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Obscure heterosporous lycophytes
Obscure heterosporous lycophytes
Barinophytes, named after Barinophyton, are a group with ambiguous affinities. They possess a strobilar structure that is reminiscent of the zosterophylls as well as G-type tracheids. Most of these taxa are heterosporous with both megaspores and microspores within the same sporangium.
Ecology & Form
Ecology & Form
Wide geographic distribution
Probably were aquatic or semi-aquatic
Axes
G-type water-conducting cells for support
This tracheid type is also found in the zosterophylls, which suggests an affinity with lycophytes.
Due to the cell type, plants were probably not very tall
Reproductive
Mostly known only from their strobili (clusters of sporangia or spore-producing organs);
Presumed individual microphylls have also been found in some strobili
The strobili have two rows of sporangia, which are arranged both laterally and terminally in Barinophyton † and terminally in Protobarinophyton †
Pectinophyton †, which has only a single sporangial row, may also be a barinophyte
Heterosporous sporangia
Both microspores and megaspores are found in the same sporangium (intrasporangial heterospory)
This is unique in the plant world; extant plants are homosporous or exhibit heterospory in different sporangia
This has been interpreted as an intermediate stage leading to complete heterospory, with megaspores and microspores separated in megasporangia and microsporangia, respectively (Taylor and Brauer, 1983; Bateman and DiMichele, 1994)
Diversity
Diversity
Barinophyton †
Barinophyton †
White, 1905, Brauer, 1980
B. citrulliforme †
B. obscurum †
Upper Devonian Catskill Formation of northern Pennsylvania
The fertile system consists of a main axis that bears alternate strobili that have a distinctive two-ranked appearance
The main axis is about 3 mm in width and bears strobili at 7-mm intervals; up to seven strobili per fertile segment.
The strobili are up to 5.5 cm in length and are probably at least 4.5 cm long when mature. They range from 0.7 to 1.0 cm in width.
The strobili appear to be borne in one plane, but this may be the result of compression. They may actually be spiral on the main axis.
B. sibiricum †
Lepechina et al. 1962
Above: A compression fossil of Barinophyton obscurum †
Early Devonian of Yunnan, China
Early eutracheophyte that may be a barinophyte
Lower Devonian (Pragian) of southeastern Yunnan, China.
Early eutracheophyte that may be a barinophyte
Krithodeophyton croftii †
Krithodeophyton croftii †
Edwards, 1968
Naked, pseudomonopodial axes with some isotomous branching
Centrarch protostele
Sporangia in terminal spikes with straight or curved bracts (enations?)
Sporangia oval and sessile, born in 2 rows on either side of the axis
Homosporous
Pectinophyton †
Pectinophyton †
Hoeg, 1935
P. bipectinatum
P. citrulliforme
P. norvegicum
? Omniastrobus dawsonii †
? Omniastrobus dawsonii †
Originally called Barinophyton dawsonii (Krausel and Weyland, 1941)
Strobili in Omniastrobus are similar to those of the enigmatic order Barinophytales and consist of two rows of lateral sporangia.
Unlike in other Barinophytales, however, sporangia within the strobili show a continuous gradient in average spore size, from those producing smaller spores (∼70–150 mm) to those producing larger spores (1200 mm), as well as some with a bimodal mix of sizes.
Strobili up to at least 4.4 cm in length and 5.4–9.6 mm wide.
Strobili bear two lateral rows of closely packed ellipsoidal to elongate sporangia
Spores triangular to elliptical, unornamented, with thin walls and small, slightly raised trilete marks.
Individual sporangia within strobili produced spores of different average sizes, from those with primarily smaller spores (∼70–150 mm in diameter) to those with primarily large spores (∼200–280 mm) and those with intermediate spore sizes. Sporangia in strobili show a spore size gradient, with smaller spores borne proximally.
Above: Compression fossils of Omniastrobus dawsonii † from Fig 1 of Bonacorsi et al., 2021
Protobarinophyton pennsylvanicum †
Protobarinophyton pennsylvanicum †
Ananiev 1955, Brauer, 1981
Early Devonian of New York and Pennsylvanian
Plant bearing terminal strobili on elongate axes.
Strobili bearing two rows of alternate sporangiferous appendages
Appendages curving downward and back toward the strobilar axis, bearing along their concave surfaces large sporangia, one per appendage.
Above: Compression fossils of Protobarinophyton †
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