gigas, Sphenophyllum thonii) are very diversified in the first but absent in the red sediments; similarly the callipterids with small pinnules (Arnhardtia mouretii, Gracilopteris strigosa, Rhachiphyllum schenkii), but also Odontopteris subcrenulata, Cordaites
borassifolius and Poacordaites which were extending from the basal Autunian into the grey sediments of the Transition zone become absent in the red sediments.
The contact represents an angular unconformity in the subsurface (Waldron and Rygel 2005) and records a pronounced biostratigraphic break marked by the appearance of Cordaites
macroflora and the incoming of the cordaitalean prepollen Florinites (Calder 1998; Utting and Wagner 2005; Utting et al.
Rudolph Florin on the evolution of the vegetative and reproductive structures of the cordaites
and early conifers.
polypodioides, Scolecopteris, Cordaites
lingulatus, Sphenophyllum costa, S.
Dawson, 'consists principally of the flattened bark of Sigillarioid and other trees, intermixed with leaves of Ferns and Cordaites
, and other herbaceous debris, and with fragments of decayed wood, constituting 'mineral charcoal', all these materials having manifestly alike grown and accumulated where we find them'.
Floated plant remains, most commonly Cordaites
leaves and Calamites stem and foliage remains, are found on the bedding planes of these ash fall deposits.
leaves, up to 22 cm in length, are common locally in red mudrock beds and channel sandstone bodies.
Most paleobotanists think that conifers either evolved from cordaites
or share an ancestor with them (Clement-Westerhof, 1988).
Cuticular studies of Cordaites
leaves from North America and Europe (Simunek 2000; Zodrow et al.
In effect, this work introduced chemotaxonomic utility into Carboniferous plant determinations, and it is currently extended to cordaites
as well, with encouraging results (Zodrow et al.