Cephalotaxus, commonly calledplum yew orcowtail pine, is a genus ofconifers comprising 11 species, either considered the only member of the familyCephalotaxaceae, or in theTaxaceae when that family is considered in a broad sense.[1][2] The genus isendemic to easternAsia, thoughfossil evidence shows it had a widerNorthern Hemisphere distribution in the past.[1] The species areevergreenshrubs and smalltrees reaching 1.0–10 metres (3–33 ft) (rarely to 20 metres (66 ft)) tall.
Theleaves 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, 4–12 centimetres (1+1⁄2–4+3⁄4 in) long and3–4 millimetres (1⁄8–5⁄32 in) broad, soft in texture, with a blunt tip; this helps distinguish them from the related genusTorreya, which has spine-tipped leaves.[2]
The species can be eithermonoecious ordioecious; when monoecious, the male and femalecones are often on different branches. The male (pollen) cones are5–8 millimetres (13⁄64–5⁄16 in) 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 adrupe-like structure with the single largenut-like seed1.5–4 centimetres (5⁄8–1+5⁄8 in) long surrounded by a fleshy covering, green to purple at full maturity. Natural dispersal is thought to be aided bysquirrels which bury the seeds for a winter food source; any seeds left uneaten are then able to germinate.[2]
Cephalotaxus species producecephalotaxine, analkaloid. Parry et al 1980 provides evidence that cephalotaxine is aphenylethylisoquinoline. However, they also find this genus to be unable to incorporatecinnamic acid into cephalotaxine, and incorporation of cinnamic acid is usually a step in phenylethylisoquinoline syntheses, throwing the phenylethylisoquinoline theory in to question.[3]
Molecular studies placeCephalotaxus as the most basal member of theTaxaceae, having a very ancient divergence from them during the lateTriassic.[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]
The taxonomy ofCephalotaxus 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]
The oldest fossils ofCephalotaxus are known from theEocene ofHeilongjiang in northeast China and theMessel Pit of Germany. The youngest fossils ofCephalotaxus in Europe date to thePliocene, and remains are also known from theMiocene of western North America.[11][12]
