Toward the Origin of Whales: Eocene Cetacea from Pakistan

走向鲸鱼的起源：来自巴基斯坦的始新世鲸类

• 批准号: 9526686
• 负责人: Johannes Thewissen
• 金额: $ 19万
• 依托单位: Northeast Ohio Medical University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-02-15 至 2000-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9526686&HistoricalAwards=false
• 关键词: Toward; Origin; Whales; Eocene; Cetacea

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.

Thewissen 9526686 该项目研究鲸目动物（鲸鱼、海豚、鼠海豚）从陆地四足动物到专性海洋游泳者的转变。 这种转变是古生物学记录的哺乳动物宏观进化变化的少数例子之一。 该项目将解释两个系统的宏观进化变化模式，这两个系统经历了普遍的改变、运动和听觉，并评估其古生态背景。 假设——将测试七个假设。 其中两个预测了早期鲸类运动模式的变化。 三种假设对鲸目动物中耳和内耳的进化和功能进行了预测。 另外两个假设涉及这种转变发生的物理环境，对古生态做出预测。 新的化石材料将从巴基斯坦北部库尔达纳组和科哈特组的淡水和浅海沉积物中收集，这是唯一发现最早和最拟形鲸类的地区。 该材料将允许检验假设。 库尔达纳/科哈特鲸目动物生活在如今结构复杂的地区的各种沉积环境中，需要进行详细的地质研究。 沉积学研究将阐明转变的物理环境。 正在进行的相关工作包括对现代鲸类耳朵发育和功能的分析，以及基于稳定氧同位素的生理限制分析。 意义——鲸类起源是脊椎动物陆地-水转变的最有记录的例子之一，并展示了几种经历普遍变化的形式-功能复合体。 鲸目动物的游泳从四足划水进化为加宽尾部的背腹摆动，而库尔达纳鲸目动物则表现出中间模式。 鲸目动物祖先的耳朵适应中频空气传播的声音，而现代鲸目动物听到水下的高音（odontocete）或低音（mys ticete）声音。 库尔达纳鲸类的位置尚不清楚，但它们的听觉形态不同于它们的陆地姐妹群和现代鲸类。 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的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沉积学可以阐明从陆地到水的过渡的生态环境。 这项研究对于哺乳动物的高等系统发育具有更广泛的意义。 它将提供形态学数据来测试抹香鲸（odotocete paraphyly）亲缘关系的系统发育以及鲸目动物与偶蹄类（artiodactyl paraphyly）的关系。 这些系统发育假说是在分子数据的基础上提出的，并且受到形态学家的极大争议。 动物区系进化研究表明，印度-巴基斯坦在白垩纪与亚洲接触。 地质数据对这一说法提出了质疑。 这项研究将为始新世古生物学数据提供关键的检验。