PZ Myers. 2005 Jan 13. Repenomamus giganticus. <http://pharyngula.org/index/weblog/repenomamus_giganticus/>. Accessed 2008 Dec 01.

Posted on M00o93H7pQ09L8X1t49cHY01Z5j4TT91fGfr on Thursday, January 13, 2005

Repenomamus giganticus

Echoed on the Panda's Thumb

I'm sure everyone has already heard about the discovery of a dinosaur-eating mammal from the Cretaceous. Here are some photos of the creature from the announcement in Nature.

I'm also sure that the scientifically-literate readers of the Panda's Thumb and Pharyngula won't be terribly surprised by this—the mammal-like reptiles are older than the dinosaurs, and mammals were contemporaries of the dinosaurs. The surprise is that what was discovered was a bandy-legged brute that was relatively large (about the size of your average dog) and was so danged uppity that it had been eating dinosaurs. That's a bit more temerity than had been expected from our long-lost relatives.

Here's the skull of the Cretaceous carnivore Repenomamus giganticus…good strong jaws there.

repenomamus
Holotype of Repenomamus giganticus

And here's the whole skeleton:

repenomamus
The holotype skeleton of Repenomamus giganticus

Repenomamus is the genus, and there are two known species. The big guy above is Repenomamus giganticus, and the other, Repenomamus robustus, is smaller, about the size of an opossum. It's the smaller individual that was found to contain a Psittacosaurus skeleton. It's not certain how the animal acquired this meal, but the authors come down on the side of predation.

It is not easy to assess whether Repenomamus was a predator or scavenger. Scavengers are relatively rare among mammals—among extant carnivorous mammals, only two species of hyenas are habitual scavengers. Compared to their hunting cousins, these hyenas have smaller second upper incisors and less jaw muscle leverage, which probably reflect their inability to capture and handle live prey. In contrast, the enlarged incisors and strong jaw muscles of Repenomamus are well shaped for catching prey, favouring it as a predator rather than a scavenger.
repenomamus
The postcranial skeleton of R. robustus (IVPP V13605). a, Ventral view of the skeleton and its stomach content. Associated partial skull and lower jaws not illustrated. b, Buccal view of lower teeth of the juvenile Psittacosaurus. c, Lingual view of two lower teeth of the juvenile Psittacosaurus. d, e, Close-up view of the stomach content (d) with identified elements highlighted in colour (e). Ca, caudal vertebra; Cl, clavicle; Fe, femur; Fi, fibula; Hu, humerus; Il, ilium; Is, ischium; L1, first lumbar vertebra; Ma, manubrium; Mu, manus; Pe, pes; Ra, radius; St, sternum; T20, twentieth thoracic vertebra; Ti, tibia; Tr1, Tr10, Tr14, first, tenth and fourteenth thoracic ribs; Ul, ulna. Measurements of the juvenile Psittacosaurus (length in mm): humerus, 21; radius, 18; ulna, 19; tibia, 36; and fibula, 35.

As was pointed out in the comments, here is the obligatory reconstruction restoration:

Repenomamus

Hu Y, Meng J, Wang Y, Li C (2005) Large Mesozoic mammals fed on young dinosaurs. Nature 433:149-152.

Posted by PZ Myers on 01/13 at 08:34 AM
Science • EvoDevo • Organisms • 0 Trackbacks • Other weblogs • Permalink
  1. PZ,

    Seeing that several cynodonts were carnivorous and probably active enough to hunt young dinosaurs (eg Cynognathus or probably even Thrinaxodon) is this really all that surprising?

    Even if the above answer is no, you must admit that this is way cool!!
    #: Posted by Michael Buratovich  on  01/13  at  09:58 AM
  2. 1) really not surprising (I mean, we do have role reversals like Komodo dragons eating mammals now, so why not mammals eating dinosaurs?) and 2) way cool fer sure.
    #: Posted by PZ Myers  on  01/13  at  10:18 AM
  3. So which hyena species were they referring to? Aardwolfs eat termites, and spotted hyenas are powerful hunters. That leaves striped and brown hyenas, but a swift google search suggests that both of those hunt small prey in addition to scavenging. Perhaps their smaller jaw muscles and incisors reflect the size of their prey rather than specialization for carrion. If that's the case, are there any mammals that are strictly scavengers?
    #: Posted by  on  01/13  at  10:37 AM
  4. One possiblity that will never occur to the creationists: what if the Chixulub event killed off all the large mammals as well as the remaining dinosaurs, and the world was left to small mammals, reptiles and birds? I think that would be a fruitful line of inquiry to pursue if you could find enough new fossil deposits to fill in some of the blanks.
    #: Posted by Engineer-Poet  on  01/13  at  10:40 AM
  5. Where's the obligatory artist's concept of what the critter looked like as it stole the baby 'saur from the cradle? It appears it would have been quite sleek. Could I get one to deal with the neighborhood dogs? .
    #: Posted by  on  01/13  at  11:09 AM
  6. Richard:

    The NYT has the obligatory pictures. Based on those, the general description of the animal and the conclusion that it "did not chew its food, but swallowed [it] in chunks" I believe they may have found an early precursor of the basset hound.
    #: Posted by  on  01/13  at  12:12 PM
  7. And the link is here:

    http://www.nytimes.com/2005/01/13/science/13mammal.html?oref=login
    #: Posted by  on  01/13  at  12:12 PM
  8. Thanks, NickM. Sort of a wolverine appearance.
    #: Posted by  on  01/13  at  12:37 PM
  9. At least it is not as big as a fox-terrier! What was the exact age? Image looks like late Cretaceous, but...
    #: Posted by coturnix  on  01/13  at  01:10 PM

  10. I’m also sure that the scientifically-literate readers of the Panda’s Thumb and Pharyngula won’t be terribly surprised by this—the mammal-like reptiles are older than the dinosaurs, and mammals were contemporaries of the dinosaurs.


    Except that there weren't any mammal-like reptiles, unless you're using the defunct paraphyletic definition of reptilia. Instead there were mammal-like (in hindsight) early synapsids.
    #: Posted by  on  01/13  at  01:37 PM
  11. Pete: I have a lot of those mammal-like things going off in my head.
    #: Posted by  on  01/13  at  01:45 PM
  12. Two points from a paleontology buff:

    1) The finds date to about 130 Ma (million years ago) which is Early Cretaceous. The painting shows a scene which looks a bit older than that. The vegetation shown is all things like cycads and conifers, whereas flowering plants had originated by the beginning of the Cretaceous (145 Ma) and dominated the vegetation by the end of the period. More tellingly, the bird in the tree is Archaeopteryx or something similar, with its wing claws and long bony tail. Archaeopteryx dates to 150-145 Ma.

    2) A nitpick: PZ referred to the painting as a reconstruction. Strictly speaking, reconstruction is when you look at crushed, scattered fossil bones and attempt to draw them as a complete skeleton. Restoration goes a step further and tries to depict the animal in life with flesh, skin, and behavior. Thus, this painting is a restoration -- but even paleontologists aren't always careful about making the distinction between these two words.
    #: Posted by  on  01/13  at  02:04 PM
  13. Vasha: points well taken.
    #: Posted by  on  01/13  at  04:29 PM
  14. Regarding Nick's question, arctic foxes are seasonally-strict scavengers, following polar bears all winter and scavenging off of their kills. In summer they hunt on their own, however.
    #: Posted by Brian S.  on  01/13  at  07:56 PM
  15. There is something about the look of R. robustus in the painting. They have Chinese eyes. Under an Imperial blue sky.
    #: Posted by  on  01/13  at  11:45 PM
  16. Dear Mr. Myers,

    Your site "Repenomamus giganticus" at http://pharyngula.org/index/weblog/comments/repenomamus_giganticus/ has been chosen as the Illuminated Site of the Week. This award recognizes those websites that, in one way or the other, illuminate the Big Picture . . . that show What Is Really Happening in our newly ordered world.

    We've featured you in today's Daily Illuminator column, which you can reach by visiting http://www.sjgames.com/ill/ You'll also be permanently listed in the Illuminated Site of the Week archives, at http://www.sjgames.com/ill/illsotw/.

    You are welcome to display the Illuminated Site of the Week award logo on your site. You (or your webmaster) can pick up the GIF file by using the following bit of code in your page, wherever you want the image to appear:

    for light-colored backgrounds:

    <center>
    Illuminated Site of the Week Winner
    </center>

    for dark-colored backgrounds:

    <center>
    Illuminated Site of the Week Winner
    </center>

    -Andy Vetromile, Sitekeeper,
    Illuminated Site of the Week
    #: Posted by  on  01/28  at  12:21 AM
  17. Hi. I'm here via the Steve Jackson Games site (Illuminated Site of the Week). Just wanted to say that all this stuff about Repenomamus is fascinating. Just when one thinks a subject has been all worked out, along comes another surprise development ....

    On the matter of scavenger versus predator, I think that there is no real differance. Almost all (if not actually all) predators are not above the equivalent of garbage can raiding - stealing and/or eating things they didn't actually kill.

    Also, predators tend to go for "easy" prey - animals that are obviously wounded, sick or weak. Something, I might add, that scavengers do as a matter of course as well. It might be stretching things to say that there is NO differance between predators and scavengers, but the two may be much closer than we think.

    There is much heated argument in acedemia about whether certain other animals are predators / scavengers. I suggest that a lot of this passion stems from our own prejudices. Predators are seen as dominant and macho. Scavengers are seen as weak and unattractive. Something to consider, anyhow.
    #: Posted by Ian Mackinder  on  01/28  at  06:09 AM
  18. You sjg n00bs might also be interested in a creationist's take on Repenomamus.
    #: Posted by PZ Myers  on  01/28  at  09:08 AM
  19. Why does the reconstruction show repenomamus with those weird, semi-spawling legs? Is it due to the creature's linege, or just bad art? Btw, the painting looks like a lunchtime's labor.

    On a completely different side, muslim creationists are no less dumber than their protestant counterparts. We also get the bs about repenomamus "destroying without doubt, the heresies of evolution" (actual translation).
    #: Posted by memo  on  01/30  at  06:04 PM
  20. Nothing as yet.Send me some information abuot this matter of stories.
    #: Posted by  on  03/02  at  12:40 AM
  21. memo, I think those weird legs are a cultural thing. Just as Romans imagined Jupiter as a XXX size Roman, the Chinese illustrator imagines this animal as a Pekinguese dog with slanted eyes.
    #: Posted by  on  03/02  at  06:26 AM