Karkeniaceae is an extinct family in the order
Ginkgoales
Ginkgoales are a gymnosperm order containing only one extant species: '' Ginkgo biloba'', the ginkgo tree. It is monotypic, (the only taxon) within the class Ginkgoopsida, which itself is monotypic within the division Ginkgophyta . The order inc ...
. It contains the single genus ''Karkenia''. It is distinguished by "Ovulate organs consisting of a
peduncle and helically arranged, up to about 100 small, orthotropous but incurved
ovules
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the '' nucellus'' (or remnant of the megasporangium), and the ...
; pedicel present;
nucellus
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the '' nucellus'' (or remnant of the megasporangium), and the fe ...
largely free." Unlike other ginkgoales, the seeds are borne on
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 ...
-like aggregations. Ovuluate organs of ''Karkenia'' are associated with leaves of the ''
Ginkgoites'', ''
Sphenobaiera'' and ''
Eretmophyllum'' types. It is known from the
Hettangian
The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassic ...
to
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago) ...
of both Hemispheres.
References
Ginkgophyta
Prehistoric plant families
{{Paleo-gymnosperm-stub