Cephalotaxus

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Cephalotaxus, commonly called plum yew or cowtail pine, is a genus of conifers comprising 11 species, either considered the only member of the family Cephalotaxaceae, or in the Taxaceae when that family is considered in a broad sense.[1][2] The genus is endemic to eastern Asia, though fossil evidence shows it had a wider Northern Hemisphere distribution in the past.[1] The species are evergreen shrubs and small trees reaching Script error: No such module "convert". (rarely to Script error: No such module "convert".) tall.

Description

The leaves are spirally arranged on the shoots, but twisted at the base to lie in two flat ranks (except on erect leading shoots); they are linear, Script error: No such module "convert". long and Script error: No such module "convert". broad, soft in texture, with a blunt tip; this helps distinguish them from the related genus Torreya, which has spine-tipped leaves.[2]

The species can be either monoecious or dioecious; when monoecious, the male and female cones are often on different branches. The male (pollen) cones are Script error: No such module "convert". long, grouped in lines along the underside of a shoot. The female (seed) cones are single or grouped two to 15 together on short stems; minute at first, they mature in about 18 months to a drupe-like structure with the single large nut-like seed Script error: No such module "convert". long surrounded by a fleshy covering, green to purple at full maturity. Natural dispersal is thought to be aided by squirrels which bury the seeds for a winter food source; any seeds left uneaten are then able to germinate.[2]

Phytochemistry

Cephalotaxus species produce cephalotaxine, an alkaloid. Parry et al 1980 provides evidence that cephalotaxine is a phenylethylisoquinoline. However, they also find this genus to be unable to incorporate cinnamic acid into cephalotaxine, and incorporation of cinnamic acid is usually a step in phenylethylisoquinoline syntheses, throwing the phenylethylisoquinoline theory in to question.[3]

Phylogeny

Molecular studies place Cephalotaxus as the most basal member of the Taxaceae, having a very ancient divergence from them during the late Triassic.[4] Historically, it was placed as the only member of the family Cephalotaxaceae, due to strong morphological differences from other members of Taxaceae,[5] but major authorities consider the family synonymous with Taxaceae.[6][7]

Extant species

The taxonomy of Cephalotaxus is difficult, because the species have been defined using characteristics that intergrade with each other, such as the length and shape of needles, bark, and stomatal band color. Cephalotaxus species have often been separated geographically rather than morphologically.[8]

Phylogeny of Cephalotaxus[9][10]

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Fossil record

File:Cephalotaxus bonseri holotype USNM P36887 img3.jpg
Cephalotaxus bonseri
Latah Formation, Miocene

The oldest fossils of Cephalotaxus are known from the Eocene of Heilongjiang in northeast China and the Messel Pit of Germany. The youngest fossils of Cephalotaxus in Europe date to the Pliocene, and remains are also known from the Miocene of western North America.[11][12]

  • Cephalotaxus akitaensis HuziokaScript error: No such module "Check for unknown parameters". - leafy twigs; Miocene, Utto Formation, Akita Prefecture, Japan
  • Cephalotaxus biumbonata MikiScript error: No such module "Check for unknown parameters". - seeds; Pliocene, Toki, Gifu, Japan
  • Cephalotaxus bonseri (Knowlton) R.W. Chaney & AxelrodScript error: No such module "Check for unknown parameters". - leafy twigs; Miocene, Latah Formation, Washington, US
  • Cephalotaxus bowerbankii Reid & ChandlerScript error: No such module "Check for unknown parameters". - seeds; Eocene, London Clay, Isle of Sheppey, England
  • Cephalotaxus californica PotburyScript error: No such module "Check for unknown parameters". - leafy twigs; Oligocene, La Porte flora, California, US
  • Cephalotaxus cretacea SamylinaScript error: No such module "Check for unknown parameters". - leafy twigs; Cretaceous, Aldan River, Yakutia, Russia
  • Cephalotaxus eigensis MaiScript error: No such module "Check for unknown parameters". - leafy twigs; Miocene, Schönau-Berzdorf, Saxony, Germany
  • Cephalotaxus europaea MaiScript error: No such module "Check for unknown parameters". - leafy twigs; Miocene, Görlitz; Czech Republic
  • Cephalotaxus francofurtana KinkelinScript error: No such module "Check for unknown parameters". - seeds; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
  • Cephalotaxus loossi KinkelinScript error: No such module "Check for unknown parameters". - seeds; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
  • Cephalotaxus messelensis WildeScript error: No such module "Check for unknown parameters". - leafy twigs; Eocene, Messel Formation, Darmstadt-Dieburg, Hessen, Germany
  • Cephalotaxus microphylla Sveshnikova & BudantsevScript error: No such module "Check for unknown parameters". - leafy twigs; Cretaceous, Salisbury Island, Arkhangelsk, Russia
  • Cephalotaxus miocenica (Kräusel) GregorScript error: No such module "Check for unknown parameters". - seeds; Miocene, Nowa Wieś Królewska, Województwo opolskie, Poland
  • Cephalotaxus multiserialis (Weyl.) Mai & WaltherScript error: No such module "Check for unknown parameters". - leafy twigs; Miocene, Düren Kreis, Rhine-Westphalia, Germany
  • Cephalotaxus obovata MikiScript error: No such module "Check for unknown parameters". - seeds; Pliocene, Toge, Hyogo, Japan
  • Cephalotaxus parvifolia (Walther) Kvaček & WaltherScript error: No such module "Check for unknown parameters". - leafy twigs; Oligocene, Seifhennersdorf, Sachsen, Germany
  • Cephalotaxus pliocaenica MädlerScript error: No such module "Check for unknown parameters". - leafy twigs; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
  • Cephalotaxus rotundata KinkelinScript error: No such module "Check for unknown parameters". - seeds; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
  • Cephalotaxus saxonica Mai & WaltherScript error: No such module "Check for unknown parameters". - leafy twigs; Eocene, Phönix-Nord, Sachsen, Germany
  • Cephalotaxus stoeckleinorum KnoblochScript error: No such module "Check for unknown parameters". - leafy twigs; Miocene, Achldorf, Bavaria, Germany
  • Cephalotaxus yubariensis Se. EndôScript error: No such module "Check for unknown parameters". - leafy twigs; Eocene, Ikushunbetsu Formation, Yubari River, Hokkaido, Japan

References

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External links

Template:Acrogymnospermae classification Template:Taxonbar

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