Palaeoenvironment and taphonomy of the Hypsilophodon Bed, Lower Cretaceous Wessex Formation, Isle of Wight

The ‘Hypsilophodon Bed’ occurs at the top of the Wessex Formation (Early Cretaceous, Barremian) on the Isle of Wight, England. Numerous remains of the small ornithopod dinosaur Hypsilophodon foxii have been recovered from the bed since the mid-19th century. Previous theories for these fossil occurrences have focused on catastrophic mass death events including miring and flood-related mortality. However, only limited sedimentological and taphonomic analyses of the horizon and its fossil assemblage have been undertaken, hindering efforts to evaluate different theories for how the assemblage formed.

Here, we undertake a sedimentological study of the bed to constrain its depositional environment, examine matrix from Hypsilophodon fossils to identify where they were collected from within the bed, and undertake taphonomic investigation of Hypsilophodon specimens. Results reveal a floodplain which became a marsh and then mudflats at the edge of a lagoon. Hypsilophodon fossils are spatially and stratigraphically distributed throughout the bed. Specimens are largely incomplete and unabraded suggesting most perished on or near to the floodplain and may have lain exposed for some time prior to burial. Overall, evidence suggests the fossil assemblage of the Hypsilophodon Bed formed as an accumulation of remains over time.