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Sphenophylls †

Woody, horsetail-like plants

The Sphenophyllophytes are an extinct group of spore-bearing, vascular plants, deriving their name from the wedge-shaped appearance of their leaves (spheno-phyll). Sphenophylls are generally regarded as members of the sphenopsid (equisetophyte) lineage. They represent an ancient side branch, rather than direct ancestors, of modern Equisetum. Their combination of whorled leaves, nodal anatomy, and reproductive organization links them to other sphenopsids.

Sphenophylls were abundant in the Pennsylvanian, exhibiting a creeping or climbing habit in overbank floodplain and lake edge habitats. The sphenophylls may have been understory shrubs (less than 1 meter tall) in the arborescent lycopsid forests of the same period.

Ecology & Form

Many sphenophylls were lianas or scrambling understory plants
They climbed through Carboniferous swamp vegetation.
This growth strategy allowed them to reach well-lit environments without developing large arborescent stems.
Found in overbank floodplain and lake-edge habitats

Stems

Morphology

Compressions exhibit distinct node/internode arrangement like horsetails
Stems up to 2 cm in diameter
Many orders of branching

Anatomy

Trilobed protostele
- Exarch maturation (similar to lycophytes)
- Mesarch maturation found in some (similar to euphyllophytes)
Some woody tissues
- Bifacial (maybe unifacial) cambium similar to lycopsids
- Cambium was determinate, with limited woody growth
- Secondary growth only in periclinal divisions; not anticlinal to add more cambial initials as the stem increases in girth
- Despite wood production, most species remained relatively slender

Leaves

Compression/impression fossils (e.g., Sphenophyllum)
Whorled arrangement
Wedge-shaped leaves ("spheno-phyll")
- Origin unknown: megaphylls, meiophylls of Pseudobornia, independent origin?

Roots

Root systems were delicate and extensively branched.
Underground axes likely played an important role in vegetative spread through swamp-margin habitats

Reproductive Structures

Sporangia aggregated into loose cones (e.g., Bowmanites)
Sporangia on modified leaves (sporophylls), unlike horsetails
- Sporophyll on a stalk that recurves toward the cone axis
Homosporous

Geologic Age

Devonian-Triassic

Classification

└Sphenophyllales †

Above: A cicada-like insect from 260 Ma that has wings that resemble Sphenophyllum leaves (Fu et al., 2025)

Diversity

Bowmanites †

Permineralized, spore-bearing cones
Pennsylvanian of USA, Belgium, and UK

B. dawsonii †

Taylor 1969, 1970

B. moorei †

Mamay 1959

Above: Compression of Bowmanites

Diversity

Cheirostrobus pettycurensis †

Scott, 1897; Neregato & Hilton, 2019
Visean of the UK
Spore-bearing cone
Cheirostrobus is one of the most anatomically important Paleozoic sphenopsid cones.
Its preservation has been central to understanding early sphenophyll reproductive evolution

Below: reconstruction of Cheirostrobus (from Neregato & Hilton, 2019 Fig. 6)

Eviostachya hoegii †

Stockmans, 1948
Famennian of Belgium
Problematic cones with leafy stems

Above: Reconstruction of Eviostachya

?Gondwanophyton indicum †

Maithy, 1974; Srivastava and Rigby, 1983; McLoughlin, 1992
Early Permian of India and Australia
Slender, articulated striate stems with paired leaves at distinct nodes
Leaves are narrow, cuneate, semicircular to reniform
Reproductive structures are unknown, making systematic determination difficult

Above: Reconstruction of Gondwanophyton

Hamatophyton †

Deng et al., 1974
Famennian of China

H. verticillatum

Li et al., 1995; Wang et al., 2006
Late Devonian of China
Pseudomonopodial with axial trichomes or spines and nodal whorls of sterile leaves
Leaves are dimorphic and sometimes contain trichomes or spines
When mature, primary xylem is exarch, and the secondary xylem lacks parenchyma

H. yiduense

Feng, 1984
Originally called Sphenophyllum yiduense

Above: Compression fossils of Hamatophyton verticillatum

Lilpopia †

Remy and Remy, 1961; Conert & Schaarschmidt, 1970; Lipiarski, 1972
Late Pennsylvanian to the Early Permian of Poland and Germany
This taxon has an unusual fructification organization

L. crockensis †

L. polonica †

L. raciborskii †

Peltastrobus †

Baxter, 1950
Cone with sporangium that bore monolete spores
Spores of the Columnisporites type

Parasphenophyllum †

Asama & Oishi, 1980
Late Triassic
Leaf taxon with radial leaf arrangement and curved veins

Paratrizygia †

Asama, 1966, 1970; Kim, 1989
Leaf taxon with trizygoid arrangement and curved veins

Rotafolia songziensis †

Wang et al., 2005; Wang et al., 2006
Late Devonian of China
Permineralized fertile stems and branches

Sentistrobus goodii †

Riggs & Rothwell, 1985
Late Pennsylvanian of Appalachian Basin
Small (1.4 cm in diameter) cones have three appendages per node, each of which dichotomizes in a horizontal plane.
Subsequent dichotomies of the upturned ends of the appendages produce spinelike tips.
Spores of the Columnisporites type

Above: Peltastrobus

Sphenophyllum †

Brongniart, 1828; Baxter, 1948; Reed, 1949
Carboniferous–Permian impression–compression specimens of wedge-shaped leaves borne in whorls

Sphenophyllum alimergenum

Sphenophyllum amadokense

Sphenophyllum angustifolium

Sphenophyllum antiquum

Sphenophyllum aquense

Sphenophyllum archangelskyi

Sphenophyllum australe

Sphenophyllum berestovianum

Sphenophyllum biarmicum

Sphenophyllum bifidum

Sphenophyllum bifurcatum

Sphenophyllum brevifolium

Sphenophyllum charmassii

Sphenophyllum churulianum

Sphenophyllum comiense

Sphenophyllum crenulatum

Sphenophyllum cuneifolium

Sphenophyllum densifoliatum

Sphenophyllum densinerve

Sphenophyllum dentatum

Sphenophyllum dianthoides

Sphenophyllum dichotomum

Sphenophyllum dissectum

Sphenophyllum elagatisfolium

Sphenophyllum elongatum

Sphenophyllum emarginatum [type]

Sphenophyllum erosum

Sphenophyllum fasciculatum

Sphenophyllum fertile

Sphenophyllum filiculme

Sphenophyllum fimbriatum

Sphenophyllum fontainianum

Sphenophyllum furcatum

Sphenophyllum geigense

Sphenophyllum gilkinetii

Sphenophyllum gilmorei

Sphenophyllum gongxianense

Sphenophyllum grabaui

Sphenophyllum hauchecornei

Sphenophyllum indicum

Sphenophyllum kidstonii

Sphenophyllum laciniatum

Sphenophyllum laterale

Sphenophyllum latifolium

Sphenophyllum longifolium

Sphenophyllum majus

Sphenophyllum marsiliifolium

Sphenophyllum microphyllum

Sphenophyllum minus

Sphenophyllum multifidum

Sphenophyllum nemejcii

Sphenophyllum oblongifolium

Sphenophyllum obovatum

Sphenophyllum orbiculare

Sphenophyllum osnabrugense

Sphenophyllum paranaense

Sphenophyllum peltatum

Sphenophyllum primitivum

Sphenophyllum pseudotenerrimum

Sphenophyllum pusillum

Sphenophyllum quadrifidum

Sphenophyllum quadriphyllum

Sphenophyllum radiatum

Sphenophyllum rariforme

Sphenophyllum rotundatum

Sphenophyllum saarense

Sphenophyllum sakoense

Sphenophyllum saxonicum

Sphenophyllum schlotheimii

Sphenophyllum scopulatum

Sphenophyllum shansiense

Sphenophyllum sino-coreanum

Sphenophyllum sismondae

Sphenophyllum spathulatum

Sphenophyllum speciosum

Sphenophyllum spiralicum

Sphenophyllum stephanense

Sphenophyllum stoukenbergii

Sphenophyllum stylicum

Sphenophyllum subrotundatum

Sphenophyllum subtenerrimum

Sphenophyllum subtile

Sphenophyllum svogense

Sphenophyllum tenuifolium

Sphenophyllum tenuissimum

Sphenophyllum thonii

Sphenophyllum tomiense

Sphenophyllum trapifolium

Sphenophyllum trifoliatum

Sphenophyllum trizygia

Sphenophyllum truncatum

Sphenophyllum waltonianum

Sphenophyllum wingfieldense

Sphenophyllum yiduense

Sphenophyllum yiyangense

Above: Reconstruction of Sphenophyllum

Trizygia †

Royle, 1879
Trizygoid leaf arrangement: bilaterally symmetrical whorls with two pairs of large and one pair of distinctly smaller leaves

T. borealis

T. filiculmis

T. jordanensis

T. maithyana

T. ominensis

T. radczenkoi

T. speciosa [type]

T. tomiensis

Xihuphyllum †

Huang et al., 2016
Upper Devonian Wutong Formation of Zhejiang Province, China
Plant characterized by a hierarchical branching pattern, with robust nodose stems up to 42.5 mm wide and two orders of lateral branches.
Internode width of stems and first-order branches is correlated with the internode length.
Leaves, cuneate, broadly cuneate, or spatulate in shape and highly variable in size, are arranged in whorls at the nodes of stems and branches.
- The leaves reach over 80 mm in length and > 3000 mm2 in area, an unusually large size for Paleozoic sphenopsids
- Xihuphyllum is reconstructed as having a stature 2–3 m in height, and represents an early, large-bodied member within the extinct Sphenophyllales.

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