In case you've mastered the art of finding camouflaged creatures against an impossibly tricky backdrop, we're throwing a new wildlife-related challenge into the mix. Can you guess which animal features in this amazing MRI?

Chances are you've narrowed your hunch down to something within the marine realm (and you're right); however, those impressive orbs might be leading you down the wrong rabbit hole. Deep-sea species have been among the most popular guesses to this riddle, and when we look at creatures such as this googly-eyed squid, it's easy to see why:

Many deep dwellers have evolved oversized eyes to survive in habitats with very little light, but the organism in the MRI is not one of them. In fact, you're more likely to find our mystery character on a local beach than fathoms below the surface. 

University of California Berkeley MRI Facility manager Ben Inglis, who posted the image to Twitter, offers a clue: you're looking at one thin cross-section of a much larger animal. Think of the image as what you'd see if you cut a watermelon in half, then photographed it head-on. The resulting snapshot would feature a flat circle, but the real structure would extend much farther back. The team didn't physically cut their study animal; the MRI did it for them. The scanners can detect such "slices" using a combination of electromagnetic fields and radio waves. 

In a follow-up tweet, Inglis posted an animation that scrolls through many of these slices, which allows us to see more of the mystery animal's anatomy. 

That hefty brain tells us we're probably looking at a mammal – and by the looks of this video, it's one with a well-developed sniffer (note the nasal cavity in the center of the face). 

Still stumped? Here's another clue: this animal has external ears. A marine mammal with a snout-like nose and external ears can only belong to one group...

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[Answer below – scroll back up if you want to keep guessing!]

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"It's a California sea lion, about one year old," says Inglis. The sea lion was sadly euthanised last week after contracting a bacterial infection known as leptospirosis.

The infection, which causes fever, muscle spasms and kidney failure (among other symptoms) is often fatal in sea lions. Affected individuals tend to haul out on beaches, and the disease is easily transmissible to dogs. This is one of the many good reasons to give pinnipeds a wide berth despite their friendly appearance and "sea puppy" nickname. Experts recommend keeping at least 15 metres (50ft) away from any sea lion. As we've discussed before, attempting to rescue or feed these animals is a generally bad idea. 

Inglis and his team are currently preparing to conduct a followup to a 2015 study that linked domoic acid, a neurotoxin produced by the algae that cause red tide, to low memory function in sea lions. Like leptospirosis, domoic-acid exposure can lead to mass sea-lion deaths. Understanding how these bacteria and toxins affect pinniped brain function could help us to mitigate stranding events in the future, so this sea lion's untimely end wasn't in vain.

"This animal crashed fast," Inglis wrote on Twitter. "Domoic acid could have been a complication, but leptospirosis was the main clinical concern."

Whale Quiz Related 2016 04 18

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ht: Live Science 

Top header image: Ben Inglis