Microvertebrates from the Lower Greensand Group (Lower Cretaceous) of Clophill, Bedfordshire, UK, and Nutfield, Surrey, UK

Abstract

The Lower Greensand of southern England (early Aptian–early Albian; c., 120–110 Ma) has yielded diverse faunas of vertebrates, but these have not been reported in detail. Here, we present rich faunas, mainly comprising sharks, bony fishes, and crocodyliforms, from two localities to the north and south of the London–Brabant Massif. The first, Clophill Quarry, near Leighton Buzzard in Bedfordshire, has yielded fossils from the Brown Sands Formation, representing an inshore, tidally influenced environment, such as an estuary mouth. The second, Patteson Court Quarry, Nutfield, Surrey, has produced fossils from the Sandgate Formation (Redhill Sands Member). The faunas of both locations are similar, and they share a remarkable assemblage of at least 23 chondrichthyan taxa, one Edaphodon-like chimaeroid, ten hybodontiform sharks, and 12 neoselachian sharks. The hybodontiform sharks comprise two morphological groups, those with high-cusped piercing teeth, sometimes with lateral cusplets and a coronal ornament of vertical ridges, and those with low-crowned crushing teeth. The 12 species of neoselachian sharks include one representative of the extinct Synechodontiformes, as well as examples of the modern orders Hexanchiformes, Lamniformes, Carchariniformes, Squatiniformes, Heterodontiformes, and Orectolobiformes. Bony fishes are represented mostly by crushing teeth of Pycnodontiformes, Aspidorhynchiformes, Amiiformes, Lepisosteiformes, and Semionotiformes. Crocodyliforms are identified from seven morphotypes of elongate, goniopholid-like teeth. Based on these fossil teeth, the fauna is 53 % chondrichthyan and 21 % osteichthyan; neoselachians represent 32–45 % of the chondrichthyans, lower than figures from the underlying Wealden.