Archaeocete Whales of Eocene Tethys: Geochronology, Paleobiology and Evolution

9714923鲸鱼的起源和早期进化是化石记录中可以研究的最深刻的进化转变之一。向鲸鱼的转变涉及到从陆地生活到水中生活的适应区域的重大转变，伴随着摄食、听力认知和运动的变化，影响了牙齿、颅骨、内颅骨和颅后骨骼的明显特征。所有这些特征变化的证据在已灭绝的始新世古近纪化石中得到了很好的保存，从而允许在地质时代的背景下进行直接调查。古生物最为人所知的是始新世时期分隔印度和北非与欧亚大陆的特提斯海新特提斯。这里要研究的特提斯鲸是在被动大陆边缘发现的，它们是在海平面变化周期的不同点上连续沉积的不同岩性的地层中发现的。这些可能反映了全球海平面的变化，这是第一个通过更好的有孔虫控制来检验的假说。鲸鱼起源于陆地哺乳动物的祖先并不是一个有争议的观点，但进化轨迹有时被设想为从类似狼的祖先，到类似熊、水獭、海豹或海狮的阶段，再到现代鲸鱼。需要检验的第二个假设是，对于早期鲸鱼在地质年代中的实际多样化而言，这种活着的食肉动物的“零演替”有多现实。模型模式和古生物模式将进行图形和定量的比较。最后，进化转变通常被认为是简单而直接的，或多或少以恒定的速度进行，需要检验的第三个假设是，在向鲸鱼转变的过程中，转变的简单性和速率的一致性(相对于繁琐)。可采用的方法包括发现方法：将从巴基斯坦东部的特提斯地层层序中收集新的始新世古鲸，可能还包括埃及和突尼斯，因为这些国家的浅海相分布广泛，暴露良好，并以出产保存完好的考古骨骼而闻名。在过去的20年里，首席调查员在巴基斯坦和埃及组织了实地考察，产生了已记录在案的属属多样性的三分之一，以及在任何地方发现的最完整的考古动物骨骼。考古学家在形态上是多种多样的，如果没有更多这样高质量的标本，他们的研究就不可能取得进展。这里将使用的其他方法包括个体发生和系统发育系列的18O同位素研究，以记录在两个时间尺度上对海水的适应，以及新开发的用于说明和古生物解释的定量图解方法，以及作为本研究的一部分，将开发多变量量化的“距离”和这些之间的变化率。这项拟议的研究很重要，因为鲸鱼享有巨大的公众利益，它们的起源为向广大受众解释和解释进化提供了机会。鲸鱼的起源可以而且应该作为研究化石记录中主要进化转变的模型，包括形态和时间中间物、这些中间物的图形表示以及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.