Tetrapod Zoology

Pentaceratops: that’s quite the skull

i-9c8c8eb42017099968a1aa4852c1cec9-OMNH Pentaceratops resize 27-9-2007.jpg

Having spent the better part of the day recovering from the birthday celebrations of last night (and working, of course), I regret that I haven’t had the time to post any of the promised articles (more SVPCA stuff to come next). So here’s a picture of the day: it depicts the incredible mounted Pentaceratops sternbergii skeleton on display at the Oklahoma Museum of Natural History, and comes courtesy of Matt Wedel…

First described by Henry Fairfield Osborn in 1923, P. sternbergii is a deep-snouted chasmosaurine/ceratopsine ceratopsid known only from the Fruitland Formation and Lower Kirtland Formation of New Mexico (for reasons that aren’t yet properly understood, many Upper Cretaceous dinosaur taxa appear to have been strongly provincial (Lehman 2001): they did not occur continent-wide, but were restricted to relatively small geographical areas). For those of you familiar with the idea that the chasmosaurine Torosaurus had the biggest skull of any terrestrial animal, you might be surprised to hear that this is no longer true: the prize now goes to Pentaceratops. The specimen shown here – OMNH 10165, described by Thomas Lehman (1998) – has a total length of about 6.8 m (making it among the biggest of ceratopsians), and a skull almost 3 m long (in the biggest published Torosaurus the skull is, at most, 2.6 m long). Notice how insanely short the tail is, and how far above the back the frill projects. So much more to say, but no time (preparing for a mammal osteology workshop, happening this Saturday): ceratopsids are definitely on the ‘to do’ list, more later.

Refs – -

Lehman, T. M. 1998. A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico. Journal of Paleontology 72, 894-906.

- . 2001. Late Cretaceous dinosaur provinciality. In Tanke, D. H. & Carpenter, K. (eds) Mesozoic Vertebrate Life. Indiana University Press (Bloomington & Indianapolis), pp. 310-328.

Comments

  1. #1 spayced
    September 27, 2007

    look how the feet and spine are placed in this model. it makes the image even more dramatic; traditionally creatures with large heads and small tails have their front shoulders higher than their back shoulders and have really thick necks. this guy has neither. amazing.

  2. #2 Nick Gardner
    September 27, 2007

    In before sauropods were big.

  3. #3 Nathan Myers
    September 27, 2007

    I like the renderings that put enormous eyespots on the crest.

  4. #4 Cameron
    September 27, 2007

    And I wish you a belated happy birthday. Too bad we don’t have a complete skull from Hatzegopteryx to see who wins in the “almost 3 meters” category. Oh how I’d like to write my own book of animal facts and feats; judging by your last comment some Carwardine guy beat me to the punch though, blah. Well, back to toil as usual…

  5. #5 chris wemmer
    September 27, 2007

    What a magnificent beast! Any speculation on the function of that cranial shield? Looks like it could cover most of the vertebral column (if the head is lifted), and that expanded sacral region looks like it shields the pelvic girdle pretty well.

  6. #6 Homie Bear
    September 28, 2007

    That’s beautiful. I remember a lecture in a paleo class once when the prof showed a drawing of a triceratops without a shield- it was contained inside the skin, causing it to be a massive humped animal- I liked that idea because it was so counter to accepted wisdom, but it;s hard to picture that being the case with an animal with such a large skull.

  7. #7 Rajita
    September 28, 2007

    Thank you for that picture. For some reason Pentaceratops became my favorite dinosaur in my school days. This is truly dramatic- exactly the points you mention. Given those hairy plumes reported on the integument of the basal ceratopsian, I wonder if these derived later forms had a such integumental structures like a peacock tail supported by their abbreviated cauda.

    I had a question for you or other experts who frequent this blog. Is the similarity reported between Sapeornis + Omnivoropteryx with the basal oviraptorosaurs real anything beyond the superficial?
    thanks
    R

  8. #8 Emile
    September 28, 2007

    That is one enormous frill, to say the least! The imagination boggles at the thought of how it would look like in real life, colors and all. It does look rather fragile, though.
    So Pentaceratops is the biggest ceratopsian then as well?

  9. #9 Dave Hone
    September 28, 2007

    Ohhhh shiny! I want one!

  10. #10 Darren Naish
    September 28, 2007

    Thanks to all for their comments. A few quick responses…

    Yes, a frill that projects that far above the back makes a mockery of the once-mooted idea that the frill might be submerged in muscle and incorporated into the back. I initially said this in the text, but then removed it as it seemed rude to John C. McLoughlin (who sometimes frequents these parts, so I understand. Hi John).

    What were these frills for? Based on their species-specific shapes and ornamentation, it seems most likely that their primary role was in species recognition and sexual selection, though they may well also have functioned in attack and defence and thermoregulation too. There’s a fairly voluminous literature on this: for starters see Farlow & Dodson (1975), Spassov (1979), Dodson (1996), Sampson (1995, 1999, 2001) and Sampson et al. (1997). The frill did anchor jaw muscles, but not the immense stretching-all-the-way-to-the-rear-margin super-sized-muscles as once proposed.

    And would the skull of the azhdarchid pterosaur Hatzegopteryx have been longer? In the submitted version of an article on pterosaurs, Dave Martill and I suggested that the Hatzegopteryx skull might have been over 3 m long. Our reviewers (one of whom was Eric Buffetaut, the describer of said beast) recommended that we tone this down to less than 3 m: in the final published version it is stated to be ‘at least 2.5 m long’.

    Oh yeah: Sapeornis and Omnivoropteryx. These two are superficially Caudipteryx-like in the skull, but they exhibit lots of other characters elsewhere in the skeleton (in the forelimb proportions, shape of the humerus, scapula and pubic boot, extent of the pubic symphysis, metatarsal and toe proportions, etc.) which make them more likely to be birds. As admittedly appealing as the notion of basal volant oviraptorosaurs is, I think that the burden of evidence indicates that they are birds with Caudipteryx-like skulls. So far as I can tell from discussion, most other theropod workers agree with this.

    Refs – -

    Dodson, P. 1996. The Horned Dinosaurs. Princeton University Press (Princeton, NJ), pp. 346.

    Farlow, J. O. & Dodson, P. 1975. The behavioral significance of frill and horn morphology in ceratopsian dinosaurs. Evolution 29, 353-361.

    Sampson, S. D. 1995. Horns, herds, and hierarchies. Natural History 6/95, 36-40.

    - . 1999. Dinosaur combat and courtship. In Farlow, J. O. & Brett-Surman, M. K. (eds) The Complete Dinosaur. Indiana University Press (Bloomington, Indiana), pp. 383-393.

    - . 2001. Speculations on the socioecology of ceratopsid dinosaurs (Ornithischia: Neoceratopsia). In Tanke, D. H. & Carpenter, K. (eds) Mesozoic Vertebrate Life. Indiana University Press (Bloomington & Indianapolis), pp. 263-276.

    - ., Ryan, M. J. & Tanke, D. H. 1997. Craniofacial ontogeny in centrosaurine dinosaurs (Ornithischia: Ceratopsidae): taxonomic and behavioral implications. Zoological Journal of the Linnean Society 121, 293-337.

    Spassov, N. B. 1979. Sexual selection and the evolution of horn-like structures of ceratopsian dinosaurs. Palaeontology, Stratrigraphy and Lithology 11, 37-48.

  11. #11 Darren Naish
    September 28, 2007

    PS – Emile, Pentaceratops is one of the big boys (up to 6.8 m), but it’s still exceeded in size by both Torosaurus and Triceratops (up to 7.9 m). This data from Lehman (1998).

    PS – I forgot to say that Lehman (1998) argued for the spelling sternbergi rather than sternbergii. I’ve opted to follow the latter as it’s still being used in authoritative sources (e.g., Dinosauria II)… and didn’t we agree previously on Tet Zoo that original spellings should be retained, even if etymologically incorrect? Sigh.

    Ref – -

    Lehman, T. M. 1998. A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico. Journal of Paleontology 72, 894-906.

  12. #12 David Marjanovi?
    September 28, 2007

    and didn’t we agree previously on Tet Zoo that original spellings should be retained, even if etymologically incorrect? Sigh.

    This one isn’t even incorrect. The describer had opted to latinise Sternberg into “Sternbergius” and then take the genitive of that. That’s explicitely allowed (www.iczn.org, somewhere around Article 31… I’m too lazy to look it up right now). It’s only forbidden to have two species whose names differ only in this feature in the same genus; such cases are treated as homonyms.

  13. #13 Laelaps
    September 28, 2007

    First, happy belated birthday, Darren!

    [from Darren: thanks Brian]

    Second, you wrote “Yes, a frill that projects that far above the back makes a mockery of the once-mooted idea that the frill might be submerged in muscle and incorporated into the back.” I actually just had a conversation with a grad student about this the other day; I almost started cracking up when I imagined Torosaurus with a muscular “hump” attached to its frill. Apparently the idea is still around in some paleo/dinosaur classes, unfortunately, as my friend had said they heard it in a “Dinosaurs & Extinction” class at another college.

    Thanks for sharing the photo, though; it’s much more impressive than the isolated skull stuck in the wall at the AMNH.

  14. #14 Brad McFeeters
    September 28, 2007

    Was there ever a paper published discussing the support for the “frill might be submerged in muscle and incorporated into the back” hypothesis? It’s one of those ideas that I’ve been aware of for a while, but I’ve never seen a cite for.

  15. #15 Mark Lees
    September 28, 2007

    Amazing picture. Forget your theropods and sauropods – the really impressive dinosaurs were all ornithischian! Certaopsians being the Creme de la Creme, with stegosaurs as close seconds. Plate 1 in Dodson’s The Horned Dinosaurs sums it up for me – entitled ‘The Meek shall inherit the Earth’ it shows a Triceratops with bloody horns trotting nonchalantly away from corpse of freshly killed Tyranosaur.

    Chris Wemmer notes that “Looks like it could cover most of the vertebral column (if the head is lifted)” – I was thinking similarly, but then wondered if that would in fact be at all practical as a defence. Would the neck actually have been flexible enough to allow it to tilt backward for the sheild to actually cover the back? Also if it was possible, wouldn’t this have resulted in the whole throat region being horribly exposed, which doesn’t seem the most sensible thing to do in the face of a predator.

  16. #16 Zach Miller
    September 28, 2007

    Awesome mount, and happy birthday, Darren! Pentaceratops is among my favorite ceratopsians, certainly moreso than that boring Triceratops that everybody is always talking about. :-)

  17. #17 Nick Gardner
    September 28, 2007

    Please, everyone knows it’s all about centrosaurines when it comes to exciting ceratopsids.

  18. #18 DDeden
    September 29, 2007

    I need a can/bottle opener, think you could downsize that baby?

    Very cool, I keep thinking of saber tooth dinocats leaping down from cliffs and getting impaled.

  19. #19 Nathan Myers
    September 29, 2007

    “Cover[ing] most of the vertebral column” with a shield that has a gaping hole seems a little silly, at first. Still, if it’s protecting against bites, not spears, a hole there might not matter so much. Furthermore, the hole might have been filled in with something lighter than bone, thus technically “soft tissue”, yet tough enough to turn teeth.

    I have to say the little bow tie at the top edge of the frill is just the accent needed to set off such a dominating feature. We still have much to learn from the fashion sense of the mighty dinosaur. (“We” being those of us geeky enough to remain fascinated with TetZoo, natch.)

  20. #20 Dr Vector
    September 29, 2007

    I had the good fortune to be working at the OMNH when this exhibit was going up. The most impressive view in the whole museum* is standing right in front of that thing and imagining four or five tons of pissed-off ceratopsian about to turn you into street pizza.

    *And that’s saying something, coming from me, because the museum also includes a 100-foot Apatosaurus duking it out with Saurophaganax (or Allosaurus maximus, if you prefer).

    A little background on that specimen and on the mount. It was recovered from the San Juan basin by one of J. Willis Stovall’s WPA crews around 1940. And then it spent the next 50 years sitting in jackets. My understanding is that preparation didn’t start until the plans for the new museum building (which opened in 2000) got the go-ahead.

    Because it is such a nice specimen, some of the people involved in planning the exhibits for the new museum had the idea that the skeleton should be mounted in a big box with black walls and a glass front, as if it was a giant beetle in a jewel case. That idea was torpedoed–thank goodness–because it would have kept people from seeing the animal from any angle other than the right side (a problem I’ve addressed elsewhere…). We ran a lot of behind-the-scenes tours through the museum as the exhibits were going up, and everyone’s favorite thing was to stand right in front of the charging ceratopsian.

    I like the mount. A LOT. You can walk about halfway around the mount and you can get right up next to it, too. The muscle attachments on the forelimbs have to be seen to be believed (the hindlimbs are a bit pancaked). But I liked it even more before they put the wall up behind it. It’s nice from the right side, but it was even better from the left. The left forelimb and hindlimb are really widely separated, and the thing looked like it was hauling some serious ass. I wish I had the photos to prove it.

  21. #21 Tengu
    September 30, 2007

    But isnt tricerotops the only one with a `solid` frill? The others had these sensible lightweight ones.
    I think they were used for display.
    (but how do you account for triceroyps being different? did it indeed take an agresssive stance and need the protection?)

  22. #22 bigcitylib
    September 30, 2007

    Dodson’s book has always been a favorite of mine and on the 20th I found a hardcover copy for .99 cents Canadian at a Salvation army store. Kismet or what?

    Also, presumably a marauding predator would be unable to tell a thick from thin frill, so the latter would be useful defensively in THAT respect. I would also think it might also help cushion the first bite.

  23. #23 Just Sayin'
    October 1, 2007

    Maybe it’s just me, but discussions of the armor value of ceratopsian shields seem to miss an important point. Up to three, in fact. It’s not like the “prey” here would just sit still and let the tyrannosaur take its best shot. If I were the predator, I’d be a lot more worried about the effect of all that kinetic energy focused on two or three tiny horn-tips, than about the possibility of busting a few teeth on the shield. It’s hard to be king of the jungle when your intestines are spilling out.

  24. #24 CortxVortx
    October 1, 2007

    I recognized that beast as belonging to SNOMNH as soon as I saw the picture. I lived in Norman for nearly three years, and visited the museum often. Took lots of pictures. One of the great layouts was having the glass-front elevator stop in front of Apatasaurus’ head — on the second floor.

    They sponsored an invertebrate fossil hunt at White Mound, a Devonian formation where the ground cover was 1/3 rocks, 1/3 brachiopods, and 1/3 goat pellets. Look hard before picking up something. Got a half-dozen curled-up trilobites, too.

    Not to mention OU’s great public lectures and horrible parking.

    Three years wasn’t long enough. I miss that town…

    — CV

  25. #25 DDeden
    October 2, 2007

    Do you recall my mention of (small) T rex types in trees (or cliffs)? Wouldn’t the eyebrow horns and frill above be selection against them?
    The frill when set on the back would be hard to bite through to crush the spine or reach the throat.

    In the same way, horns and antlers developed in ungulates (due to elevated-predator selection at water holes) against types of saber toothed cats attacking from the same vantage point. The elk/wapiti has similar eye protection and back protection during the rut, when herding the females takes priority over caution.

    Mario Petronovich theorises that the smilodon specifically jabbed the eyes of it’s prey. The following link does not contradict that (nor do I):

    http://www.nature.com/news/2007/071001/full/071001-2.html

  26. #26 DDeden
    October 2, 2007

    Sorry, my memory lapsed, this is what Mario said regarding saber tooth cats and the linked article:

    “This is perfectly in tune with what I am claiming. That
    sabre-toothed cats were aquatic predators. They would swim after the prey, they would grab it from behind, and bite through eyeballs. Possibly all the way to the brain, or just blind a prey, and then do whatever they want with it in water (in water body of prey isn’t anchored to the ground, so forces aren’t great). Their tooths have to be lateraly compressed, so that they are lateraly elastic, so that they can adjust to various inter-eye distances that various prey has”. — Mario Petrinovich

    I tend to think they ambushed from above first, and only secondarily (possibly a mate) drove their prey into the deeper water to pursue as Mario states.

    DDeden

  27. #27 David Marjanovi?
    October 2, 2007

    Do you recall my mention of (small) T rex types in trees (or cliffs)?

    I don’t, and that’s probably better that way. :-) How would such an animal climb up a tree trunk or a cliff?

    The frill when set on the back

    As you can see above, it wasn’t set on the back, at least not in Pentaceratops. Ceratopsian necks are not very flexible.

    would be hard to bite through to crush the spine or reach the throat.

    That probably isn’t what tyrannosaurs tried to do. It’s more likely they took a huge bite out of, say, the thigh muscles. Why bother killing prey when just immobilizing it is much less dangerous? Wolves attacking bison and lions attacking elephants use the same strategy, except it’s a lot more messy because of their completely pathetic teeth.

    In the same way, horns and antlers developed in ungulates (due to elevated-predator selection at water holes) against types of saber toothed cats attacking from the same vantage point.

    No predator is stupid enough to jump on the head from above, horns or no horns.

    The elk/wapiti has similar eye protection and back protection during the rut, when herding the females takes priority over caution.

    So “the elk/wapiti” is always an adult male? How does it reproduce? :-}

    Mario Petronovich theorises

    No, he doesn’t. He speculates — and his speculations are based on thin air, not on evidence, see below:

    that the smilodon specifically jabbed the eyes of it’s prey.

    The good man is entitled to his own opinions, but not to his own facts.

    - Sabertooths were no better swimmers than any other cat. This is obvious from their skeletons. Not a single extra adaptation for swimming.
    - Do you know what a saber tooth looks like? Not just in a 2D drawing from a side; what it looks like in 3D. Like an ordinary theropod tooth: it’s flattened from side to side, not round in cross-section like mammalian canines usually are, so it has cutting edges, and these edges are serrated, not smooth. Such teeth, which are almost unique among mammals, are not for stabbing. They are for cutting. For cutting throats and limb muscles, probably.
    - For a surviving animal with such teeth, see the Komodo monitor. The only differences are that it has lots of middle-sized ones rather than a single pair of huge ones, and that it can afford breaking or losing them once in a while.

  28. #28 DDeden
    October 3, 2007

    Do you recall my mention of (small) T rex types in trees (or cliffs)?

    I don’t, and that’s probably better that way. :-) How would such an animal climb up a tree trunk or a cliff?

    feathers on forelimbs fulfilled what function?

    The frill when set on the back

    As you can see above, it wasn’t set on the back, at least not in Pentaceratops. Ceratopsian necks are not very flexible.

    Oh, they could not bulk up their shoulders (pangolin-like when bipedal) or bend their head up?

    would be hard to bite through to crush the spine or reach the throat.

    That probably isn’t what tyrannosaurs tried to do.

    Right, because of the frill and horns.

    Perhaps something else did. T rex was highly specialized and ground based, I’d think. I’m thinking of smaller versions, midsize. The same way that a siberian tiger doesn’t usually climb trees but a much smaller clouded leopard does for ambush.

    It’s more likely they took a huge bite out of, say, the thigh muscles.

    Perhaps, but did the ~tops just stand and wait for that?

    Why bother killing prey when just immobilizing it is much less dangerous?

    Was T rex venomous?

    Wolves attacking bison and lions attacking elephants use the same strategy, except it’s a lot more messy because of their completely pathetic teeth.

    Wolf packs and lion prides act as a team, were Rex’s pack animals?
    I thought they were loners.

    In the same way, horns and antlers developed in ungulates (due to elevated-predator selection at water holes) against types of saber toothed cats attacking from the same vantage point.

    No predator is stupid enough to jump on the head from above, horns or no horns.

    From behind.

    The elk/wapiti has similar eye protection and back protection during the rut, when herding the females takes priority over caution.

    So “the elk/wapiti” is always an adult male? How does it reproduce? :-}

    Caribou have similar rack on both male and female. Other deer have racks during their most exposed time, the rut, when their normal caution is reduced to procreate.

    Mario Petronovich theorises

    No, he doesn’t. He speculates — and his speculations are based on thin air, not on evidence, see below:

    that the smilodon specifically jabbed the eyes of it’s prey.

    The good man is entitled to his own opinions, but not to his own facts.

    - Sabertooths were no better swimmers than any other cat. This is obvious from their skeletons. Not a single extra adaptation for swimming.

    Unknown, since soft tissues aren’t known. Tigers can dive if trained.

    - Do you know what a saber tooth looks like? Not just in a 2D drawing from a side; what it looks like in 3D. Like an ordinary theropod tooth: it’s flattened from side to side, not round in cross-section like mammalian canines usually are, so it has cutting edges, and these edges are serrated, not smooth. Such teeth, which are almost unique among mammals, are not for stabbing. They are for cutting. For cutting throats and limb muscles, probably.

    How else could it eat? Yes, it’s teeth were for some kind of cutting. It couldn’t just jab and swallow like a rattlesnake.

    - For a surviving animal with such teeth, see the Komodo monitor. The only differences are that it has lots of middle-sized ones rather than a single pair of huge ones, and that it can afford breaking or losing them once in a while.

    Posted by: David Marjanovi? | October 2, 2007 8:46 AM

    Thanks.

  29. #29 johannes
    October 6, 2007

    > How else could it eat? Yes, it’s teeth were for
    > some kind of cutting. It couldn’t just jab and
    > swallow like a rattlesnake.

    Carnivorous mammals use their premolars – and in some cases molars – to cut meat. Canines, especially those of “sabertooth” form, are for killing prey, self defence or sexual display, not for processing food.

  30. #30 David Marjanovi?
    October 6, 2007

    DDeden, it would make your posts much easier to read if you put <blockquote> in front and </blockquote> behind quoted material.

    How would such an animal climb up a tree trunk or a cliff?

    feathers on forelimbs fulfilled what function?

    Not climbing. And not flying either in such large animals. Apart from that, the only tyrannosaur with preserved feathers so far, Dilong, lacks wing feathers.

    Oh, they could not bulk up their shoulders (pangolin-like when bipedal)

    No. Dinosaur shoulders are in general rather immobile.

    or bend their head up?

    Not much. The first three neck vertebrae are even fused into a single bone to better withstand the stresses of carrying the huge head.

    That probably isn’t what tyrannosaurs tried to do.

    Right, because of the frill and horns.

    It’s not likely they did that to hadrosaurs either. Try crushing a neck of that size.

    Perhaps something else did. T rex was highly specialized and ground based, I’d think. I’m thinking of smaller versions, midsize. The same way that a siberian tiger doesn’t usually climb trees but a much smaller clouded leopard does for ambush.

    Where Tyrannosaurus lived, the next largest predator was Dromaeosaurus, with a total length not much longer than the head of Tyrannosaurus

    It’s more likely they took a huge bite out of, say, the thigh muscles.

    Perhaps, but did the ~tops just stand and wait for that?

    Did you read the post on how lions hunt elephants here a few months ago?

    Was T rex venomous?

    Nope, it used sheer brutality. When you have a gap the size of a non-LCD computer monitor in a leg, you can’t run away, and you can’t run your horns into the predator.

    Wolf packs and lion prides act as a team, were Rex’s pack animals?

    Maybe — a few have recently been found together. But why should that matter?

    No predator is stupid enough to jump on the head from above, horns or no horns.

    From behind.

    Fine — the tyrannosauroids all seem to have been pursuit-and-bite predators, like wolves for example, but unlike leopards.

    Caribou have similar rack on both male and female. Other deer have racks during their most exposed time, the rut, when their normal caution is reduced to procreate.

    You need to consider the question of why most deer species lack antlers except in adult males, and even that only during certain seasons. The usual explanation is sexual selection. What you propose fails to explain the problem altogether.

    - Sabertooths were no better swimmers than any other cat. This is obvious from their skeletons. Not a single extra adaptation for swimming.

    Unknown, since soft tissues aren’t known.

    The soft tissues cannot deviate very much from the skeleton, because that’s where the muscles are anchored and that’s where the stiffness comes from. Just because you haven’t seen the research done in the last 200 years (comparative anatomy) doesn’t mean it doesn’t exist.

    Tigers can dive if trained.

    They still aren’t crocodiles. I think you get my point.

  31. #31 Raymond
    October 6, 2007

    “Wolves attacking bison and lions attacking elephants use the same strategy, except it’s a lot more messy because of their completely pathetic teeth.”

    Yeah, it’s really odd that carnivorans have done so well with such, er, crappy basal mammalian dentation that hasn’t been altered much except for those carnassials.Looking at the hypersharp, hihypsodont teeth of *Thylacoleo*, *Thylacosmilus* and grasshopper mice shows it can’t be strictly because they’re mammals.Even with set adult teeth, entelodonts and mesonychids were somewhat squalodont and ziphodont.It’s one of those mysteries I guess.

  32. #32 johannes
    October 8, 2007

    > Where Tyrannosaurus lived, the next largest
    > predator was Dromaeosaurus, with a total length
    > not much longer than the head of Tyrannosaurus…

    What about Palaeosaniwa?

    > Looking at the hypersharp, hihypsodont teeth
    > of (…) grasshopper mice

    Give them another 5-10 million years (shudder)…

  33. #33 David Marjanovi?, OM
    October 8, 2007

    Good call about Palaeosaniwa. You are probably right: it was bigger than Dromaeosaurus. Still, at maybe 3 m in total length, probably less if the comparisons were based on the Komodo monitor, there’s still a huge gap between it and the 13- or 14-m-long Tyrannosaurus.

    And the grasshopper mice will do us all in as soon as they get the chance.

  34. #34 DDeden
    December 3, 2007

    link

    for information (and a referenced paper) about dense vertebrae bone in sabercats, dense rear limbs in sea otters and densely boned Homo erectus.

  35. #35 David Marjanovi?, OM
    December 4, 2007

    Doesn’t mention the supposedly dense vertebrae of sabertooths, but why aren’t the limb bones and the ribs pachyostotic, and how do you imagine a semiaquatic predator on an ice-age continent?

    Semiaquatic tapinocephalians are not an option either. They are found in pretty dry environments, AFAIK, and don’t show the slightest adaptation to swimming. You explicitely mention in your post that you don’t know much about them — so go learn!

    Look, my thesis supervisor is Michel Laurin, the guy whose lab works on how to tell whether a tetrapod is/was terrestrial, amphibious, or aquatic based on long-bone cross-sections. (A few papers have come out, several more are in the pipeline.) Localized bone thickenings somewhere in the body don’t mean anything. Instead, generally, amphibious tetrapods have very thick bone cortices, and fully aquatic ones have more or less no medullary cavity and spongy bone (osteoporosis) throughout.

    What would a thickened occiput in a diver be good for? The head is heavier than water anyway.

  36. #36 Allen Hazen
    December 4, 2007

    Quote from earlier discussion (DDeden,DMarjanovics):
    You need to consider the question of why most deer species lack antlers except in adult males, and even that only during certain seasons. The usual explanation is sexual selection. What you propose fails to explain the problem altogether.

    —->I remember reading once that deer, even if they have antlers, defend themselves from predators (and/or more generally conduct all combat other than that with rivals in rut) with their hooves. Having “try to kick them if you can’t run away” hard-wired* would be good strategy for most deer most of the time, and (speaking as a designer of limited intelligence) it would add complexity to have to over-ride in the few months of the year that a minority of males have dangerous antlers. There’s an empirical question here: has anyone watched a significant number of predator attacks on antlered deer? What do they do?

    *Metaphor: I’m not suggesting anything about deer brain anatomy.

  37. #37 Cody
    April 6, 2010

    I got to see the thing today and is bigger than it looks

  38. #38 Cody
    April 6, 2010

    I got to see the thing today and is bigger than it looks in pictures and is one of the most magificant creatures that GOD has created

  39. #39 Christopher Taylor
    April 6, 2010

    one of the most magificant creatures that GOD has created

    Personally I’ve always found the Guinea worm to be much more in character.

  40. #40 Hai~Ren
    December 29, 2010

    If you haven’t heard the latest news, this specimen has been described by Nick Longrich as a new species Titanoceratops ouranous, and is the earliest known member of a chasmosaurine clade known as Triceratopsini.