Cephalotaxus

''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. The genus is endemic to eastern Asia, though fossil evidence shows it had a wider Northern Hemisphere distribution in the past. The species are evergreen shrubs and small trees reaching (rarely to ) 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, long and broad, soft in texture, with a blunt tip; this helps distinguish them from the related genus ''Torreya'', which has spine-tipped leaves.

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 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 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.

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.

Phylogeny

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

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.

Fossil record

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 of western North America.
*'' Cephalotaxus akitaensis'' - leafy twigs; Miocene, Utto Formation, Akita Prefecture, Japan
*'' Cephalotaxus biumbonata'' - seeds; Pliocene, Toki, Gifu, Japan
*'' Cephalotaxus bonseri'' - leafy twigs; Miocene, Latah Formation, Washington, US
*'' Cephalotaxus bowerbankii'' - seeds; Eocene, London Clay, Isle of Sheppey, England
*'' Cephalotaxus californica'' - leafy twigs; Oligocene, La Porte flora, California, US
*'' Cephalotaxus cretacea'' - leafy twigs; Cretaceous, Aldan River, Yakutia, Russia
*'' Cephalotaxus eigensis'' - leafy twigs; Miocene, Schönau-Berzdorf, Saxony, Germany
*'' Cephalotaxus europaea'' - leafy twigs; Miocene, Görlitz; Czech Republic
*'' Cephalotaxus francofurtana'' - seeds; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
*'' Cephalotaxus loossi'' - seeds; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
*'' Cephalotaxus messelensis'' - leafy twigs; Eocene, Messel Formation, Darmstadt-Dieburg, Hessen, Germany
*'' Cephalotaxus microphylla'' - leafy twigs; Cretaceous, Salisbury Island, Arkhangelsk, Russia
*'' Cephalotaxus miocenica'' - seeds; Miocene, Nowa Wieś Królewska, Województwo opolskie, Poland
*'' Cephalotaxus multiserialis'' - leafy twigs; Miocene, Düren Kreis, Rhine-Westphalia, Germany
*'' Cephalotaxus obovata'' - seeds; Pliocene, Toge, Hyogo, Japan
*'' Cephalotaxus parvifolia'' - leafy twigs; Oligocene, Seifhennersdorf, Sachsen, Germany
*'' Cephalotaxus pliocaenica'' - leafy twigs; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
*'' Cephalotaxus rotundata'' - seeds; Pliocene, Klärbecken Flora, Niederrad, Frankfurt am Main, Germany
*'' Cephalotaxus saxonica'' - leafy twigs; Eocene, Phönix-Nord, Sachsen, Germany
*'' Cephalotaxus stoeckleinorum'' - leafy twigs; Miocene, Achldorf, Bavaria, Germany
*'' Cephalotaxus yubariensis'' - leafy twigs; Eocene, Ikushunbetsu Formation, Yubari River, Hokkaido, Japan

References

External links

Gymnosperm Database
*Photos

{{Taxonbar, from=Q933520

Conifer genera