Ectothermic vertebrates, climate and environment of the West Runton Freshwater Bed (early Middle Pleistocene, Cromerian)

The ectothermic vertebrate fauna from the early Middle Pleistocene West Runton Freshwater Bed (WRFB; England, Norfolk) comprises 21 species (10 fishes, 8 amphibians and 3 reptiles). All recorded species are referred to recent forms, except a large newt (Triturus sp. nov.) probably belonging to the Triturus cristatus group, and an indeterminate colubroid snake showing viperid affinities. This indicates that the Cromerian herpetofauna of the British Isles is more diverse than previously thought and contains extinct species. Two fish species are new for the WRFB: the white bream (Abramis bjoerkna), and the ide (Leuciscus cf. idus). Based on the faunal composition the aquatic ecosystem can be reconstructed as a densely vegetated, large eutrophic freshwater body, representing a slow-flowing river or oxbow lake. The terrestrial ecosystem in the surrounding area represents moist woodland habitats. There are no indications of open landscapes in the immediate vicinity. The estimated palaeoclimatological parameters indicate similar summer temperatures to today (16-17 °C), probably cooler winters (−6 to −1.4 °C) and mean annual temperatures (6-8 °C), and significantly higher mean annual precipitation compared to present-day conditions.