The Fayetteville Formation of northwestern Arkansas (upper Mississippian/middle Chesterian) contains two compression plant fossil assemblages (one in situ) that represent plant communities, and an allochthonous permineralized assemblage recovered from marine strata that represents the landscape. This preservation of spatial ecological subunits (communities) nested within a larger subunit (landscape) provides a snapshot of vegetation patterns within a Late Mississippian clastic swamp. Fifteen whole plants are recognized. Seed ferns are the most speciose group and lycopsids account for most biomass. Seed fern taxa known only as permineralized specimens include one canopy tree ( Megaloxylon ), two understory trees, and five herbaceous layer plants. Two herbaceous layer seed ferns are observed only as compressions. Lycopsids are represented as two canopy trees that are known from both permineralizations and compressions. Archaeocalamites is also known from both permineralizations and compressions but was an understory tree. Ferns are rare and are preserved only as fragments of permineralized rachises from two species. As revealed by the in situ compression assemblage, the two species of lycopsid canopy trees co-occur and they formed communities that occupied ever-wet bottomlands, with Archaeocalamites occupying the understory, and a single species of seed fern comprising the herbaceous layer. Lycopsids do not co-occur with Megaloxylon . Megaloxylon probably formed a second community type in somewhat water-stressed areas of the swamp with an understory of small arborescent seed ferns, some Archaeocalamites , and an herbaceous-layer seed fern. Ferns probably formed a third type of community in disturbed sites.

The Horton Group (late Famennian to Tournaisian) of Atlantic Canada provides an unusually complete record of Early Mississippian wetland biota. Best known for tetrapod fossils from “Romer's Gap,” this unit also contains numerous horizons with standing vegetation. The taphonomy and taxonomy of Horton Group fossil forests have remained enigmatic because of poor preservation, curious stump cast morphology, and failure to recognize the unusual sedimentary structures formed around standing plants. Four forested horizons within the Horton Group are preserved as cryptic casts and vegetation-induced sedimentary structures formed by the interaction of detrital sediment with in situ plants. Protostigmaria , the lobed base of the arborescent lycopsid Lepidodendropsis , occur as sandstone-filled casts attached to dense root masses. Mudstone-filled hollows formed when a partially entombed plant decayed, leaving a void that was later infilled by muddy sediment. A scratch semi-circle formed where a current bent a small plant, causing it to inscribe concentric grooves into the adjacent muddy substrate. Obstacle marks developed where flood waters excavated erosional scours into sandy sediment surrounding juvenile Lepidodendropsis . These cryptic lycopsid forests had considerably higher densities than their Pennsylvanian counterparts. Vegetation-induced sedimentary structures are abundant in Horton Group strata and could easily be misidentified as purely hydrodynamic or soft-sediment deformation structures without careful analysis. Recognition of these structures in early Paleozoic strata has great potential to expand our knowledge about the distribution of early land plants.

Abstract The correlation of Tournaisian and Visean platform carbonate successions of Britain and Ireland initially relied upon the development of coral and brachiopod zonations. However, such zones are strongly facies-controlled and are only of local to regional significance. Over recent years, emphasis has been placed upon the use of foraminifers, and notably conodonts, to define international stages. They have been studied increasingly within the Tournaisian and Visean successions of Britain and Ireland, but are of limited stratigraphical value in younger Carboniferous strata. Ammonoids (goniatites) provide the greatest biostratigraphical resolution for the late Visean, Namurian and early Westphalian stages. Some ammonoid biozones can be recognized across Western Europe and some biozones are applicable globally. However, the marine bands that contain these ammonoids may be absent towards basin margins and marine influence is lost entirely throughout late Westphalian and Stephanian times. Within strata lacking ammonoids, biostratigraphical correlation initially relied upon the recognition of non-marine bivalve zonation, but over recent decades palynomorphs (miospores) and plant macrofioras have assumed greater importance.