Ever since we started tackling marine cryptids (not to be confused with real cryptic species) during our annual Week of Ocean Pseudoscience, people occasionally e-mail me with new “rotting rodent” style monsters. This news story - Behold: The San Diego Demonoid - has been making the twitter and e-mails rounds today. Like the Montauk Monster a few years back, a waterlogged, decomposed critter washed up on a beach, this time in San Diego, and people unfamiliar with what decomposing varmints look like branded it some sort of cryptid. To the right is the uncredited photo (now credited to Josh Menard) that’s been cropping up in various corners of the internet. Like many “cryptic critter” photos leaked to the press, the ones associated with this story fail to show the entire animal or provide any sense of scale. That should be red flag #1 that it is, in fact, a common local resident that is being dressed up to appear more monstrous than it really is.
Now, I’m not a marsupial specialists, but I’ve seen my fair share of possums (Opposums for our non-southern readers) in all states of decay, so those nasty teeth immediately clued me in. Here’s a possum skull (from a Virginia possum) for comparisons:
And here, just for good measure, is a juxaposition of a dead possum’s head on top of the original photograph:
Sorry folks, this one is just an old, waterlogged, partially decomposed possum.
Andrew is a post-doctoral researcher in North Carolina focused on population and conservation genetics in hydrothermal vent communities.



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You say skeptic like it’s a bad thing.
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I’m pretty sure the same critter is the source of the “giant sewer rats” legend in New York City.
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sweet photoshop job you’ve got me sold…
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those teeth of your “possom” aren’t even NEAR the same size Goob!
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Actually, if you look at the skull, they’re exactly the same proportions. And what is a “possom”? Is that anything like a possum?
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is that anything like an opossum?
Actually, as a San Diego resident, I have to disagree with the “lack of scale” statement. While not perfect, anyone who has walked along the beach here knows the “typical” size of the kelp blade and float that washes up. Looking at those bits and then the picture, my initial inference was “medium-small sized dog.”
Sure kelp structures can vary, but take a look at a typical San Diego beach, and you know that your “monster” could be dealt with fairly easily!
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Yeah, I’ve seen hundreds, maybe thousands, of possums in my life, and that is very clearly a possum, sir. Honestly, I don’t see how anyone could think it was anything else unless they’d never seen one before, really.
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You’ve seen thousands of possums? Where do you live, friend? I’ve only seen a few.
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Didn’t you live in SC for, like, 3 years? And NC for 5 years before that? How have you not seen hundreds of possums?
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