Scientists from St. Petersburg University, the Geological Institute of the Russian Academy of Sciences, the Zoological Institute of the Russian Academy of Sciences, and Charles University have studied the remains of ancient reptiles found in the territory of northern Eastern Siberia. Their conclusions showed that in the Late Cretaceous period, about 100 million years ago, the average sea water temperature was much higher and roughly corresponded to the water temperature in the modern Mediterranean Sea. This is confirmed by findings of thermophilic reptiles in the sea.
Remains of ancient reptiles were found in the valley of the Pyasina River in the north of the Krasnoyarsk Territory during expeditions organized by staff of the Geological Institute of the Russian Academy of Sciences in 2021 and 2022. The bones found belonged to plesiosaurs, mosasaurs and turtles – reptiles of the Late Cretaceous period. Plesiosaurs were reptiles that used four flippers when swimming, which is not found in modern reptiles: turtles, crocodiles, lizards and others. Ancient representatives of this class of animals reached 20 meters in length and were an important part of the Mesozoic fauna.
As a result of detailed study of remains scientists were able to establish that in the north of the West Siberian Sea, on the territory where scientists found the bone remains of marine reptiles in the Late Cretaceous, there were typical for other regions of this time representatives of two families plesiosaurs. These are the short-necked Polycotylidae and the giant long-necked Elasmosauridae. In addition to adult bones, the remains of baby plesiosaurs and fragments of ancient tortoise shells were also found.
Isotope analysis showed that the water temperature during the Upper Cretaceous period in this region was 14-16 °C. This is considerably warmer than at present. Paleontologists of St. Petersburg State University argue that this indicates that climatic conditions on the Earth are changing and that even in the northern regions the climate was much warmer in the past.
This finding is further evidence that climate change on Earth is not only happening now, but also occurred in the past. Studying past climate change can help scientists better understand how the climate will change in the future.
Paleontologists at St. Petersburg State University have extensive experience in studying ancient animals from preserved fossils. In late 2022, an international team of researchers that included specialists from St. Petersburg University excavated the remains of a prehistoric Jurassic amphibian tailed amphibian in the rocks of Scotland. It turned out to be the world’s second-oldest whole salamander skeleton ever found. Later, scientists from St. Petersburg University, along with colleagues from Spain and Portugal, studied the fossil remains of crocodilomorph Portugalosuchus found earlier in Portugal. It turned out that this species, which lived about 100 million years ago, is one of the oldest ancestors of modern crocodiles.
