Corallian (Upper Jurassic) trace fossils from England and Normandy

Using the trophic group approach, seventeen macroinvertebrate and one trace-fossil association have been described quantitatively, using 170 bulk collections, from the Middle and Upper Oxfordian of Normandy, Dorset, Oxfordshire, and Yorkshire. Most associations are dominated by bivalves and gastropods, whilst echinoderms and brachiopods are less important. Sedimentary and biostratinomic evidence indicate that, with few exceptions, the associations are the autochthonous or parautochthonous relics of ancient communities. The taphonomy and environments of each association have been discussed and comparisons have been drawn with other Mesozoic benthic associations. The highly abundant oyster Nanogyra nana is interpreted as an opportunistic species and the abundance of the pectinid Chlamys is regarded as a feature typical of Corallian faunas. The scarcity of brachiopods, which are also uncommon elements in many other Jurassic and Cretaceous benthic faunas, is thought to be related to the short dispersal time of their larvae, combined with competition by bivalves and changing environments.