Sturgeons, paddlefishes and their fossil relatives form a small group of fishes from the Northern hemisphere called Acipenseriformes that is believed to have split off from other ray-finned fishes (the actinopterygians) some 150 million years ago. The morphology of living sturgeons (25 species) has remained largely unchanged since they first evolved. Although there have been many studies of sturgeon morphology, there never has been a study that is detailed or comprehensive enough to allow modern studies of their evolution. The new study of the skeleton of fossil and living sturgeons by Hilton, Grande and Bemis has two main goals. The first objective is to describe in detail the skeleton of the shortnose sturgeon (Acipenser brevirostrum), a small species of sturgeon found in coastal rivers of eastern North America. This study will be based on several types of specimens, including dry skeletons, hand cleaned skeletons that are stored in alcohol, and cleared and stained skeletons (in which the soft tissue is made clear, cartilage is stained blue and bone is stained red). Specimens representing all life history stages will be studied, from the earliest embryos to the oldest specimens available. Such an approach allows observations of changes of morphology due to growth and development of the skeleton. The results of this study will be published in a large format monograph, illustrated with photographs for documentation and line drawings for interpretation, accompanied by clear text descriptions. The intention is that this monograph will serve as a lasting contribution to the knowledge of the anatomy of sturgeons and a standard reference for anatomical studies of primitive ray-finned fishes. The second part of this study concerns tracing evolutionary relationships among living and fossil sturgeons. Most fossils that are identified as sturgeons are very fragmentary, and only after a detailed study of the living members of a group can such specimens be properly interpreted. Additionally, new comparative data generated during the first part of the study will be used to formulate new hypotheses of relationships. All previous morphological studies of the relationships of sturgeons are inadequate for various reasons. For instance, many studies have looked only at relationships of sturgeons from a particular geographic region or country. Evolution has not occurred within political boundaries, and Hilton, Grande and Bemis' study will be the first to incorporate morphological data for all sturgeons on a worldwide scale. All species of sturgeons are afforded some form of protection, with many listed as endangered. The precarious conservation status of many sturgeons make studies of their evolutionary history even more critical.
