Extinct genus of cycads
Eostangeria is a morphogenus of fossil foliage belonging to the Cycadales.
Taxonomy.
Some leaflets of "Eostangeria" had previously described as ferns such as "Angiopteris". As late as 1999 there was uncertainty regarding the familial affinities of the genus, with suggested relationship to with either "Stangeria" or the Colombian "Zamia restrepoi". However, with the redescription of "E. ruzinciniana" by Uzunova, Palamarev, and Kvacek (2002) the genus was placed in the cycad family Zamiaceae as the type genus of the monotypic subfamily Eostangerioideae.
Distribution.
"Eostangeria" was first described based on material "E. saxonica" from the Eocene of the Geisel valley. Subsequently "E. ruzinciniana" was described from the Middle Miocene Krivodol Formation of Bulgaria, while "E. pseudopteris" was detailed from Paleocene through Eocene sediments in Western North America including Wyoming and Oregon.
Description.
Leaflets of "Eostangeria" have a notable midrib from which parallel veins diverge fusing only rarely in the margin of the leaflet. Dispersed leaflets are often retrieved, suggesting the presence of an abscission layer at the base. Cuticles have isodiametrical to elongated cells, with dark-staining and light-staining pavement cells and sunken stomata. If the cuticle is not preserved, leaflets of "Eostangeria" can be confused with fern leaflets of the genus "Allantodiopsis".
References.
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