Sphenophyllales is an extinct order of articulate land plants and a sister group to the present-day Equisetales ( horsetails). They are fossils dating from the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

to the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

. They were common during the Late Pennsylvanian to

Early Permian 01 or 01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), ''01'' (Richard Müller album), 2001 * 01 (Urban Zakapa album), ''01'' (Urban Zakapa album), 2011 * ''01011 ...

, with most of the fossils coming from the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

period.

Description

Sphenophyllales are small, slender branching plants, usually growing to a height of less than tall. The long stems range from to in diameter. The stems are jointed and ribbed with weak

habits A habit (or wont, as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. A 1903 paper in the ''American Journal of Psychology'' defined a "habit, from the standpoint of psychology, ...

, making it probable that these plants were vine or shrub-like when alive, and formed a portion of the understory in Carboniferous forests. The stem anatomy is protostelic (root">Stele (biology)#Protostele">protostelic (root-like), containing a solid primary xylem">root.html" ;"title="Stele (biology)#Protostele">protostelic (root">Stele (biology)#Protostele">protostelic (root-like), containing a solid primary xylem core with secondary xylem tissue present in some species. The leaves, which can be several centimeters long, are borne on each node in whorls (called verticels) and are wedge-shaped, fan-shaped, linear, or forked. Reproductive parts are either long terminal cones (consisting of two lobes, a sterile lower lobe and the fertile upper lobe bearing the sporangia) or loose strobili. All sphenophylls are homosporous, with monolete or trilete spores.

Taxonomy

Sphenophyllales was first described by the British

botanist Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

and geologist Albert Seward in 1898. The name comes from the

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words σφήν ("wedge") and φύλλον ("leaf"). Sphenophyllalean taxonomy is often derived from isolated

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 preserve ...

ized parts of plants and classification may be based on the morphology and

anatomy Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

of sterile plant parts (like

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

) or fructifications (mainly the fossilized cones and the stratigraphically-important spores found near them). This results in species that may actually by

synonymous A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

. Sphenophyllales is typified by the genus '' Sphenophyllum''.

Phylogeny

The probable relationships within Equisetidae are shown in the cladogram below. The possible position of ''Ibyka'' has been added.

References

{{Taxonbar, from=Q2899203 Horsetails Fern orders Prehistoric plant orders Devonian plants Carboniferous plants Permian plants Triassic plants Devonian first appearances Triassic extinctions Mississippian plants Pennsylvanian plants