Researchers study evolutionary origins of tooth and jaw development in living sharks
The origins of a pretty smile have long been researched in the fearsome jaws of living sharks which have been viewed as living fossils reflecting the ancestral condition of vertebrate tooth development and inference of its evolution. However, this view ignores true fossils which more closely reflect the nature of ancient ancestors.
New research from the University of Bristol and the Naturalis Biodiversity Center published in Nature’s ecology and evolution reveals that the dentitions of parents of living sharks are absolutely not representative of the last shared ancestor of jawed vertebrates.
The study reveals that while teeth have evolved once, complex dentitions have been acquired and lost several times in the history of evolution, and tooth replacement in living sharks is not the best model in the research into therapeutic solutions to human dental pathologies.
Lead author Martin Rücklin from the Naturalis Biodiversity Center in Leiden, the Netherlands, said:
We used high-energy X-rays on the TOMCAT beamline of the Swiss light source at the Paul Scherrer Institute in Switzerland, to study the structure and development of teeth and jaw in shark ancestors. These Ischnacanth Acanthodians had marginal dentitions consisting of multiple rows of successive teeth, which are quite different from the dental whorls that occur in front of the jaw in Acanthodians and across the jaws of chondrichthyans. “
Co-author Professor Philip Donoghue, School of Earth Sciences, University of Bristol, said: “Vertebrate dentitions are characterized by an organized arrangement to allow for occlusion and efficient feeding throughout. the life of an animal. This organization and crackling of the teeth is thought to originate in a universal developmental mechanism, the dental lamina, seen in sharks. The condition we see in successive rows of teeth cannot be explained by this mechanism. “
Co-author Benedict King of the Naturalis Biodiversity Center said: “Using state-of-the-art probabilistic ancestral state estimation methods, we are building on this finding to show that teeth existed in the ancestor crown of gnathostomes, so that complex dentitions, dental whorls, lamina and coordinated replacement, all evolved independently and were lost several times in the early evolution of vertebrate jaws. “
Rücklin, M., et al. (2021) Acanthodian dental development and origin of gnathostomic dentitions. NOTature ecology and evolution. doi.org/10.1038/s41559-021-01458-4.