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These skulls are for talking about

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

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Bored? Looking for things to do? No, me neither. But have some fun and look at these skulls — then identify them (taking care to note your identifications in the comments below). And then…

Photo taken at undisclosed location, by Darren Naish.

Photo by Darren Naish.

… see if you can go that extra bit further and say something especially interesting*, since there’s lots of neat stuff going on here that’s worthy of comment. And, come on, not the same old stuff that we’ve all heard a million times before.  And sorry for not saying where the photos are taken. Hey, why not score extra points and see if you can answer that too! If you’ve never registered for comments and want to play, now is the time. I’ll be monitoring comments and will add thoughts once we reach a critical mass (usually 100 comments, but anything over the magic number will be good enough. What’s ‘the magic number’? Well…).

*… about whatever’s depicted in the images, I mean.

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 He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at! 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. Hai~Ren 6:56 am 05/16/2013

    Their synapsid features show that they are from the Synapsida but the dentition features and tremendous cranial ridges show that they are of the Permian gorgonopsian group. It is a shame that there is no scale in the picture becuase this is making the skulls look small, they must really be large and this would show their gorgon identity best. I have done a big study of these animals and know this.


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  2. 2. Dartian 7:16 am 05/16/2013

    Hmm. Caiman skull above, crocodile skull below?

    And sorry for not saying where the photos are taken. Hey, why not score extra points and see if you can answer that too!

    The obvious answer to that would be “In a museum”, but I’m going to go with “In Darren Naish’s apartment”. ;)

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  3. 3. pmurphy98 7:18 am 05/16/2013

    Actually, the features are only convergently reminiscent of gorgonopsians. An easy to mistake to make of course, as these skulls undoubtedly both belong to one of the more derived of ropen lineages.

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  4. 4. Eriorguez 7:31 am 05/16/2013

    I’d say the upper one is a Caimanine; maybe Paleosuchus, but it seems juvenile. As for the lower, I would say Crocodylus (not that it helps much), but the shape of the notch for the large lower tooth is intriguing; looks somewhat broken, and, at least from that angle and to my untrained eye, the lower teeth would be hidden from sight if the mouth was fully closed, which is an Alligatorid character… Or I may be overthinking it.

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  5. 5. Lars Dietz 7:54 am 05/16/2013

    I agree about the similarity to gorgonopsians. However, the arrow on the mandible is absolutely characteristic of the clade Gryphi. Ichthyosaurs, plesiosaurs, and pseudotheropods are excluded for obvious reasons, so the upper one is clearly a basal squamate related to pterosaurs, which explains the similarity to ropens. The lower one, however, is more difficult, I’d say it’s probably a fake, with the lower jaw being probably from a basal hypercarnivorous monotreme, while the rest is from a juvenile cadborosaur.
    As for where the photo was taken, it’s at the Chosonuke Okamura Institute for Creative Paleontology (Nagoya, Japan), as can be seen by the world’s only specimen of a stuffed phytosaur, part of which is visible on the right of the photo.

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  6. 6. Chabier G. 8:11 am 05/16/2013

    Perhaps Alligator sinensis above, and Crocodylus niloticus below?

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  7. 7. ectodysplasin 8:13 am 05/16/2013


    I’d say the upper one is a Caimanine; maybe Paleosuchus

    Paleosuchus should have a palpebral bone. My guess is that you’re looking at Caiman crocodilus.

    The crocodile isn’t a New World croc or a Nile. There’s no large bump on the middle of the snout. I’m going to guess it’s Crocodylus palustris.

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  8. 8. David Marjanović 9:51 am 05/16/2013

    Caiman skull above, crocodile skull below?

    Definitely, but that’s all I can say.

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  9. 9. Heteromeles 11:10 am 05/16/2013

    Gee, and here I was going to guess kaiju scout beasts from the Squamozoic world, coming through a midatlantic rift to scout both sides of that ocean for possible colonization. (Sorry, just saw the latest trailer for Pacific Rim).

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  10. 10. Yodelling Cyclist 12:06 pm 05/16/2013

    Simple, they’re obscure otogenetic morphs of Triceratops.

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  11. 11. greg_t_laden 1:11 pm 05/16/2013

    They are crocs for sure because the lower tooth has a little house it lives in in the upper jaw.

    The one on the bottom looks like a salt water crocodile, Australian.

    The one on the top looks like a juvenile alligator which can’t be right. So maybe an African Dwarf croc.

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  12. 12. r.grant86 2:50 pm 05/16/2013

    The upper skull is a small caiman species and the lower one possibly the american croc C. acutus. Both too big for a African dwarf croc and neither looks like a gator. On the lower skull, the two maxillary and possibly the single mandibular indentation are from being bitten by another croc in “croc youth” Such damage heals very slowly.. Perhaps the teeth stop them from filling in completely. It’s not a gator because the lower 4rth tooth protrudesI suspect Cuba or Central or South America. I think they’re both wild- look too healthy for zoo beasts.

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  13. 13. jwmorenob 2:58 pm 05/16/2013

    OK, I should be working right now, but I cannot resist the temptation.

    The one on top is either a juvenile black caiman (Melanosuchus niger) or a broad snouted caiman (Caiman latirostris). They can be distinguished by the strong facial “canthi” (the crests that run on the surface of the rostrum.

    The second is a species of Crocodylus. Look for example at the lack of overbite and the different shape of the retroarticular process in the back of the jaw. It´s probably a member of the indo-pacific assemblage, as there is a short crest on the rostrum running from the orbit. At least I can say it´s not a salt water crocodile, C. porosus, as the crest does not extend to half the lenght of the rostrum.

    The crocodile (skull at bottom) has something weird on the notch for the 4th mandibular tooth. There is a lesion or postmortem breakage of the specimen (not clear from the photo), that left a circular hole. Also, there are strong pits on the side of the mandible for the maxillary teeth 2 to 6. I have seen similar ones before, but not frequently, so I can´t say how abnormal they are.

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  14. 14. vdinets 4:00 pm 05/16/2013

    I am not very good at this, but just off the top of my head I’d say a black caiman and a mugger. Both were probably around 90-150 cm at the time of death, and it is possible that the caiman had spent some time in captivity, although this is not certain. Also, the crocodile was more likely a female because she was wearing a nose pin or some similar kind of jewelry.

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  15. 15. Yodelling Cyclist 5:02 pm 05/16/2013

    What base is being used for the 100 comments, btw?

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  16. 16. Heteromeles 5:43 pm 05/16/2013

    When are we going to let the Newbies know that these are the New Britain and Papuan species of Ropen? Rather cleanly prepared, actually, given how often those skulls sustain crashlanding damage from being brought down…

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  17. 17. naishd 5:44 pm 05/16/2013

    What base? (re: comment # 15). This base: the article where people were asked to identify a squirrel.

    The funny thing is, I’m about to leave for a conference anyway, so not sure I’ll get to post answers. But keep playing :)


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  18. 18. Heteromeles 6:05 pm 05/16/2013

    Oh yeah, I forgot to add the scientific names. If I recall, the Papuan Ropen is Ignifatuus pseudobscurus, and the New Britain Ropen is Ignifatuus obscuroideus. I know there’s been a lot of revisions recently from Sanderson’s on that group, so I hope this is correct.

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  19. 19. Yodelling Cyclist 6:10 pm 05/16/2013

    From 17:

    I think this is Darren’s way of telling us to amuse ourselves while he’s away.

    I wonder if this is how parenting operates in the Naish household: “Daddy’s going away for two weeks, but in the meantime, here’s a low resolution image of the metatarsal of a holocene tetrapod to amuse yourselves with”.

    This is a joke meant in good humour, I would like to point out.

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  20. 20. Oenitholestes 7:23 pm 05/16/2013

    I’m going to go out on a limb and guess that the bottom skull is a mugger crocodile (Crocodylus palustris)

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  21. 21. JAHeadden 11:24 pm 05/16/2013

    The upper skull is a caiman, on which limb may be hung Paleosuchus palpebrosus; the orbits are exceptionally large, so it’s a juvenile. This also implies the other skull is a juvenile.

    However, most interesting of these is not the premaxillo-maxillary notch for the large fifth dentary crown, or the lack of a seeming bridge that encloses the notch as it penetrates the bones to project through the snout roof, but the lateral mandibular ridge. This ridge marks a transition between the rough, keratinous laterous and ventral surface of the maxilla, and the smoother dorsal surface which was covered in epithelium. This is clear evidence that, as in ornithischian dinosaurs, this “croc” had a large fleshy cheek as in mammals, and was in fact a relative of ornithischians. It may show that crocs and ornithischians are indeed more more closely related than either are to “dinosaurs,” and thus that the theory advanced by Galton in 1969 and 1970 is true: that ornithischians were the origin of birds. But I modify this by showing that the classic position of crocs outside of “classic” dinosaurs is also true, and that ornithischians and birds are, indeed as Heilmann and others suggested, a more appropriate relative to crocodilians. This also firmly places the ornithischian-like and predentary-bearing silesaurids within ornithischians, and that predentary-bearing birds and the rostrally-beaked crurotarsans like Macelognathus and aetosaurs presage the development of the ornithischo-avian jaw. Avian toothlessness is merely a continuation of the trend seen in crocs and ornithischians, and their teeth are so similar!

    (I don’t need to be serious to have fun with these images.)

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  22. 22. r.grant86 3:58 am 05/17/2013

    On 2nd thought, I like the idea of an infection causing the spherical indentation because it is so spherical. It seems likely that an infection might radiate out in all directions I have seen pits persisting from bites, even several in a row correspondng to teeth in the jaw of another gator, but they’ve never been spherical. I wonder if somehow the jaws were held together which might explain the erosion on the dentary, but how would it eat (unless captive)? Jaime’s comment makes me think the caiman could be a juvenile of one of the large Central or South American caimans.

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  23. 23. David Marjanović 8:44 am 05/17/2013

    “Daddy’s going away for two weeks, but in the meantime, here’s a low resolution image of the metatarsal of a holocene tetrapod to amuse yourselves with”


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  24. 24. BilBy 10:59 am 05/17/2013

    I have a, albeit pretty crushed, skull of a juvenile American alligator – it looks pretty similar to the top skull, but the orbits of the skull in the pic look bigger along both axes than in my specimen. Unfortunately the snout in my specimen is pretty damaged. The 2nd skull is a croc but that’s as far as I can go.

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  25. 25. ectodysplasin 11:27 am 05/17/2013

    Wait, that’s not a mugger. That’s C. rhombifer.

    The pits are probably the result of a malocclusion of the lower jaw; you can see additional erosional pics lateral to the teeth of the dentary where the maxillary teeth seem to have been pressing up against the bone. This specimen specifically could have suffered an injury earlier in development or it could have simply been a long-term captive animal (captivity tends to do bad things to jaw and palate growth in crocodilians).

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  26. 26. naishd 5:52 am 05/18/2013

    Thanks to everyone for playing – really love the answers so far (for those who don’t know: lots of in-jokes here that reference stuff from previous Tet Zoo quizzes). Will try and provide some enlightenment later today.

    Soon to leave for the International Pterosaur Symposium in Rio.


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  27. 27. Mahay 9:27 am 05/18/2013

    My first thoughts were black caiman and mugger crocodile. Not really sure why. The first one is obviously a caiman and the black caiman seems to be the most ubiquitous species. With the second, I suppose the size and broadness of the snout were are a clue.

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  28. 28. Mark Evans 9:31 am 05/18/2013

    Similar pits for mis-aligned teeth were described in the “second Westbury pliosaur” by Sasson et al. (2012). Watch out for more on this specimen soon…

    Sassoon JS, Noè LF, Benton MJ (2012) Cranial anatomy, taxonomic implications and palaeopathology of an Upper Jurassic pliosaur (Reptilia: Sauropterygia) from Westbury, Wiltshire, UK. Palaeontology 55: 743–773.

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  29. 29. andrewwright73 11:16 am 05/18/2013

    Quick guess: Yacare Caiman and Cuban Crocodile.

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  30. 30. Gigantala 7:07 pm 05/18/2013

    The former is defenitely an alligatorid of some sort.

    The latter should theoretically be too, but I’m thinking more in the lines of “poser prep”.

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  31. 31. LeeB 1 7:29 pm 05/18/2013

    Darren, have you been using your time machine again.
    And using skulls of juveniles which because of extreme ontogenetic changes don’t look anything like the adult skulls.
    The first is obviously a juvenile Voay robustus; the second a juvenile of a large Crocodylus.
    At first I thought possibly C. anthropophagus or C. thorbjarnarsoni, but then I realised it had to be the big Crocodylus from Socotra Island, the one not yet discovered in this timestream and hence unnamed.
    The one that used to feed on the dwarf elephants and hippos and was their main predator along with the giant eagle that was the real origin of the roc legend.
    When that swooped down and carried off a young elephant it really looked impressive.
    I bet no-one else gets this.


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  32. 32. John Harshman 9:30 am 05/19/2013

    Uh-oh. We seem to have stalled out short of 100, and for this reason only I’ll contribute something. The best I can manage is to be assured that the top skull clearly belongs to Alligatoridae and the bottom one to Crocodylidae. So why do they both (and crodocylians generally) have that odd sculpturing of the bone surface?

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  33. 33. naishd 9:33 am 05/19/2013

    That’s ok, we’re still well over the “magic number”.


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  34. 34. John Scanlon FCD 10:20 am 05/20/2013

    “why do… crodocylians… have that odd sculpturing of the bone surface?”

    (1) It’s a side-effect of the shrink-wrapping.
    (2) The pits are for trapping tooth tips during intraspecific wrassling, so the bitten individual can transmit torque to the biter without getting facial flesh shredded.
    (3) The pits seem to have most of the melanocytes, and probably have important thermoregulatory, cryptic and sensory functions too.

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  35. 35. r.grant86 12:09 pm 05/20/2013

    Socotra Island is south of the coast of Yemen of which country it is a part It is known as the Galapagos of the Arabian Sea due to its unusual flora and fauna. I passed up a trip to it this spring but plan to go next year if the the opportunity is available again.

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  36. 36. JAHeadden 3:06 pm 05/20/2013

    John Harshman @32: Crocodilian facial sculpturing is a result of two things. 1) pitting due to the presence of a pair of types of sensory organs, which are electro and chemosensory in nature and help the animal to detect variance in pressure on either side and their relative strength, so it can detect vibrations in the water, determine their direction and intensity and thus distance, and find prey easily. And 2) Close adherence of the dermal tissues to the skull, which in part benefits (1), and also allows the bone tissue to emphasize ornamentation rather than the dermal tissues by themselves (doing two jobs instead of 1).

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  37. 37. LeeB 1 4:48 pm 05/20/2013

    Socotra is justly famous for it’s plants and less so for it’s animals.
    A lot of offshore islands had interesting fauna before people got to them; whenever palaeontologists look at them they find interesting things.
    Socotra has limestone rocks with caves and I suspect if they were prospected for fossils interesting things will turn up.
    Certainly some of the plants on Socotra look as if they were adapted to being browsed, they only spread out their foliage when they reach a certain height, the Dragons Blood trees being a classic example.
    Also a study of the phytochemistry of some of the plants from there a few decades ago discovered nasty tasting chemicals just like the ones found in their relatives on the mainland; and the plants have survived being browsed by donkeys and camels and goats since people arrived.
    And the islands may be within swimming distance of the mainland by elephants and hippos especially during glacial low sea levels.
    So enjoy your trip; the plants alone will make it worthwhile.


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  38. 38. David Marjanović 8:59 am 05/21/2013

    1) pitting due to the presence of a pair of types of sensory organs, which are electro and chemosensory in nature and help the animal to detect variance in pressure on either side and their relative strength, so it can detect vibrations in the water, determine their direction and intensity and thus distance, and find prey easily.

    …I knew about the pressure receptors. But electro- and chemosensation are news to me, and chemosensation ( = taste!) doesn’t even make sense. Reference, please!

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  39. 39. Yodelling Cyclist 2:11 pm 05/21/2013

    Going off track, I am a little surprised that no animals have a sophisticated method of detecting chemicals through the skin – after all we do have a crude method for doing so (I spilled a little dichloromethane on a glove an hour ago and can still feel the burning!).

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  40. 40. Heteromeles 8:45 pm 05/21/2013

    @38: Don’t catfish have taste buds on their skin? I think some flies might have taste buds on their feet too.

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  41. 41. JAHeadden 4:42 am 05/22/2013

    David: There are probably a few others, but this comes up in the discussion of the domed pressure receptors and their homology. In this case, it’s about sensitivity to salt solution without having to open the mouth.

    Jackson, K. & Brooks, D. R. 2007. Do crocodiles co-opt their sense of “touch” to “taste”? A possible new type of vertebrate sensory organ. Amphibia-Reptilia 28: 277-285.

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  42. 42. Habibi 9:02 am 05/22/2013

    Expanding on my FB comment (sorry Darren, it’s taken me this long to sign up for Tet Zoo!) This photo looks so like a display in the “educational” section of a gift shop in a croc farm or wildlife park; you know, next to the badly-stuffed souvenirs (one of which is visible on the far right, and I bet it has marbles for eyes). I’ll take a stab at the undisclosed location – guessing it’s somewhere that CITES has a regular battle on their hands keeping everyone honest … southeast Asia? Phillipines?

    Top skull – no idea, looks a bit like an alligator. Bottom skull – Crocodylus porosus.
    Both appear to be skulls of juveniles; large eye sockets in relation to the size of the skull, but neither have had the opportunity to develop the “jowly” heavily-boned look of older animals.

    Arrows perhaps point to the diagnostic difference between the two (i.e. visible tooth = alligator, not visible = croc).

    That’s some abscess scar on the lower skull. Or maybe a hole drilled to smuggle diamonds, or drugs, in a badly-stuffed souvenir.

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  43. 43. David Marjanović 9:37 am 05/22/2013

    I think some flies might have taste buds on their feet too.

    Insects often have sensory organs for taste on their feet; but they’re not homologous, AFAIK, to anything vertebrates have.

    I don’t know about catfish.

    In this case, it’s about sensitivity to salt solution without having to open the mouth.

    Huh. Interesting. Thanks for the ref, I’ll try to check it out at some point. I thought crocodile mouths aren’t watertight in the first place (lack of lips)?

    (i.e. visible tooth = alligator, not visible = croc)

    Alligatorids, including caimans, have an overbite: all lower teeth are lingual to all upper teeth. Crocodylids have all teeth in the same “plane”, and the 4th lower tooth is enlarged and visible from the outside.

    (Incidentally, the plesiomorphic condition is to have both the larger 4th lower tooth and an overbite for all other teeth.)

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  44. 44. Raptormimus456 11:55 am 05/23/2013

    The top skull looks like either a juvenile crocodile/alligator or some form of caiman.

    The bottom skull looks much like either a gorgonopsid, a dwarf caiman or some form of juvenile crocodilian.

    My bets on the skulls, I guess, would be a juvenile Crocodylus/Alligator and a Palaeosuchus skull.

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  45. 45. Crown House 5:23 pm 05/31/2013

    @26: ;)

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  46. 46. Heteromeles 10:24 am 06/6/2013

    Well, at least we know how those poor little crocodilians died. They wanted to know what they were, and they kept waiting. And waiting. And waiting. And now only their bleached bones are left. Poor things.

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  47. 47. naishd 10:26 am 06/6/2013

    I haven’t forgotten you, bleached skulls… I just haven’t found the time. Will try and do so tonight.


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  48. 48. Heteromeles 10:40 am 06/7/2013

    Got distracted again? Perhaps you can put this thread to bed with post #49.

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  49. 49. Heteromeles 2:21 pm 06/12/2013

    So the lower one is Crocodylus niloticus because it is living in a state of abject denial?

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  50. 50. Heteromeles 4:22 pm 06/17/2013




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  51. 51. AlexanderBerg 8:34 pm 08/1/2013

    *tumbleweed rolls by*

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