Toward the Origin of Whales: Eocene Cetacea from Pakistan

这个项目调查了鲸类动物（鲸鱼、海豚、鼠海豚）从陆地四足动物向海洋游泳者的转变。这种转变是为数不多的古生物学记录的哺乳动物宏观进化变化的例子之一。该项目将解释两个系统的宏观进化变化模式，它们经历了普遍的变化，运动和听觉，并评估其古生态背景。假设。——检验7个假设。其中两项研究预测了早期鲸类动物运动方式的变化。三种假说对鲸类动物中耳和内耳的进化和功能做出了预测。另外两个假说探讨了这种转变发生的物理环境，对古生态学做出了预测。新的化石材料将从巴基斯坦北部Kuldana和Kohat组的淡水和浅海沉积物中收集，这是唯一发现最早和最具多形鲸类的地区。这种材料将允许对假设进行检验。Kuldana/Kohat鲸类动物生活在各种沉积环境中，现在是一个结构复杂的地区，需要详细的地质研究。沉积学研究将阐明这一转变的物理背景。相关的正在进行的工作包括分析现代鲸类动物的耳朵发育和功能，以及基于稳定氧同位素的生理限制分析。的意义。鲸类动物的起源是脊椎动物陆-水过渡的最佳记录之一，并展示了几种形式-功能复合物经历了普遍的变化。鲸类动物的游泳从四足划水进化到加宽尾巴的背腹摆动，库尔达那鲸类动物表现出中间模式。鲸类祖先的耳朵被调谐到中频的空中声音，而现代鲸类则能听到水下的高频（齿状齿）或低频（齿状齿）声音。库尔达纳鲸类的位置尚不清楚，但它们的听觉形态与它们的陆地姐妹群和现代鲸类不同。在已建立的系统发育背景和现代水生哺乳动物提供的背景下解释化石形态阐明了这些进化模式。研究记录这些形态模式的岩石的沉积学，阐明了陆地到水过渡的生态背景。本研究对哺乳动物的高等系统发育具有更广泛的意义。它将为测试抹香鲸（odotocete paraphyly）的亲缘关系和鲸类动物与偶蹄动物（artiodactyl paraphyly）的关系提供形态学数据。这些系统发育假说是在分子数据的基础上提出的，形态学家对此有很大的争议。对动物进化的研究表明，印度-巴基斯坦在白垩纪与亚洲接触。地质数据反驳了这种说法。这项研究将为始新世的古生物学资料提供重要的检验。

Thewissen 9526686 This project investigates the transition of cetaceans (whales, dolphins, porpoises) from terrestrial quadrupeds to obligate marine swimmers. This transition is one of the few paleontologically documented examples of macroevolutionary change in mammals. The project will interpret patterns of macroevolutionary change in two systems that underwent pervasive modifications, locomotion and hearing, and evaluate its paleoecological context. Hypotheses.-- Seven hypotheses will be tested. Two of these make predictions about changes in the modes of locomotion in early cetaceans. Three hypotheses make predictions about evolution and function of the cetacean middle and inner ear. Another two hypotheses address the physical environment under which this transition took place, making prediction about paleoecology. New fossil material will be collected from freshwater and shallow marine sediments of the Kuldana and Kohat Formations of Northern Pakistan, the only area where the earliest and most plesiomorphic cetaceans are found. This material will allow testing of the hypotheses. Kuldana/Kohat cetaceans lived across a variety of depositional environments in what is now a structurally complex area, requiring detailed geological study. Sedimentological study will elucidate the physical setting of the transition. Related, ongoing work includes analyses of modern cetacean ear development and function, and an analysis of physiological constraints, based on stable oxygen isotopes. Significance.-- Cetacean origins is one of the best documented examples of land-water transitions among vertebrates, and showcases several form-function complexes that underwent pervasive change. Cetacean swimming evolved from quadrupedal paddling to dorsoventral oscillation of the broadened tail, and the Kuldana cetaceans display intermediate modes. The ears of cetacean ancestors were tuned to mid-frequency airborne sounds, whereas modern cetaceans hear underwater high- (odontocete) or low- (mys ticete) sounds. The position of the Kuldana cetaceans is unclear, but their auditory morphology is different from their terrestrial sister group and modern cetaceans. Fossil morphologies interpreted in an established phylogenetic context and against a background provided by modern aquatic mammals elucidates these evolutionary patterns. Studying the sedimentology of the rocks that document these morphological patterns clarifies the ecological setting of the land-to-water transition. This study is of broader significance for the higher phylogeny of mammals. It will provide morphological data to test phylogenies of the affinities of sperm whales (odotocete paraphyly) and the relationship of cetaceans to artiodactys (artiodactyl paraphyly). These phylogenetic hypotheses were proposed on the basis of molecular data, and are greatly disputed by morphologists. Studies of faunal evolution have suggested that Indo-Pakistan contacted Asia in the Cretaceous. Geological data dispute this claim. This study will provide a critical test for the Eocene paleontological data.