The predominant types of fossils found in the Westphalian strata of South Yorkshire belong to three general groups, each representing the ecosystem associated with one of three principal paleo-environments, namely: low-lying, swampy land areas adjacent to meandering river channels; waterlogged swamps or shallow, deltaic lakes; and the shallow sea bed formed from the previous two environments when the sea level rose periodically to flood extensive areas of river delta and coastal plain before retreating again. These groups are as follows:
Various types of fern foliage, such as Neuropteris and Pecopteris, make up the most common plant fossils of the Westphalian. In addition, swamp-loving lycopods, like Lepidodendon and Sigillaria, and the giant horse-tail, Calamites, have been recorded in several places. Primitive gymnosperms, such as Cordaites, represent plants living in drier conditions on higher ground.
Bands of mussel shells occur at several horizons and are distinguished by evolutionary adaptations over time. These fresh water bivalves probably lived in a vertical position, buried beneath the surface of muddy sediment below shallow bodies of standing water. Ostracods, small crustaceans, serpulids and occasional fish remains have also been recorded.
Representing a relative rise in sea level, the 'marine bands' contain salt water marker fossils which have been of significant value in determining stratigraphy. Marine Bands contain brachiopods, bivalves, gastropods, ostracods and crinoids, but of particular interest are the cephalopods, such as goniatites, which are restricted to major incursions. The brachiopod, Lingula, is common throughout and may be associated with foraminifera, conodonts and sponge spicules.