Waseda researchers discover the world’s oldest true dolphin species – rewrite the known fossil record
Tue, Aug 5, 2014-
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In an article published in the “Journal of Vertebrate Paleontology”, Waseda Department of Earth Sciences researchers (lead author Mizuki Murakami) conclude that the specimen, which was originally categorized in 1977 as Stenella kabatensis, actually belongs to the Eodelphis kabatensis species. This means that true dolphins existed 2 to 7 million years earlier than had been previously suggested by fossil records, and aligns with the results of molecular studies.
This work also includes the most comprehensive analysis yet of the relationships within the group of marine mammals that encompasses toothed whales such as orcas and sperm whales.
Eodelphis kabatensis skull (original by Mizuki Murakami) ©Society of Vertebrate Paleontolog
Eodelphis kabatensis (simulation by Robert W. Boessenecker) ©Society of Vertebrate Paleontology
In another study, Murakami and a team of researchers also described the oldest known dolphin fossil with an asymmetrical skull, and created a new simulation of their evolution.
Diagram of the ancient dolphin’s asymmetrical skull (by Mizuki Murakami)
It has been accepted theory that dolphin ancestors earlier than 10 million years ago all had symmetrical skulls, and that asymmetry was the result of subsequent evolution. This study suggests a different evolutionary path for the marine mammals.
Links
Journal of Vertebrate Paleontology
Society of Vertebrate Paleontology press release
Palaeontological Society of Japan
