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Contributions to the diversity in cryptogamic covers in the mid-Palaeozoic: 'Nematothallus' revisited

Edwards, Dianne, Axe, Lindsey and Honegger, Rosmarie 2013. Contributions to the diversity in cryptogamic covers in the mid-Palaeozoic: 'Nematothallus' revisited. Botanical Journal of the Linnean Society 173 (4) , pp. 505-534. 10.1111/boj.12119

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Compression fossils from the Silurian and Devonian of southern Britain, composed of cuticles and tubes, were described by W. H. Lang as the genus Nematothallus and placed, with Prototaxites, in Nematophytales, related neither to algae nor tracheophytes. Dispersed cuticles of Nematothallus and perforated forms assigned to Cosmochlaina were frequently recovered in macerates, their affinities being unresolved. New collections from a Lochkovian locality in the Welsh Borderland permitted the reconstruction of the stratified thalli of these nematophytes; they comprise a superficial cortex (which produced the cuticles) overlying a palisade zone composed of septate, parallel tubes, presumed to be hyphae, and a basal zone comprising wefts of randomly interwoven hyphae. Excellent three dimensional preservation allows the erection of a new species of Nematothallus, N. williamii. A similar anatomy is seen in a new group of fossils with either circular incisions in the cortex or complete separation of thickened cortical cells, presumably comprising a developmental sequence. By their stratified organization the nematophytes differ from extant and extinct algae and bryophytes and the enigmatic Spongiophyton. A complex anatomy and septate tubes suggest affinity with lichenized fungi. Limited data support a fungal rather than embryophyte chemistry, but a photobiont is missing. Nematophytes, globally widespread in cryptogamic covers from mid-Ordovician times, added to the biodiversity in early terrestrial ecosystems and enhanced chemical weathering.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QK Botany
Uncontrolled Keywords: algae; bryophytes; Cosmochlaina; embryophytes; fungi; lichens; Lochkovian; Prototaxites; weathering; Welsh Borderland
Publisher: Linnean Society of London
ISSN: 0024-4074
Date of First Compliant Deposit: 30 March 2016
Last Modified: 07 Jul 2017 09:33

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