Mammoths are not an unusual find in the Channel Islands National Park, a small archipelago just west of Los Angeles. But a well-preserved mammoth skull recently excavated from a creek bed on Santa Rosa Island left paleontologists scratching their heads, reports Sara Kaplan for The Washington Post.
National Park Service biologist Peter Larramendy found the skull in 2014, dubbing it Larry in his honor, according to a press release. There are several things that remain a puzzle about the find. First, Larry's size is a problem. The skull is too large to belong to the diminutive pygmy mammoth, but too small to fit nicely in with the mainland Columbian mammoth, which stood 14 feet tall. The second sticking point is its tusks. The right one is over four feet long and curls like the tusk of an adult mammoth, but the left tusk is short and sloping like a juvenile.
The scientists have narrowed possibilities down to three: either the specimen is an unusually large dwarf mammoth, a teenage Columbian mammoth or a newly discovered intermediary species—this last option, according to the researchers, is a long shot.
Despite its puzzling origins, the exquisite preservation of the skull makes this an important specimen. “This mammoth find is extremely rare and of high scientific importance. It appears to have been on the Channel Islands at the nearly same time as humans,” mammoth researcher Justin Wilkins says in the press release. “I have seen a lot of mammoth skulls and this is one of the best preserved I have ever seen.”
The skull also brings into question the timeline of when mammoths arrived on the Channel Islands. Researchers believe that Columbian mammoths swam to the islands, which were connected as one mass during the ice ages. The isolation on an island, where there are commonly limited resources, often causes miniaturization of species, a process called insular dwarfism.
The presence of this small skull suggests that there were multiple waves of migration to the island, according to Dan Muhs, researcher with the U.S. Geological Survey. The first wave likely began during the last glacial period about 30,000 years ago and a second during the preceding glacial period roughly 150,000 years ago, he says in the press release. This second wave of migration would have meant that the dwarf and regular-sized mammoth species could have co-existed for some time.
Dating of charcoal found near the skull indicates the mammoth died roughly 13,000 years ago, which coincides with the date of Arlington Man, one of the earliest human remains found in North America, which was also discovered on Santa Rosa Island. They may be related, according to Muhs. “There’s a possibility the mammoths died out before humans arrived, and it's possible humans ... hunted them to extinction,” he tells Paul Vercammen at CNN. “But there's a third possibility that at the end of the last glacial period, mammoths could have been under stress with limited food resources with sea levels rising at the islands. Then the arrival of humans delivered the final blow.”
Scientists may soon be able to answer some of the questions about Larry. The specimen has been covered in burlap and plaster for transport to the Santa Barbara Museum of Natural History where studies of the animal’s teeth will help researchers determine its age and species.