page_title: Hans Thewissen
section_title: Discovery of Pakicetus
hierarchical_section_title: Hans Thewissen / Selected works / Discovery of Pakicetus
caption_attribution_description: English: Pakicetus Ambulocetus Skeletons comparison
context_page_description: Johannes Gerardus Marie "Hans" Thewissen is a Dutch-American paleontologist and anatomist.
  Thewissen and co-workers discovered bones of four transitional fossils that show steps in the transition from land to water in whales: Ambulocetus, Pakicetus, Indohyus and Kutchicetus. He also studies modern bowhead and beluga whales in Alaska to learn about their biology and their implications for management and conservation.
  His laboratory investigates morphological adaptations in whale evolution with an interdisciplinary approach involving paleontology, anatomy, embryology, cell biology and imaging.
  He has published more than 100 scientific papers.
context_section_description: Teeth of Pakicetus were first found and recognized as cetaceans by the American paleontologist Robert West in 1980. However, the Kala Chita Hills in Pakistan is a bone bed where cetaceans and other animals were buried together, so anatomical association between different parts is lost, and West was unable to determine which skeleton bones were associated with the teeth.
  Thewissen excavated the site further, discovering hundreds of bones of different mammal species. Whale teeth were by far the most common teeth recovered, and there were no mammals of the same sizes.  This allowed the researchers to identify bones of the Pakicetus skeleton in a preliminary fashion.  They later tested these identification by studying the stable isotopes of the bones, which matched the stable isotopes of the teeth and not those of the teeth of other mammals.
caption: Ambulocetus (on top) Pakicetus Skeletons comparison
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