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

希尔顿鲟鱼、白鲟鱼和它们的化石近亲组成了一个小鱼群，据信是在大约1.5亿年前从其他射线鳍鱼(放线蕨类)中分离出来的，并有“活化石”的美誉。埃里克·希尔顿和兰斯·格兰德对鲟鱼化石和活着的研究是一个长期项目的继续，该项目探索鲟鱼的骨骼解剖、古生物学和进化。这项研究的第一个目标是详细描述北美东部沿海河流中的一种小型鲟鱼--短吻鲟鱼(Acipenser Brevirostrum)的骨骼。这项研究将基于几种类型的标本，包括干燥的骨骼，保存在酒精中的手工清洗的骨骼，以及清除和染色的骨骼(其中软组织清晰，软骨被染成蓝色，骨骼被染成红色)。将研究代表许多生命历史阶段的标本，从最早的胚胎到可用的最古老的标本。这种方法允许观察由于骨骼的生长和发育而引起的形态变化。这部分研究将作为比较所有现存鲟鱼物种的基线。此外，大多数被确认为鲟鱼的化石都非常零碎，只有在对一个群体中的活着成员进行详细研究后，才能正确地解释这些标本。这项研究的第二部分涉及到生物和化石鲟鱼之间的进化关系。格兰德和希尔顿从蒙大拿州获得了一种7000万年前的鲟鱼化石的新标本。这个新标本代表了科学上的一个新物种，保存得很好--它的骨骼可以被描述得令人难以置信的详细，并可以直接与活着的鲟鱼的骨骼进行比较。通过将新化石中的数据与现存鲟鱼骨骼的新数据相结合，希尔顿和格兰德将对所有鲟鱼物种之间的关系提出新的假设。鲟鱼可能是鱼子酱的主要来源。所有种类的鲟鱼都得到了某种形式的保护，其中许多被列为濒危物种。许多鲟鱼物种的保护状况岌岌可危，这使得研究它们的进化史变得至关重要。明确而详细的研究严格描述物种并调查关系模式，是构建濒危物种保护和管理计划的重要基线。由于各种原因，以前所有关于鲟鱼关系的解剖学研究都不够充分。例如，许多研究只关注了来自特定地理区域或国家的鲟鱼之间的关系。希尔顿和格兰德的研究首次纳入了所有鲟鱼的形态数据，无论它们来自地质时间或地理空间的哪里。

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.