Which was the biggest dinosaur? (Answer: it’s complicated)

October 20, 2015

I just gave an answer to this question on Quora, and it occurred to me that I ought to also give it a permanent home here. So here it is.


This is a great example of a question that you’d think would have a simple, clear answer, but doesn’t. In fact, as a palaeontologist specialising in dinosaur gigantism, I have an abiding fear of being asked this question in a pub quiz, and not being able to produce the name that’s written on the quizmaster’s answer sheet.

First, what do we mean by “biggest”? Diplodocus was longer than Apatosaurus, but Apatosaurus was heavier. Giraffatitan was taller than either. Let’s simplify and assume we want to know the heaviest dinosaur.

Second, estimating the masses of extinct animals is incredibly hard even when we have a pretty complete skeleton. For example, the gigantic mounted brachiosaur skeleton in Berlin (which used to be called “Brachiosaurus” brancai but is now recognised as the separate genus Giraffatitan) has been subject to at least 14 estimates in the published scientific literature, as summarised here. They vary from 13,618 kg to 78,258 kg — a factor of 5.75 for the same individual. That’s like looking at a human skeleton and not knowing whether its from Kate Moss or Arnold Schwazenegger. (There are reasons for this and I urge you to read the linked article.)

Third, the big dinosaurs tend to be very poorly represented. Giraffatitan is probably the heaviest dinosaur known from a more or less complete skeleton (though even that is put together from several different individuals) so I could give that as the answer to the hypothetical pub-quiz — though the answer sheet would probably be out of date and call it Brachiosaurus.

Fourth, which individual of a given species do we mean? I said Giraffatitan is known from a more or less complete skeleton. And my best guess is that that individual massed, say, 30,000 kg. But an isolated fibula of the same species is known that’s 12.6% longer than the one in the skeletal mount. That suggest an animal that masses 1.126^3 = 1.43 times as massive as the mounted skeleton — say 43,000 kg. There might be yet bigger Giraffatitan individuals. On the other hand, there is some evidence that Apatosaurus, which is usually thought of as not being so big, might have got even bigger.

Fifth, the very biggest specimens tend to be known from only a handful of bones. A good example here is the titanosaur Argentinosaurus, which is known from several vertebrae and a few limb bones, but not all from the same individual. It’s a good bet that it massed 60-70 tonnes — so maybe about twice as much as Giraffatitan, but much less than the often-cited 100 tonnes. Other, more recently discovered, titanosaurs seem to be in the same size class: Puertasaurus, Futalognkosaurus, Dreadnoughtus and more. They they are hard to compare directly due to the paucity of overlapping material, or at least described overlapping material. (Scientists are working on getting more of this stuff properly described in the literature, which will help.)

But, sixth, the very biggest dinosaurs tend to be apocryphal. There’s Amphicoelias fragillimus, known only from E. D. Cope’s drawing of the upper half of a single vertebra. This may have been 50 m long and massed 80 tonnes; but other published estimates say 58 m and 122 tonnes. We really can’t say from the very poor remains.

So if you get asked this question in a pub quiz, your best bet is to roll a dice, pick an answer, close your eyes and hope. Roll 1 for Giraffatitan, 2 for Brachiosaurus, 3 for Apatosaurus, 4 for Argentinosaurus, 5 for Dreadnoughtus and 6 for Amphicoelias fragillimus. Good luck!

 

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30 Responses to “Which was the biggest dinosaur? (Answer: it’s complicated)”

  1. Matt Wedel Says:

    Good summary, except that on the final d6 roll I’d swap Dreadnoughtus out and replace it with Puertasaurus. Puertasaurus is even more poorly represented than Argentinosaurus but it is at least clearly in the same size class. Right now, there is no compelling reason to think that Dreadnoughtus even deserves consideration: the largest known individual is only ~75% of the linear size of the largest Argentinosaurus (so, ~40% of the mass if scaled isometrically), and although it is not skeletally mature, “not skeletally mature” does not equal “going to more than double in mass”.

  2. DK Fennell Says:

    Mike, you are not suggesting that Cope fabricated the Amphicoelias specimen by using “apocryphal,” are you? (But isn’t that what it literally means?)

  3. Matt Wedel Says:

    No (and no). Most sources give the definition of apocryphal as “of doubtful authenticity”, without necessarily implying fabrication. That’s perfectly appropriate for Amphicoelias. Doesn’t have to be fakery, could be simple mismeasurement or mistaken reporting (the position taken by Woodruff and Foster 2014). The key thing is that the fossil is lost so we can’t verify it, hence the doubtful authenticity.

  4. WarrenB Says:

    Can’t help but think Cope must’ve had one big sofa.

  5. spinodontosaurus Says:

    Is Puertasaurus really that big? I was under the impression that the only preserved dorsal is barely any larger than the corresponding one in Futalognkosaurus, and although Dreadnoughtus is not known from a corresponding vertebrae, the dorsal vertebrae that are known aren’t that much smaller than Puertasaurus’ either.

    Both Futalognkosaurus and Dreadnoughtus would be considerably out-massed by the likes of Argentinosaurus and Alamosaurus, so I would have assumed Puertasaurus would be too.

    The vertebra is very wide, but isn’t that to be expected from a dorsal from the very front of the torso?

  6. William Miller Says:

    What about Bruhathkayosaurus?

  7. Allen Hazen Says:

    Under “Fourth” there is the line “there is some evidence that Apatosaurus,” with a clickable link. Clicked, a page saying “Not found” comes up. Is this a subtle message?

    (Oh. Nice short review of issue. I hope the people it would help find it!)

  8. Mike Taylor Says:

    spinodontosaurus: like I said, it’s complicated :-) Someone should really do a comprehensive review of the claims of the various big sauropods; but this is not that.

    William Miller, yes Bruhathkayosaurus is another important one, but I didn’t want to over-prolong an answer intended for a general and casual audience.

    Thanks, Allen, for spotting the broken link — now fixed.

  9. William Miller Says:

    Was there ever any further news on Bruhathkayosaurus? I remember it was discussed on here 5 or 6 years ago…

  10. Luigi Says:

    The described dorsals of _Puertasaurus_ are about the same size as the corresponding dorsals of _Argentinosaurus_, but those of _Puertasaurus_ have wider diapophyses, which in turn suggests an animal similar in linear dimensions to _Argentinosaurus_, but with a wider torso, and thus, I am inclined to believe that the two are similar in length, but _Puertasaurus_ is slightly more massive.

    _Alamosaurus_ is known from a referred tibia that is around 1.65 meters long, and Scott Hartman estimates that individual to be in the same ballpark as _Puertasaurus_ and _Argentinosaurus_.

    Although _Futalognkosaurus_ and _Dreadnoughtus_ are indeed gigantic, they come up a couple tons behind _Alamosaurus_, _Argentinosaurus_, and _Puertasaurus_. There’s also the Oklahoma _Apatosaurus_.

    My bet on the biggest dinosaur is probably on _Puertasaurus_, _Alamosaurus_, _Apatosaurus_ sp., or the overrated _Argentinosaurus_.

    P.S I don’t know how to italicize on this website, so I’m trying the underscore trick. Forgive me if it doesn’t work properly.


  11. Interesting for a non-specialist. Please change “dice” to “die” (and no need to publish comment).

  12. Mike Taylor Says:

    Bruhathkayosaurus is gone — destroyed in monsoon rains. There are no good photos of the material. We really should write about it properly some time, but every time we start to, we’re overwhelmed with grief.

    Luigi, your list of big-ass sauropods is fine, but for nearly all of them we simply don’t have nearly enough material to make a mass estimate that we can be confident about with a margin of say 50% either way. (Remember we’re not even confident about the mass of the very well represented MB.R.2181.) So I would not be anywhere near as confident as you are in ranking them by size.

    (For italics, bold and suchlike, just use HTML tags.)

    Mark, “dice” or “die”? Although I tend to be a prescriptivist in language use, I think this one has now drifted enough in common parlance that “die” sounds like an attempt to be hyper-correct — like “whom”, another word that I have abandoned.

  13. Matt Wedel Says:

    The described dorsals of _Puertasaurus_ are about the same size as the corresponding dorsals of _Argentinosaurus_, but those of _Puertasaurus_ have wider diapophyses, which in turn suggests an animal similar in linear dimensions to _Argentinosaurus_, but with a wider torso, and thus, I am inclined to believe that the two are similar in length, but _Puertasaurus_ is slightly more massive.

    Yeah, I’m familiar with this argument. But it seems like a big leap from wider diapophyses to wider torso. We know that a lot of sauropods have fairly slab-sided torsos – maybe widening the diapophyses allows the ribs to be more vertical. I don’t know if that would be advantageous or not, I’m just pointing out that it’s a possibility that hasn’t been falsified. Rib geometry is about much more than holding in guts, it also has a lot to do with (and may be primarily driven by) ventilating the lungs and air sacs, and we don’t know what the constraints were on sauropod respiratory systems.

    Anyway, I think it’s a useful cautionary exercise to think of the number of other times that simplistically scaling out from one element of a poorly-known sauropod would have given the wrong answer.

    Bottom line, Puertasaurus *might* have had a wider torso than Argentinosaurus, but maybe is a long way from probably, let alone definitely. And what if the torso was wider, but shorter anteroposteriorly, or less deep dorsoventrally? There’s just too much we don’t know.

  14. LeeB Says:

    How about one that doesn’t get enough discussion.
    Is the Archbishop a large dinosaur comparable in mass to Giraffatitan or Brachiosaurus?
    Or is there not enough material to tell.

    Or do we have to wait for the paper to find out?

    LeeB.

  15. Mike Taylor Says:

    The Archbishop is in the same class as the better known pair of brachiosaurs, but I think a little smaller than both. Not by much. I’ll include my best estimate in the paper, of course … but first I need to figure out a way to make that estimate.

  16. jerrold12 Says:

    Do you have any info as to which giant titanosaur is coming soon to AMNH?

  17. William Miller Says:

    “Bruhathkayosaurus is gone — destroyed in monsoon rains.”

    Well that’s … unfortunate. None of the material was collected then?

  18. LeeB Says:

    Thanks for that Mike.

    @jerrold12: it sounds like the new unnamed titanosaur which they found multiple skeletons of in 2014.

    If they already have enough prepared material to put a skeletal reconstruction together then they must be working fast.

    LeeB.

  19. luigigaskell Says:

    “Yeah, I’m familiar with this argument. But it seems like a big leap from wider diapophyses to wider torso. We know that a lot of sauropods have fairly slab-sided torsos – maybe widening the diapophyses allows the ribs to be more vertical. I don’t know if that would be advantageous or not, I’m just pointing out that it’s a possibility that hasn’t been falsified. Rib geometry is about much more than holding in guts, it also has a lot to do with (and may be primarily driven by) ventilating the lungs and air sacs, and we don’t know what the constraints were on sauropod respiratory systems.

    Anyway, I think it’s a useful cautionary exercise to think of the number of other times that simplistically scaling out from one element of a poorly-known sauropod would have given the wrong answer.

    Bottom line, Puertasaurus *might* have had a wider torso than Argentinosaurus, but maybe is a long way from probably, let alone definitely. And what if the torso was wider, but shorter anteroposteriorly, or less deep dorsoventrally? There’s just too much we don’t know.”

    Hmm, never considered this before. Thanks for bringing it up, Matt!

    I’ve only read the papers for Futalognkosaurus and Puertasaurus , so I don’t know much about the morphology and proportions of Mendozasaurus , so on a scale of slab-sided to “really voluminous and wide ribcage”, where would the Lognkosauria fall on that scale?

  20. Mike Taylor Says:

    Jerrold, no, I have no information about the AMNH’s giant titanosaur plans. If anything, I’d have hoped you would be able to tell us about it!

    William Miller: yes, “unfortunate” about covers it. At some stage, we should pull together all we know about Bruhathkayosaurus and write a blog post about it. I can tell you now that that post, when it comes, will be distressingly short, low on illustrations, and deeply sad.

  21. Mike Taylor Says:

    (Luigi, and anyone else who wants to know: italics in comments on WordPress blogs are done using HTML tags. So it’s <i>italicised text</i>.)

  22. luigigaskell Says:

    I figured it out, thanks so much sir! And thanks for

  23. luigigaskell Says:

    …..putting up with the repeated spam posts of me trying to italicize.

  24. Chase Says:

    Mike, last time I spoke with Mark Norell I asked him about the giant unnamed titanosaur and he assured me it was really darn big. Apparently the AMNH mount is going to measure 122 feet long.
    Here’s a link to a rendering of the skeleton: http://www.washingtonpost.com/video/national/health-science/giant-dinosaur-coming-to-amnh/2015/09/18/cf8ce474-5d83-11e5-8475-781cc9851652_video.html

  25. Matt Wedel Says:

    I’ve only read the papers for Futalognkosaurus and Puertasaurus , so I don’t know much about the morphology and proportions of Mendozasaurus , so on a scale of slab-sided to “really voluminous and wide ribcage”, where would the Lognkosauria fall on that scale?

    Good question. Not sure, although the skeletal recons I’ve seen for Futa show a pretty wide torso. That might be legit – although I doubt the ribs are in good enough shape to be very informative, the pelvis is certainly very wide, with flaring preacetabular blades on the ilia. Presumably those are no wider than the ribcage, and possibly a bit narrower. Would be nice to know from extant animals how well pelvis width correlates with torso width.

  26. Dinophile Says:

    I’ve been very curious. I understand that the specimens of Brachiosaurs, even the largest known ones, come from subadults. Is it possible that the huge four out of five vertebral sacrum that has been named Brachiosaurus nougaredi is just the sacrum of an adult Brachiosaurus altithorax, and that’s how big they really got at full size? Or is it definite that the sacrum is a distinct species of Brachiosaur from Brachiosaurus altithorax?

  27. luigigaskell Says:

    Maybe Scott Hartman could help? He did produce skeletals of Futalognkosaurus and Puertasaurus .
    Would it be reasonable to think that Puertasaurus would have resembled a scaled-up Futalognkosaurus due to phylogenetic proximity?

  28. Mike Taylor Says:

    Dinophile, you are correct that the well-known large specimens of Brachiosaurus (FMNH P25107) and Giraffatitan (MB.R.2181) are both subadult — we can tell because their coracoids are not fused to their scapulae. But we don’t know the ontogenetic status of the rather larger specimen XV2, since it’s only represented by a fibula.

    The “Brachiosaurusnougaredi sacrum is longer than any sacrum known from a brachiosaur (and possibly any other known sauropod sacrum, for that matter, which I think would make it the longest known sacrum of anything.) But (A) it’s very narrow, and (B) it’s not particularly likely to be a brachiosaur, and certainly not Brachiosaurus. It’s overdue a good solid re-study (if it even exists any more — I don’t know its status.)

  29. Mike Taylor Says:

    Luigi, Scott is a fine and very careful artist, but he’s working from the same information as the rest of us. He’d be the first to say that there is nothing in the fossils that can tell us anything about how wide the torso of Puertasaurus. (Well: Matt was first, and now I’m second. But Scott will probably be third.)

  30. luigigaskell Says:

    Yeah. Preservation biases and sh*t. Now I can relate to your PeerJ preprint about it.

    The reason I brought up Scott Hartman was because I remember him on several occasions on both Deviantart.com and http://www.skeletaldrawing.com mentioning that he thinks Puertasaurus was slightly larger than Argentinosaurus. I’ll go look for that source right now.


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