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

[04:1455 . 52]鲟鱼、白鲟和它们的化石亲戚组成了一小群鱼类，据信这些鱼类大约在1.5亿年前从其他鳍状鱼类（放光鳍目）中分离出来，被称为“活化石”。埃里克·希尔顿和兰斯·格兰德对化石和活鲟鱼的研究是探索鲟鱼骨骼解剖、古生物学和进化的长期项目的延续。本研究的第一个目标是详细描述短鼻鲟（Acipenser brevirostrum）的骨骼，短鼻鲟是一种来自北美东部沿海河流的小型鲟鱼。本研究将基于几种类型的标本，包括干燥的骨骼，存放在酒精中的手清洗骨骼，以及清除和染色的骨骼（其中软组织被清除，软骨被染成蓝色，骨骼被染成红色）。代表许多生命历史阶段的标本将被研究，从最早的胚胎到最古老的标本。这种方法允许观察由于骨骼生长和发育而引起的形态学变化。研究的这一部分将作为比较所有现存鲟鱼物种的基线。此外，大多数被确定为鲟鱼的化石都是非常零碎的，只有在对一个群体的现存成员进行详细研究之后，才能正确地解释这些标本。本研究的第二部分涉及活鲟鱼和化石鲟鱼之间的进化关系。格兰德和希尔顿从蒙大拿获得了一个7000万年前的鲟鱼化石的新标本。这个新标本代表了一个科学上的新物种，它保存得足够好，以至于它的骨骼可以被描述得非常详细，可以直接与现存鲟鱼的骨骼进行比较。通过将新化石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。鲟鱼可能是最著名的鱼子酱的主要来源。所有种类的鲟鱼都受到某种形式的保护，其中许多被列为濒危物种。许多种类的鲟鱼的不稳定的保护状况使得研究它们的进化史至关重要。清晰细致的研究，严谨地描述物种和调查关系模式，是建立濒危物种保护和管理计划的重要基础。由于各种原因，以前所有关于鲟鱼关系的解剖学研究都是不充分的。例如，许多研究只关注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结合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个地方。

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.