Helicoprion facts for kids

Kids Encyclopedia Facts

Quick facts for kids Helicoprion Temporal range: Cisuralian to Guadalupian (Artinskian to Roadian), 290–270Ma PreЄ Є O S D C P T J K Pg N As. S Artin. Kung. Road. W Ca. Wu. C

Tooth-whorl of H. davisii from the Phosphoria Formation of Idaho, Utah Field House of Natural History
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	†Eugeneodontida
Family:	†Helicoprionidae
Genus:	†*Helicoprion* Karpinsky, 1899
Type species
Helicoprion bessonowi Karpinsky, 1899
Other species
H. davisii (Woodward, 1886) H. ergassaminon Bendix-Almgreen, 1966
Synonyms
List of synonyms Genus synonyms Lissoprion Hay, 1907 Parahelicoprion? Karpinsky, 1916 Synonyms of H. bessonowi H. nevadensis Wheeler, 1939 H. svalis? Siedlecki, 1970 Synonyms of H. davisii H. ferrieri (Hay, 1907) H. sierrensis Wheeler, 1939 H. jingmenense Chen et al., 2007 Indeterminate species H. karpinskii Obruchev, 1953 H. mexicanus Müllerried, 1945

Helicoprion is an extinct genus of giant shark-like cartilaginous fish. It lived between 290 and 270 million years ago during the Early to Middle Permian periods. Its name comes from two Ancient Greek words that mean "spiral saw".

Scientists place this strange creature in an extinct order called Eugeneodontiformes. Even though it looked like a shark, it was more closely related to modern chimaeras or ratfish.

It is famous because of its bizarre, spiral-shaped tooth whorl. For more than a century, fossil hunters wondered where this saw-like wheel fitted on the animal's body.

Discovery and the mystery of the spiral
- Wild guesses about the spiral saw
- Solving the jaw puzzle with modern scans
What did Helicoprion look like?
How Helicoprion hunted
- A prehistoric squid-eater
Life in the Permian seas
Extinction
Images for kids
See also

Discovery and the mystery of the spiral

Lithographic figures of various eugeneodont fossils, the holotype of H. davisii (WAMAG 9080) being shown at the top (fig. 1)

The very first piece of Helicoprion ever found was a curved row of 15 teeth. A gold prospector named Mr. Davis discovered it near the Gascoyne River in Western Australia. The specimen was sent to England, where British paleontologist Henry Woodward studied it in 1886. Woodward thought the teeth belonged to a prehistoric fish genus called Edestus. He named the find Edestus davisii in honor of Davis.

Later, in 1899, Russian geologist Alexander Karpinsky studied more complete fossils found near Krasnoufimsk in Russia. These rocks had complete circular spirals of teeth. Karpinsky realized this animal was totally new. He created the genus name Helicoprion and named the type species Helicoprion bessonowi. He also realized that the Australian specimen belonged in this new genus as well.

Wild guesses about the spiral saw

Karpinsky's 1899 first hypothesis of the placement of the tooth whorl on H. bessonowi.

Because soft bodies rot away, only the mineralized teeth usually survived as fossils. This caused huge confusion among early paleontologists. Karpinsky first drew the creature with a spiral curling out from its nose like an elephant trunk. He later wondered if the wheel was attached to a dorsal fin or curled up on its tail like a seahorse.

Other scientists guessed the whorl might be a protective spine on the back or a weapon like a stingray tail. An artist named F. John drew Helicoprion on a collectible trading card in 1910. He showed the spiral hanging downward from the tip of the chin. Modern artists like Ray Troll drew similar pictures for years. Some scientists even suggested the spiral was hidden deep inside the creature's throat to help swallow food.

Solving the jaw puzzle with modern scans

"Idaho 4" (IMNH 37899), a tooth whorl of H. davisii from the Phosphoria Formation being notable for preserving the articulated jaw cartilages

The mystery was finally solved using a remarkable fossil nicknamed "Idaho 4." Found in Idaho in 1950, this specimen preserved actual jaw cartilage around the tooth spiral.

In 2013, researchers used medical CT scans to look inside the rock. The high-tech scans proved that the spiral did not stick out of the mouth at all. Instead, it was completely nestled inside the center of the lower jaw. The animal had an autodiastylic jaw, where the upper jaw attached directly to the skull without help from the hyomandibula. As new teeth grew at the back, older, smaller teeth were pushed forward and rolled inside a hidden spiral pocket.

What did Helicoprion look like?

Life restoration of H. davisii.

Like modern sharks, Helicoprion had a skeleton made of cartilage rather than bone. Except for the jaws, cartilage decomposes rapidly after death, leaving few full body fossils behind. Scientists must use smaller cousins, such as Caseodus, Fadenia, and Romerodus, to picture its body.

Helicoprion had a sleek, fusiform body shaped like a fast torpedo. It possessed large pectoral fins, a single triangular dorsal fin, and a tall, symmetrical caudal fin. It lacked pelvic and anal fins. In overall shape, it looked very similar to modern tuna, swordfish, or open-ocean lamnid sharks.

Incredible size

Estimated size of exceptionally large Helicoprion, with a speculative skull shape and body outline

Helicoprion was an enormous predator. A small tooth whorl measuring 35–40 cm (14–16 in) belonged to an animal roughly 5–8 m (16–26 ft) long. That is as big as a modern basking shark!

The largest tooth whorl ever found is kept at the Idaho Museum of Natural History. It measures 56 cm (22 in) wide. Paleontologists calculate that the owner of this whorl reached 9.7–12 m (32–39 ft) in total length. That makes it one of the largest ocean hunters of the entire Permian period.

The spiral saw teeth

Diagram of the teeth within the spiral

The spiral whorl was an amazing piece of natural engineering. Dozens of sharp, enameloid-covered teeth grew along a coiled logarithmic spiral. Each tooth was triangular, flattened from side to side, and had fine serrations like a steak knife. The smallest teeth in the very center represented the teeth the creature grew as a baby. The newest and largest teeth grew near the back, reaching up to 10 cm (3.9 in) tall.

Unlike modern sharks, which shed their old teeth when they wear out, Helicoprion kept every single tooth it ever grew. The old teeth simply rolled inward and downward into the lower jaw. Tiny odontode scales also covered parts of its body, giving it a rough skin.

Different species

Tooth whorl of H. ergassaminon on display at the Idaho Museum of Natural History in Pocatello

Scientists have named over ten species over the years, but a 2013 study showed that many were just normal variations or different growth stages. Today, only three species are recognized as valid:

Helicoprion bessonowi: This species had closely spaced teeth with backward-curved tips.
Helicoprion davisii: This species had taller, widely spaced teeth with tips that curved forward.
Helicoprion ergassaminon: This species had traits in between the other two, with tall but closely packed teeth.

Names like H. ferrieri, H. sierrensis, and H. jingmenense are now considered synonyms of H. davisii. Other names, such as H. mexicanus, are considered doubtful because their fossils are incomplete or lost.

How Helicoprion hunted

Jaw motion of Helicoprion after Ramsay et al. (2015)

Scientists once wondered how an animal could eat with a circular buzzsaw inside its mouth. In 2015, researchers used computer models to recreate the jaw movements of Helicoprion.

Because its snout was so slender, it could not use suction feeding. Instead, it was an active bite feeder. When the jaws snapped shut, the tooth whorl moved backward in a tight curved arc. The front teeth hooked slippery prey, while the middle and back teeth sliced and pushed it deeper toward the gullet. The rounded teeth on the roof of the mouth acted like a stone pavement, squeezing food firmly against the turning blade.

A prehistoric squid-eater

Permian seas were full of soft-bodied creatures, especially cephalopods. Helicoprion fed mainly on ancient squid relatives, such as belemnoids, nautiloids, and spiral-shelled ammonoids.

When clamping down on a hard-shelled ammonoid, the circular jaw worked like a mechanical can opener. The blade could hook into the soft body parts, pulling the animal cleanly out of its outer shell. The bite force was measured to be up to 2,391 newtons. With such power, it could also easily slice through cartilaginous and bony fish, or soft annelid worms crawling along the sea floor.

Life in the Permian seas

Outdated illustration of an H. bessonowi based on the hypothesis of a prognathous lower jaw proposed by Janvier in 1996

Fossils of Helicoprion have been dug up across the globe, including the United States, Russia, Australia, China, Japan, Kazakhstan, Laos, Mexico, and Norway. This shows it lived across open oceans worldwide as a pelagic swimmer.

Many of the best fossils come from the Phosphoria Formation in Idaho and Wyoming. During the Artinskian age, this area was a deep, nutrient-rich inland sea with muddy, low-oxygen waters. Because so many young and adult fossils were found here together, scientists think this inland sea was a major hunting ground or even a nursery habitat. Resting at the top of the food chain, Helicoprion reigned as an apex predator for 20 million years.

Extinction

Helicoprion completely vanished around 270 million years ago, near the end of the Roadian age of the Middle Permian. Its disappearance happened through normal background extinction, long before the catastrophic end-Permian mass extinction wiped out most ocean life.

Because Helicoprion was so large and needed a specialized diet of cephalopods, small shifts in ocean temperatures or prey populations may have driven this amazing spiral-toothed predator to extinction.