School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ UK.
Biol Lett. 2012 Dec 23;8(6):952-5. doi: 10.1098/rsbl.2012.0487. Epub 2012 Jul 4.
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.
牙形石元素是最早的脊椎动物牙齿结构。负责食物断裂的牙形石元素上的牙齿工具——尖齿和小齿——通常由层状冠组织（假定的釉质同源物）和神秘的“白质”组成。白质是牙形石所特有的，据推测是牙形石作为牙齿使用的一种功能适应。我们使用有限元分析对此进行了定量测试。我们的结果表明，与仅由层状冠组织组成的尖齿相比，白质使尖齿和小齿能够承受更大的拉伸应力。牙齿的微结构变化与饮食和加载差异明显相关，因此牙形石系统发育过程中白质的次要损失可能反映了饮食和元素咬合运动学的变化。因此，白质的存在、发育和分布可能为第一个脊椎动物牙齿结构的功能提供限制。
