A marine microvertebrate fauna from a temporary exposure of the Atherfield Clay Formation, Reigate, Surrey

Abstract

A temporary exposure of the nearshore marine Atherfield Clay (Lower Greensand Formation, Aptian, Early Cretaceous) in the Reigate area (Wonham Mill) of Surrey was sampled for microvertebrate remains in Autumn 2013. Samples amounting to 858 kg of sediment were washed, dried, and sieved to 0.325 mm and the residue searched for all fossil content. This is the first definitive study of the Atherfield Clay chondrichthyan fauna of Surrey. The samples yielded teeth of hybodont sharks (Planohybodus ensis, Lonchidion breve), neoselachian sharks (Heterodontus sulcatus, Cretascyllium hassei, Protospinax sp., Protolamna sokolovi, Lamnid indet., Scyliorhinus muelleri, Scyliorhinus gen. et sp. indet., Protoscyliorhinus sp.) and batoids (Belemnobatis picteti, Squatirhina sp.). The neoselachian sharks and rays all constitute the first confident records for the various genera in the Atherfield Clay of the United Kingdom. Dermal denticles and bony fish teeth are also present in the samples, which also yielded small numbers of invertebrates (ammonite and crustacean), microcoprolites (Tomaculopsis tomaculopsis) and plant remains (fern indusia). The state of preservation of the chondrichthyan material suggests that none of the specimens are derived from older strata; the fauna is indigenous. The Surrey Atherfield Clay fauna is distinct from that recorded from the Atherfield Bone Bed on the Isle of Wight and the roughly coeval boreal fauna of the Speeton Clay.