Cosmochlaina

Cosmochlaina (from Greek: kosmos=ornament; xlaina=wrapper/cloak) is a form genus of nematophyte – an early (Siluran – Devonian) plant known only from fossil cuticles,^[1] often found in association with tubular structures.^[2]

The form genus was put forwards by Dianne Edwards, and is diagnosed by inwards-pointing flanges and randomly oriented pseudo-cellular units.^[3] Projections on the outer surface are always present, and sometimes also appear on the inner surface; however, the surface of the cuticle itself is always smooth.^[3] The holes in the cuticle are often covered by round flaps, loosely attached along a side.^[3]

Where Nematothallus was sometimes used to relate only to tube-like structures, Cosmochlaina was used in reference to the cuticle fragments. Material discovered later revealed its internal anatomy, which comprises a lichen-like mat of 'hyphae'.Edwards, Dianne; Axe, Lindsey; Honegger, Rosmarie (2013). "Contributions to the diversity in cryptogamic covers in the mid-Palaeozoic:Nematothallusrevisited". Botanical Journal of the Linnean Society: n/a. doi:10.1111/boj.12119. 

It has been suggested that the pores of Cosmochlaina represent broken-off rhizoids, on the basis that rotting and acid treatment of extant liverworts produces a similar perforated texture.^[4] However, the status of this form genus in any one kingdom is not secure; members could, for example, represent arthropod cuticle.^[5] Alternatively, different species may in fact represent different parts of the same organism.^[3] Based on the more recent material, a lichen affinity seems most plausible.^[6]

See also

• Nematothallus, a closely related sister taxon
• Evolutionary history of plants

References

1. ↑ Kenrick, P.; Crane, P.R. (1997). "The origin and early evolution of plants on land". Nature 389 (6646): 33–39. Bibcode:1997Natur.389...33K. doi:10.1038/37918.  Cite uses deprecated parameters (help)
2. ↑ Gensel, P.G.; Johnson, N.G.; Strother, P.K. (1990). "Early Land Plant Debris (Hooker's" Waifs and Strays"?)". PALAIOS 5 (6): 520–547. doi:10.2307/3514860. JSTOR 3514860.  Cite uses deprecated parameters (help)
3. ↑ 3.0 3.1 3.2 3.3 Edwards, D. (1986). "Dispersed cuticles of putative non-vascular plants from the Lower Devonian of Britain". Botanical Journal of the Linnean Society 93 (3): 259–275. doi:10.1111/j.1095-8339.1982.tb01025.x. 
4. ↑ Graham, L.E.; Wilcox, L.W.; Cook, M.E.; Gensel, P.G. (2004). "Resistant tissues of modern marchantioid liverworts resemble enigmatic Early Paleozoic microfossils". Proceedings of the National Academy of Sciences 101 (30): 11025–11029. Bibcode:2004PNAS..10111025G. doi:10.1073/pnas.0400484101. PMC 503736. PMID 15263095.  Cite uses deprecated parameters (help)
5. ↑ Taylor, T.N. (1988). "The Origin of Land Plants: Some Answers, More Questions". Taxon 37 (4): 805–833. doi:10.2307/1222087. JSTOR 1222087. 
6. ↑ Edwards, Dianne; Axe, Lindsey; Honegger, Rosmarie (2013). "Contributions to the diversity in cryptogamic covers in the mid-Palaeozoic:Nematothallusrevisited". Botanical Journal of the Linnean Society: n/a. doi:10.1111/boj.12119. 

v t e Early land flora Related links Evolutionary history of plants Rhynie chert External link directory The first...? Vascular plant, Cooksonia Tree, Wattieza Lycopods, the Drepanophycales and the zosterophylls Fungus fossil, Ornatifilum Lichen, Spongiophyton Enigmatic taxa Cuticular remains: Bitelaria Cosmochlaina Nematothallus Orestovia Protosalvinia Spongiophyton Other: Pachytheca Prototaxites. Sister taxa Green algae: Charophyta, from which land plants evolved Chaetocladus, an early alga