Tetrapod Zoology

Tet Zoo picture of the day # 16

i-a5c4fe1e9d1c2f419258f83fac3f806f-skull new.jpg

I can’t see that I’m going to have the chance today to post an article, so here’s another picture. Sorry it’s not the best photo in the world. But the question is…

… whose skull is it? Well, I know what it is of course – but do you? Invariably the reaction from laypeople has been that it must be from a dinosaur. But then, I lost count of how many children identified a horse skull as that of a Tyrannosaurus rex at the recent Springwatch festival. And no cheating from those who have seen the exact same photo before! This reminds me – I never gave Adam Yates his prize for being king of the dinosaur nerds and successfully identifying multiple books in Jacques Gauthier’s office. Your prize Adam: an enormous sense of self-satisfaction – well done you!


  1. #1 Jason
    June 20, 2007

    I’ll take a crack at it (although my paleontological/zoological ID skills are very rusty and about 10 years out-of-date) and guess a primitive elephant, like Moeritherium.

  2. #2 Greg Morrow
    June 20, 2007

    Heterodont dentition, single mandible, and synapsid skull openings say mammal. Apparent size and robustness indicate a very large mammal. The zygomatic arch’s extreme robustness tells me that this is probably a guy who does a lot of chewing, but the dentition doesn’t look like it’d stand up to grazing, so this is probably a soft-plant browser. The skull doesn’t appear particularly old.

    Despite not knowing anything about xenarthere dentition, I’m going to guess ground sloth, North America, last interglacial.

  3. #3 Sordes
    June 20, 2007

    This is without any doubt the skull of a big pinniped. It is not an elephant seal, perhaps a sea lion, given the robustness most probably a male of one of the large subspecies, perhaps of a Steller´s sea-lion.
    By the way, even if this is no skull of an elephant seal, have you ever taken a closer look to their dentition? It looks really strange. They have very strange occlusal “bulbs” and shocking incissors.

  4. #4 Sordes
    June 20, 2007

    If it isn’t a Steller’s sea lion, it could be also those of a male shouthern sea lion.

  5. #5 Jan-Maarten
    June 20, 2007

    Just guessing: Some condylarth on it’s way to becoming a whale? (the high nasal opening)

  6. #6 Neil
    June 20, 2007

    It looks like part of the carnivora and is ‘stocky’ so ill guess cave bear

  7. #7 alipio
    June 20, 2007

    perhaps a creodont?

  8. #8 Zach Miller
    June 20, 2007

    It’s not a Steller’s sea lion. We have those up here, and there’s a mounted skeleton at the Seward Sealife Center. Steller sea lions have longer, less robust skulls. I’m going to go with elephant seal.

  9. #9 Zach Miller
    June 20, 2007

    It’s not a Steller’s sea lion. We have those up here, and there’s a mounted skeleton at the Seward Sealife Center. Steller sea lions have longer, less robust skulls. I’m going to go with elephant seal.

  10. #10 Dan Varner
    June 20, 2007

    Just a guess. It looks a bit like the “bear-dogs” like Borophagus and Hemicyon, but it does have a seal-like look to it, too, I must admit.

  11. #11 Carel
    June 20, 2007

    I’m quite sure that’s the skull of a girl I met at the Dead Goat Saloon in July of 1984. Sad that it came to this.

  12. #12 Sordes
    June 20, 2007

    The skull seems not to be fossilized, only a bit unclean, as many older bones are. It has the typical anatomical features of carnivores. The lower jaw is unusual massive as it is only seen in the males of some seals, same thing with the massive lower canines, which are enlarged for fighting. Therefore there are no real carnassials to chew threw flesh, but comparably small and nearly homodont premolars and molars. The opening of the nose seems lesser posterior orientated than in elephant seals, so I suppose it is not an elephant seal.
    I would still say it is some kind of sea lion. There is a huge difference in robustness between males and femalse, and perhaps the mounted skeleton in the Seward sealife centre is from a female or subadult male.The proportions of the skull seems to be more Otariidae-like than Phocidae-like. There is a huge variety of skull shapes between the different subspecies of sea lions, and if we would only know their skeletons, they would surely be seen as different species. There are especially differences in the sagital shape, which can be quite different. Those of southern sea lions seems to be more domed at the posterior part of the skull, without the change from a concave to a convex sagital line which is seen is Steller´s sea lions.
    Fur seals have very different skulls and also much larger orbitas.
    Mediterranean monk seals have also similar looking skulls, but their lower incisors are much lesser robust, as well as the jaws themselves.

  13. #13 Tengu
    June 20, 2007

    whatever it is, it did a hell of a lot of chewing

    not a bear, too big a lower jaw. (I have handled cave bear skulls and Im glad I wasnt born back then.)

    not a seal, skull not doglike. (not sure of sea lions)

  14. #14 Zippo
    June 20, 2007

    Is ithis a kind of bear? What ever it is (or was) it’s certainly seen better days.

  15. #15 Zach Miller
    June 20, 2007

    Well, I’ve done some research, and it’s definately NOT an elephant seal. Elephant seals have recessed nares and lack the orbital bars seen in this animal. Sea lions, however, are a better possibility. This could be a very old, very scary-looking male stellar sea lion. A paper on geographic variation in Stellar sea lion populations is available but I’m unable to get to it. There are apparently several distinct “morphs,” but for here, I’m going to go with generalized “Stellar sea lion” and leave it at that.

  16. #16 David Marjanovi?
    June 20, 2007

    Wow, I came much too late… yes, it must be a seal*. something close to an elephant seal, but I’d expect even more retracted nostrils from an elephant seal.

    But do seals normally have such huge jaw muscles? It’s not just the zygomatic arch — look at that crest at the rear!

    * Synapsid, temporal fenestra continuous with orbit — mammal, tritheledontid, or tritylodontid. The latter two drop out because of the size, the canines, the deep lower jaw, the fused nares, and the teeny tiny premolars. It’s not a bear (those have huge premolars & molars). It’s not a sloth (those have no incisors or canines whatsoever, and bigger premolars & molars). The combination only leaves seals.

  17. #17 Susan
    June 20, 2007

    Looks seal like, judging by the wear on the teeth, a really old seal. Maybe it’s some sort of prehistoric, frozen in the ice cave seal or something. Doesn’t look like a fossil to me anyway. I’d say it’s some sort of male sea lion or fur seal.

  18. #18 sinuous tanystropheus
    June 20, 2007

    A big old male California or Stellar Sea Lion that probably had a toothache. That or perhaps something stranger. There’s rumored to be a cryptid pinniped that’s sort of the northern equivalent of the leopard seal…

    [from Darren: I presume you’re talking about Steller’s sea ape?]

  19. #19 sinuous tanystropheus
    June 20, 2007


    I’m not sure, I’m not really familiar with Stellar or his reports about the Stellar Sea Ape. The cryptid I was referring to I believe was ethnoknown to the Inuit or other northern tribe and had a name in that language. If memory serves it was allegedly dangerous (sort of like the leopard seal) and reportedly could be attracted by going to a specific area and banging on the side of the boat. It would reportedly come to investigate – also very leopard seal-like. I guess its possible that this might have been what Stellar saw. I forget where I read about this, I’ll try to find it and I’ll link something later if I do.

  20. #20 sinuous tanystropheus
    June 20, 2007

    Found it – google “Tizerhuk” and “Pal Rai Yuk”. Reported by Roy Mackal.

  21. #21 Andrés Rinderknech
    June 20, 2007

    The cientific name of this taxa is: Otaria flavescens (one old male).
    Andrés Rinderknecht, Montevideo, Uruguay.

  22. #22 Cameron
    June 20, 2007

    Roy Mackal mentioned those “Northern Leopards Seals” in his Searching for Hidden Animals. IIRC he attached it to myths of the Tizheruk and Pal-Rai-Yűk. Due to its hyper-obscurity and lack of any recent evidence (or much evidence to begin with), it seems like a myth that only coincidentally bears any resemblance to the leopard seal. Interesting idea though.

    I will agree that it appears to be some otariid skull, but more robust than any examples I can find. I wish I could read that tag, I imagine there is an interesting story to go along with this…

  23. #23 Rafael Tosi
    June 20, 2007

    I think It´s an old male of Otaria flavescens (South American Sea Lion)

  24. #24 Stevo Darkly
    June 20, 2007

    I am a rank, rank amateur layperson, so don’t laugh at me … but the heavy lower jaw reminds me of some of the larger mammals of the early Cenozoic. Barylambda? Pantolambda? Titanoides? But others have remarked that the skull looks pretty recent.

    Is it just my ignorance, or is there something weird going on with the pointed flanges sticking out horizontally from the brows?

  25. #25 John Scanlon
    June 21, 2007

    I see a few people have got in before me (including the omnipresent David M, who possibly never sleeps). Certainly a seal; I was thinking Mirounga (elephant seal) but the nasal opening gives no hint of a trunk and there seems to be more of a ‘chin’ than I recall seeing in the South Australian Museum’s specimens, but it’s something on the same scale. I guess that only leaves Steller’s.

  26. #26 ian
    June 21, 2007

    i’m guessing it’s one of those possible hybrid skulls i’ve been reading about, thought to be a cross betwixt a southern sea lion, otaria byronia, and a zalophus californianus. i can’t seem to find a picture anywhere though.

  27. #27 Dave Hughes
    June 21, 2007

    My immediate thoughts were along the same lines as Stevo Darkly above, ie. some archaic Early Tertiary mammal The first name that came to mind was the Palaeocene taeniodont Psittacotherium, which had a massive lower jaw and some whopping great dentures. But now I think there’s no way a 50-million year old fossil could look that fresh, so I’m going with the ‘old male sea lion’ people. I don’t know them well enough to identify the species but the Steller’s and southern South American sea lions seem to grow pretty big so I’ll guess it’s one of those.

  28. #28 johannes
    June 21, 2007

    My guess would be some kind of seal, too. I would have said walrus, but it lacks the tusks.

    Dan, borophagines were canids, and Hemicyon was a bear (see here); so none of them was an amphicyonid or bear-dog in the strict sense. Of course, borophagines, hemicyonids and amphicyonids were all large carnivores that looked somewhat like a cross between a modern dog and a modern bear (or a hyaena in the case of the “classic” borophagines), and they were contemporary with each other, so some kind of competition and interaction between them must have occured.

  29. #29 David Marjanovi?
    June 21, 2007

    (including the omnipresent David M, who possibly never sleeps).

    Heh heh. I rise around midday or later and currently go to bed between 2 and 3 at night… I need 10 hours of sleep per night. You’re in Australia, right?

    The first name that came to mind was the Palaeocene taeniodont Psittacotherium, which had a massive lower jaw and some whopping great dentures.

    Yes, yes, but the tiny premolars only fit a seal.

  30. #30 johannes
    June 21, 2007

    > The first name that came to mind was the Palaeocene taeniodont
    > Psittacotherium, which had a massive lower jaw and some whopping
    > great dentures.

    But the canines and incisors are different: Psittacotherium had chisel-like canines and upper incisors, adapted for cutting and gnawing (the hard enamel was limited to the front of the teeth, thus giving them a self-sharpening cutting edge, like in modern rodents).
    Our animal, on the other hand, has the pointed piercing canines primitive for eucynodonts and retained in carnivores (among others).
    Psittacotherium also had huge upper and lower canines, plus enlarged upper incisors. Our animal, on the other hand, has large lower canines, but the upper canines are of normal size, and the incisors are downright tiny (or worn with age).

  31. #31 Don
    October 25, 2007

    Certainly a sea lion – most likely a southern; if i could see the dentition I could tell immediately if it was a Stellars or not.

  32. #32 Robert Boessenecker
    November 11, 2007

    It appears to be a male southern sea lion skull (Otaria byronia). The single rooted postcanine teeth and supraorbital processes (little bony shelves above the orbit) denote it as an Otariid (sea lions and fur seals).
    Its too large and robust to be a fur seal, true seal, or either new zealand or australian sea lion (Neophoca and Phocarctos).

    Also, not an elephant seal (Mirounga); Mirounga has a “prenarial shelf” (for the proboscis) and much smaller postcanine teeth, and a domed forehead.

    The lack of a sagittal crest excludes it from california/galapagos/japanese sea lion (Zalophus). The slope of the narial region is to gradual for northern/steller’s sea lion. These features, and the extremely robust mandible denote this as a male skull of the southern sea lion.

    The relatively grotesque appearance of the skull is due to the fact that the skull either appears damaged or pathologic (diseased).

    All of the terrestrial carnivores you guys have been mentioning (canids, amphicyonids, ursids, etc.) all have double rooted premolars, which are lacking in this critter; they also lack the enlarged supraorbital processes, which are a synapomorphy of the otariidae.


    [from Darren: thanks for your comments. Please do look at the next article!!]

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