page_title: Nematothallus
section_title: Affinity
hierarchical_section_title: Nematothallus / Affinity
caption_attribution_description: English: Aperture in cuticle of Nematothallopsis, showing spheroid structures (spores?)
context_page_description: Nematothallus is a form genus comprising cuticle-like fossils. Some of its constituents likely represent red algae, whereas others resemble lichens.
context_section_description: Some material assigned to Nematothallus closely resembles certain lichens, suggesting a lichenous habit – although as the lichens evolved at least six times independently, this does not fully establish the genetic affinity.  The biochemistry of the organism is not inconsistent with an algal affinity, but Edwards (1982) considers it unlikely that algae would be preserved as coalified impressions.  However, Edwards does note that the surface patterning could have been produced in a similar fashion to surface layers in green algae – that is, by the ends of tightly packed filaments causing indentation on the surface layer. (Just because they were formed in the same way doesn't mean they were formed by green algae, though.)  The most likely affinity, for the aperture-bearing cuticles, is with the coralline red algae; the absence of biomineralization suggests a stem-group level affiliation.  Whereas Smith & Butterfield contend that this material is separate from the charcoalified lichen-like material, Edwards insists that all the material comes from the same lichen-like organism.
caption: Spores surrounding an aperture in Nematothallopsis
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