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Mike Keesey  

Introducing Mapusaurus

April 4th, 2006 by Mike Keesey :: 11 Comments

(And Papusaurus, and Sonnypusaurus, and Babypusaurus … okay, bad joke.)

Many of us may remember when Tyrannosaurus rex, after 90 years of being The World’s Largest Known Theropod, lost that title to a South American newcomer, Giganotosaurus carolinii Coria & Salgado 1995. And some may recall how, not terribly long after G. carolinii was published, reports began surfacing of an even bigger relative, known from a whole family of individuals, with a full range of ages.

I know I remember, because, as the author of The Dinosauricon, I kept getting questions for years. “I heard about this new theropod even bigger than Giganotosaurus. Do you know if it has been published?” I can’t count the number of times I had to say, “Not yet—these things take time, you know.” I even asked Coria about it in person once, on behalf of those dino-fans.

Well, it’s finally out: Mapusaurus roseae Coria & Currie 2006. “Mapu” is Mapuche (a native language of the Argentinian pampas) for “Earth”. It forms a subclade of Carcharodontosauridae with Giganotosaurus, which the authors named Giganotosaurinae. (Another South American carcharodontosaurid, the awesomely-named Tyrannotitan chubutensis, may also be a giganotosaurine.)

There are at least seven (quite possibly nine) individuals from a bonebed that contains no other identified species. Individuals range in size from 5 to 11+ meters in length. So it’s not exactly bigger than G. carolinii—more like the same size.

And, somewhat unfortunately for M. roseae, all that careful preparation and research delayed the paper just long enough that it’s no longer a contender for The World’s Largest Known Theropod. That title was usurped by a species that has been known a long time, but whose original remains were obliterated in World War II. New remains (dal Sasso et al. 2006) and new study of rediscovered photographs of the holotype (Smith et al. 2006) have affirmed that Spinosaurus aegyptiacus is the Largest Known Theropod. (In other words, Jurassic Park got it right for once.)

So what about all the individuals of different ages together? Was it a family? A pack? Results are inconclusive so far—the authors allow that it may represent “a long term or coincidental accumulation of carcasses”. Nonetheless, the find is quite important for increasing our understanding of carnosaur ontogeny.

(Incidentally, this marks the first time in a while I’ve shown Carney and Carnita with a species that is actually from the same place as them—although M. roseae lived much earlier than Carnotaurus sastrei, in the early Late Cretaceous rather than near the end of the Late Cretaceous.)

References (including link to the Mapusaurus paper in PDF form):

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