Meeting Abstract
Current understanding of the Chondrichthyan phylogeny lags behind that of many other vertebrate classes. Many of the studies conducted to date have produced conflicting topologies. In an effort to address the lack of consensus on Chondrichthyan phylogeny, the Chondrichthyan Tree of Life project was developed. One component of the Tree of Life examines the morphological variation across Chondrichthyans through the use of Computed Tomography (CT). CT is a nondestructive method for viewing internal structures of extant and fossilized specimens. Reconstruction programs can be used to manually segment the data into separate skeletal structures, creating 3-Dimensional representations of the structures which can then be viewed digitally or printed in 3D. The quality and ease of segmentation is tightly tied to the visible contrast between study structures and other tissues in the organism. In most groups of vertebrate organisms, skeletal structures are made of calcified bone which has high radiopacity, leading to greater contrast between the skeleton and soft tissues. Chondrichthyans, by comparison, have skeletons composed of cartilage which is much less radiopaque than bone, resulting in lower contrast with surrounding tissues. We will describe the basis of the anatomical component of the Chondrichthyan Tree of Life and the processes which go into creating interactive digital representations of the CT scan data. Additionally, some of the unique skeletal structures we have encountered will be presented.
