Scientists are stunned by the discovery of sharks growing teeth on their foreheads.

A new study shows that ghost sharks have the ability to grow teeth right on their foreheads, challenging the long-held notion in evolutionary biology that teeth only appear in the mouths of vertebrates.

Ghost sharks are not actually sharks, but belong to the chimera group, distant relatives of sharks and rays - Photo: University of Florida

In a study recently published in the Proceedings of the National Academy of Sciences (PNAS) , researchers from the University of Washington and the University of Florida (USA) studied ghost sharks living off the coast of Washington state, especially in the waters of San Juan Island in Puget Sound.

This is a cartilaginous fish with glowing green eyes, an average length of about 60 cm, often called the "ocean ghost" because of its body that sparkles in the dark.

The team discovered that males of this species possess a special structure called a tenaculum located in the middle of their foreheads. On this appendage, tiny sharp points that were once thought to be horn spines are actually… real teeth.

Using histological experiments and molecular analysis, the team demonstrated that the teeth in the tenaculum share the same genes and developmental patterns as those in the fish’s mouth. Even the tooth-supporting tissue, called the dental lamina, previously only seen in the jaw, has been found in the forehead.

"This is the first clear evidence that vertebrates can grow teeth outside their mouths. This discovery overturns centuries of assumptions in evolutionary biology," said researcher Karly Cohen (University of Washington).

Through underwater footage, scientists have found that male ghost sharks use their frontal teeth to grip the female’s pectoral fins during mating. When not in use, the tenaculum folds up and stores in a small groove on the forehead.

Dr Gareth Fraser, an evolutionary biologist at the University of Florida, described: "The teeth in the tenaculum are arranged in multiple rows, operating like a conveyor belt similar to shark teeth. This is truly a spectacular mechanism that we have never seen in any other species in the animal kingdom."

This discovery not only sheds light on the long-standing mystery of the ghost shark's strange structure, but also opens up new research directions on the evolution of teeth in vertebrates.

Scientists have long believed that teeth only form in the mouth. But now evidence from ghost sharks suggests that teeth can grow outside the jaw, as long as there is a suitable tissue base.

Although scientists cannot yet fully explain the evolutionary mechanism of this special phenomenon, they affirm that the discovery has fundamentally changed our understanding of tooth biology, while emphasizing the amazing diversity of life in the deep ocean.

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MINH HAI

Source: https://tuoitre.vn/phat-hien-ca-map-moc-rang-tren-tran-khoa-hoc-sung-so-20250911102726748.htm