2008-08-21 – Campo di caccia per belemniti (Belemnotheutis), Giurassico, Gran Bretagna

‘Calamari killing field’ fossils found in sea that covered middle England

By Paul Eccleston

Last Updated: 4:01pm BST 21/08/2008

 

 

Scientists have unearthed evidence of a Jurassic killing field in a sea that once covered a wide area of middle England. Fish fossil is oldest to have ‘fun sex’ Dinosaur professor to lure tourists with fossils Missing link fossil settles frog evolution debate Fossil evidence points to cataclysmic events which would have killed millions of fish and other soft-bodied marine creatures.

Complete specimen of the largely soft-bodied squid-like creature Belemnotheutis clasping a fish in its arms; collected in the mid-nineteenth century

 In turbulent environmental conditions 160m years ago the waters may have been poisoned by a volcanic eruption or suddenly deprived of oxygen wiping out much of the sea life.

Dramatic and newly discovered fossil images reveal how voracious squid-like creatures were lured to the area to feed on the huge numbers of dead fish. Some held prey in their tentacles at the very moment they also succumbed in the deadly waters.

The scientists believe it developed into a predator-trap in which victims acted as a draw on new shoals entering the area before they were themselves overcome in a perpetual deadly cycle.

The Jurassic Oxford Clay provided almost unique conditions for the preservation of ammonites, fish and crustaceans but became world famous for squid-like cephalopods and belemnites with fossilized soft-parts.

There are only a handful of areas in the world where creatures have been preserved in this way.

Soft-bodied creatures such as worms and jellyfish probably dominated marine ecosystems at the time but they rarely show up in the fossil record because they decompose and vanish. Much more is known about creatures with decay-resistant hard-parts, such as bones, teeth or shells.

But in some areas – such as the rediscovered site in Wiltshire which the ancient sea once covered – the normal process of decay didn’t happen and outlines of anatomy – even soft flesh areas such as gut, muscle and eye – were perfectly preserved partly because of the chemical make-up of the sediment.

The areas are known as Fossil Lagerstätten and provide a much more accurate picture of ancient ecosystems.

The site – discovered by chance as the Great Western Railway was constructed in the 1840s – provided a fossil bonanza for palaeontologists.

Many of the best fossils were removed and taken to London for safety but ironically were destroyed in German air raids a century later.

Because of its rich resources the location of the site was jealously guarded by a local carpenter who was an amateur fossil hunter. He collected many of the samples but provided misleading information about the exact location of the site and took his secret to the grave.

Over time the railways cuttings became overgrown and flooded and were eventually lost.

But now they have been rediscovered by scientists from the British Geological Society (BGS) and their work will form part of The Fossil Detectives an eight-part series for BBC FOUR, funded by The Open University (OU) and produced by the BBC’s Natural History Unit, BBC TV series.

In the programmes Dr Hermione Cockburn, an associate lecturer with the OU, leads a team of fossil experts and geologists around Britain looking for the best fossil treasures and mysteries.

Celebrity fossil hunters such as Sir David Attenborough, musician and writer Alex James, and singer/songwriter Billy Bragg also make appearances.

Prior to the new excavation it was unknown whether all of the fossil squid collected in the 1840s had come from one or more level but it showed for the first time that the squid were concentrated at several different levels proving that mass mortality events repeatedly hit the area killing vast numbers of the squid and fish.

The prehistoric shallow sea covered an area from Lincolnshire to Dorset and was bordered by coastal swamps where dinosaurs would have roamed.

Dr Phil Wilby of the BGS described the area as ‘a calamari killing field’.

He said it would have been an unstable environment in which the bottom waters continually switched from being able to support life to becoming hostile to life with fluctuations in oxygen level a constant threat.

“As a preservation site for soft-bodied creatures it is as good as it comes and is recognised by palaeontologists the world over. What we don’t yet know what triggered the preservation. It may be that there was a build up of phosphorous in the sediment and when the creatures died and sank into it the chemical structure was changed,” he said.

The Fossil Detectives is being shown on BBC Four beginning on Thursday August 21.