to two species he described, ''C. megalophylla'' and ''C. microphylla'', in 1828, seeing characteristics akin to living

Robert Brown Robert Brown may refer to: Robert Brown (born 1965), British Director, Animator and author Entertainers and artists * Washboard Sam or Robert Brown (1910–1966), American musician and singer * Robert W. Brown (1917–2009), American printmaker ...

and Mr. Loddiges of Loddiges Nursery in Hackney had seen living cycads and urged him to name the fossils after them. The original type specimens of both taxa have not been located, so new type material has been chosen. Classification of species within the genus is very difficult, as several trunks have been described as species, and a further fourteen species are known from detached

leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...

remains, but there is no way of telling which leaf remains go with which trunk remains (if any).

Description

Cycadeoidea_marylandica_-_National_Museum_of_Natural_History_-_IMG_1978

''Cycadeoidea'' stems were "short and barrel-shaped," with a "crown of

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and ...

leaves" atop the stem. 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. The genus may have undergone

self-pollination Self-pollination is a form of pollination in which pollen arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms) of the same plant. The term cross-pollination is used for the opposite case, where pollen from ...

, although it is also possible that

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s were involved in the process. 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.

Fossil sites and species

The following species have been described: *''Cycadeoidea cylindrica'' (Brongn. ex Mantell) *''Cycadeoidea deshayesii'' (Saporta) *''Cycadeoidea duvalii'' (Pomel) Doweld *''Cycadeoidea gibsoniana'' (Carruthers) Seward *''Cycadeoidea maccafferyi'' *''Cycadeoidea megalophylla'' Buckland *''Cycadeoidea microphylla'' Buckland The

Isle of Portland The Isle of Portland is a tied island, long by wide, in the English Channel. The southern tip, Portland Bill, lies south of the resort of Weymouth, Dorset, Weymouth, forming the southernmost point of the county of Dorset, England. A barrier ...

was the site of the first specimens recovered, described by Buckland as ''C. megalophylla'' (the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

) and ''C. microphylla''. ''Cycadeoidea gibsoniana'' is a species collected from

Lower Greensand The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian ages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were d ...

from Luccombe Chine on the

Isle of Wight The Isle of Wight (Help:IPA/English, /waɪt/ Help:Pronunciation respelling key, ''WYTE'') is an island off the south coast of England which, together with its surrounding uninhabited islets and Skerry, skerries, is also a ceremonial county. T ...

, notable for the remarkable state of preservation of its plant parts. The original specimen was found by Thomas Field Gibson and was extensively broken and sliced to examine its anatomy. Four well preserved cones of a species ''C. maccafferyi'' were uncovered in the

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cret ...

Haslam Formation The Haslam Formation is a black shale geologic formation exposed on Vancouver Island and the Gulf Islands, British Columbia, Canada. It preserves primarily marine fossils dating back to the Santonian age of the late Cretaceous period, including s ...

Vancouver Vancouver is a major city in Western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the cit ...

and

Hornby Island Hornby Island of British Columbia, Canada, is one of the two northernmost Gulf Islands, the other being Denman Island. It is located near Vancouver Island's Comox Valley, A small community of 1,225 residents (as of the 2021 census), Hornby is ...

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

. The distribution of the species is primarily Cretaceous in age, though some remains of the genus may date to the Jurassic.

References

{{Taxonbar, from=Q3699835 Bennettitales Jurassic plants Cretaceous plants Prehistoric plant genera Jurassic life of Europe Jurassic life of North America Cretaceous life of Europe Cretaceous life of North America Jurassic first appearances Cretaceous extinctions Taxa named by William Buckland Fossil taxa described in 1828 Prehistoric plants of North America