''Ctenis'' is a genus of fossil foliage attributable 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 ...

, being one of the most common genera of cycad fossil leaves in the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

Taxonomy

The genus was first erected by Lindley and Hutton in "The fossil flora of Great Britain", based on material of ''Ctenis falcata'' from the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

Yorkshire Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...

. This species was later synonimized with ''Cycadites sulcicaulis,'' leading to the new combination ''Ctenis sulcicaulis'.'' Later, Seward,

Florin The Florentine florin was a gold coin struck from 1252 to 1533 with no significant change in its design or metal content standard during that time. It had 54 grains (3.499 grams, 0.113 troy ounce) of nominally pure or 'fine' gold with a purcha ...

, and

Harris Harris may refer to: Places Canada * Harris, Ontario * Northland Pyrite Mine (also known as Harris Mine) * Harris, Saskatchewan * Rural Municipality of Harris No. 316, Saskatchewan Scotland * Harris, Outer Hebrides (sometimes called the Isle o ...

added details of the cuticle to the diagnosis of the genus.

Description

The leaves of ''Ctenis'' are once pinnate, and the pinnae have multiple parallel veins that often anastomosize (i.e. fuse together). The cuticle of ''Ctenis'' has stomata with guard cells arranged in a random fashion, and the stomatal apparatus has often a cuticular ring surrounding the stomatal pit. The cuticular surface is usually striate.

Distribution

Though ''Ctenis''-like leaves are known from the

Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

Umm Irna Formation The Umm Irna Formation is a geological formation in Jordan. It is found in several outcrops in Jordan in the area around the eastern shore of the Dead Sea. It is Late Permian (likely Changhsingian) in age, and is the oldest unit in the succession, ...

Jordan Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ' is a country in Western Asia. It is situated at the crossroads of Asia, Africa, and Europe, within the Levant region, on the East Bank of the Jordan Rive ...

, ''Ctenis'' becomes more common from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

onwards. In the

, many ''Ctenis'' species are retrieved from Europe, North America, and Asia. In the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

, ''Ctenis'' is still found in Europe (i.e. in the Wealden) and Asia, but from the Late Cretaceous it seems to retreat to more Northern Latitudes in the Siberian region and North America and Southern latitudes in Australia. The last members of this genus are found in the

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

of North America.

Paleoecology

Little is known about the ecology of the ''Ctenis''-producing plants. However, in the Big Cedar Ridge locality in

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

(

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

), ''Ctenis'' is found in the fern wetland together with ferns from the

Dipteridaceae The Dipteridaceae is a family (biology), family of ferns in the order Gleicheniales of the class Polypodiopsida. They are commonly known as umbrella ferns and contain two genera, ''Cheiropleuria'' and ''Dipteris'', with a total of nine species c ...

Gleicheniaceae The forked ferns are the family Gleicheniaceae, which includes six genera and about 160 known species. The formerly independent families Dicranopteridaceae and Stromatopteridaceae are generally included in the Gleicheniaceae, whereas the Dipterid ...

, and

Matoniaceae Matoniaceae is one of the three families of ferns in the Gleicheniales order of the Polypodiopsida class. Fossil records reveal that Matoniaceae ferns were abundant during the Mesozoic era (about 250-million to 66-million years ago), during which ...

. This suggests that at least some members of the genus inhabited wet environments with peaty soils.

References

{{Taxonbar, from=Q60898408 Cycads Prehistoric gymnosperm genera Mesozoic plants Cenozoic plants Clarno Formation