''Spongiophyton'' was a

thallose Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...

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 ...

of the early to mid-

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...

, which is notoriously difficult to

classify Classification is a process related to categorization, the process in which ideas and objects are recognized, differentiated and understood. Classification is the grouping of related facts into classes. It may also refer to: Business, organizat ...

. ''Spongiophyton'' displayed dichotomous branching, and a flattened/elliptical cross section with a thick (20–80 μm) upper cuticular surface.Fletcher (2004) It is also perforated with pores resembling those of some liverworts. It probably grew on the banks of rivers. ''Spongiophyton'' has been mistakenly interpreted as

tree resin In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

and lycopod cuticle, and was later identified as the cuticle of a thalloid plant. It has most recently been interpreted on morphological and isotopicJahren ''et al.'' (2003) grounds as a lichen—which would place it with Winfrenatia among the earliest known representatives of this group.Retallack (1994) suggested that the

Ediacaran biota The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-shaped, mostly sessi ...

were lichens, but has since refined this hypothesis (Retallack, 2007). The significance of the isotopic data has, however, been called into question. Jahren ''et al.'' argued that

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta ('' sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and ...

es and

liverworts The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of g ...

had a signature of under ‰, and lichens were exclusively > ‰. But in deducing this they relied solely on their own data, neglecting to include published datasets or

bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants ( embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited ...

s from a wide range of habitats. They also failed to take into account any adjustment necessary to overcome post-burial alteration of the , or to compensate for the different isotopic composition of the early Devonian atmosphere. Repeating Jahren's experiments with these factors taken into account shows that most major groups' values overlap significantly, and do not provide a

statistically significant In statistical hypothesis testing, a result has statistical significance when it is very unlikely to have occurred given the null hypothesis (simply by chance alone). More precisely, a study's defined significance level, denoted by \alpha, is the p ...

case for the inclusion of ''Spongiophyton'' in any group.

Notes

References

* * * * * Lichens Devonian life Paleozoic life of Ontario Paleozoic life of New Brunswick {{devonian-plant-stub