Nanomechanical variability in the early evolution of vertebrate dentition
Fecha
2022Autor
Shohel, Mohammad
Ray, Kamal K
Tivanski, Alexei V
McAdams, Neo E. B (TTU)
Bancroft, Alyssa M
Cramer, Bradley D
Forbes, Tori Z
Metadatos
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Conodonts are an extinct group of primitive jawless vertebrates whose elements represent the
earliest examples of a mineralized feeding apparatus in vertebrates. Their relative relationship within
vertebrates remains unresolved. As teeth, conodont elements are not homologous with the dentition
of vertebrates, but they exhibit similarities in mineralization, growth patterns, and function. They
clearly represent an early evolutionary experiment in mineralized dentition and ofer insight into
analogous dentition in other groups. Unfortunately, analysis of functional performance has been
limited to a handful of derived morphologies and material properties that may inform ecology and
functional analysis are virtually unknown. Here we applied a nanoscale approach to evaluate material
properties of conodont bioapatite by utilizing Atomic Force Microscopy (AFM) nanoindentation to
determine Young’s modulus (E) along multiple elements representing diferent ontogenetic stages of
development in the coniform-bearing apparatus of Dapsilodus obliquicostatus. We observed extreme
and systematic variation in E along the length (oral to aboral) of each element that largely mirrors the
spatial and ontogenetic variability in the crystalline structure of these specimens. Extreme spatial
variability of E likely contributed to breakage of elements that were regularly repaired/regrown in
conodonts but later vertebrate dentition strategies that lacked the ability to repair/regrow likely
required the development of different material properties to avoid structural failure.