Looking for copper, they found a dinosaur: what they found at a depth of 473 m in China

In Inner Mongolia, China, geologists searching for copper ores discovered fossilized bones of a dinosaur that lived about 115 million years ago in a drill core from a depth of 473.2 m. How the tail vertebrae got into the well, who they could belong to, and why the find cannot yet be called a new species are described in the Izvestia article.

How the search for copper ended with an encounter with a dinosaur

The fossil was discovered in the Guaizihu area, located in the western part of the Ingen-Edzinaki basin in Inner Mongolia. The discovery was not made during the usual paleontological excavations. Geologists studied copper ore reserves and extracted a core from the well, a long cylindrical column of rock that allows them to study the sequence of underground layers.

At a depth of 473.2 m, the drill passed through the rock in which the fossilized bones were located. The sample was assigned catalog number 208GPV01. One of the vertebrae was partially damaged by drilling, but a significant part of the material was preserved and suitable for morphological analysis.

The depth of the discovery does not mean that the dinosaur lived almost half a kilometer underground or fell into a deep hole. About 115 million years ago, its remains ended up in sediments on or near the surface. In the following million years, new deposits accumulated above the ancient layer, and the rocks themselves became compacted and could shift. As a result, the layer of bones appeared deep under the modern surface.

What is preserved in the stone cylinder

There was no complete skeleton inside the core. The scientists found a sacral rib, four bodies of tail vertebrae, six nerve arches, several transverse processes and fragments of ossified tendons.

The vertebral body is its main massive part. A neural arch is attached to it from above, forming a space for the spinal cord, and the transverse processes serve as attachment points for muscles and other tissues. Judging by the shape and proportions of the preserved elements, they belonged to the initial part of the tail, located closer to the pelvis.

The vertebrae and nerve arches did not have time to fully fuse. This indicates that the bones most likely belonged to a young individual that was still growing. For the same reason, individual structural features could be related not to belonging to a particular species, but to the age of the animal.

How the tail gave away a bird-like dinosaur

Even a few vertebrae can retain features characteristic of a particular evolutionary group. In the found animal, the transverse processes were located relatively low, near the junction of the vertebral body and the neural arch. They were thin and gradually narrowed towards the ends.

In many predatory theropods, such processes are located higher and have a wider lamellar shape. The structure of the vertebrae also differed from the features characteristic of long-necked sauropods. Another clue was the ossified tendons running along the upper side of the tail vertebrae. Similar structures strengthened the spine and were widely found in bird-like dinosaurs.

Based on the totality of the signs, the researchers attributed the find to Ornithischia, bird—like dinosaurs. This large group consisted primarily of herbivorous animals, including stegosaurs, ankylosaurs, duckbills, and horned dinosaurs. At the same time, the term "bird-like" describes the structure of the pelvis and does not mean that modern birds originated from this particular group.

Why was the find compared to Psittacosaurus?

To identify possible relatives of the animal, the scientists used geometric morphometry. They marked nine control points on the images of the tail vertebrae and compared their location in the new specimen and other avian dinosaurs.

This method allows you to evaluate not just the size of bones, but their shape and the ratio of individual parts. The data was then processed using principal component analysis, a statistical method that identifies the main directions of differences between samples. The first three components explained more than 88% of the detected shape variability.

In terms of the proportions of the vertebrae, the find turned out to be closest to psittacosaurs, the early representatives of the horned dinosaur lineage. These relatively small herbivorous animals with beaks inhabited the territory of East Asia in the Early Cretaceous period.

The remains of Psittacosaurus gobiensis have previously been found in the Bayan-Gobi formation. However, the tail vertebrae of this specimen have not been preserved, so it is impossible to directly compare the two finds. The similarity of the shape also does not prove that the discovered dinosaur really belonged to the genus Psittacosaurus. The tail vertebrae of small bird—like dinosaurs may have had a similar structure, while other parts of the skeleton — primarily the skull, limbs, and pelvis - are not available to researchers.

What kind of holes were found in the vertebrae

The most unusual feature of the specimen was the small holes on the lateral surfaces of several tail vertebrae. On the second, third, and fourth preserved vertebral bodies, they were arranged in a relatively regular sequence.

At first, the structures could resemble pneumatic holes — cavities connected to air bags. Such features are widespread in the vertebrae of theropods and sauropods, but they are usually absent in ornithischian dinosaurs.

Examination of the internal structure showed that the bones were dense and did not contain characteristic air cavities. Therefore, scientists have ruled out the pneumatic origin of the holes. Most likely, these were nutritional or neurovascular openings through which blood vessels and nerves passed during the animal's lifetime.

Separate similar structures were found in other ornithischian dinosaurs, but their such a correct arrangement on several consecutive tail vertebrae had not previously been described.

How One Find Changed the Dinosaur Map

The main significance of a fossil is not related to the discovery of a new species, but to the location of its discovery. The Bayan-Gobi formation was already known for the remains of several dinosaurs, however, almost all published finds came from the eastern part of the Ingen-Edzinaki basin.

The new specimen has become the westernmost known dinosaur find in this formation. It shows that the animals were distributed over a wider area than previous paleontological data had confirmed.

The fauna of Bayan Gobi is similar to the fauna of almost the same age deposits of western Liaoning. Scientists assume that both territories could be part of the distribution area of the Zhehe biota, a rich community of plants and animals that existed in East Asia in the Early Cretaceous period.

The discovery from the drilling core expands the geography of the famous Bayan-Gobi dinosaurs, but at the same time shows how incomplete the paleontological record of the region remains. If the fossil was discovered by chance during geological drilling, there may be other remains in the western part of the basin that conventional excavations have not yet reached.