Palaeoenvironment and palaeoecology of the Early Mississippian tetrapod locality Willie's Hole

The Early Mississippian site of Willie's Hole in south-eastern Scotland hosts some of the earliest terrestrial tetrapods. This study reports on the palaeoenvironment, micropalaeontology and palaeoecology of this important locality. The 8 m thick section comprises saline–hypersaline lake facies (dolostones, evaporites), fluvial facies (conglomerate lags, rippled, planar-laminated, and cross-bedded sandstones and siltstones) and overbank facies (laminated grey siltstones, sandy siltstones, very fine sandstones and palaeosols). Numerous exposure surfaces characterised by rooting, desiccation or brecciation indicate the repeated wetting and drying of the floodplain. Vertebrate, invertebrate and plant fossils are concentrated in the overbank facies association, particularly in sandy siltstones. Macro- and microfossils present are tetrapods, rhizodonts, actinopterygians, gyracanthids, dipnoans, chondrichthyans (Ageleodus), bivalve molluscs, eumalacostracans, myriapods (diplopods), eurypterids, scorpions, branchiopods, ostracods, Spirorbis, Serpula, Calcitarcha, Monocraterion trace fossils, plant stems, arborescent lycopsids (Stigmaria, Lepidodendron) and megaspores of the creeping lycopsid Oxroadia conferta. Various palaeoenvironments coexisted on a tropical, coastal, low-lying floodplain: evaporitic saline lakes, small meandering river channels, brackish salinity temporary lakes, wet marshes and sub-aerial dry land with scrubby vegetation and trees. Tetrapods inhabited waterlogged floodplain marshes and were transported post-mortem by meteoric flooding events into brackish lakes and pools. The abundance of tetrapod and other fossils is attributed to taphonomic concentration and preferential preservation during rapid burial. The Willie's Hole succession gives a window into the rich ecology and habitats on coastal floodplains after life recovered from the end-Devonian extinction and tetrapods walked on land.