Not sharks, not dinosaurs; the sharpest teeth belonged to a tiny ancient creature

For much of the twentieth century, sharks and large reptiles were assumed to define the upper limits of dental sharpness in the history of life. That assumption has been revised by detailed measurements of fossilised tooth structures from conodonts, extinct marine animals that lived hundreds of millions of years ago. Conodonts were small, eel-like vertebrates whose feeding apparatus was built from mineralised elements rather than jaws. Research drawing on high-resolution microscopy and quantitative comparison, published in The Royal Society Publishing, has shown that the tips of some conodont elements were sharper than the teeth of any living vertebrate. These findings have become relevant beyond palaeontology because they connect biological form with mechanical limits on sharpness.Conodonts initially appeared in the fossil record during the Cambrian epoch and remained until the end of the Triassic. They are better recognised for their copious tiny elements made primarily of calcium phosphate, rather than their rare entire bodies. These pieces vary in design and are frequently tooth-shaped, with sharp points and cutting edges. They were organised in the mouth as a complicated feeding device rather than a single row of teeth. The study that served as the foundation for this article looked at conodont elements assigned to species from the Late Carboniferous, a period when conodont diversity was great and their elements were highly diversified in shape.Conodont elements, unlike shark and mammalian teeth, did not grow from a jawbone. They have been replaced during their lives and exhibit signs of wear at the tips. Their composition is identical to vertebrate enamel, making them ideal for fine-scale measurement and comparison. Conodont elements are typically less than a few millimetres long, therefore their cutting edges can be retained in the fossil record with minimal distortion.Appearance alone does not define sharpness. The radius of curvature at the tip of a tooth or cutting edge was used to quantify sharpness in the study that is referenced here. A sharper point is associated with a smaller radius. Researchers used scanning electron microscopy on tooth tips to get pictures at a very high magnification in order to make these measurements. After that, digital profiles were taken throughout the tip, and a mathematical calculation was made to determine the curvature.The same method was applied to a range of modern biological and non-biological cutting tools, including mammal teeth, shark teeth and steel blades. This allowed direct comparison between conodont elements and objects whose function and performance are well understood. Importantly, the measurements were taken from unworn or minimally worn areas to avoid confusion between original sharpness and damage caused by use. The study did not rely on subjective judgment of sharpness but on repeatable numerical values derived from the geometry of the tip.Together, these features suggest that conodont elements functioned as active tools rather than passive structures, interacting directly with food items and experiencing mechanical stress consistent with repeated contact during feeding.The measured radii of curvature for conodont element tips were extremely small. In some specimens, values were lower than those recorded for any modern vertebrate tooth included in the comparison. They were also comparable to, and in some cases sharper than, manufactured steel blades measured using the same approach. These results indicate that conodont elements reached a level of sharpness close to the physical limits imposed by the strength of the material.The wear patterns recorded on the fossil pieces indicate that the tips have been flattened or blunted, thus implying that the original sharpness has been reduced during feeding. The production of wear is thus a demonstration that these sharp edges were used in life and not just incidental features of growth. The paper points out that conodont elements still had some tips sharper than those of many living animals, even after wear. Hence, the extreme initial sharpness coupled with the observable wear is an argument for conodont elements being adapted for cutting or slicing food.This approach allowed sharpness to be treated as a physical parameter rather than a descriptive trait, enabling comparison across organisms separated by evolutionary time and built from very different biological materials.When compared with shark teeth, conodont elements differ in both scale and microscopic construction. Shark teeth are bigger and are held by a cartilaginous jaw, whereas conodont elements were minute and located in soft tissue along the oral cavity. The research revealed that shark teeth, while being good cutting tools, have larger radii of curvature at their tips than conodont elements, making conodonts exceptionally sharp for their size. It does not mean that sharks are less efficient predators, but rather that sharpness alone is not the main factor determining overall feeding efficiency.Mammalian teeth, including those of carnivores, were also included in the comparison. These teeth generally showed much blunter tips when measured at the same scale. The difference reflects constraints imposed by tooth size, loading forces and the need for durability over long periods of use. Conodont elements, by contrast, could be replaced frequently, which may have allowed them to function with extremely sharp but fragile tips.The study discusses the relationship between sharpness and material strength. As a cutting edge becomes sharper, the stress at the tip increases, raising the risk of fracture. Calcium phosphate, the main component of conodont elements, has known mechanical properties that limit how sharp a stable edge can be. The measured sharpness of conodont elements approaches these limits, suggesting that their form represents an extreme case of biological optimisation within material constraints.These findings place conodonts in a broader context of studies that link biological structures with engineering principles. By quantifying sharpness rather than describing it qualitatively, the research provides a way to compare extinct and living organisms on the same mechanical basis. The data also offer a reference point for understanding how natural selection can produce structures that operate at the edge of physical possibility, even in animals that were only a few centimetres long.The results also offer data for engineers studying micro cutting tools and wear-resistant edges. Fossil specimens preserve shapes that are difficult to maintain in modern materials, providing models for sharpness at very small scales.Fossilised conodont elements thus remain a rare record of how biological tissues once achieved extreme edge geometry, preserved at scales that allow direct measurement of form, wear, and material limits within ancient marine ecosystems.Seen in this light, conodonts shift from obscure fossils to benchmarks of biological engineering, showing that extreme sharpness emerged early in vertebrate history and was governed as much by physics and material limits as by ecology.Also Read | Are wild animals really getting drunk in nature?