Monograph: Crytospores from the Type Area of the Caradoc Series in Southern Britian

Cryptospores, which are interpreted as sub aerially dispersed spores derived from early land plants, are described from the type area for the Caradoc Series in southern Britain. They are present in palynomorph assemblages isolated from a number of horizons in a sequence of predominantly nearshore shallow marine deposits. The cryptospores are described systematically; they comprise monads, dyads and tetrads, many of which are enclosed within an envelope which is either laevigate or sculptured. Difficulties associated with interpretation of cryptospore morphology are discussed and associated implications for systematics outlined. The cryptospore assemblages are similar in composition throughout the type Caradoc sequence, suggesting stasis, and are similar to previously described cryptospore assemblages of Ordovician and early Silurian age. Data on Llanvirn (Ordovician)-Llandovery (early Silurian) sporomorph assemblages indicate little variation in composition (taxa and morphotypes) during this interval, until the inception of trilete spores in the late Llandovery when there was an important change in the nature of sporomorph assemblages. The biostratigraphical, palaeophytogeographical and palaeobiological implications of the new data are discussed. Significant findings include confirmation of the presence of unfused dyads (true dyads) in the Caradoc and documentation of the high abundance of dyads in the assemblages.