Triassic dinosaur footprints from south Wales: Their context and preservation

Two types of dinosaur footprint, both belonging to the ichnogenus Anchisauripus, are described from the Triassic (Norian) of South Glamorgan, South Wales. They occur on the surfaces of thin-bedded, graded sandstones which are shown to be of sheet flood origin. Other lithofacies associated with the footprints are temporary lake deposits, soil horizons and ephemeral stream conglomerates and sandstones. The overall environment where these dinosaurs lived was that of the low-lying area (piedmont), adjacent to a mountain range (now the South Wales Coalfield) flanked by alluvial fans and talus slopes, and marginal to the Keuper Marl lake.The preservation of the footprints is for the most part perfect, but others are deformed somewhat or simply vague depressions (squelch marks) where the sediment was very muddy and wet. The footprints have been preserved as a result of (1) their impression into a slightly damp muddy sediment (which imparted the best moulding characteristics); (2) slight desiccation during subaerial exposure which made the surface firm and scour-resistant; and (3) burial of the surface by a thin sheet flood of low turbulence, which quickly covered the footprints, and only locally eroded into them.The nature of the footprint trackways indicates that the animals were bipedal and travelling at a strolling pace. There is no indication that they were carnivores or herbivores, but in either case, there is evidence for a food source being available.