SYNCHROTRON TOMOGRAPHY: A NEW INSIGHT INTO THE MOST PRIMITIVE VERTEBRATE SKELETON (Invited Presentation)

Conodonts are an extinct group of primitive vertebrates that are, perhaps, the earliest members of our evolutionary lineage to possess a mineralized skeleton. As such, the conodont skeleton is of great significance because of the insights it provides into the biology and function of the skeleton of the most primitive vertebrates. Our knowledge about those topics has been debated for more than a century, mainly limited by the available techniques, remaining almost every conodont paleobiology aspect controversial. However, in the last decade, the developing of novel quantitative approaches have facilitated a new insight into the conodont skeleton with an unprecedent detail, allowing us a better understanding of the nature of their skeleton, accurated reconstructions of the apparatus, and permiting to test hypothesis of element function.

In this talk, I will show the usage of the last computational methods including Synchrotron Radiation X-ray Tomographic Microscopy and Ptychographic X-ray nanotomography to obtain high resolution virtual models of conodont elements to test hypotheses of biological affinities and conodont function. The tomographic analysis of the conodont elements has allowed to characterize fully the nanostructure of the conodont tissues, showing subtle detail in the Calcium Phosphate material from which the elements are comprised, facilitating the recognition of significant small vacuities, growth lines, even internal discontinuities (microwear), with important consequences of the usage of conodont elements as archives of ocean chemistry. Additionally, the volumetric information derived from the tomographic data has been used for accurated reconstructions of the apparatus and for testing hypothesis of element function. Finite Element analyses, Occlusal and Microwear analyses of the ensuing dataset of those models have provided conclusive support for an occlusal tooth-like function for elements of many conodont species, allowing us to test hypothesis of structural adaptation within the crown tissue microstructure. But most interesting, we have been able to expand our functional analysis to the study of a classical conodont morphological evolutionary sequence, establishing a framework in which the functional ecology of conodont elements can be read from their rich taxonomy and phylogeny (morphological variation).