The trophic structure of the biota of the Peterborough Member, Oxford Clay Formation (Jurassic), UK

Abstract

The Peterborough Member of the Oxford Clay Formation is organic-rich and contains an abundance of well-preserved vertebrate and invertebrate fossils. A high nutrient input supported a diverse biota. Phytoplankton was exceptionally abundant in the surface water, and formed the basis for an intricate food web in both surface and bottom waters. Top predators include some of the largest known Mesozoic marine reptiles. A giant teleost fish was analogous to modern filter feeding whales and sharks. Benthic faunas depended on organic matter sinking from surface waters, and two parallel food webs may have existed. Trophic partitioning allowed the higher level predators to become diverse, especially the plesiosaurs. Productivity was high in the surface waters, probably high in the mid-water column, and high on the sea floor at times, although benthic diversity may have been reduced due to substrate consistency and/or dysoxia. Bacterial activity within the sediment was also intense. The contribution of organic material to the sea floor was high, but heterotrophic reworking probably reduced the abundance considerably during early diagenesis. A decrease in organic carbon content in the Upper Callovian and Lower Oxfordian parts of the Oxford Clay Formation parallels a decreasing abundance of vertebrate fossils.

Brittle stars from the British Oxford Clay: unexpected ophiuroid diversity on Jurassic sublittoral mud bottoms

“…Apart from unpublished observations and logs compiled by Dr. N. Hollingworth, the Oxford Clay at Coln Quarry is poorly known. Much about this locality is therefore here inferred by comparison with the better-known type locality for the Peterborough Member, near Peterborough, Bedfordshire, which was heavily studied in the early 1990s (e.g., Martill, 1991, 1994;MacQuaker, 1994;Martill et al, 1994). The Peterborough Member at Coln is composed of a richly fossiliferous series of shales and calcareous mudstones, dominated by the ammonite Kosmoceras and by bivalves and gastropods (N. Hollingworth, personal communication, 2015) although contextual material collected (by J. Whyman, 2008) along with the ophiuroids at Coln Quarry includes teleost and shark teeth, short sections of isocrinid pluricolumnals, crustaceans, brachiopods, and belemnites.…”

“…Land probably lay close by, to the northeast, where marginal marine facies are seen in the East Midlands (Cox and Sumbler, 2002). The bottom waters of the sea are suspected to have been euroxic, with the high carbon content attributed to high Ewin and Thuy-Brittle stars from the British Oxford Clay productivity (MacQuaker, 1994;Martill et al, 1994) as at the type locality for the Peterborough member.…”

Stable isotope (δ18O and δ13C) sclerochronology of Callovian (Middle Jurassic) bivalves (Gryphaea (Bilobissa) dilobotes) and belemnites (Cylindroteuthis puzosiana) from the Peterborough Member of the Oxford Clay Formation (Cambridgeshire, England): Evidence of palaeoclimate, water depth and belemnite behaviour

“…Whilst fossil evidence indicates that surface and near-surface waters supported a diverse marine ecosystem during the deposition of the Peterborough Member, it has been argued that benthic life may have been periodically restricted by low oxygen levels Belin and Kenig, 1994;Hudson and Martill, 1994;Macquaker, 1994;Martill et al, 1994;Kenig et al, 2004). Lower horizons within the Peterborough Member show such changes particularly well, with organic-rich shales, such as bed 10, deposited when the seabed was possibly euxinic, and shell beds, such as beds 9 and 11 (Fig.…”

First direct evidence of a vertebrate three-level trophic chain in the fossil record

“…Among fossil organisms, inferences of trophic interactions are generally based on indirect evidence such as tooth morphologies, tooth marks produced by predators or scavengers and coprolites, whereas gut contents and softbodied structures are rarely preserved (Martill et al 1994;Cavin 1996;Richter & Baszio 2001;McAllister 2003). Moreover, empirical behavioural data offossil predator-prey relationships are generally limited to isolated cases of single ingested prey items and most of these finds are generally considered to represent isolated occurrences without or with little potential for deeper insights into past trophic organizations or community structures (Maisey 1994).…”