Sphenophyllales is an extinct order of articulate land plants and a sister group to the present-day

Equisetales Equisetales is an order of subclass Equisetidae with only one living family, Equisetaceae Equisetaceae, sometimes called the horsetail family, is the only extant family of the order Equisetales, with one surviving genus, ''Equisetum'', which ...

(

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 (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

. They were common during the Late Pennsylvanian to Early Permian, with most of the fossils coming from the 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 A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themsel ...

or shrub-like when alive, and formed a portion of the understory in Carboniferous forests. The stem anatomy is protostelic (

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the su ...

-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 cyc ...

) or loose

strobili A strobilus (plural: strobili) is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but some botanists restrict the use of the term cone to th ...

. All sphenophylls are homosporous, with monolete or trilete spores.

Taxonomy

Sphenophyllales was first described by the British botanist 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, Cambrid ...

in 1898. The name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

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 preserved ...

ized 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) 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 Triassi ...

''.

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