A dinosaur from Madagascar was found to have a two-month cycle of tooth change

A dinosaur from Madagascar was found to have a two-month cycle of tooth change

Scientists have discovered that a predatory dinosaur living in Madagascar changed teeth every two months. Compared to his immediate family, it is very fast, the difference is 2 to 14 times. Apparently, this is due to the fact that it gnawed a lot of the bones of the victims, because of which the teeth quickly wore out.

The speed of tooth changes is associated with many factors – ranging from the type of food and diet to the habitat and size of the animal. It is known, for example, that in dinosaurs the rate of formation of teeth and the speed of their change was inversely proportional to their size, that is, the smaller the tooth, the longer it grew. This means, apparently, that the growth rate depended primarily not on the size of the tooth or the dinosaur itself, but on some internal reasons.

Such a reason could be the rate of enamel wear, which is directly dependent on the diet. It is believed that Herbivorous dinosaurs erased teeth faster than predators, and therefore changed more often. Twenty years have passed since this hypothesis emerged, during which scientists have discovered many new fossil species and collected many new samples.

A team of scientists led by Eric Lund from Ohio university decided to take advantage of the new data and trace evolutionary strategies for the rate of tooth growth. They scanned 52 teeth of Majungasaurus, a small predatory dinosaur from Madagascar, as well as his relatively close relatives, Allosaurus and Ceratosaurus. The researchers then cut some of the teeth to determine the thickness of the growth lines on the tooth enamel – the substances in it are deposited regularly, like layers of annual rings in trees, but not every year, but every day.

The thickness of the growth lines of all dinosaurs turned out to be approximately the same – 14-23 micrometres, but the number of lines in one tooth varied. Comparing the length and age of the teeth, the researchers derived the average shift time – for Majungasaurus it was only 56 days, while for its relatives – 104 and 107.

The scientists then compared this growth rate with the already known speeds for other dinosaurs with different types of food. They found that for the predatory animal Majungasaurus changed teeth unexpectedly quickly: his closest relatives had a generation of teeth living twice as long, and a little more distant Tyrannosaurus – as much as 14 times longer, 777 days.

The speed of tooth change at Mayungasaurus was comparable to herbivorous dinosaurs. Researchers attribute this to the fact that the Majungasaurus, apparently, ate, among other things, bones and bone marrow, which wore out its teeth more than meat.

Above: the evolutionary dinosaur tree and the lifetime of one generation of teeth. Red is the shortest, green is the intermediate, blue is the longest. Bottom: distribution of tooth change speed depending on the size and type of food: blue – predatory, yellow – herbivorous dinosaurs.
D’Emic / PLOS One, 2019

Thus, the hypothesis that the type of nutrition determines the speed of the change of teeth was confirmed and supplemented by exceptions and refinements. But the researchers did not find any dependence on body weight, as well as their predecessors.

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