Chemotaxonomy of some problematic palaeozoic plants

Chemical data are given on the remains of nine fossil genera ranging from Precambrian to Carboniferous in age (Chuaria, Sporangites, Taeniocrada, Orestovia, Parka, Protosalvinia, Spongiophyton, Solenites, Botryococcus). It is suggested that such chemical data are useful additional criteria in making taxonomic assignments in palaeontology. Analyses indicate a high level of organic chemical diversity, although the original composition has evidently been altered by temperature and pressure over a long period of time. The labile chemical constituents are retained within a more chemically inert carbon matrix, which shows a progressive alteration of the ratios of C, N, O and H with respect relative age, similar to that seen in the coalification process.The chemical composition of Sporangites specimens is more suggestive of an animal rather than a plant affinity; it is here suggested that this genus represents in part the remains of some animal egg test. Hydrolytic products of Solenites and Taeniocrada indicate the presence of aliphatic hydroxy acids suggesting the presence of cutin and suberin. The chemical compositions of Orestovia, Parka, Protosalvinia, Spongiophyton and Botryococcus are interpreted as being consistent with an algal rather than a vascular plant affinity. Evidence for extreme diagenesis of the acritarch-like Chuaria greatly limits chemotaxonomic consideration. The possible role of thermal and biotic-thermal degradation patterns seen in palaeochemistry is discussed.