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Researchers have discovered true teeth growing on the head of male spotted ratfish, overturning the long-held belief that vertebrate teeth only develop in the jaws. The teeth, located on a structure called the tenaculum, share genetic origins with oral teeth and are used during mating. This finding could reshape our understanding of dental evolution in vertebrates.
October 16, 2025
Source:
Science Daily
Breakthrough in Vertebrate Anatomy
Scientists have identified genuine teeth growing on a structure atop the male spotted ratfish’s head, a distant shark relative. The appendage, called the tenaculum, is covered in several rows of hooked, retractable teeth. This finding is documented in the journal Proceedings of the National Academy of Sciences and reported by Science News and Discover Magazine.
Tenaculum: More Than Just a Spike
Location: The tenaculum sits between the eyes of adult males.
Structure: Up to eight rows of barbed, retractable teeth.
Function: Used during mating to grasp and hold females.
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Source:
Science Daily
Genetic and Evolutionary Insights
Advanced micro-CT scanning and developmental analysis confirmed the head teeth are structurally and genetically equivalent to jaw teeth. Unlike skin denticles found on sharks, these teeth originate from dental lamina tissue—the same source as oral teeth.
Implications for Evolution
Challenging Old Beliefs: Teeth were thought to originate and evolve only in jaws; this discovery shows tooth development can occur elsewhere.
Ancient Traits: Fossils suggest similar structures existed in the ratfish’s ancestors, indicating deep evolutionary roots.
Expert Opinions
"This spectacular feature flips the long-standing assumption in evolutionary biology that teeth are strictly oral structures," said Karly Cohen of the University of Washington. Gareth Fraser from the University of Florida added, "If these strange chimaeras are sticking teeth on the front of their head, it makes you think about the dynamism of tooth development more generally."
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Source:
IFLScience
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