Archaeocete Whales of Eocene Tethys: Geochronology, Paleobiology and Evolution

始新世特提斯群岛的始祖鲸：地质年代学、古生物学和进化

• 批准号: 9714923
• 负责人: Philip Gingerich
• 金额: $ 24万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-15 至 2003-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9714923&HistoricalAwards=false
• 关键词: Archaeocete; Whales; Eocene; Tethys; Geochronology

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.

[9714923]金格里奇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适应区从陆地生物到水中生物的重大转变，随之而来的是进食、听力认知和运动的变化，这些变化影响了牙齿、颅骨、颅内和颅后骨骼形态的显著特征。所有这些特征变化的证据在已灭绝的始新世古鲸亚目化石中得到了很好的保存，这使得在地质时代背景下进行直接调查成为可能。始新世时期将印度和北非与欧亚大陆分隔开来的新特提斯海是古生菌最为人所知的。这里要研究的特提斯鲸是在被动大陆边缘的不同岩性地层中发现的，这些地层沉积在海平面变化周期的不同点上。这些可能反映了海平面上升的全球变化，这是第一个在这里用更好的有孔虫控制来测试的假设。鲸鱼的祖先是陆地哺乳动物，这一观点没有争议，但人们有时认为，鲸鱼的进化轨迹是从类狼的祖先，经过熊、水獭、海豹或海狮等阶段，再到现代鲸鱼。第二个要测试的假设是，这种现存食肉动物的“零演替”作为早期鲸鱼在地质时期实际多样化的模型有多现实。模型模式和古生物模式将在图形和数量上进行比较。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，而第三个需要测试的假设是转变的简单性（相对于“商业”）和转变为鲸鱼的速度的一致性。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东部的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，并且已知能产生保存完好的古鲸骨架。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，获得了三分之一的有记录的种类多样性和在任何地方发现的最完整的古ocetes骨架。古生菌形态多样，如果没有更多的古生菌标本，古生菌的研究就无法向前发展。本研究还将采用其他方法，包括对个体发生和种系系列的18O同位素研究，以记录两个时间尺度上对海水的适应；以及新开发的定量图形方法，用于说明和古生物解释，并将对这些方法之间的“距离”和变化率进行多元量化，作为本研究的一部分。拟议的研究很重要，因为鲸鱼享有巨大的公众利益，它们的起源提供了一个机会，向广大观众说明和解释进化。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，这些转变的图形表示，以及地质时期的定量比较。