Ancestral euphyllophytes †

Eophyllophyton bellum †

• Hao & Beck, 1993; Hao et al., 2003

• Pragian (Early Devonian) of Yunnan, China

• Plant represents the earliest record of megaphyllous leaves

• The leaves of Eophyllophyton bellum were borne laterally or terminally on the axis. 

• They are small and fan-shaped, with the laminae highly dissected; are either vegetative or fertile; and range in width from 1.7 to 4.8 mm, in length from 2.2 to 5.0 mm, and in thickness from 40 to 200 mm. 

• They seem to occur in clusters at the ends of small lateral branches. Their dichotomous pattern of division reflects an isotomous or anisotomous venation, with each subdivision of the lamina served by a single vein. 

• In some instances, the pattern of division of the lamina is almost pinnate

Gmujij tetraxylopteroides † 

• Pfeiler & Tomescu, 2020

• Early Devonian (Emsian) of the Gaspe Peninsula

• Small axes with four-lobed primary xylem and secondary xylem. 

  • Primary xylem maturation mesarch, with several shallow protoxylem strands along midplanes of xylem lobes and one central protoxylem strand. 

  • Primary and secondary xylem tracheids with Psilophyton-type secondary wall thickening. 

  • Multiplicative divisions and rays present in secondary xylem.

Hostinella  † 

• Barrande, 1882

• Upper Silurian (Ludlow) of Bathurst Island, Canada, and Early Devonian Senni beds

• Dichotomously branching stems (axes); stems are approximately 1.2 mm in diameter

  • Axes have a striated external appearance 

  • Axes contain xylem with tracheids, 40 µm in diameter.

• No known sporangia 

• It is known to co-occur with the barinophyte, Krithodeophyton

H. bohemica

• Kräusel & Weyland, 1932

H. crispa

• Arnold, 1939

H. globosa

• Lang, 1925

H. heardii

• Edwards 1980

H. hercynica

• Mägdefrau, 1938

H. hostinensis

• Barrande, 1882

H. racemosa

• Lang, 1925

H. racheneuri

• Ledoux-Marcelle, 1927

H. silurica

• Banks, 1974

H. strictissima

• Høeg, 1942

H. wahnbachensis

• Kräusel & Weyland, 1935

Oocampsa catheta †

• Andrews et al. 1975

• Eifelian (Middle Devonian) of New Brunswick

• Central axis with spirally arranged first-and second-order branches

• Second-order branches dichotomize some what irregularly to produce ultimate fertile branchlets, located at varied distances along the second-order axes, so that the terminal, erect sporangia occur over a linear distance rather than in dense terminal clusters.

• The sporangia are ovoid with pointed apices and contain spores that are trilete, zonate, and ornamented with cones and spines

Pauthecophyton gracile †

• Xue et al., 2012

• Lower Devonian (Pragian) Posongchong Formation near Zhichang Village of Wenshan District, southeastern Yunnan, China.

• This plant consists of pseudomonopodially and dichotomously branched main axes and lateral branches. 

• Some laterals are pseudomonopodially divided producing three to four times dichotomously branched systems terminating in sporangia; other branches are isotomously divided six to eight times terminating in sporangia. 

  • Fusiform sporangia are grouped as fertile units; each unit, generally with two, three or four sporangia, is subtended by a branch which generally divides once or twice. 

  • Sporangia lacking twisting have a longitudinal dehiscence and contain similarly sized spores with laevigate and folded exine. 

• Pauthecophyton probably occupies a basal position within the euphyllophytes, as one of the earliest divergent clades.

• It is more similar to the genus Psilophyton than to others in branching, as well as sporangial shape, terminal position and longitudinal dehiscence

• Pauthecophyton and Psilophyton are interpreted as "leafless", but have distal axes with lateral, three-dimensional, synchronously dichotomous trusses that have been called “incipient fronds”, “pinnules”, “dichotomous pinnule-like appendages”, and “proto-leaves” (Kenrick & Crane 1997; Beerling & Fleming 2007)

• These were referred to as Branch-Leaf Complexes (BLC) by Hao & Xue (2013)

Shougangia bella †

• Wang et al., 2015

• Late Devonian (Famennian), Wutong Formation of Anhui and Jiangsu Provinces, South China

• Fern-like euphyllophyte that evolved tone of the earliest known laminate structures (leaves?)

• Stems contain a dissected stele with a four-ribbed and an elongate curved primary xylem segments changing to three elongate and slightly curved segments.

• Primary branches have a dissected stele with three similar primary xylem segments as in stems.

• The primary xylem of the stems and primary branches is mesarch, and individual primary xylem segments bear peripheral protoxylem strands and are surrounded by secondary xylem.

Stenoloboxyla ambigua †

• Bickner and Tomescu, 2019

• Emsian of Gaspé (Quebec, Canada)

• Small axes (~2 mm diameter)

• Primary xylem bar-shaped to trilobed in cross section

• one of the lobes shallow, sometimes barely protruding

• Inconspicuous mesarch protoxylem strands at rib tips, central protoxylem strand absent

• Psilophyton-type secondary wall thickenings

• Inner cortex wide, parenchymatous, with groups of large, thick-walled sclerenchyma forming a discontinuous layer around the xylem

• Outer cortex thin, consisting primarily of thin-walled sclerenchyma with some interspersed parenchyma

• Epidermis with ± isodiametric parenchyma

Wilhowia phocarum †

• Gensel, 2022

• Early Devonian (Emsian) of Gaspe Bay, Canada

• Plant with at least three levels of branching; perhaps up to 1 m tall

• Main axes branch pseudomonopodially, bearing helically arranged, single or paired, long first-order axes

• First-order axes produce helically arranged, cruciately dichotomous ultimate axes, terminating in acuminate, recurved tips or in clusters of paired, fusiform sporangia. 

• Sporangia in each pair curve or bend around each other near distal tips

• All axis orders covered with small, sharply tapered, multicellular emergences.

• Main axis a mesarch, three-ribbed actinostele composed of primary xylem with P-type and occasionally circular pitting

• Protoxylem present at center and near the tips of each rib, sometimes represented by lacunae and evident as median bands or elongate regions in some ribs

• Xylem parenchyma absent. 

• Trace formation via tangential elongation of rib tip, then separation of an oval trace with central elongate protoxylem. 

• Cortex two zoned, inner cortex not preserved, outer cortex with irregularly patterned, thin- to moderately thick-walled cells.

• Paired first-order branches with cortex of thinner-walled parenchyma cells produce a vascular trace with central protoxylem dividing either before or after its separation from ribs, resulting in two and sometimes three (perhaps four?) oval traces

• First-order traces elongate at one end to produce a smaller round-oval second order trace

• Epidermis consisting of small, tightly packed, square to rectangular cells

• Undoubted stomata not present, but gaps in epidermis/ outer cortex present. 

• Emergences multicellular, broader at base, and sharply tapered. Cortex composed of parenchyma cells of varying thickness, possible remnants of phloem present.