''Cycadeoidea'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of bennettitalean plants known from the

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

and

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

in North America, Europe and Asia.

Taxonomy

William Buckland William Buckland DD, FRS (12 March 1784 – 14 August 1856) was an English theologian who became Dean of Westminster. He was also a geologist and palaeontologist. Buckland wrote the first full account of a fossil dinosaur, which he named ' ...

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

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

s. Robert Brown 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 any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

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

Description

''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 in ...

leaves" atop the stem. The majority of ''Cycadeoidea'' species were "bisexual". The genus may have undergone

self-pollination Self-pollination is a form of pollination in which pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen is transferred ...

, although it is also possible that

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...

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 An isle is an island, land surrounded by water. The term is very common in British English British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct fr ...

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

type species In 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 species that contains the biological type specime ...

) 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 stages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were ...

from Luccombe Chine on the

Isle of Wight The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...

, notable for the remarkable state of preservation of its plant parts. The original specimen was found by

Thomas Field Gibson Thomas Field Gibson FGS (3 March 1803 – 12 December 1889) was a Unitarian silk manufacturer and philanthropist. He supported several novel initiatives to enhance British manufacturing quality and international trade while improving life fo ...

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 younger 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 ''creta'', th ...

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 Epoch of the Cretaceous period Period may re ...

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 ...

and

Hornby Island Hornby Island of British Columbia, Canada, is one of the two northernmost Gulf Islands, located near Vancouver Island's Comox Valley, the other being Denman Island. A small community of 1,016 residents (as of the 2016 census), Hornby is home to ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

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