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The Pakicetus skeleton reveals several details regarding the creature's unique senses and provides a newfound ancestral link between terrestrial and aquatic animals. As previously mentioned, the Pakicetus' upward-facing eye placement was a significant indication of its habitat. Even more so, however, was its auditory abilities.
Johannes Gerardus Marie (Hans) Thewissen is a Dutch-American paleontologist known for his significant contributions to the field of whale evolution.Thewissen's fieldwork has led to the discovery of key fossils that have shed light on the transition of whales from land to water, including the discovery of Ambulocetus, Pakicetus, Indohyus, and Kutchicetus.
Robert West was the first to identify pakicetids as cetaceans in 1980 and, after discovering a braincase, Phillip Gingerich and Donald Russell described the genus Pakicetus in 1981. During the following two decades, more research resulted in additional pakicetid cranial material and by 2001 postcranial material for the family had been described.
Pakicetus attocki skeleton. Pakicetus had a pelvic bone most similar to that of terrestrial mammals. In later species, such as Basilosaurus, the pelvic bone, no longer attached to the vertebrae and the ilium, was reduced. [62]
Jaw fragments. Diacodexis is the oldest known even-toed ungulate.In life, it would have resembled a modern duiker, measuring about 50 centimetres (1.6 ft) in body length, but with a much longer tail.
The base of the skull is wide compared to other archaeocetes, more like that of modern cetaceans. The narrow infraorbital space, made of primarily the pterygoid processes, also occurs in Remingtonocetus and Pakicetus. The pterygoids connect as far back as the middle ear, much farther than other archaeocetes including the more ancient Pakicetus.
One of the oldest members of ancient cetaceans (Archaeoceti) is Pakicetus from the Middle Eocene of Pakistan. This is an animal the size of a wolf, whose skeleton is known only partially. It had functioning legs and lived near the shore. This suggests the animal could still move on land. The long snout had carnivorous dentition. [73]
When his technician accidentally broke one of the skulls they had found, Thewissen recognised the ear structure of the auditory bulla, formed from the ectotympanic bone in a shape which is highly distinctive, found only in the skulls of cetaceans both living and extinct, including Pakicetus. [3]