Article: Silurian cryptospores and miospores from the type Wenlock area, Shropshire, England
The earliest occurrence of sculptured hilate cryptospores and miospores is near the base of the cf. protophanus-verrucatus Sporomorph Zone, now more accurately located within the lundgreni Graptolite Biozone in the type Wenlock area. Palynofacies studies indicate that this event is unrelated to changes in the depositional environment. All the Sheinwoodian sporomorphs are laevigate (six species) and have either a crassitate or patinate structure. The oldest known sculptured specimens of trilete miospores (two or three species) and hilate, crassitate/patinate cryptospores (four species) appear almost synchronously in the Homerian (upper part of lundgreni Graptolite Biozone). Additional sculptured taxa (two species) appear in the later Homerian but there are no innovations in structure. In North Africa (Gondwana) a closely comparable sequence of structural and sculptural events occurs. Three groups of sporomorphs described from the Buildwas, Coalbrookdale and lower Much Wenlock Limestone Formations are permanently fused cryptospore tetrads (one species), hilate cryptospores derived from dyads (eight species), and trilete miospore (six species). Systematic descriptions of seventeen species in eight genera are provided. Two genera Laevolancis and Artemopyra, three species Laevolancis plicata, Hispanaediscus wenlockensis, and Artemopyra brevicosta, and one combination are new, and the genera Hispanaediscus and Dyadospora are emended.