When a trio of beaked whales surfaced off Mexico’s Pacific coast, researchers thought they’d found the elusive Perrin’s beaked whale (Mesoplodon perrini), an endangered species that’s never been officially sighted alive. But upon closer inspection, the researchers realized they may have stumbled upon something even rarer — a new species of beaked whale altogether.

On Nov. 17, the research team was sailing aboard the Martin Sheen, a vessel operated by conservation group Sea Shepherd, when they spotted the three beaked whales about 160 kilometers (100 miles) north of Mexico’s San Benito Islands. They managed to capture photos and video recordings of the animals, and also dropped a specialized microphone underwater to record the animals’ acoustic signals.

Beaked whales communicate via echolocation clicks above the frequency of human hearing. But when Henderson and her colleagues analyzed the acoustical data, they found that these whales’ clicks were slightly different from those produced by Perrin’s beaked whales. The whales also appeared to have distinct physical characteristics.

“The Perrin’s beaked whale [has] teeth … right at the end of the rostrum, they’re right at the end of the jaw,” Henderson said. “And so when we started looking at the photos, we realized that the teeth are further back, so they couldn’t be Perrin’s. And then when we started to look at other characteristics, including different color patterns and its size …. it’s like a jigsaw puzzle. Once we started putting all the pieces together, we realized that not only was it not Perrin’s, but it really didn’t seem to match any of the other characteristics of described beaked whales.”

While the scientists say they are “highly confident” they found a new species, they took water samples near the whales in order to analyze the environmental DNA, or eDNA, which Henderson says will help assess whether the beaked whales were definitely a new species.