Fish – or squid on the menu: In what is now southern Germany, certain species of pterosaurs apparently hunted different marine animals 182 million years ago. This emerges from fossilized stomach contents that researchers discovered in two pterosaur fossils. The evidence of the squid meal is particularly significant because it is the first clear evidence of this food source in pterosaurs. The find also provides evidence that the winged squid hunters were nocturnal, say the researchers.
What did prehistoric animals once feed on? Paleontologists can often only infer diets indirectly based on characteristics such as body shape and dental structures. But in rare cases there is also clear evidence: in some fossils, traces of the former stomach contents have been preserved. Certain remains sometimes make it possible to precisely identify the animal’s last meal. In the case of pterosaurs, however, such finds are rare despite the extensive fossil record. This is probably because they digested relatively quickly so as not to burden themselves with heavy bellies while flying. This is why fossilized stomach contents have only been found in a few pterosaurs. They showed that at least some representatives of the late Jurassic period consumed fish.
The study by researchers led by Samuel Cooper from the State Museum of Natural History Stuttgart, on the other hand, sheds light on the diet of representatives of winged lizards from the early Jurassic for the first time. The discovery came about as part of renewed examinations of fossils from the museum’s collection, which come from a special rock formation in the region around Holzmaden in Baden-Württemberg: The approximately 182 million year old Posidonia slate has preserved fossils of various animals that were then in lived in the region characterized by a subtropical sea.
The last meal of two pterosaurs
As the researchers report, in the course of re-examining the museum holdings, they came across fossilized stomach contents in two fossils of the pterosaur species Dorygnathus and Campylognathoides. In the case of Dorygnathus, closer analysis of the remains then revealed fish bones in the material. This is now evidence of this prey from a pterosaur from the early Jurassic period. However, the findings with the second fossil were more surprising: In Campylognathoides, the researchers found small hooks in the fossilized stomach contents instead of bones. As they explain, these are clearly the remains of an eaten squid. In some species of cephalopods, these structures are located on the tentacles.
By comparing the characteristics of the ticks, the researchers were also able to assign them to a specific representative of the squid, whose fossils are often found in the Posidonia shale. The last meal of the Campylognathoides pterosaur was a Clarkeiteuthis squid. According to the researchers, there has so far only been one indirect indication of the consumption of squid by pterosaurs: a tooth of a pterosaur was found in the fossil of a cephalopod. But the current find is now the first clear evidence of the consumption of squid, say the researchers.
Night squid hunting?
But they also see an important result in the combination with the second find. The different diet suggests that the two pterosaur species specialized in different diets. Further evidence for this is that they had different dental and skull characteristics, which were probably adapted to their respective diets. “This allowed Dorygnathus and Campylognathoides to coexist in the same habitat without much competition for food between these two species,” says Cooper.
As the researchers finally report, the evidence of squid hunting provides another interesting clue. As they explain, it can be assumed that the Clarkeiteuthis squids, like their modern relatives, only migrated to the surface of the sea at night. Accordingly, Campylognathoides could have been a nocturnal hunter that flew over the ocean surfaces in the twilight and picked up its prey. It is also fitting that this pterosaur had very large eye sockets compared to Dorygnathus, say the researchers. “However, our assumption of a nocturnal lifestyle in Campylognathoides still needs to be further tested,” the authors conclude.
Source: State Museum of Natural History Stuttgart, specialist article: Journal of Vertebrate Paleontology, doi: 10.1080/02724634.2024.2403577