Paleontological and molecular evidence indicates that early whales are most closely related to artiodactyl land mammals, probably early anthracothere artiodactyls that were close to the ancestry of living hippos. Two stages of Eocene archaeocete evolution are now well known morphologically: (1) an early protocetid stage represented by 47 million-year-old early middle Eocene Rodhocetus; and (2) a generalized basilosaurid stage represented by 37 million-year-old middle-to-late Eocene Dorudon. Field work carried out through 2004 in collaboration with the Geological Survey of Pakistan demonstrates that it is possible to collect well-preserved and virtually-complete skeletons of archaeocete whales from upper Ypresian through Priabonian strata deposited in eastern Tethys and now exposed spectacularly in the Sulaiman Range of central Pakistan. New field and laboratory research proposed here includes three successive annual field expeditions to Pakistan, with two objectives: 1. Recovery and study of articulated skeletons of primitive archaeocetes from 48-50 million-yearold strata of the marginal-marine low-sea-stand Baska Formation of central Pakistan. The hypothesis to be tested is that whales of Pakicetus-grade were terrestrial. Whether the hypothesis is corroborated or not, good skeletal remains from this interval will greatly enhance our understanding of the cetacean transition from land to sea. 2. Recovery and study of articulated skeletons of protocetid-to-basilosaurid archaeocetes from 38- 45 million-year-old strata of the shallow marine upper Domanda, Pir Koh, and lower Drazinda formations of central Pakistan. The hypothesis to be tested is that advanced protocetids like Georgiacetus were fully aquatic and lacked connection of the pelvic girdle to the vertebral column, precluding support of their weight on land. Whether the hypothesis is corroborated or not, good skeletal remains from this interval will greatly enhance our understanding of the transition from foot-powered swimming like that of primitive protocetids to tail-power swimming like that of basilosaurids and modern whales. Field methods to be employed are standard GPS/GIS-enhanced methods, preparation and replication of fossils will take place in a state-of-the-art preparation facility at the University of Michigan, and analysis will involve extensive quantitative description and functional interpretation in comparison with living and extinct semiaquatic mammals. The intellectual merit of this research is recovery of tangible evidence of new morphologically and temporally intermediate stages of early whale evolution that enable assessment of many aspects of adaptation to life in water. Such new evidence is essential for advancing knowledge of early whale evolution and for enhancing our understanding of macroevolution across adaptive zones (in this case in the transition from land to sea). Broader impacts of this project include enhancement of infrastructure for research and education through discovery of new skeletons representing stages of whale evolution that are presently poorly known. The project will provide international research experience for American and foreign nationals. The greatest impact may be enhanced public understanding of evolution through better geological and paleontological evidence for one of the principal evolutionary transitions of wide interest. Whale skeletons collected by previous expeditions are now exhibited in museums, illustrated in textbooks, and discussed in classrooms all over the world.
