DIGITIZED RECONSTRUCTION OF THE INTERNAL HARD-PART ANATOMY OF ARTICULATE BRACHIOPODS

Articulate brachiopods typically have a pair of ventral hinge teeth that fit into corresponding sockets on the dorsal valve. Williams et al. (1997) noted that the deltidiodont tooth originated in the mid-Cambrian and is typical of extinct strophic-hinged groups for the most part. A second type of structure, the cyrtomatodont tooth, is typical of post-Paleozoic forms and is more elaborately curved and often hooked-shaped. Cyrtomatodont teeth make post-mortem disarticulation difficult. Carlson (1989) noted Their knob or hook-shape results from resorption during growth, which results in more complex three-dimensional shapes and interlocking hinge structures that cannot be disarticulated without breakage; deltidiodont teeth are not locked into the sockets, but merely rest in them, using the hinge line as a fulcrum about which valve rotation occurs. Studying the internal morphology of brachiopods with cyrtomatodont teeth often necessitates the use of transverse serial sectioning to reconstruct the key structures. Depending on the type of preservation it is possible to utilize CT scans that produce higher resolution images. Since the internal anatomy is important for accurate taxonomic identification, any technique that enables workers to clarify it is invaluable. Our method for generating detailed three-dimensional (3-D) reconstructions of the internal skeletal features of brachiopods uses SPIERS (serial paleontological image editing and rendering system) software. The software can be adapted for registration, virtual preparation, and interactive visualization after digitization of acetate peels using a digital camera. The software system generates detailed 3-D images of internal structures such as dental plates, cardinalia, and brachidia. We are able to construct pairs of split screen or anaglyph images that show the internal skeletal structures in a 3-D aspect. We have successfully sectioned numerous specimens from Lower Devonian (Paleozoic) strata in Germany, Morocco, North America and South China and Jurassic (Mesozoic) strata from Jordan that have been converted to anaglyph stereo images. These images have enabled us to view the cardinalia of specimens from the Jurassic of Jordan in 3-D and identify shells to the species level with a high degree of certainty.