More genes versus environment
More genes versus environment
复制标题
更多基因与环境
作者：
B. Waksman
马里的辐射总是保留着祖先的散乱步态。来自始新世的两个完整的肱骨以立体照片的形式发表，显示了支持这一观点的特征8，包括肱骨头和肘关节之间原始扭转的明显残留物。塞里诺和麦凯纳现在从他们的漂亮标本——一个小的、晚白垩纪多结节前肢——的特征论证说，它很像兽类的前肢，并且在相当大的范围内是副柱状摆动的。一个推论是，单孔动物和多孔动物都有这种进步，单孔动物没有表现出来。非古生物学家应该注意，这些研究中使用的方法并不是对死亡骨骼如何连接和移动的推测性描述：相当多的骨骼特征被客观地评分，以评估功能和系统发育的相关性。然而，许多化石标本显示裂缝和扭曲，这可能使生物识别不准确。对于这些新的结论，有必要保持谨慎。这些细节来自于长寿命辐射中的一两个物种，它们必须适应各种生态位。在这么长的时间跨度内，所有的多结节都局限于低频听力的可能性有多大？如果前肢是在白垩纪进化的，在始新世进化的，来自同一个taeniolabidoid类群，那么关于进化时间的假设有多可靠呢？我们从有袋类动物和胎盘类动物那里获得了广泛的适应性知识，但单孔目动物，鸭嘴兽和针鼹，在运动和听觉方面非常专业，我们仍然只能猜测原始祖先的形式。随着澳大利亚古生物学家的努力和最近美国-蒙古探险队的重要新材料的出现，我们可以希望更多保存完好的骨骼发现将为我们家族历史中这段被忽视的部分提供有趣的答案和惊喜。D
malian radiation always retaining something of the ancestral sprawling gait. Two complete humeri from the Eocene have been published as stereophotographs and show features to support this8, including a marked residuum of the primitive torsion between humeral head and elbow condyle. Sereno and McKenna2 now argue from the features of their beautiful specimen of a small, Late Cretaceous multituberculate forelimb that it was very like that of therians and was swung parasagittally over a considerable range. A corollary is that therians and multituberculates share this advance, not shown by monotremes. Non-palaeontologists should note that the methods used in these studies are not speculative descriptions of how the dead bones may have articulated and moved: a considerable number of osteological features are scored objectively to evaluate functional and phylogenetic correlations. However, many fossil specimens show cracks and distortions which can make biometrics inexact. There is need for caution in relation to these new conclusions. The detail is obtained from one or two species in a long-lived radiation that must have adapted to a variety of niches. How likely is it that all multituberculates over this huge time span were restricted to low-frequency hearing? If the forelimb was advanced in a Cretaceous form and primitive in an Eocene form, from the same taeniolabidoid group, how secure is any assumption about the timing of the advance? We derive from marsupials and placentals knowledge of a broad range of adaptions, but the monotremes, platypus and echidna, are very specialized in locomotion and hearing, and we still only guess at the primitive ancestral form. With important new material coming from the efforts of Australian palaeontologists and from the recent American-Mongolian expeditions, we can hope that more well preseived skeletal finds will provide both interesting answers and surprises within this somewhat neglected part of our family history. D
影响因子：
56.9
作者：
FUJINAMI, RS;OLDSTONE, MBA
通讯作者：
OLDSTONE, MBA