Protopyrate, or Helicoprion (Helicoprion bessonovi), is a giant (up to 12 meters long) shark that lived on our planet about 300 million years ago.
The history of the discovery of helicopryon began with a find made by the inspector of public schools in Krasnoufimsky district, Mr. A. G. Bessonov, who in 1897 discovered in one of the quarries located on the slope of Divya Gora near the city of Krasnoufimsk, a kind of mysterious fossil. In its spiral shape, it resembled the shells of the cephalopods of the goniatites, which were found in abundance in the same layers. However, hefty teeth sat on the mysterious spiral.
Upper rolling jaw version
A. G. Bessonov, after reflecting on the find, sent its photograph to the Academy of Sciences, a geologist famous throughout Russia and widely known abroad, academician A. P. Karpinsky.
Various fossils of the jaws of hylicoprions
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The academician puzzled over the images for a long time and came to the conclusion that in front of him was an image of the jaw of a huge extinct shark (the presence of teeth played the main role in making this decision). Karpinsky told the inquisitive inspector that as a reward for the find, the shark was named Bessonov's helicopryon.
The strange fossil has raised many questions in the scientific community. It was not clear if it was the upper jaw or the lower one. Some even suggested that the "spiral" was not the jaw at all, but a growth on the anterior dorsal or even caudal fin. But the presence of teeth refuted these assumptions.
Soon, new finds were made, and then it turned out that it could be twisted in a spiral like the upper jaw of a helicopryon. and the bottom. And sometimes both at once. The only thing that is not clear - why did sharks need this "circular saw" at all?
Of course, the protopirate used his circular saw jaw to get food for himself. But how? Tore the bottom? Scraping shellfish off stones? Maybe the shark burst into shoals of small fish, crumbled them with its saw to the right and left, and only then sat down with the remains of those who were unlucky? Scientists have not found a definite answer to this question.
It is possible that helicopryon and its related forms ate ammonite mollusks. In this case, the spiral made it possible, for example, to cut off the tentacles, and the jaw teeth to crush the shells. But, possibly, helicopryons fed on fish (the spiral inflicted serious wounds on the victim, and the rest of the teeth allowed them to eat thick-scale prey).
Remains of helicopryons are known from the Early Permian of the Urals, Japan, Australia, Spitsbergen, and the USA. The most recent (2008) hypothesis put forward by the American paleontologist R. Prudy suggests the placement of a spiral in the pharyngeal region. Proudi suggested that the spiral represents the pharyngeal teeth, while it was not visible from the outside. He substantiates his assumption by the absence of traces of wear on the teeth, as well as by considerations of hydrodynamics.