Scientists examine more than 60 stegosaur teeth from Yakutia

The discoveries made it possible to understand that these herbivorous dinosaurs were sedentary, eating very solid food, changing their teeth frequently, not suffering from tooth decay, and also having more complex jaw movements than was previously thought.

The powerful, squat dinosaurs are now one of the most recognizable: they are easily recognizable by the spines on the tail and the bony plates on the back – the bony skin. Representatives of this group lived about 165-125 million years ago, during the Jurassic and early Cretaceous period. It was five to seven meters long and had a disproportionately small head. So their teeth were very small – almost a centimeter high and almost wide.

Paleontologists from St. Petersburg University worked with colleagues from: the Institute of Zoology of the Russian Academy of Sciences. Borysiak Paleontology Institute of the Russian Academy of Sciences; University of Bonn and the Institute of Diamond Geology and Precious Metals of the Siberian Branch of the Russian Academy of Sciences. Research materials were collected during a series of expeditions to the Republic of Sakha in 2012 and 2017-2019. On the banks of the Tete Stream, not far from the small town of Suntar Yakut, there is a large dinosaur area which has yet to be fully examined. In the Cretaceous period, these areas were located near the North Pole, which means they could shed light on the life of polar dinosaurs. Were the native fauna different from those in the southern regions? What is the climate here? How were animals affected by the polar day and the polar night? Scientists are trying to find answers to these questions, including by studying the teeth of ancient creatures.

“We have found animal teeth of different ages – adults and cubs alike,” said Pavel Scotchs. This indicates that polar stegosaurids are more likely to be stable: they multiplied and raised offspring in the same area throughout the year. In addition, almost all finds are eliminated: many of them have two or three sides – eroded edges from contact with adjacent teeth.

This feature led researchers to believe that second teeth in polar stegosaurids could occur quickly enough. So scientists have been studying “temporary rings” – so-called von Ebner lines, which can be used to calculate the number of days required for teeth to form. It only took Yakut stegosaurs about 95 days to complete this task, although other dinosaur species typically lasted 200 days or more. These Yakut residents are likely not to suffer from tooth decay as it takes longer to appear.

The fact that the teeth formed quickly, they quickly grinded and changed rapidly, is likely to indicate that the stegosaurus from Yakutia ate some kind of tough food. We cannot yet say with 100% certainty that we have found a polar adaptation, as there is, in principle, very little information about stegosaur teeth. However, their teeth, which are found in the southern regions, usually only have one wear surface. In short, this is a new question for ancient botanists – what hard plant that grows in polar regions that sapphire stegosaurus ate? Notice Pavel Skutschas.

Another cool thing made it possible to take a different look at the structure of the jaws of these animals: on the surface of the erosion of the teeth, scientists were able to discover small curved pits. Paleontologists used to assume that very simple jaw movements were characteristic of stegosaurids – up and down, like scissors. However, thanks to the drilling patterns on the sides, it became apparent that the jaw motions were more complex and involved a longitudinal stage.

Another finding turns out to be related to the wavy structure of enamel. It was thought to be unique to younger, late Cretaceous dinosaurs, which had complex teeth, such as hadrosurids. However, paleontologists saw this feature in stegosaurus from Yakutia and decided to examine the teeth of another dinosaur from the early Cretaceous period, a relative of Triceratops – Psittacosaurus. Turns out, this unique feature was prevalent among dinosaurs in general.

Stegosaurs is one of the most famous and popular dinosaurs that is often seen on T-shirts and various pictures. However, we still know very little about them. This research raised many new questions that can be solved without embarking on an expedition, but by studying materials that have been stored in museums for hundreds of years. We were able to show the features that polar stegosaurids possessed. But what is “normal” and “standard” stegosaurus? Pavel Skochas confirmed that this has not yet been investigated.


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