Survived despite injury: An around 180 million year old marine dinosaur fossil from near Bayreuth bears witness to a successful fight for survival in the prehistoric sea. The well-preserved relics of the 6.60 meter long ichthyosaur reveal that it suffered serious injuries to a pectoral fin and lower jaw. However, the ichthyosaur survived – and apparently adapted to its permanent disability, as evidenced by wear marks on its teeth. The fossil find is also one of the youngest representatives of the Temnodontosaurus genus in southern Germany, as the paleontologists report.
The ichthyosaurs were the rulers of the Jurassic and Cretaceous seas. These dolphin-like reptiles, up to 25 meters long, were among the top predators of their time. Fossil analysis suggests that these marine dinosaurs were good swimmers and could hunt and eat even large prey. Ichthyosaurs were also present in large numbers in what is now Central Europe, as fossil finds, especially from southern Germany, show. During the Jurassic period, around 201 to 145 million years ago, this region was largely covered by a shallow, warm, tropical sea.
Relics of a 6.60 meter long ichthyosaur
A new ichthyosaur fossil from near Bayreuth now provides further insight into the diversity and life of these marine dinosaurs in the Bavarian Jurassic Sea. The exceptionally well-preserved relic was discovered in the Mistelgau clay pit, where numerous marine dinosaur fossils from the early Jurassic have been found since the 1990s. “This site represents a unique collection of marine reptiles from the end of the Lower Jurassic,” explain Stefan Eggmaier and Ulrike Albert from the Upper Franconian Prehistoric World Museum in Bayreuth.
The two paleontologists examined a 180-million-year-old ichthyosaur fossil from Mistelgau in more detail, which stands out in several respects. The relics discovered in 2012 include parts of the skull and lower jaw, the shoulder girdle, the front fins, the spine and over 100 teeth. The good state of preservation provides detailed insights into previously rarely preserved anatomical structures, such as the area of the palate, eyes and fins. Based on these characteristics, the team assigns this ichthyosaur to the genus Temnodontosaurus. During its lifetime, the animal was probably around 6.60 meters long.
Marine dinosaur suffered serious injuries…
A first special feature of the fossil is its age: “Our Temnodontosaurus fossil is one of the youngest finds of this ichthyosaur genus,” reports Albert. “So far we know their representatives mainly from older finds such as the Posidonia slate from Holzmaden. The find from Mistelgau now shows that these large marine reptiles survived in the southwest German sea basin longer than previously documented.”
The second peculiarity are traces of severe but healed injuries to the shoulder joint and jaw joint of the marine dinosaur. They caused extensive bone adhesions and stiffening. “These severe wounds must have caused severe pain,” explain the paleontologists. “They are also likely to have significantly restricted the animal’s ability to catch prey.” This meant that the ichthyosaur was no longer able to properly move its right pectoral fin, which is normally essential for changing direction and steering. His lower jaw was also weakened and less mobile due to the injury.
…but lived on
Despite these serious injuries, the marine dinosaur was able to survive, as the fossil also reveals. There are atypical signs of wear on the teeth and skeleton, which indicate that the ichthyosaur has adapted to its disabilities. An example of this are unusually deep notches in the left clavicle, which could have been caused by excessive, compensatory use of the left pectoral fin, as Eggmaier and Albert report.
“All of the animal’s teeth also show severe wear, which is not yet known from other representatives of the temnodontosaurs,” said the paleontologists. They therefore suspect that the marine dinosaur had to change its diet because of the jaw injury: instead of the usual larger prey, the injured animal could have hunted and eaten more cephalopods. Their hard beaks and possibly sandy stomach contents could have worn down their teeth more than normal.
Stomach stones are rare in ichthyosaurs
Another, third special feature of the marine dinosaur from Mistelgau are stomach stones discovered in its abdominal cavity. Such stones are usually found in birds, some dinosaurs and crocodiles. They specifically swallow smaller stones as a digestive aid, for example to grind down swallowed food. However, such stomach stones are a real rarity for ichthyosaurs: “Such gastroliths have only been found three times so far,” write Eggmaier and Albert.
How and why the marine dinosaur, which was disabled due to its injuries, ingested the stomach stones is still unclear. However, it is conceivable that he swallowed the stones because he had limited use of his jaw and perhaps also because he ate prey that contained such stones.
Source: Stefan Eggmaier and Ulrike Albert (Urwelt-Museum Oberfranken, Bayreuth), Zitteliana, 2026; doi: 10.3897/zitteliana.100.172724