Microvertebrate-rich gutter casts from the basal Wessex Formation (Wealden Group, Lower Cretaceous) of Dungy Head, Dorset: Insights into the palaeoecology and palaeoenvironment of a non-marine wetland

Abstract

A detailed taxonomic, taphonomic and sedimentological examination of a newly discovered microvertebrate-rich horizon within the non-marine, Lower Cretaceous Wessex Formation (Wealden Group) of Dungy Head, Dorset, aids the ecological and palaeoenvironmental reconstruction of southern England's Early Cretaceous wetlands. Historically, the Wessex Formation of Dungy Head has been neglected due to its partially vegetated state and landslipped coastal exposure; here the section's palaeontological and stratigraphical significance is realised. Non-marine, cypridoidean ostracods indicate a depositional age of late Berriasian–early Valanginian; consequently, the faunal assemblage recorded here represents the oldest fauna to be described from the Wessex Formation to date. Significantly, winnow-induced gutter casts are shown to be an important repository of mixed aquatic and terrestrial microvertebrate remains. Hydraulic sorting within a fluvial environment has resulted in the formation of multi-taxic, microvertebrate-rich gutter casts that through close lateral and stratigraphical association form a unique, bone-rich taphofacies. The recorded assemblage is typical of wetland biodiversity containing a minimum of 25 taxa including, non-marine molluscs, ostracods, elasmobranchs, osteichthyans, and tetrapods. Importantly, the gutter casts permit the taxonomic evaluation of a primarily aquatic biota in which albuliform fishes are recorded from the Wessex Formation for the first time. The biota also includes a diverse elasmobranch fauna, including hybodontoid sharks and a rhinobatid ray. Furthermore, lepidosaurs, including both scincomorphs and, tentatively, an anguimorph, are confirmed in the Wessex Formation of Dorset.