Marine mammal experts continue to investigate the death of a dolphin found washed up on Ocean Beach Monday, saying that the beached beast is a relative rarity for the Bay Area.

Marine Mammal Center spokesperson Laura Sherr confirms SFist's report that at least one dead sea lion and a dead dolphin were discovered on the San Francisco beach Monday by a National Parks Service beach patrol team.

Sherr says that teams from the Marine Mammal Center and the California Academy of Sciences responded to the report of adult male bottlenose dolphin at around 2 p.m. Monday, but that "the dolphin was not alive when the rescue team arrived."

The dolphin, which was about 9 feet long and weighs 755 lbs, was loaded into the beach patrol truck for transport to the Marine Mammal Center's Sausalito headquarters. That's where experts performed a full necropsy "to attempt to determine a cause of death and learn as much about this animal as possible," Sherr says.

"We’ll look at every organ. We’ll try to look for signs of disease and we’ll connect samples for studies,” biologist Lauren Rust told CBS5.

“We don’t exactly know, it could be change in prey, change in water temperature. There could be a lot of factors that could change there.”

While the dead sea lion and a deceased elephant seal also spotted that day are fairly common for Ocean Beach, this dolphin is a relative rarity for the Bay Area: according to Sherr, this is only the 12th bottlenose dolphin they've responded to since 1975.

In the other 11 cases, "two in San Luis Obispo County were found alive and successfully relocated, another was treated and released, and the other eight were either found dead or died in treatment" Sherr told the Ex.

According to Golden Gate Cetacean Research co-founder Bill Keener, the dead dolphin is "pretty unusual." He'll be working to determine of this specific dolphin has been spotted before.

“If it’s one of 82 in our catalog, we’ll be able to see where it had been earlier in its life, where it might have spent time hanging out,” Keener told the Ex.

“It would be very interesting to find out more of its life history.”

Previously: Multiple Marine Mammals Found Dead Along Ocean Beach Monday

Lauren Rust, Research Biologist at The Marine Mammal Center, examines the teeth of an adult bottlenose dolphin that was reported stranded on Ocean Beach in San Francisco on July 6, 2015. Photo © The Marine Mammal Center