''Cycas'' is a

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 plants belonging to a very ancient lineage, the

Cycadophyta 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 ...

, which are not closely related to palms, ferns, trees or any other modern group of plants. They are

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, whic ...

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...

s which achieved their maximum diversity in 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 ...

periods, when they were distributed almost worldwide. At the end of the Cretaceous, when the non-avian dinosaurs became extinct, so did most of the cycas in the Northern Hemisphere. ''Cycas'' is the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

and the only extant genus recognised in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Cycadaceae. About 113

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

are accepted. ''Cycas circinalis'', a species endemic to India, was the first

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 ...

species to be described in western literature, and was the type of the generic name, ''Cycas''. The best-known ''Cycas'' species is ''

Cycas revoluta ''Cycas revoluta'' (Sotetsu apanese ソテツ sago palm, king sago, sago cycad, Japanese sago palm) is a species of gymnosperm in the family Cycadaceae, native to southern Japan including the Ryukyu Islands. It is one of several species used f ...

''.

Range

The genus is

native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...

to the Old World, with the species concentrated around the equatorial regions - eastern and southeastern Asia including the Philippines with 10 species (9 of which are endemic), eastern Africa (including Madagascar), northern Australia, Polynesia, and Micronesia. Australia has 26 species, while the Indo-Chinese area has about 30. India has 9 species. The northernmost species (''C. revoluta'') is found at 31°N in southern Japan. The southernmost (''C. megacarpa'') is found at 26°S in southeast Queensland. Due to the occurrence of large number of ''Cycas'' species in China, Australia and India, those countries are considered as centres of ''Cycas'' diversity.Kew World Checklist of Selected Plant Families
/ref>

Evolution

''Cycas'' is though to have split from all other living cycads at least 200 million years ago, possibly much earlier. Fossil seeds from the Middle Jurassic of England and British Columbia, were suggested in a 2017 study to be more closely related to ''Cycas'' than other cycads, were assigned to the same family, Cycadaceae. However, a later study suggested that these seeds could not be assigned to the

stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

of ''Cycas'' with confidence due to lacking the double vascular system that characterises the seeds of all living cycads. The earliest

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s assignable to ''Cycas'' are known from the Paleogene of East Asia, such as ''Cycas fushunensis'' from the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

Northeast China Northeast China or Northeastern China () is a geographical region of China, which is often referred to as "Manchuria" or "Inner Manchuria" by surrounding countries and the West. It usually corresponds specifically to the three provinces east of ...

, with East Asia likely representing the ancestral homeland of the genus.

Morphology

The plants are dioecious, and the family Cycadaceae is unique among the cycads in not forming seed

cone A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines con ...

s on female plants, but rather a group of leaf-like structures called megasporophylls each with seeds on the lower margins, and pollen cones or strobilus on male individuals. The caudex is cylindrical, surrounded by the persistent petiole bases. Most species form distinct branched or unbranched trunks but in some species the main trunk can be subterranean with the leaf crown appearing to arise directly from the ground. There are two types of leaves - foliage leaves and scaly leaves. The foliage leaves are

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 ...

(or more rarely bipinnate) and arranged spirally, with thick and hard keratinose. They are not permanent and fall off leaving back leaf-bases. The leaflets are articulated, have midrib but lack secondary veins. The scaly leaves are persistent, brown in colour and protective in function.

Megasporophyll A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or ...

s are not gathered in cones.

Pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...

takes place by air.

Reproduction

The plant takes several years to grow, sexual reproduction takes place after 10 years of exclusive vegetative growth which occurs by bulbils arising at the base of the trunk.

Conservation status

''Cycas'' species are threatened worldwide and almost all the species are listed in IUCN Redlist. ''Cycas beddomei'' is the only species of the genus ''Cycas'' listed in Appendix I of CITES. ''

Cycas rumphii ''Cycas rumphii'', commonly known as queen sago or the queen sago palm, is a dioecious gymnosperm, a species of cycad in the genus ''Cycas'' native to Indonesia, New Guinea and Christmas Island. Although palm-like in appearance, it is not a pal ...

'' and '' Cycas pectinata'' have the most widespread distribution

List of species

Cycas platyphylla with new flush of fronds

*'' Cycas aculeata'' *'' Cycas aenigma'' *''

Cycas angulata ''Cycas angulata'' is a species of cycad in the genus ''Cycas'', native to Australia in northeast Northern Territory (lower reaches of the Foelsche, Robinson and Wearyan Rivers near Borroloola) and northwest Queensland ( Bountiful Islands). ...

'' *'' Cycas annaikalensis'' *'' Cycas apoa'' *'' Cycas arenicola'' *'' Cycas armstrongii'' *'' Cycas arnhemica'' *'' Cycas badensis'' *'' Cycas balansae'' *'' Cycas basaltica'' *'' Cycas beddomei'' *'' Cycas bifida'' *'' Cycas bougainvilleana'' *'' Cycas brachycantha'' *'' Cycas brunnea'' *'' Cycas cairnsiana'' *'' Cycas calcicola'' *'' Cycas campestris'' *'' Cycas canalis'' *'' Cycas candida'' *'' Cycas cantafolia'' *'' Cycas chamaoensis'' *'' Cycas changjiangensis'' *'' Cycas chenii'' *'' Cycas chevalieri'' *''

Cycas circinalis ''Cycas circinalis'', also known as the queen sago, is a species of cycad known in the wild only from southern India. ''Cycas circinalis'' is the only gymnosperm species found among native Sri Lankan flora. Taxonomy ''C. circinallis'' is native ...

'' *'' Cycas clivicola'' *'' Cycas collina'' *'' Cycas condaoensis'' *'' Cycas conferta'' *'' Cycas couttsiana'' *'' Cycas cupida'' *'' Cycas curranii'' *'' Cycas debaoensis'' *'' Cycas desolata'' *'' Cycas diannanensis'' *'' Cycas distans'' P.I.Forst. & B.Gray *'' Cycas dolichophylla'' *'' Cycas edentata'' *'' Cycas elephantipes'' *'' Cycas elongata'' *'' Cycas falcata'' *'' Cycas fairylakea'' *'' Cycas ferruginea'' *''

Cycas fugax ''Cycas fugax'' is a species of cycad endemic to Vietnam. It has only been recorded in the wild from Phu Tho Province, Vietnam, but may be reasonably common in cultivation in Hanoi.Whitelock, Loran M. 2002. ''The Cycads''. Portland: Timber Press. ...

'' *'' Cycas furfuracea'' *'' Cycas glauca'' *'' Cycas guizhouensis'' *'' Cycas hainanensis'' *'' Cycas hoabinhensis'' *'' Cycas hongheensis'' *'' Cycas indica'' (=''Cycas swamyi'') *'' Cycas inermis'' *''

Cycas javana ''Cycas javana'' is a species of cycad in Indonesia. It is found primarily in Java, as well as southern Sumatra and possibly the Nusa Tenggara Barat, western Sunda Islands. References

Cycas, javana Flora of Java Flora of Sumatra {{cyca ...

'' *'' Cycas lacrimans'' *'' Cycas lane-poolei'' *'' Cycas lindstromii'' *'' Cycas litoralis'' *'' Cycas maconochiei'' *'' Cycas macrocarpa'' *'' Cycas media'' *'' Cycas megacarpa'' *'' Cycas micholitzii'' *'' Cycas micronesica'' *'' Cycas montana'' *'' Cycas multipinnata'' *'' Cycas nathorstii'' *'' Cycas nayagarhensis'' *'' Cycas nitida'' *'' Cycas nongnoochiae'' *'' Cycas ophiolitica'' *'' Cycas orientis'' *'' Cycas orixensis'' *'' Cycas pachypoda'' *'' Cycas panzhihuaensis'' *'' Cycas papuana'' *'' Cycas pectinata'' *'' Cycas petraea'' *'' Cycas platyphylla'' *'' Cycas pranburiensis'' *'' Cycas pruinosa'' *''

'' (Sago palm) *'' Cycas riuminiana'' *''

'' Miq. *'' Cycas sancti-lasallei'' *'' Cycas sainathii'' *'' Cycas saxatilis'' *'' Cycas schumanniana'' *'' Cycas scratchleyana'' *''

Cycas seemannii ''Cycas seemannii'' is a species of cycad found in Fiji, Vanuatu (in Efate), Tonga, and New Caledonia.Whitelock, Loran M. 2002. ''The Cycads''. Portland: Timber Press. In Vanuatu, the cycad is known as namele and is an important symbol of tra ...

'' A.Braun *'' Cycas segmentifida'' *'' Cycas semota'' *'' Cycas sexseminifera'' *'' Cycas shanyaensis'' *'' Cycas siamensis'' *''

Cycas silvestris ''Cycas silvestris'' is a species of cycad. It is native to Queensland, where it is confined to the Cape York Peninsula Cape York Peninsula is a large peninsula located in Far North Queensland, Australia. It is the largest unspoiled wilder ...

'' *'' Cycas simplicipinna'' *'' Cycas sphaerica'' *'' Cycas sundaica'' *'' Cycas szechuanensis'' *'' Cycas taitungensis'' *'' Cycas taiwaniana'' *'' Cycas tanqingii'' *'' Cycas tansachana'' *'' Cycas thouarsii'' *'' Cycas tropophylla'' *'' Cycas tuckeri'' *'' Cycas vespertilio'' *''

Cycas wadei ''Cycas wadei'' (Wade's pitogo) is a species of cycad endemic to Culion island, Philippines. There is only one subpopulation of about 5,000 mature individuals, located in a small area to the east of Halsey Harbor.Whitelock, Loran M. 2002. ''The C ...

'' *'' Cycas xipholepis'' *'' Cycas yorkiana'' *'' Cycas yunnanensis'' *'' Cycas zambalensis'' *'' Cycas zeylanica''

References

External links

* *Hill, K.D.(1998–2004) The Cycad Pages, Royal Botanic Gardens Sydney. http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/index.html
Virtual Cycad Encyclopedia
edited by the Palm & Cycad Societies of Florida *David, J. de Laubenfels
Cycas Taxonomy
* * *Singh, R & JS Khuraijam (2013-) Cycads of India. http://www.cycadsofindia.in/ * * *Terrence Walters & Roy Osborne (eds.) (2004), ''Cycad Classification: Concepts and Recommendations'', CABI publishing, {{Taxonbar, from=Q161073