Ever wondered why your teeth are so sensitive to pain or even just cold
drinks? It might be because they first evolved for a very different
purpose than chewing half a billion years ago.
The origin of vertebrate teeth and evolution of sensory exoskeletons
Abstract
The earliest record of tooth antecedents and the tissue dentine, an early-vertebrate novelty, has been controversially represented by
fragmentary Cambrian fossils identified as Anatolepis heintzi.
Anatolepis exoskeletons have the characteristic tubules of dentine that prompted their interpretation as the first precursors of teeth, known as odontodes. Debates over whether Anatolepis is a legitimate vertebrate6,
have arisen because of limitations in imaging and the lack of
comparative exoskeletal tissues. Here, to resolve this controversy and understand the origin of dental tissues, we synchrotron-scanned diverse
extinct and extant vertebrate and invertebrate exoskeletons. We find
that the tubules of Anatolepis have been misidentified as dentine
tubules and instead represent aglaspidid arthropod sensory sensilla
structures. Synchrotron scanning reveals that deep ultrastructural
similarities between odontodes and sensory structures also extend to
definitive vertebrate tissues. External odontodes of the Ordovician
vertebrate Eriptychius feature large dentine tubules that are
morphologically convergent with invertebrate sensilla.
Immunofluorescence analysis shows that the external odontodes of extant chondrichthyans and teleosts retain extensive innervation suggestive of
a sensory function akin to teeth. These patterns of convergence and
innervation reveal that dentine evolved as a sensory tissue in the
exoskeleton of early vertebrates, a function retained in modern
vertebrate teeth. Middle-Ordovician fossils now represent the oldest
known evidence for vertebrate dental tissues.
Open access:
https://www.nature.com/articles/s41586-025-08944-w
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