Archaeocete Whales of Eocene Tethys: Geochronology, Paleobiology and Evolution

小行星9714923 鲸鱼的起源和早期进化是化石记录中最深刻的进化转变之一。 向鲸鱼的过渡涉及适应区从陆地生活到水中生活的重大转变，伴随着摄食，听觉认知和运动的变化，影响了牙齿，颅骨，颅内和颅后骨骼形态的明显特征。 所有这些特征变化的证据在已经灭绝的始新世古鲸亚目的化石中保存得很好，允许在地质时间的背景下进行直接调查。 古生物最著名的是在始新世将印度和北非与欧亚大陆分开的特提斯海。 这里要研究的特提斯鲸是在被动大陆边缘发现的，它们位于海平面变化周期中不同地点沉积的一系列不同岩性的地层中。 这些可能反映了全球海平面的变化，这是第一个在这里通过更好的有孔虫控制来检验的假设。 鲸类起源于陆地哺乳动物的祖先并不是一个有争议的想法，但有时认为进化轨迹是从一个类似鲸鱼的祖先，经过类似熊，水獭，海豹或海狮的阶段，到现代鲸鱼。 第二个有待检验的假设是，作为早期鲸鱼在地质时期实际多样化的模型，这种食肉动物的“零继承”有多现实。 模型和古生物模式将进行图形和定量比较。 最后，进化的转变通常被认为是简单而直接的，或多或少是恒定的速度，第三个要检验的假设是转变的简单性（相对于“繁忙”）和向鲸鱼转变的速度的一致性。 所采用的方法包括发现的方法：新的始新世古鲸将从巴基斯坦的东特提斯地层序列中收集，可能还有埃及和突尼斯，因为这些国家的浅海相分布广泛，暴露良好，并且已知会产生保存完好的古鲸骨骼。 在过去的20年里，首席研究员在巴基斯坦和埃及组织了实地考察，产生了三分之一的有记录的属的多样性和最完整的古生物骨架。 古生物在形态上是多种多样的，如果没有更多这样质量的标本，对它们的研究就无法推进。 这里采用的其他方法包括18O同位素研究的个体发育和系统发育系列文件适应海水的时间尺度上，和新开发的定量图解方法的说明和古生物学的解释，与多变量量化的“距离”和这些之间的变化率将开发作为本研究的一部分。 这项拟议中的研究很重要，因为鲸鱼享有极大的公众利益，它们的起源提供了一个向广大观众说明和解释进化的机会。 鲸鱼的起源可以而且应该作为一个模型，在化石记录中的形态和时间的中间，图形表示这些方面的主要进化转变的调查，并通过地质时间的定量比较。

9714923 Gingerich The origin and early evolution of whales is one of the most profound evolutionary transitions that can be studied in the fossil record. The transition to whales involved a major shift of adaptive zone from life on land to life in water, with concomitant changes in feeding, hearing cognition, and locomotion that affected conspicuous features of dental, cranial, endocranial, and postcranial skeletal morphology. Evidence of change in all of these characteristics is well preserved in fossils of the extinct Eocene suborder Archaeoceti, permitting direct investigation in the context of geological time. Archaeocetes are best known from the Tethys Sea Neo-Tethys separating India and North Africa from Eurasia during Eocene time. Tethyan whales to be studied here are found on passive continental margins in a succession of strata of different lithologies deposited at different points in cycles of sea level change. These may reflect global change in eustatic sea level, which is the first hypothesis to be tested here with better foraminiferal control. The origin of whales from land-mammal ancestors is not a controversial idea, but the evolutionary trajectory is sometimes conceived proceeding from a wolf-like ancestor through bear-like, otter-like, and a seal or sea lion-like stages to modern whales. The second hypothesis to be tested is how realistic such a 'null succession' of living carnivores is as a model for the actual diversification of early whales through geological time. Model and paleontological patterns are to be compared graphically and quantitatively. Finally, evolutionary transitions are often thought of as simple and straight, at more or less constant rate, and the third hypothesis to be tested is the simplicity (versus 'bushiness') of the transition and uniformity of rates during the transition to whales. Methods to be employed include those of discovery: new Eocene archaeocete whales are to be collected from eastern Tethyan stratigraphic sequences in Pak istan, and possibly Egypt and Tunisia because these are countries where shallow marine facies are widely distributed, well exposed, and known to yield well preserved archaeocete skeletons. The principal investigator has organized field expeditions in Pakistan and Egypt over the past 20 years yielding one-third of the documented generic diversity and the most complete skeletons of archaeocetes found anywhere. Archaeocetes are diverse morphologically and their study cannot be advanced without more specimens of such quality. Other methods to be employed here include 18O isotopic study of ontogenetic and phyletic series to document adaptation to sea water on both time scales, and newly developed quantitative graphical methods for illustration and paleobiological interpretation, with multivariate quantification of 'distance' and rates of change between these to be developed as part of this research. The proposed research is important because whales enjoy great public interest and their origin provides an opportunity to illustrate and explain evolution to a wide audience. The origin of whales can and should serve as a model for investigation of major evolutionary transitions in the fossil record in terms of morphological and temporal intermediates, graphic representation of these, and quantitative comparison through geological time.