Karkenia

Karkenia
Temporal occurrence
Hettangium to Aptium
200 to 112 million years
Locations
worldwide
Systematics
Department : Vascular plants (tracheophyta) Subdivision : Seed plants (Spermatophytina) Class : Ginkgo plants (Ginkgoopsida) Order : Ginkgoales Family : Karkeniaceae Genre : Karkenia
Scientific name of the  family
Karkeniaceae
Krassilov
Scientific name of the  genus
Karkenia
Archangelsky

Karkenia is an extinct relative of the ginkgo and the only genus in the Karkeniaceae family.

features

The genus differs from the other representatives of the Ginkgoales in the following features: The seed-forming organs consist of a stem on which up to 100 small, anatropic , but curved ovules sit in a spiral arrangement . The nucellus is mostly free. In the type species , Karkenia incurva , each ovule is around 3 mm long and sits on the axis with a slender stem. The largest seed organs are Karkenia cylindrica from Iran: the axes are up to 12 cm long, the ovules form a kind of cone.

The leaves can have their own petiole or be absent. The leaves belong to the Ginkgoites , Sphenobaiera and Erethmophyllum types : leaves of the Ginkgoites tigrensis type were found in Karkenia incurva . Karkenia Hauptmannii from Germany is associated with short shoots that have leaves of the Sphenobaiera spectabilis type . The pollen grains are monocolpat (have a germ pore) and belong to the Ginkgoitocladus ( Entylissa ) type and were found in the seed organs.

distribution

The genus Karkenia occurs from the Hettangian ( Lower Jurassic ) to the Aptian ( Lower Cretaceous ). There are sites in Argentina, Cina, Germany, Iran, Mongolia and Russia.

supporting documents

• Zhi-Yan Zhou: An overview of fossil Ginkgoales . Palaeoworld, Volume 18, 2009, pp. 1–22, doi : 10.1016 / j.palwor.2009.01.001 .
• Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, ISBN 978-0-12-373972-8 . P. 752f.