Helicoprion

Helicoprion is an extinct genus of shark-like fishes that lived during the Devonian before going extinct in the Early Triassic Period, long before the emergence of dinosaurs. They’re presented in the fossil records by petrified whorls of teeth that look like a buzz-saw. This is the only part of this cartilaginous fish preserved in fossil records, making it difficult for scientists to describe the appearance and features of this fish. Helicoprion is a relative of the chimaeras, a type of ratfish found in deep waters all over the world. 

Description and Size

Helicoprion is a genus of poorly known fossil fish that lived back in the Permian. The modification of its lower jaw into a spirally arranged cluster of teeth (teeth whorls) is the fish’s most prominent feature. In fact, the fish is named after the circular teeth whorls. The genus name translates as “spiral saw.”

While the curled-up teeth are often well-preserved, biologists have sparse information about the rest of this fish’s body. That’s because the Helicoprion had a cartilaginous skeleton. This means that unless its skeleton was preserved by exceptional circumstances, it began to decay almost immediately after it died. This has made describing other parts of the fish’s body a bit challenging. 

Experts think Helicorpion had a torpedo-shaped body plan similar to open-water fishes like lamnid sharks, tuna, and swordfish. It reached an impressive size of about 20 to 25 feet long and probably weighed up to a thousand pounds. This would be around the same weight range as the modern basking sharks. Helicoprion is one of the largest aquatic cartilaginous creatures of all time.

They had a single large dorsal fin and a forked caudal fin. Helicoprion and other fishes in the same order also lacked pelvic and anal fins. The highlight of the Helicoprion’s appearance was the tooth whorls. This typically consisted of dozens of teeth embedded in a single spiral-shaped tooth root. The teeth at the center were the youngest and had a hooked appearance. The others were older and had a triangular shape. The teeth grew bigger away from the center, with the largest ones being over 3.9 inches in length. This unusual arrangement was an adaptation that enabled the fish to feed on prey with soft bodies.

History and Evolution

Although this fish is built like a shark, has a cartilaginous skeleton, and is often compared to sharks due to its apex predator status, Helicoprion is not related to modern sharks, nor was it in the lineage that evolved into true sharks. They’re categorized into a separate group (Holocephali or Euchondrocephali) which evolved differently from sharks (Elasmobranchii).

Their evolutionary relationship is often characterized based on their unusual tooth whorls. There have been varying hypotheses about how these whorls evolved and what they were used for. Edestus, a related genus of shark-like fish, had similar whorls which they used to slash prey.

The Helicoprion’s autodiastylic jaw structure is common in many prehistoric euchondrocephalans. However, this feature is missing in modern animals except in embryonic chimaeriforms, which are their closest living relatives.

Diet—What Did Helicoprion Eat?

Helicoprion was a carnivorous aquatic animal. There are conflicting opinions about what this shark-like predator fed on due to the unique nature of their dentition. The prevailing thought is that they fed on a diet of soft prey such as squids. Some experts have proposed a suction-feeding habit, while others believe they were bite-feeders. The external teeth were probably for hooking and dragging out prey. The middle teeth were for cutting and piercing, while the posterior teeth cut prey into pieces and pushed it into its oral cavity.

Another theory proposes that the Helicoprion ate hard-shelled prey, such as cephalopod ammonoids. In this case, the teeth whorls would have served the purpose of deshelling the prey before sucking it into the open mouth. 

Studies have shown that the Helicoprion had a high bite force (1,192 to 2,391N). With such a large bite force, marine vertebrates like the bony fish and other cartilaginous fish species were probably on the menu too. 

Habitat—When and Where Helicoprion Lived?

Helicoprion existed from the Early Permian Period, which was about 290 million years ago, to the Early Triassic—40 million years ago. Paleontologists have found fossils across Australian, Asian, European, and American regions proving that Helicoprion had extended distribution across the world’s oceans during the Permian. More than 50% of its fossil specimens are from Idaho, and another 25% are from the Ural Mountains in Russia.

Researchers believe that due to the widespread distribution of these fossils, there is a high possibility that Helicoprion lived off the southwestern coast of the supercontinent Gondwana and later on Pangaea. It survived the Permian-Triassic extinction event that destroyed 90% of all marine animals and 70% of all land animals.

Threats and Predators

Helicoprion was shark-like in nature and appearance, meaning it was an apex aquatic predator of its time, swimming through global oceans and preying on smaller animals. Thanks to its 360-degree spiral teeth and sheer size, this fish didn’t have any notable natural enemies or threats. 

Discoveries and Fossils

Scientists discovered the first and oldest fossil of the Helicoprion in the 19th century. The first specimen was a 15-tooth fragment of a tooth whorl. It was found on a tributary of the Gascoyne River in western Australia. However, earlier studies erroneously assigned this fossil to the Edestus genus. 

Alexander Karpinski named the first species (H. bessonowi) in 1899. Karpinski, who invested a large portion of his life trying to understand the creature, also reassigned the first fossil to the Helicoprion genus. Many more fossils like this have been found in Australia.

Helicoprion fossils have been discovered in Russia, Japan, and, most recently, the Gufo Mountains in China. Fossil discoveries were also made in Eurasia in the early seventies, Pakistan in the late ’70s, Indochina in 1933, and Iran in 1978. In Mexico, fossil deposits have been found in the northern states of Coahuila and Chihuahua in the mid-forties and early sixties, respectively. 

Most recently, in March 2000, a Helicoprion specimen was found in Puebla, Mexico. It represented the southernmost finding of Helicoprion in the western hemisphere. Most of these fossil discoveries have been tooth whorls. A considerable lack of fossil evidence has led to a series of technologically enhanced visual reconstructions that attempt to explain the practical use of tooth whorls and possible body structure for this fish. 

Extinction—When Did Helicoprion Die Out?

There is inadequate information in regard to the extinction of the Helicoprion, especially because it lived through one of the greatest mass extinction events of all time—the Permian extinction. The general belief is that it must have struggled, but it stayed alive for a few million years before eventually succumbing to extinction. More research is required to understand why it died out after reigning through a handful of eras.

Similar Animals to the Helicoprion

Similar animals to the Helicoprion include: 

• Ornithoprion — Although this fish existed during the Carboniferous, it belongs to the eugeneodont order like Helicoprion. This fish’s skull helped scientists establish more facts about the Helicoprion and how it might have looked beyond the spiral teeth whorl.
• Sarcoprion – Sacroprion was a 20-foot-long fish that lived in Greenland during the Permian. Just like the Helicoprion, Sarcoprion had large tooth whorls. However, the whorls of the Sarcoprion were more compact. 
• Chimaera – Chimaera are cartilaginous fishes found in deep-water environments in temperate seas. This fish is the closest living relative to the Helicoprion. 

Related Animals 

• Chimaera
• Megamouth Shark
• Viper Shark (dogfish)