In 1925, Remington Kellogg described a fossil specimen found in California’s Miocene Monterey Formation. He reported that the fossil belonged to the genus Ontocetus, which at the time was an enigmatic tooth taxon but now identifies species with walrus tusks. However, Alexandra Boersma and Nicholas Pyenson, of the Smithsonian’s National Museum of Natural History, have devoted a new study to those fossil specimens and discovered they belong to a new genus of sperm whale.
“The type specimen consists if a partial rostrum, both mandibles, an isolated upper rostrum fragment, and incomplete tooth fragments,” the researchers write in PLOS One. “Although incomplete, these remains exhibit characteristics that, when combined, set it apart morphologically from all other known physeteroids.”
Extant sperm whales are represented by three species: Physeter macrocephalus, Kogia breviceps, and Kogia sima. All three are found throughout the world’s oceans. Physeter macrocephalus is the largest toothed whale, reaching approximately 18 m in length. The Kogia relatives are pygmy sperm whales (Kogia breviceps) and the dwarf sperm whale (Kogia sima), the former reaching 2.7 m in length and the latter 3.5 m.
The reanalyzed fossils are around 15 million years old.
The team bestowed the new name Albicetus oxymycterus to the specimen. Albicetus means “white whale.” According to PLOS, the name was derived from the fossils’ white color, and a homage to Herman Melville’s “Moby Dick.”
The researchers developed a 3-D model of the specimen’s rostrum and mandibles, which weigh around 100 kg. You can play with the 3-D model here. Based on the evidence, the researchers believe the extinct whale would have reached a total length around 6 m.
Further, the researchers said Albicetus boasted large teeth relative to its size. “This find means that, around 15 million years ago when there were a lot of large sperm whales with big teeth like Albicetus, it may have been a moment of peak richness in the number and diversity of marine mammals serving as prey to these whales,” said Boersma.
Albicetus’ menu, the researchers believe, included large prey like marine mammals, such as seals and other smaller whales. Today’s sperm whales predominantly feed on squid.