Sphenophyllales is an extinct

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

of articulate land plants and a sister group to the present-day Equisetales (

horsetails ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass ...

). They are fossils dating from the Devonian to the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

. 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), 2001 * ''01'' (Son of Dave album), 2000 * ''01'' (Urban Zakapa album), 2011 * ''O1'' (Hiroyuki Sawano ...

, with most of the fossils coming from the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous ...

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.

, 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-like), containing a solid primary

xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...

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 A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

) or loose strobili. All sphenophylls are

homosporous In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

, with monolete or trilete

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

Taxonomy

Sphenophyllales was first described by the British

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

and geologist

Albert Seward Sir Albert Charles Seward FRS (9 October 1863 – 11 April 1941) was a British botanist and geologist. Life Seward was born in Lancaster. His first education was at Lancaster Grammar School and he then went on to St John's College, Cambridge ...

in 1898. The name comes from the Greek words σφήν ("wedge") and φύλλον ("leaf"). Sphenophyllalean taxonomy is often derived from isolated fossilized parts of plants and classification may be based on the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

and

anatomy Anatomy () is the branch of biology concerned with the study of the 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 science, having it ...

of sterile plant parts (like

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

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

Sphenophyllum ''Sphenophyllum'' is a genus in the order Sphenophyllales 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 to the Triass ...

''.

Phylogeny

The probable relationships within

Equisetidae Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails. They typically grow in wet areas, with whorls of needle-lik ...

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