Two paleontologists from the University of Bonn in Germany analyzed previously unclassified fossil bones, possibly belonging to ichthyosaurs, and discovered a number of unusual features in their structure.

Samuel Stutchbury, a 19th-century English naturalist and geologist, once discovered large fragments of fossil bones in the Aust Cliff bone bed in the Bristol area. But it was not possible to convincingly attribute them to a specific animal. Various representatives of tetrapods have already been found in similar geological layers. After Stutchbury’s discovery, a debate arose in the paleontology community: To whom do the discovered pieces belong?

There were several assumptions. The “dinosaur hypothesis” has existed for a long time. It consisted in the fact that the fossil fragments were a sword or fragments of the femur or tibia of the stegosaurus. However, this version was later contradicted by the geological record and typical histological features: the structure of the bones found did not correspond to the structure of sauropods.

According to another hypothesis, the pieces found in the 19th century belonged to a giant ichthyosaur. Following Stutchbury’s article, bones thought to belong to a giant marine predator were unearthed in France, Germany and Switzerland. The version was based on a comparison of a similar find in Great Britain with the described skeleton of an ichthyosaur from North America, whose length was estimated at 21 meters.

Two paleontologists from the University of Bonn (Germany) solved the mystery of “declassified” bones whose owners could not be identified for more than 150 years. They compared in detail samples of many of the European bone fragments that probably belonged to giant ichthyosaurs with other terrestrial and aquatic tetrapods. The researchers also performed osteohistological analysis of the samples. The results of the scientific study are published in the journal. PeerJ.

The authors examined thin sections of fossilized bones with the aid of a polarizing light microscope; They evaluated the porosity of the samples and the ratio of vein area to mineralized area. They identified four features in the structure of the fragments: strictly longitudinal vascular structure, closely spaced growth marks, many secondary osteons within primary osteons (these are cylindrical formations with bone plates inside).

The fourth feature – the structure of the internal fibers, which turned out to be rough and oriented not longitudinally, but like a web or rods – rejected the “dinosaur hypothesis” and showed that the examined fragments were the bones of the lower jaw of an ichthyosaurus. . Additionally, the researchers compared the histology of these bones with those of other Triassic animals (archosaurs, dicynodonts, phytosaurs, and others), but did not find any relationship between them.

According to the authors of the article, the determined properties were similar to ossified tendons of high strength. Based on this, scientists hypothesized that the unusual structure of internal bone fibers allowed the large jaws of ichthyosaurs to withstand a normal meal or, as paleontologists assume, the rams of other marine animals. At the same time, the bones had to remain quite flexible and grow quickly.