Water magazine No. 7 Helicoprion

Helicoprion is an extinct genus of cartilaginous fish from the Carboniferous and Permian periods. The complete remains of the helicoprion have not yet been found. It is not entirely clear exactly how the spiral grew. Initially, it was believed that the largest teeth were the newest and, accordingly, were located closer to the place of attachment of the "spiral" on the jaw (the lower jaw could be bent down). Academician L. P. Tatarinov considered this unlikely — most likely, the teeth grew from the center of the spiral, and the smallest teeth are the youngest. This is confirmed by the direction of the "spurs" on the teeth — in all related species they are directed backwards. As they grew, the larger old teeth were pushed forward and shed. The spiral was "packed" into the symphysis cavity and only large "old" teeth were visible from the outside. The dental spiral of helicoprion is one of the most mysterious fossils of the Permian period. It consists of a series of sharp teeth-blades having a common spiral-rolled root with 80-190 teeth. The diameter of the spiral of the typical type of helicoprion reached 25 cm. This assumes the length of the entire fish is about 2-3 meters. Spirals up to 90 cm in diameter are described in the literature. The length of their owner could reach up to 9-12 meters. These fish are not sharks in the modern sense of the word, but representatives of primitive cartilaginous, close to the ancestors of chimeras and sharks.

Helicoprion Dental Spiral 

Comparison of the growth of the dental spiral of a helicoprion with the jaw of a shark: in helicoprions, old teeth were preserved in a spiral, in sharks they fall out (FT — functioning teeth, NT — new, not yet functioning teeth). A is the dental spiral of the helicoprion, B is the jaw of a shark, C, D is a schematic representation of the position of the spiral in the jaw of the helicoprion. CR — skull; EC, JC, LBC — cartilage; OE — epithelium of the oral cavity; PQ — palatine-squared cartilage (upper jaw); MC — Meckel's cartilage (lower jaw); RT — tooth root; TW — dental spiral.  

  Options for reconstructing the appearance of the Helicopter, starting from the earliest (top left — Karpinski reconstruction) to later (bottom left), the most modern reconstruction is shown on the right.