古代魚が敏感な歯の起源?(Sensitive teeth? Blame these ancient fish)

2025-05-23 シカゴ大学

CT scan of the front of a skate showing the hard, tooth-like denticles on its skin (shown in orange). Image courtesy of Yara Haridy

<関連情報>

• https://news.uchicago.edu/story/sensitive-teeth-blame-these-ancient-fish
• https://www.nature.com/articles/s41586-025-08944-w

脊椎動物の歯の起源と感覚外骨格の進化 The origin of vertebrate teeth and evolution of sensory exoskeletons

Yara Haridy,Sam C. P. Norris,Matteo Fabbri,Karma Nanglu,Neelima Sharma,James F. Miller,Mark Rivers,Patrick La Riviere,Phillip Vargas,Javier Ortega-Hernández & Neil H. Shubin
Nature  Published:21 May 2025
DOI:https://doi.org/10.1038/s41586-025-08944-w

Abstract

The earliest record of tooth antecedents and the tissue dentine^1,2, an early-vertebrate novelty, has been controversially represented by fragmentary Cambrian fossils identified as Anatolepis heintzi^3,4,5. Anatolepis exoskeletons have the characteristic tubules of dentine that prompted their interpretation as the first precursors of teeth³, known as odontodes. Debates over whether Anatolepis is a legitimate vertebrate^6,7,8 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^9,10. 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^11,12,13 feature large dentine tubules¹ 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^14,15,16. 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 teeth¹⁶. Middle-Ordovician fossils now represent the oldest known evidence for vertebrate dental tissues.