Don’t believe the hype: Patagotitan was not bigger than Argentinosaurus

August 9, 2017

“But wait, Matt”, I hear you thinking. “Every news agency in the world is tripping over themselves declaring Patagotitan the biggest dinosaur of all time. Why are you going in the other direction?”

Because I’ve been through this a few times now. But mostly because I can friggin’ read.

Maximum dorsal centrum diameter in Argentinosaurus is 60cm (specimen MCF-PVPH-1, Bonaparte and Coria 1993). In Puertasaurus it is also 60cm (MPM 10002, Novas et al. 2005). In Patagotitan it is 59cm (MPEF-PV 3400/5, Carballido et al. 2017). (For more big centra, see this post.)

Femoral midshaft circumference is 118cm in an incomplete femur of Argentinosaurus estimated to be 2.5m long when complete (Mazzetta et al. 2004). A smaller Argentinosaurus femur is 2.25m long with a circumference of 111.4cm (Benson et al. 2014). The largest reported femur of Patagotitan, MPEF-PV 3399/44, is 2.38m long and has a circumference of either 101cm (as reported in the Electronic Supplementary Materials to Carballido et al 2017) or 110cm (as reported in the media in 2014*).

TL;DR: 60>59, and 118>111>110>101, and in both cases Argentinosaurus > Patagotitan, at least a little bit.

Now, Carballido et al (2017) estimated that Patagotitan was sliiiiightly more massive than Argentinosaurus and Puertasaurus by doing a sort of 2D minimum convex hull dorsal vertebra area thingy, which the Patagotitan vertebra “wins” because it has a taller neural spine than either Argentinosaurus or Puertasaurus, and slightly wider transverse processes than Argentinosaurus (138cm vs 128cm) – but way narrower transverse processes than Puertasaurus (138cm vs 168cm). But vertebrae with taller or wider sticky-out bits do not a more massive dinosaur make, otherwise Rebbachisaurus would outweigh Giraffatitan.

Now, in truth, it’s basically a three-way tie between Argentinosaurus, Puertasaurus, and Patagotitan. Given how little we have of the first two, and how large the error bars are on any legit size comparison, there is no real way to tell which of them was the longest or the most massive. Still, to get to the conclusion that Patagotitan was in any sense larger than Argentinosaurus you have to physically drag yourself over the following jaggedly awkward facts:

  1. The weight-bearing parts of the anterior dorsal vertebrae are larger in diameter in both Argentinosaurus and Puertasaurus than in Patagotitan. Very slightly, but still, Patagotitan is the smallest of the three.
  2. The femora of Argentinosaurus are fatter than those of Patagotitan, even at shorter length. The biggest femora of Argentinosaurus are longer, too.

So all of the measurements of body parts that have to do with supporting mass are still larger in Argentinosaurus than in Patagotitan.

Now, it is very cool that we now have a decent chunk of the skeleton of a super-giant titanosaur, instead of little bits and bobs. And it’s nice to know that the numbers reported in the media back in 2014 turned out to be accurate. But Patagotitan is not the “world’s largest dinosaur”. At best, it’s the third-largest contender among near equals.

Parting shot to all the science reporters who didn’t report the same numbers I did here: instead of getting hype-notized by assumption-laden estimates, how about doing an hour’s worth of research making the most obvious possible comparisons?

Almost immediate UPDATE: Okay, that parting shot wasn’t entirely fair. As far as I know, the measurements of Patagotitan were not available until the embargo lifted. Which is in itself odd – if someone claims to have the world’s largest dinosaur, but doesn’t put any measurements in the paper, doesn’t that make your antennae twitch? Either demand some measurements so you can make those obvious comparisons, or approach with extreme skepticism – especially if the “world’s largest dino” claim was pre-debunked three years ago!

* From this article in the Boston Globe:

Paleobiologist Paul Upchurch of University College London believes size estimates are more reliable when extrapolated from the circumference of bones.

He said this femur is a whopping 43.3 inches around, about the same as the Argentinosaurus’ thigh bone.

‘‘Whether or not the new animal really will be the largest sauropod we know remains to be seen,’’ said Upchurch, who was not involved in this discovery but has seen the bones first-hand.

Some prophetically appropriate caution from Paul Upchurch there, who has also lived through a few of these “biggest dinosaur ever” bubbles.

References

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27 Responses to “Don’t believe the hype: Patagotitan was not bigger than Argentinosaurus

  1. arctometatarsus Says:

    I definitely agree that tucking your measurements away in the ESM in a paper where you are making your big point about the size of the animal is a bit… odd.

  2. Matt Wedel Says:

    It invites investigation, and comment. I am happy to oblige.

  3. Kenneth Carpenter Says:

    The hype is because “mine is bigger” sounds better than “yet another the same size or smaller” (yawn).

    By the way, ever notice the “mine is bigger” announcements come from GUYS? Hmmm. Wonder what Freud would say …..

  4. Ian Corfe Says:

    Their main point in calling Patagotitan the largest in the paper seems to be that you can’t estimate mass for Argentinosaurus even from the known femora (“Body mass estimates for giant titanosaurs such as Argentinosaurus [13] and Puertasaurus [14] cannot be calculated using scaling equations due to the absence of limb elements) as they state you need both femoral and humeral circumferences. That’s not really what the Campione & Evans paper says – while humerus or humerus plus femur measurements are best, r2 (r squared, sorry!) regression values of just femoral circumference are very close (femur = 0.979, humerus = 0.986, femur+humerus = 0.988). (And since all of these are better mass estimates than limb length, the fact that femur length seems longer for the circumference in Patagotitan than Argentinosaurus doesn’t really matter since the broken Argentinosaurus femur was clearly longer anyway).

    I guess the reviewers let them off with the statement that you needed both stylopodial limb circumferences to make the scaling equations work…

  5. Ian Corfe Says:

    I should have read the supplementary info properly! They discuss why they think the Argentinosaurus femora can’t be used: 1) there is no femur in the holoype, so other femora can’t be assigned to Argentinosaurus; 2) the shorter but seemingly more complete Argentinosaurus femur used by Benson et al 2014 is fragmentary and heavily reconstructed (“most of it is reconstructed with plaster”) so measurements are not reliable; 3) They say percent prediction error from only femoral measurements is higher than femur and humerus – which is true, but I think you can use it, just with higher error.

    However, I think they also confuse the two specimens by saying the more fragmentary but probably longer femur MLP-DP- 46-VIII-21-3 used by Mazetta et al 2004 is 111cm in diameter, not the 118cm recorded by Mazzetta et al. (Unless they remeasured it as smaller, though it seems a coincidence that if they did the new measurement is the same as the one for the more reconstructed, smaller specimen used by Benson et al 2014).

    I didn’t know the details of the specimens or the assignment of them to Argentinosaurus, so maybe their take on that is fair enough – any thoughts? They do say ‘current data indicates a sauropod with a longer femoral circumference than that of Patagotitan existed in the Huincul Formation’ which to my mind means likely a heavier animal, and it is mass they are using to consider it as the largest.

    I guess this is all quite picky but I’d agree with Matt that it’s cool it’s so well known, but almost certainly not the largest/heaviest even if close…

  6. ijreid Says:

    All this is based on Patagotitan *not* being the same as Argentinosaurus. They do share a lot of similarities, and only 4 features are listed as specifically separating them, with a few character overlap between those and the diagnosis. Compared to “related” lognkosaurians, they both have tall neural spines, not-as-long diapophyses, wide centra and strong hypo-hypa articulations. Possibility, but of course its subjective. If they *are* the same them we would have actually a decent specimen of Argentinosaurus for once …

  7. teddy461 Says:

    But they indicate these Patagotitans individuals were not full grown, which suggest their final size would have exceeded this.

    So in some ways, the hype is deserved ?


  8. ijreid: Given that extant mammal and bird genera have typically lasted 5-10 million years (and occasionally as long as 25 million years), I too wouldn’t be surprised if Patagotitan and Argentinosaurus were congeneric. The age difference isn’t too grand: 102 Ma for Patagotitan, 96-95 Ma for Argentinosaurus. Of course, it all depends whether the two are recovered as sister taxa in future studies

  9. Matt Wedel Says:

    Quickly popping in to address a few things:

    They discuss why they think the Argentinosaurus femora can’t be used: 1) there is no femur in the holoype, so other femora can’t be assigned to Argentinosaurus;

    Feeble. It doesn’t matter what name we attach to the Mazzetta femur, it’s still bigger in circumference. Just because it _might_ not belong to Argentinosaurus doesn’t magically make the Patagotitan femur bigger than that femur.

    2) the shorter but seemingly more complete Argentinosaurus femur used by Benson et al 2014 is fragmentary and heavily reconstructed (“most of it is reconstructed with plaster”) so measurements are not reliable;

    Big deal, it wasn’t the biggest referred femur to start with.

    3) They say percent prediction error from only femoral measurements is higher than femur and humerus – which is true, but I think you can use it, just with higher error.

    And again, this in no way magically makes the Patagotitan femur bigger in circumference than the biggest referred Argentinosaurus femur! It doesn’t matter that that femur doesn’t have a humerus to go with it, the lack of a humerus doesn’t mean that they can gaze into the crystal ball and intuit that Patagotitan’s humerus was enough bigger to overcome the deficit in femur size.

    The big femur referred to Argentinosaurus – whatever it might actually belong to – is bigger than the biggest femur of Patagotitan. Period. Ditto for the vertebral centra. I am still waiting for some form of arm-waving that generates enough airflow to disperse those stubborn facts.

    Oh, and I’ve seen people say that Patagotitan might still have been growing. Well, the same is true for Argentinosaurus. Or at least that possibility has not yet been falsified. It can’t be counted as a win for Patagotitan and a loss for Argentinosaurus.

  10. Jean-Michel Benoit Says:

    So, Matt, what is the consensus? Is P. mayorum the biggest to date? I don’t have access to the paper, I cannot make myself an opinion.. Cheers :)
    (bloddy paywalls..)

  11. Kevin Says:

    Are 60cm measurements for Argentinosaurus and Puertasaurus made on the anterior or the posterior surface of the largest dorsal vertebra?

  12. Ian Corfe Says:

    1 – Name doesn’t matter – agreed. I guess they are saying no named sauropod is bigger (=heavier)!

    2 – Reconstructed femora – agreed also, and I think they have confused the two specimens/measurements too, as above.

    3 – Yep, it comes down to them saying ‘the only way to estimate mass is from a scaling equation with both circumferences or a almost complete skeleton and body outline – all other methods are bad, which means we ignore larger specimens that can’t be analysed with those two methods.

    Growth – someone needs to take a Martin Sander-style drill to the two ‘Argentinosaurus’ femora! Not sure how feasible that is with only 2 vs lots of long bones for Patagotitan…

  13. Shahen Says:

    I make some calculation and estimate total length around 32 m . Especially tail was so long I Think.
    https://www.sendspace.com/file/kih4m7
    What do you think about this?

  14. Matt Wedel Says:

    Are 60cm measurements for Argentinosaurus and Puertasaurus made on the anterior or the posterior surface of the largest dorsal vertebra?

    For Argentinosaurus it is definitely posterior. From Bonaparte and Coria (1993: 5): “The posterior face of the vertebral body shows a marked opisthocoelia, and it measures 47 cm by 60 cm wide.” Not sure about Puertasaurus, it doesn’t seem to be stated in the text. In fact, the diameter of the centrum doesn’t seem to be stated in the text. I wonder if that 60 cm is pulled from the figure. I have some intellectual archaeology to do.

    Aaanyway, here’s a fun game. Why not just compare the surface areas of the centrum faces in Argentinosaurus and Patagotitan? The area of an ellipse is (pi)(r1)(r2). For Argentinosaurus that’s (pi)(30)(23.5)=2210 cm^2. For Patagotitan that’s (pi)(29.5)(21.25)=1970 cm^2. And that’s for the biggest Patagotitan centrum, that of MPEF-PV 3400/5, which has smaller centra both ahead and behind. The Argentinosaurus dorsal has 112% the surface area of the Patagotitan dorsal. If you’re trying to estimate overall size or mass, that seems like a more meaningful comparison that the neural-spine-driven polygon method. Curious that nobody got to it before now.

  15. Matt Wedel Says:

    I make some calculation and estimate total length around 32 m . Especially tail was so long I Think.

    All I know is that the tail in the skeletal recon seems awfully long, with a lot of missing elements. Now, maybe it was that long, but how would we know? I’d like to see it worked out in a convincing fashion. Extraordinary claims and all that.

  16. Kevin Says:

    Thanks for the answer Matt. I was asking that because it seems that the posterior face might be slightly large so that the anterior face of the next vertebra would fit inside it.
    I think Andrea Cau shares the same sentiment that centra size being a good rough estimate for overall weight. I remember him discussing that regarding Tyrannotitan.

  17. Jahn Says:

    So Matt, where does Alamosaurus now fit between said big three – Argentinosaurus, Puertasaurus, and Patagotitan – ? I was under the impression Alamosaurus was second only in size to Agrentinosaurus.

  18. dadler Says:

    The biggest dinosaur ever claim was especially odd considering how many of the articles reporting it massed Patagotitan at 69 short tons, or about the size estimated for Argentinosaurus and plenty of other large sauropods. It feels like there are now dozens of sauropods sized at around as big as Argentinosaurus.

  19. HikaruAmano Says:

    Could it be that Patagotitan mayorum is the ancestor of Argentinosaurus huinculensis? If that is the case, wouldn’t it be more convenient or parsimonious to classify Patagotitan as a second species of Argentinosaurus (A. mayorum)?

  20. Mike Taylor Says:

    A reminder to those who can’t read the paper due to paywalls: Sci-Hub was created precisely for people in your position.

  21. Illiterate Scholar Says:

    Wouldn’t BYU 9024 still make Argentinosaurus, Pataotitan, and whatever else a joke, though? They would still be fighting by a distant second place.

  22. Andrea Cau Says:

    Even Paralititan stromeri humerus is apparently larger than Patagotitan humerus (169 cm vs 167.5 cm). I know humerus length alone is bad proxy of body size, but at least this shows that even in that bone Patagotitan is just another big titanosaur among a well known gang of titans, not a supersized one.

  23. Matt Wedel Says:

    About Alamosaurus and BYU 9024 –

    Embarrassingly, I had forgotten about monster tibia, probably referable to Alamosaurus, described by Rivera-Sylva et al. (2006). The element is incomplete, but the existing bits are 1350mm long together, and the complete element was probably more like 1700mm. That implies a femur in the neighborhood of 2.6 meters, which would narrowly edge out even Argentinosaurus. There is also the big neck at the Perot Museum in Dallas, which probably does not exceed the size of Patagotitan and Argentinosaurus, but is certainly big-league. (Note to self: need to do a post rigorously comparing those verts with other giant sauropod cervicals.) So, yeah, Alamosaurus deserves to be in the conversation.

    About BYU 9024 – if it is Barosaurus, as Mike and I suspect, it’s a monster. As Mike pointed out in this post, it’s twice the length of C9 in AMNH 6341. If that 2x linear multiplier carried through the rest of the animal (and it might not have, neck length seems to be positively allometric among sauropods both through ontogeny and across phylogeny), then the mass would be 8x greater, and even a light 10-tonne AMNH 6341 would imply an 80-tonne BYU 9024. Positive neck allometry and (probably) increased pneumaticity might have reduced that a bit, but it’s hard for me to imagine the animal didn’t mass upwards of 60 tonnes.


  24. […] glasses up nose]…Argentinosaurus was still biggest” tack I’ve taken both in my post yesterday and on Facebook. So let me elaborate a […]

  25. teddy461Ted Says:

    Regarding BYU 9024, Taylor and Wedel (2013) cited Parrish (2006) for the neck growing with an exponent of 1.35, so with a neck twice the size, the rest of the body would still be 1.67 times the linear size and 4.7 times as massive. With the mass of the neck being doubled and the AMNH Barosaurus being at least 12.5 tonnes in mass, we’re probably looking at something around 60 tonnes here.

    So quite a contender but would be a tad lighter than the three south-american titanosaurs discussed here. What do you think Mike ?


  26. […] estimates of other massive (but far less complete) sauropod skeletons — paleontologist Mathew Wedel argues the competition for World’s Largest Dinosaur™ is closer to a “three-way tie” […]


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