Spongiophyton

Devonian fossil of a plant-like thallose organism

Spongiophyton
Temporal range: Early Devonian – Middle Devonian[1]
PreꞒ
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
Scientific classification Edit this classification
Kingdom: Plantae
Division: incertae sedis
Family: †Spongiophytaceae
Genus: †Spongiophyton
Kräusel (1954)
Type species
†Spongiophyton lenticulare[2][3]
(Barbosa) Kräusel (1954)
Species
  • †S. articulatum Kräusel (1954)
  • †S. hirsutum Kräusel (1954)
  • †S. lenticulare (Barbosa) Kräusel (1954)
  • †S. minutissimum Kräusel (1954)
  • †S. nanum Kräusel (1954)

Spongiophyton was a thallose fossil of the early to mid-Devonian, which is notoriously difficult to classify.

Spongiophyton displayed dichotomous branching, and a flattened/elliptical cross section with a thick (20–80 μm) upper cuticular surface.[4] It is also perforated with pores resembling those of some liverworts.[4] It probably grew on the banks of rivers.[5] Spongiophyton has been mistakenly interpreted as tree resin[6] and lycopod cuticle,[7] and was later identified as the cuticle of a thalloid plant.[8] It has most recently been interpreted on morphological[9] and isotopic[10] grounds as a lichen—which would place it with Winfrenatia among the earliest known representatives of this group.[11]

The significance of the isotopic data has, however, been called into question. Jahren et al. argued that mosses and liverworts had a δ13C signature of under −26‰, and lichens were exclusively > −26‰. But in deducing this they relied solely on their own data, neglecting to include published datasets or bryophytes from a wide range of habitats. They also failed to take into account any adjustment necessary to overcome post-burial alteration of the δ13C, or to compensate for the different isotopic composition of the early Devonian atmosphere.[4] Repeating Jahren's experiments with these factors taken into account shows that most major groups' δ13C values overlap significantly, and do not provide a statistically significant case for the inclusion of Spongiophyton in any group.[4]

Notes

  1. ^ Taylor, W. A.; Free, C.; Boyce, C.; Helgemo, R.; Ochoada, J. (2004). "SEM Analysis of Spongiophyton Interpreted as a Fossil Lichen". International Journal of Plant Sciences. 165 (5): 875–881. doi:10.1086/422129. S2CID 85382155.
  2. ^ "Spongiophyton". IRMNG.
  3. ^ "Spongiophyton". IFPNI.
  4. ^ a b c d Fletcher (2004)
  5. ^ Gensel et al. 1991; Griffing et al. 2000; in Fletcher (2004)
  6. ^ Penhallow (1889) in Fletcher (2004)
  7. ^ Barbosa (1949) in Fletcher (2004)
  8. ^ Kräusel (1954) in Fletcher (2004)
  9. ^ Taylor et al. (2004)
  10. ^ Jahren et al. (2003)
  11. ^ Retallack (1994) suggested that the Ediacaran biota were lichens, but has since refined this hypothesis (Retallack, 2007).

References

  • Fletcher, B. J.; Beerling, D. J.; Chaloner, W. G. (2004). "Stable carbon isotopes and the metabolism of the terrestrial Devonian organism Spongiophyton". Geobiology. 2 (2): 107–119. doi:10.1111/j.1472-4677.2004.00026.x. S2CID 85079041.
  • Jahren, A. H.; Porter, S.; Kuglitsch, J. J. (2003). "Lichen metabolism identified in Early Devonian terrestrial organisms". Geology. 31 (2): 99. Bibcode:2003Geo....31...99J. doi:10.1130/0091-7613(2003)031<0099:LMIIED>2.0.CO;2. ISSN 0091-7613. S2CID 49241170.
  • Retallack, G. J. (1994). "Were the Ediacaran fossils lichens?" (PDF). Paleobiology. 20 (4): 523–544. doi:10.1017/S0094837300012975. S2CID 129180481. Archived from the original (PDF) on 2009-02-25.
  • Retallack, G. J. (2007). "Growth, decay and burial compaction of Dickinsonia, an iconic Ediacaran fossil" (PDF). Alcheringa: An Australasian Journal of Palaeontology. 31 (3): 215–240. doi:10.1080/03115510701484705. S2CID 17181699.
  • Taylor, Wilson A.; Chris Free; Carolyn Boyce; Rick Helgemo; Jaime Ochoada (2004). "SEM analysis of Spongiophyton interpreted as a fossil lichen". International Journal of Plant Sciences. 165 (5): 875–881. doi:10.1086/422129. S2CID 85382155.


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