Fish And Crab Coprolites From The Latest Triassic Of The Uk: From Buckland To The Mesozoic Marine Revolution

Coprolites from the Rhaetian bone beds in south-west England can be assigned to crustaceans and fishes. Here, we report crustacean microcoprolites, including Canalispalliatum and Favreina, the first records from the British Rhaetian, from Hampstead Farm Quarry near Bristol, evidence for diverse lobsters and their relatives not otherwise represented by body fossils. Further, we identify five fish coprolite morphotypes that differ in shape (cylindrical, flattened) and in presence or absence of a spiral internal structure. Many coprolites show bony inclusions on the surface, often relatively large in proportion to the coprolite; these show little or no evidence for acid damage, suggesting that the predators did not have the physiological adaptations of many modern predatory fishes and reptiles to dissolve bones. CT scanning has revealed the nature, packing and identity of inclusions within the coprolites, mainly fish scales, and some coprolites can contain more than twenty. An extraordinary discovery in one coprolite comprises a single sculptured skull element of the large bony fish Severnichthys together with two caudal vertebrae of the marine reptile Pachystropheus: did the coprolite producer, likely a fish, scavenge some flesh from the head of Sevemichthys and then bite off the tail of the reptile? Assigning coprolites to producers is difficult, but it seems that Gyrolepis was preyed on by nearly every predator. The faunas and trophic relations revealed by the coprolites show that this was a modern-style marine ecosystem, with abundant crustaceans and several species of durophagous fishes, evidence for an early stage in the Mesozoic Marine Revolution. (C) 2020 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.