GIGANTIC SPERM WHALE TOOTH (CF. LIVYATAN) FROM THE MIOCENE OF SOUTHERN CALIFORNIA

A fossil tooth from the middle-upper Miocene Monterey Formation in the Orange County Cooper Center paleontology collection suggests that a gargantuan sperm whale once inhabited the Miocene seas of Southern California. Though difficult to diagnose to genus level based upon a single, incomplete tooth, comparisons with known Miocene physteroid whales provides key insight into the affinities of this fossil. Even though the tip is broken, the entire tooth measures over 250 mm long, and 86 mm in diameter. It has enamel only on the tip of the broken crown, and no enamel coating over the rest of the tooth. The rest of the tooth consists of cementum layers over a core of ossified dentin. It is just slightly smaller than the largest teeth of the largest member of Physeteridae, the South American Miocene Livyatan, a genus that has never been found outside of the Southern Hemisphere. It is also just slightly smaller than similar gigantic teeth reported from South Africa and Australia. Other Miocene members of the family that were relevant for comparisons included Albicetus, Hoplocetus, Scaldicetus, and Zygophyseter, but none have teeth as large as this one. It is bigger than the known specimens of other Miocene physteroid whales, including the other whale from the Monterey Formation, Albicetus oxymycterus. This fossil suggests that giant physteroid whales closely related to Livyatan lived in North America. It represents a substantial geographic range extension for giant physteroid whales, previously known only from the Miocene of the Southern Hemisphere.