Wednesday November 19, 2025
Phys —
In a study appearing in Fossil Record, researchers Martin Ebert and Martina Kölbl-Ebert analyzed the remains of a unique fossil type: the decapitated head of Aspidorhynchus, with its gastrointestinal tract (guts) still attached. These extraordinary fossils are likely unique in the fossil record, revealing not only what these ancient predators ate but also how they were decapitated.
The fossil fish Aspidorhynchus
The Aspidorhynchus fossils examined were recovered from the Solnhofen Archipelago located in Bavaria, Germany. The site, known for its exceptional preservation of fossils dating to the Late Jurassic period, was once home to Aspidorhynchus. This was a large predatory fish that comprised approximately 4% of all known fish fauna in the area. Growing up to 1 meter long, the fossil fish is characterized by a long, spear-like upper jaw, similar to those of modern marlins or swordfish.
“Judging from their body shape and fin morphology, it is highly likely that Aspidorhynchus was a pursuit predator. From its stomach contents, we know that it fed mainly on small teleosts (Orthogonicleithridae). There is evidence that the Orthogonicleithridae were schooling fish, and it is assumed that Aspidorhynchus, with its long upper jaw, may have used a hunting technique similar to modern swordfish,” explained Dr. Ebert.
A total of 343 Aspidorhynchus specimens were analyzed, of which 16% were found to have been completely decapitated with only their guts still attached. This provided an opportunity to examine the prey species of Aspidorhynchus unobscured by the remaining fish body.
All previous descriptions of the gut contents of Aspidorhynchus had been made using complete fish, limiting some of the observations that could be made due to the specimen being covered in thick ganoid scales.
Gut contents of the Aspidorhynchus
It was found that several specimens contained the remains of small juvenile teleost (bony) fish, which likely would have easily been swallowed whole by the Aspidorhynchus. Although other specimens, such as GZG.RF.999, indicated that they sometimes targeted larger prey. GZG.RF.999 was approximately 56 cm long, yet it had managed to swallow an Allothrissops that was 16 cm long.
Additionally, some unusual gut contents were found, including specimen GZG.RF.998, which had a small ganoin-scaled fish stuck in its mouth, rendering it unable to absorb enough oxygen and effectively drowning. A similar phenomenon can be observed in modern fish when they swallow prey too large for them.
Finally, a specimen was observed with a crustacean of the species Knebelia schuberti in its stomach. Crustaceans are not known to have formed part of Aspidorhynchus’s diet, and thus the researchers are uncertain as to how or why this Knebelia was fed upon.
The hunters become hunted
While the gut remains revealed unique insights into the feeding ecologies of Aspidorhynchus, the research also revealed insights into how these fish were decapitated.
The researcher proposes that these specimens were predated upon by large, grabber predators. Grabber predators, unlike Aspidorhynchus, which swallow prey whole, typically grab their prey by the tail, using violent headshakes and bites to detach the head before consuming the more nutritious and easier-to-process body portions. This feeding strategy would explain why the Aspidorhynchus fish were found as an isolated skull, with their guts still attached.
Additionally, a weakness in the anatomy of the Aspidorhynchus may have facilitated this predation, namely the incompletely ossified vertebral centra, which created a weakness at the junction between the skull and the body, making decapitation during violent predation easier.
If this decapitation occurred at a specific location near the head, it would also result in the internal intestines being detached alongside the skull. According to David Bellwood in the study, during scientific gut content analysis, one should “cut the head at the dorsal connection with the spine, then pull the head off, and the guts come with it.”
It is likely the predators responsible for the decapitation were large ichthyosaurs, marine crocodiles, and Pliosaurs, explained Dr. Ebert, “In the Solnhofen archipelago, we know of 2–4 m long Ichthyosaurus, marine crocodiles, and even larger Pliosaurs, for whom this was certainly no problem.”
The study provides insights into the feeding ecology and predation of Aspidorhynchidae while also highlighting the exceptional preservation capabilities of the Solnhofen Archipelago.