A fish-eat-fish world: Fossilised faeces unearthed in Gloucestershire reveals England’s sea life was mostly carnivorous 200 million years ago
- University of Bristol researchers found the fossils near Chipping Sodbury
- CT scans and analysis shows many of them contain bones and scales
- Researchers say this is proof that almost all fish in English waters 200 million years ago were carnivorous
Analysis of fossilised fish faeces from ancient seabeds in Gloucestershire reveals the vicious dynamics of the British waters 200 million years ago.
Researchers found the ancient faeces, known as coprolites, in the Rhaetian bone bed near Chipping Sodbury in south Gloucestershire.
They discovered that almost all animals living in the water, including sharks, fish and lobsters, were carnivorous.
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Pictured left, a fossilised piece of fish faeces and right, the CT scan showing various fish scales found inside
CT scan of coprolite specimen, BRSMG Cf15546, in different views, showing tuberculated bone (blue) from a fish skull, and two vertebrae from the tail of the marine reptile Pachystropheus, in yellow and green
Marie Cueille, a visiting student at the University of Bristol’s School of Earth Sciences, said: ‘The ancient fishes and sharks of the Rhaetian seas were nearly all carnivores.
‘Their coprolites contain scales, teeth, and bones, and these tell us who was eating whom.
‘In fact, all the fish seem to have been snapping at each other, although the general rule of the sea probably applied: if it’s smaller than you, eat it.’
The CT scans of one tiny coprolite, measuring a centimetre or so in length, contained only three bones.
Images taken of the inside of the fossil reveal one was a fragment of skull from another fish, while two were vertebrae from a marine reptile called Pachystropheus.
Pictured, various smooth-surfaced coprolite morphs analysed as part of the study
Pictured, coprolites which were found in Gloucestershire and categorised as being in the ‘spiral’ morph due to their shape
The range of coprolites discovered includes crabs and lobsters and allows the researchers to create a food web. The marine reptiles and sharks were feeding on smaller fishes, which in turn fed on even smaller fishes and lobsters
Dr Chris Duffin says the shark that produced this faeces likely ate the head of an already dead fish and after it had scavenged this meal ‘snapped at a Pachystropheus swimming by and had a chunk of its tail’.
However, because the bones were almost entirely in tact in the faeces, it meant there was little in the way of digestion.
Some modern-day animals, such as some sharks and crocodiles, also eat animals whole, but these animals have potent stomach acid to break down the bones, ensuring the act of defecating is as smooth as possible.
However, 200 million years ago, evolution had not yet brought this useful adaptation to Britain.
‘These ancient fishes must have had a painful time passing their faeces which were absolutely bristling with relatively large chunks of bone,’ says Professor Mike Benton, who co-supervised the study.
The range of coprolites discovered includes crabs and lobsters for the first time and allows researchers to create a food web.
The marine reptiles and sharks were feeding on smaller fishes, which in turn fed on even smaller fishes and lobsters.
Some also had crushing teeth adapted to feeding on oysters and other molluscs.
The full findings are available in the journal Proceedings of the Geologists’ Association.