title: Testing microstructural adaptation in the earliest dental tools.
abstract: Conodont elements are the earliest vertebrate dental structures. The dental tools on elements responsible for food fracture-cusps and denticles-are usually composed of lamellar crown tissue (a putative enamel homologue) and the enigmatic tissue known as 'white matter'. White matter is unique to conodonts and has been hypothesized to be a functional adaptation for the use of elements as teeth. We test this quantitatively using finite-element analysis. Our results indicate that white matter allowed cusps and denticles to withstand greater tensile stresses than do cusps comprised solely of lamellar crown tissue. Microstructural variation is demonstrably associated with dietary and loading differences in teeth, so secondary loss of white matter through conodont phylogeny may reflect changes in diet and element occlusal kinematics. The presence, development and distribution of white matter could thus provide constraints on function in the first vertebrate dental structures.
authors: School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ UK. david.jones@bris.ac.uk
authors: David
authors: D
authors: Jones
authors: Alistair R
authors: AR
authors: Evans
authors: Emily J
authors: EJ
authors: Rayfield
authors: Karen K W
authors: KK
authors: Siu
authors: Philip C J
authors: PC
authors: Donoghue
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D005580:Fossils; D013718:Tensile Strength; D014070:Tooth / Q000033:anatomy & histology* / Q000502:physiology; D014714:Vertebrates / Q000033:anatomy & histology*