At a Glance
- Researchers from the University of Chicago found that supposed early vertebrate teeth were actually sensory organs resembling structures seen in arthropods like crabs and barnacles.
- High-resolution CT scans of Cambrian fossils, including Anatolepis, revealed internal tubules more consistent with sensilla than true tooth anatomy.
- The findings support the outside-in hypothesis, which proposes that external sensory structures predated and possibly gave rise to internal oral features like teeth.
- This study suggests that convergent evolution occurred between arthropods and early vertebrates, with arthropods developing similar surface structures to survive ancient environmental pressures.
- Although it did not reveal the first vertebrate teeth, the research reshapes our understanding of early sensory evolution and highlights the value of modern imaging techniques.
A new study led by researchers from the University of Chicago has overturned previous beliefs about the origins of teeth in early vertebrates. The research suggests that what were once thought to be the first tooth-like structures in vertebrates are actually sensory organs similar to those found in modern arthropods, like crabs and barnacles. These findings, published in Nature, challenge the long-standing theory that teeth evolved directly from early vertebrate armor.
The team was investigating fossils of early fish from the Cambrian period, hoping to uncover the earliest examples of vertebrate teeth. Using high-resolution CT scans, they studied fossils, including one called Anatolepis, that appeared to show tubules filled with dentin, which forms the inner layer of modern teeth. However, after further comparisons with arthropod fossils, the researchers realized that the structures in Anatolepis were more akin to sensory organs, or sensilla, found on the shells of arthropods.
This discovery supports the “outside-in” hypothesis of tooth evolution, which suggests that sensory structures on exoskeletons preceded the development of teeth. According to this theory, these early structures helped animals sense their environment, like how teeth help modern animals respond to their surroundings by detecting pressure and temperature. The study shows that similar structures evolved independently in arthropods and early vertebrates, leading to a better understanding of how sensory systems evolved.
While the researchers did not find the earliest vertebrate fish as initially hoped, their discovery opens up new insights into the evolutionary history of teeth. It suggests that the earliest vertebrates and arthropods shared common traits in their armor-like exoskeletons, which may have been crucial for survival in ancient environments. This work also emphasizes the importance of studying fossils with advanced techniques to uncover new clues about the development of life on Earth.
References
- Haridy, Y., Norris, S. C. P., Fabbri, M., Nanglu, K., Sharma, N., Miller, J. F., Rivers, M., La Riviere, P., Vargas, P., Ortega-Hernández, J., & Shubin, N. H. (2025). The origin of vertebrate teeth and evolution of sensory exoskeletons. Nature, 642(8066), 119–124. https://doi.org/10.1038/s41586-025-08944-w
- University of Chicago. (2025, May 21). Teeth first evolved as sensory tissue in the armored exoskeletons of ancient fish, fossil scans find. Phys.Org; University of Chicago. https://phys.org/news/2025-05-teeth-evolved-sensory-tissue-armored.html
