Jurassic calamari: amazing fossil proves that flying reptiles preyed on squid

An incredible fossil brought to light in a new research paper reveals the feeding habits of extinct flying reptiles. The beautifully preserved specimen is a Jurassic squid which has a broken pterosaur tooth actually embedded in its body – evidence of a violent interspecies struggle that took place 150 million years ago,

Studying the dietary habits of prehistoric creatures is not an easy task. Fossilised food remnants are sometimes found inside the stomachs of particularly well preserved specimens, or inside coprolites (fossilised excrement). But these tend to be hard, indigestible body parts like bones and shells, so may be unrepresentative of the animal’s overall diet.

The specimen described in the journal Scientific Reports is a 29cm long cephalopod called Plesioteuthis subovata. It looked more like a present day cuttlefish than a squid, with short arms and a rigid, bonelike structure (called a gladius) running along inside the body or mantle. This particular specimen, at the University of Zurich, is unique for two reasons: the clearly visible, dark ink sac – and a 2cm long tooth sticking into the creature’s back.

Jordan Bestwick, a palaeobiologist in the School of Geography, Geology and the Environment at the University of Leicester, worked with colleagues from Germany and Switzerland to identify this tooth. After discounting possible marine predators such as pliosaurs, ichthyosaurs, sharks and crocodiles, the team concluded that it belonged to the flying reptile Rhamphorhynchus.

With a wingspan of up to 1.8 metres, Rhamphorhynchus is the largest known pterosaur from that period, comparable in size to a modern day gannet. It lived around bodies of water, feeding on fish like modern seabirds. However, this is the first evidence of Rhamphorhynchus preying on Plesioteuthis. It is unclear whether this squid died from the unsuccessful attack or whether it survived for some time with the tooth lodged in its body until it died from other causes. In either case, the creature’s body sank down to the silt bed where low oxygen levels helped to preserve it in stunning detail.

One possibility which had to be considered and eliminated was that the reptile tooth may have become embedded in the squid after the latter had died. It would have taken considerable force to embed the tooth into the squid’s muscular mantle, which might have been possible in a strong current. This fossil however was found in an area of Germany called the Solnhofen Archipelago, which in the Jurassic period was a collection of placid lagoons. It is also unlikely that this was an incidence of scavenging: dead cephalopods very quickly break down so the squid must have rapidly sunk after death in order to retain its overall shape so well. (Besides which, even the most inept predator should be able to pick up a dead squid without breaking a tooth!)

The most plausible explanation is that a patrolling Rhamphorhynchus, flying low over the surface, made a grab for an unwary Plesioteuthis which fought back, eventually dropping back into the water with a broken tooth as a trophy of the reptile-vs-mollusc tussle.

“We are confident that Rhamphorhynchus largely fed on fish based on several specimens that have fish scales and bones preserved within their throats and stomachs,” said Jordan Bestwick, co-author of the study. “However, this is the first evidence that the Rhamphorhynchus diet also included squid.

“Other Plesioteuthis specimens have been described with remains of fish and/or other squid preserved in their stomachs which highlights that Plesioteuthis was itself a predator. That our new specimen shows that the squid was also prey indicates that Plesioteuthis was a mesopredator in Jurassic seas, similar to modern day jackals in the African savannah.”

Dr David Unwin, Associate Professor of Museum Studies at the University of Leicester and a noted expert on pterosaurs, said: “Catching squid while on the wing is difficult, demanding and dangerous, and provides yet further evidence of pterosaurs' excellent flight capabilities. This fossil association and other finds from the same deposits reveal the uniquely intricate complexity of Late Jurassic ecosystems.”

Back in 2012 a fossil was discovered of a particularly unlucky Rhamphorhynchus entangled within the jaws of a large, predatory fish called Aspidorhynchus. This newly described fossil therefore reveals a four-level chain of predation in and above the waters of the prehistoric lagoon. Small fish were preyed upon by squid who were, in turn, hunted by flying reptiles which were also food for larger fish. This is a fascinating insight into an environment 150 million years in the past.

• ‘Pterosaurs ate soft-bodied cephalopods (Coleoidea)’ DOI:10.1038/s41598-020-57731-2