''Eostangeria'' is a

morphogenus Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of sc ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

foliage belonging to the

Cycadales Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or f ...

Taxonomy

Some leaflets of ''Eostangeria'' had previously described as ferns such as ''

Angiopteris ''Angiopteris'' is a genus of huge evergreen ferns from the family Marattiaceae, found throughout the paleotropics from Madagascar to the South Pacific islands. Species of smaller stature with elongate synangia and creeping rhizomes are s ...

''. As late as 1999 there was uncertainty regarding the familial affinities of the genus, with suggested relationship to with either ''

Stangeria ''Stangeria eriopus'' is a cycad endemic to southern Africa. It is the sole species in the genus ''Stangeria'', most closely related to the Australian genus ''Bowenia'', with which it forms the family Stangeriaceae. Description ''Stangeria erio ...

'' or the Colombian ''

Zamia restrepoi ''Zamia restrepoi'' is a species of cycad in the family Zamiaceae The Zamiaceae are a family of cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and ...

''. However with the redescription of ''E. ruzinciniana'' by Uzunova, Palamarev, and Kvacek (

2002 File:2002 Events Collage.png, From left, clockwise: The 2002 Winter Olympics are held in Salt Lake City; Queen Elizabeth The Queen Mother and her daughter Princess Margaret, Countess of Snowdon die; East Timor gains independence from Indonesia and ...

) the genus was placed in the cycad family

Zamiaceae The Zamiaceae are a family of cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and subtropical regions of Africa, Australia and North and South Americ ...

as the type genus of the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

subfamily Eostangerioideae.

Distribution

''Eostangeria'' was first described based on material ''E. saxonica'' from the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

of the

Geisel valley The Geisel valley (german: Geiseltal) is a valley in Saxony-Anhalt, Germany, situated west of Merseburg, Saalekreis district. It is named after the River Geisel which rises in Mücheln and is a tributary of the Saale, just under long. Its mai ...

,. Subsequently ''E. ruzinciniana'' was described from the Middle Miocene Krivodol Formation of

Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Mac ...

, while ''E. pseudopteris'' was detailed from

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

through

sediments in Western North America including Wyoming and Oregon.

Description

Leaflets of ''Eostangeria'' have a notable

midrib This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...

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 Abscission () is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a ...

at the base. Cuticles have isodiametrical to elongated cells, with dark-staining and light-staining

pavement cells Pavement cells are a cell type found in the outmost epidermal layer of plants. The main purpose of these cells is to form a protective layer for the more specialized cells below. This layer helps decrease water loss, maintain an internal temperatur ...

and sunken

stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bo ...

ta. If the cuticle is not preserved, leaflets of ''Eostangeria'' can be confused with

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except ...

leaflets of the genus '' Allantodiopsis''.

References

Prehistoric gymnosperm genera Zamiaceae {{paleo-cycad-stub