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“San Diego Demonoid”: you mean that dead opossum?

The views expressed are those of the author and are not necessarily those of Scientific American.


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By night, I work as a technical research scientist, writer of papers and so on, but by day I walk the beaches of the world, looking for partially decomposed mystery carcasses and identifying them. Kidding: of course I don’t, but you get the idea – thanks in no small part to the Montauk Monster flap of 2008, I’ve become known as the guy who identifies weird carcasses. In fact, so many queries of this sort come in via email that I don’t have time to blog about them anymore.

On the 1st of February I was emailed by the people at vice.com about a weird mammal carcass they’re calling the “San Diego Demonoid”. Loren Coleman (at Cryptomundo) has since referred to it as the “San Diego Diablo”. I suggest we call it “a dead opossum”, because that’s what it is and it’s nothing special. At least two photos were taken by Dylan Dessureault, the discoverer of the carcass.  I looked at the photos and was mightily unimpressed by the dead Virginia opossum Didelphis virginiana I could see staring back at me. I passed this identification on to my friends in the sceptic community, and indeed Sharon Hill at Doubtful Newsblog and Ben Radford at DiscoveryNews have both covered the opossum identification of the carcass already.

As usual, there are some silly ideas out there: that it might be a dog, raccoon, tapir (!!!), or an escaped mutant from a lab (of course). The term Chupacabra has been used a lot, since it now seems to be a word that people associate with any ugly, long-snouted mammal that has pointed canines. And a popular idea this time round is that it might be a fake or work of art, perhaps composited from the remains of other animals.

I don’t want to be seen to be giving publicity to yet another of those waste-of-time, publicity-seeking “monster carcass” stories, but at the same time I feel it’s worth helping to spread an evidence-based identification of this carcass, since its true identity is so frikkin’ obvious.

Why is the identification “obvious”? The carcass is a mammal with a long, rat-like snout, a rather high number of small incisors, closely spaced premolars with pointed cusps, and especially long, curved upper canines. We can guess from the sand and seaweed (and from Castoro’s shadow and shoe-print in one of the photos) that it’s mid-sized – not tiny, not huge, but something like 60 cm long. Note that, unlike dogs, foxes and so on, it doesn’t have an obvious rhinarium (the area of dark, distinctly textured skin that surrounds the nostrils in such animals). These features all immediately screamed “opossum” to me. Partly this is because I’ve handled opossum skulls and am familiar with their surprisingly big upper canines and high number of incisors (there are five uppers and four lowers for each side) [opossum skull here borrowed from Cryptomundo]. Even the fur looks opossum-like (mammal carcasses typically slough fur after they’ve been decomposing in water for a while, and this explains the naked face). When you add all this to the fact that the Virginia opossum is a common, widespread mammal in California, we have an obvious and uncontroversial identification.

Incidentally, the Virginia opossum isn’t native to California. It was introduced there in about 1910 from Tennessee and swiftly became extremely abundant. There have been numerous other opossum introduction events across the west as well.

For previous Tet Zoo articles on the identification of carcasses, see…

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Banksy 9:42 am 02/5/2012

    Way to spoil all the fun : (

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  2. 2. Cameron McCormick 10:27 am 02/5/2012

    In fact, so many queries of this sort come in via email that I don’t have time to blog about them anymore.
    So apparently before Montauk people who found these carcasses interpreted them as dead mid-sized mammals and moved on with their lives? Truly we are in a golden age of credulity.

    I suggest we call it “a dead opossium”
    Nah, let’s call it an opossum instead :P

    (it’s not native to the state, by the way, but was introduced there from the east)
    You can probably delete this since you state it again more elaborately half a sentence later.

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  3. 3. naishd 10:37 am 02/5/2012

    Cameron: dammit.. I wrote the article at the same time as filling out an overdue tax return form, so I guess my mind wasn’t on the job. And I initially called it ‘demonid’ instead of ‘demonoid’. Anyway, thanks.

    Darren

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  4. 4. TonyB 11:06 am 02/5/2012

    Opossum are native here in Ohio. I cannot remember a day that I haven’t seen a road-killed one, they are that common.
    It amazes me how many people misidentify them even here in their native range.People freak out over the “giant rat” if they see a live one walking around…

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  5. 5. BilBy 12:16 pm 02/5/2012

    I have an opossum skull here by my desk: when I found it I was astonished at the size of the canines. They are undeniably odd-looking beasts – I saw one wandering along the other morning and they always waddle in an uncomfortable way that looks – if you’ll excuse the image – like they have been caught embarrassingly short and filled their trousers. Oh, and please please please let this post bring out the weirdos.

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  6. 6. CaptinCrypto 12:32 pm 02/5/2012

    Weirdos? WEIRDOS?? YOUR’RE THE WEIRDO. This is no opossum. it is a part of the chupacabra plague that is appearing now across large expanses of the USA and soon the world. sCIENTists like Naish are following groupthink and refusing to think about the evidence. Opossum? Ha ha ha ha aha ha. Chupacabra? Like the other chupacabras? I give the evidence.

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  7. 7. Jerzy New 12:59 pm 02/5/2012

    Elementary. Demonoids are never found in places named with “San” or “Saint”, “Holy” or “Salvador”.

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  8. 8. Jerzy New 1:28 pm 02/5/2012

    PS. Darren, want to be famous? Find a decomposing muntjac. Those are the teeth!

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  9. 9. BilBy 1:34 pm 02/5/2012

    Thanks CaptinCrypto!

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  10. 10. vdinets 2:17 pm 02/5/2012

    What is really amazing about this story is that the photos are not sufficiently crappy to make any identification difficult, and there is even something for scale in one of them (albeit unintentionally).

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  11. 11. naishd 3:02 pm 02/5/2012

    Jerzy – indeed I have several muntjac skulls, have long meant to write about them here.

    Darren

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  12. 12. Therizinosaurus 5:59 pm 02/5/2012

    As the owner of thirteen opossum skeletons, I agree the identification’s obvious. I once mounted an example for my room.

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  13. 13. falcon121 6:42 pm 02/5/2012

    Is the rhinarium reduced in opossums or simply unspecialized compared to the rhinarium of a canid? …

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  14. 14. llewelly 11:37 am 02/6/2012

    Virgina opossum not native to CA? That seems surprising to me – I had thought they were found over large areas of the Americas, and had always assumed CA was part of that.

    I’m guessing, based on that, they probably are not native to Washington either. I saw many roadkilled and several live opossums when I lived in Washington. They often looked quite disturbing even though I knew what I was looking at.

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  15. 15. Halbred 2:07 pm 02/6/2012

    Ha! I’m happy to say there’s a ‘possum skull sitting on my desk, and I immediately recognized the rotting carcass’ teeth as matching up. I’m a little shocked whenever I look at it how small the brain cavity is, especially compared to the raccoon skull sitting next to it. Do marsupials generally have small brains for their body size, or is that a ‘possum-specific thing?

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  16. 16. Mike from Ottawa 3:58 pm 02/6/2012

    Darren Naish starring in ‘CSI:Monster’.

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  17. 17. Heteromeles 8:37 pm 02/6/2012

    Speaking of CSI:monster, I’m still trying to figure this one out (the language is Icelandic). I’m thinking robot sub and fake python, but who knows?

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  18. 18. NCSUCSD 9:51 pm 02/6/2012

    Hello everyone,

    I’m from San Diego and have had good luck getting answers to random questions in the comment threads here before, so here goes:

    The other night, walking home from work late, I saw a large owl circling slowly in the sky (making overlapping circles drifting off to one side) while constantly making a slight squeaking noise (like a squeaky wheel). Every once in awhile, it would stop making the noise and briefly drop with wings extending, almost like it was catching something in the air. It reminded me a lot of watching bats and was wondering if this behavior was what it initially appeared to be to me (that is, echolocation). I suspect it was a barn owl from its completely pale underside. It did this for at least 20 minutes, at probably 50-100 feet altitude (it was near the tops of some sizable eucalyptus trees).

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  19. 19. Jerzy New 6:38 pm 02/7/2012

    @naishd
    Maybe put muntjac skulls in places where people litter to scare them of horned demonoids spawning from pollution. ;)

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  20. 20. Disgruntled Katie 6:47 pm 02/13/2012

    Owls do not have echolocation abilities. What they do have is a highly developed hearing that can pinpoint direction and distance with amazing accuracy. They eat mice, squirrels, rabbits, birds, insects, and reptiles. You probably saw the owl eating insects.

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