Comparative Osteology and Phylogenetic Systematics of Fossil and Living Sturgeons (Actinopterygii, Acipenseriformes), Part 2

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0414552Hilton Sturgeons, paddlefishes and their fossil relatives form a small group of fishes that is believed to have split off from other ray-finned fishes (the actinopterygians) some 150 million years ago, and have a reputation as "living fossils." This study of fossil and living sturgeons by Eric Hilton and Lance Grande is the continuation of a long-term project exploring the skeletal anatomy, paleontology, and evolution of sturgeons. The first goal of this study is make a detailed description of the skeleton of the shortnose sturgeon (Acipenser brevirostrum), a small species of sturgeon from the 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 many 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. This part of the study will serve as a baseline for comparisons among all living species of sturgeons. Additionally, most fossils identified as sturgeons are very fragmentary, and only after a detailed study of the living members of a group can such specimens properly be interpreted. The second part of this study concerns the evolutionary relationships among living and fossil sturgeons. Grande and Hilton have obtained a new specimen of a 70 million-year old fossil sturgeon from Montana. This new specimen, which represents a species new to science, is preserved well-enough that its skeleton can be described in incredible detail and can be compared directly with the skeletons of living sturgeons. By combining data from the new fossil with new data on the skeletons of living sturgeons, Hilton and Grande will formulate new hypotheses of relationships among all sturgeon species.Sturgeons are perhaps best known as the premier source of caviar. All species of sturgeons are afforded some form of protection, with many listed as endangered. The precarious conservation status of many species of sturgeons makes studies of their evolutionary history critical. Clear and detailed studies that rigorously describe species and investigate patterns of relationships serve as an important baseline for the construction of conservation and management plans for endangered species. All previous anatomical 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. Hilton and Grande's study is the first to incorporate morphological data for all sturgeons no matter where they come from in geologic time or geographic space.