"This is a fantastically complete mammoth skull and in great condition," Monica Bugbee, a member of the project, told CNN about the discovery on Santa Rosa Island.
"It is likely the best-preserved mammoth skull, Columbian or pygmy, to be recovered from the Channel Islands. The size of the skull is quite interesting," she said Wednesday.
What's piqued the scientists about the skull unearthed this week is it's not big enough to qualify as a Columbian mammoth and not small enough to be a pygmy.
The pygmy mammoths, just 4 to 6 feet tall, roamed the island's grass lands and forests during the Pleistocene era, according to the National Park Service, which manages the islands.
"This (skull discovery) opens the possibility that this mammoth was intermediate in size between the two species," Bugbee said. "It could represent a transitional animal, somewhere on the way to becoming a completely dwarfed pygmy mammoth."
The National Park Service and Bugbee's Mammoth Site of Hot Springs, South Dakota, made the discovery.
The U.S. Geological Survey dated charcoal samples next to the skull to 13,000 years ago.
This places the mammoth at about the same time as Arlington man
, believed to be the oldest human remains in North America, found on the very same Santa Rosa Island.
The scientists say one of the questions is whether the humans and mammoths ever coexisted on the island.
"There's a possibility the mammoths died out before humans arrived and it's possible humans caused their extinction, hunted them to extinction," said geologist Dan Muhs of the U.S. Geological Survey.
"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."
The National Park Service reports the mammoth skull, a scapula and a tooth turned up in an eroding stream bank on the 53,000-acre island.
Muhs recorded another rare find: mammoth footprints.
The dig team also consisted of paleontologist Justin Wilkins from the Mammoth Site and retired National Park Service archaeologist Don Morris.
Scientists nicknamed the mammoth Larry to honor their late distinguished colleague, Larry Agenbroad, a world leader in paleontology.