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DrScottHartman — Dreadnoughtus - huge, but not the 'hugest'
#dinosaur #longneck #mesozoic #sauropod #skeletal
Published: 2018-06-01 20:41:05 +0000 UTC; Views: 18928; Favourites: 323; Downloads: 0
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Description
Massive props to the authors of the Dreadnoughtus papers, this has to be one of the best documented and figured sauropods of all time, and in quite a short span of time (the specimen was just named four years ago!).Of course what everyone wants to discuss is the size of Dreadnoughtus. The mass has been downsized a few times since the initial description's claim of 59 tonnes; I don't have anything new to add other than what has been said previously (i.e. it wasn't as big as Argentinosaurus, Patagotitan, the Mexico "Alamosaurus" or Puertasaurus).
Length-wise I get 23 meters along the curve of the back, a bit shorter than the 26 meters in the original paper. Most of that is due to my interpreting a large cervical as the 10th rather than the 9th cervical. Doing so has a knock-on effect that shortens the estimate for most of the cervical vertebrae. It's still got a heck of a long neck, even for a titanosaur. I'd be remiss not to point out that there's no way to tell which position is correct at this point - we will need more Dreadnoughtus cervicals to know for certain, but in the absence of any additional data I'm going with the more conservative interpretation.
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Comments: 67
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Why is Dreadnoughtus usually restored with a skull like that of Tapuiasaurus? Was Tapuiasaurus a close relative of Lognkosauria?
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Also, it seems to me like on your skeletal the 11th rather than the 10th cervical looks more similar to the one shown on the paper in terms of elongation.
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The holotype was an adolescent on death.
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And according to yours work, which one will be the heaviest? I mean Argentinosaurus, Alamosaurus, Puertasaurus or Patagotitan? Is possible to check this with GDI?
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I haven't done GDI estimates, and honestly with what is known the error bars would be too big to tell for sure anyhow. But Patagotitan looks almost exactly the same size as my estimate for Puertasaurus (which assumes it's a scaled up Futalognkosaurus), and both have smaller torsos (in side view) than Argentinosaurus, so if they are all equally rotund (which we don't know) I'd assume Argentinosaurus is larger. Scaling my composite adult Alamosaurus isometrically up to the size of the Mexican tibia also puts in in the same ballpark as Argentinosaurus, but again, we don't know enough about the three-dimensional shape of the rib cage to really know which is the largest with any precision.
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I'm happy you did this. It turned out very elegant.
I've wondered many times if sauropods could have had a partly scaly and partly pachyderm skin, like tortoises have.
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Which one was the one that was said to be the biggest sauropod with the best fossil material, this or Patagotitan? I thought it was Dreadnaughtus, but maybe not...
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It was said about both. First for Dreadnoughtus in 2014 (though subsequent papers have challenged the size claim) and more recently for Patagotitan. Both have significant portions of the skeleton known, though neither are known from a single articulated specimen - Dreadnoughtus is known from two specimens, while Patagotitan is known from several. It's easier to cross-scale elements in Dreadnoughtus, and for now at least Dreadnoughtus is described in much greater detail.
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Would that tail really be long/heavy enough to keep it from tipping?
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What Majestic says - note for example that brachiosaurs had even shorter tails. In all likelihood the animals would not have fallen over even if their tails were surgically removed. The tail is less for balance in quadrupeds than it is an anchor for the most important leg retraction muscles.
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The neck is much lighter than it seems because its density is low. Most of the animal's mass is located in the torso, which is probably a lot heavier than tail and neck put together.
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You guys ever just think “Woah these creatures were real, I am walking on the same planet as giants did millions of years ago.”
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I tend to have those feelings of reverie in the field more than when I'm working on reconstructions, but it's certainly an experience I've had more than once.
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Dreadnoughtus certainly lives up to its name: "fearer of nothing".
Not the biggest guy, but a dino that will give you a run for its money. Kudos to the love of sauropods!
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Yeah, it's a great name, and it's hard to imagine that full grown adults (of which these two specimens were not!) would have had much of anything to fear.
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This Taxon and Patagotitan truly deserve your touch, they are fairly complete and good described by giant titanosaur standard.
Truly a Great work!
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Thanks. Patagotitan is a WIP, though it's not figured nearly as well (yet) as Dreadnoughtus is.
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I completely agree! Also, I can't wait for his touch on Argentinosaurus!
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Already done, just waiting for when it can be set loose.
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Cool! By the way, does Patagotitan's description change anything for the other lognkosaurs? I mean, are your Futalognokosaurus and Puertasaurus as good as always, or updates need to be made? What about Argentinosaurus? Did Patagotitan's material help you make up for the poor preservation of Argentinosaurus?
I'm asking this because, if I recall correctly, a recent analysis put Patagotitan extremely close to Argentinosaurus.
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It was actually the Patagotitan description itself that found it to be a sister taxa with Argentinosaurus (things that make you go hmm....). It hasn't required me to alter my Futalognkosaurus skeletal yet (though I'll probably swap in a more Antarctosaurus/Bonitasaura skull for it soon), but it will almost certainly influence my Argentinosaurus - at the very least, I will probably have to shorten the tail.
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Oh, yes. That's correct.
That's good to know. I like your Futalognkosaurus.
It's funny that you may have to shorten the tail because a few new Argentinosaurus skeletals (that use Patagotitan as a guide) are assuming the opposite. Some think Patagotitan may have had an extremely long tail and the same is being applied to Argentinosaurus.
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Yeah, but the actual fossils (and the published measurements) provide no support for that idea. The caudals are actually really quite small, very similar to Dreadnoughtus in their scaling in fact. The only way you can make the tail long is to assume (without evidence) that Patagotitan added way more caudals like diplodocids (and looking at the skeletal, added a whole lot of mid-caudals rather than distal caudals). Almost like making the animal as long as possible was important...
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Would you have a clue how the mounted skeleton ended up so freakishly big? Even with the odd 15 cervical count (against Futalognkosaurus with 14 in a fully complete neck) and taking for granted the huge tail of the mount, the measurements still fall way short of the reported 122 feet (and that's with me assuming the caudal measurements were excluding the condyle, which I now think was a mistake).
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I wouldn't take the 122 feet claim at face value, since the mounted skeleton of Sue is claimed to be 42 feet (12.8 m) long by the Foeld Museum, but we know since Hutchinson et al. (2011) that it's actually 12.3 m long. I wouldn't say anything about the size of the mounted skeleton of Patagotitan until we (maybe) get a peer-reviewed paper about it's length like in the case of Sue, and like in the case of the mounted Argentinosaurus skeleton from Museo Carmen Funes.
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The mounted skeleton of Sue can be 12.8 m long, however. That's what you get measuring along the top of the spines instead of the centra, which is probably easier to do in a mount, though less accurate (I'd guess it's also why the BHI Stan is listed as 12.2 m instead of the 11.8 of Hutchinson 2011). But yes, I've given up on using the Patagotitan mount as reference for anything.
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How it would be 12.8 m long along the top of the spines if the skeletal of Franoys is a few centimeters longer than the mounted skeleton along the centra, but even the skeletal of Franoys isn't 12.8 m along the top of the spines?
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It changes depending on the pose/articulation, that's why it's less reliable than along the centra. I think Scott's Sue is also 12.8 m along the top of the spine.
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I don't have any inside information on how the Patagotitan mount was put together, but in general most of the work done on any mount is done by non-paleontologists, with professional input only at certain stages. This almost always results in compromises (I oversaw about two-dozen mounts at the Wyoming Dinosaur Center, and I believe in general they are more accurate than 95% of other mounts out there, but every single one of those still has compromises that had to be made due to the realities of the material preserved, reconstruction or distortion, and simply the physics of hanging bones or bone replicas in the air).
Putting up the WDC Supersaurus may be extra-relevant though: We got a not-insignificant part of the funding for that project by putting the mount and the fossils in a temporary display in another country, and we were required to get a scientific description of the specimen out before it went up, meaning we were both under a deadline and subject to some outside pressure - perhaps not unlike the Patagotitan mount and description process. As a result some of the bones were not 100% prepped at the time of description, but perhaps more to the point we got pressure from various people (media, backers, and even some internal dissent) to make the tail of our Supersaurus mount look more like Diplodocus (rather than like Apatosaurus). Now I don't want to sell the backers short, they didn't want to do anything inaccurate, they just wanted to make sure we weren't underestimating anything, if you get my meaning. Once I made it clear that fossil evidence could not support a Diplodocus-like tail (and that I was really sure, even if we only had a dozen or so caudals) it was dropped. Yet even after this a subcontractor offered to make an extra 6 feet of whiplash, because "who knows how many there were??". (FWIW, that didn't get put on the mount either)
How easy would it be to simply not chase down these arguments, or for a scientific advisor who doesn't specialize in functional anatomy to just say "I guess we don't really know" and let them take the larger estimate? For that matter , how often are some of the details not even get brought up with a scientific advisor - you need to make a hundred decisions a day on these projects, and sometimes people don't do a good job of deciding which ones they need to ask about. Just remember that mounts are not literal representations of extinct animals, they are part heuristic tool and part sculpture - at their best best they may capture much about the animal they are based on, but even in ideal situations there are always compromises, and in less-than-ideal situations (say 90% of the time) those compromises can add up pretty fast.
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Titanosaurs definitely did go the way of elongating their tails with more caudal vertebrae. The more derived the titanosaur the more numerous the caudal vertebrae, depending what branch. An unnamed abstract taxon ("Rincon titanosaur") has a complete tail of 65 caudals, Tangvayosaurus has a complete tail of 60, Epachthosaurus preserves 41 and probably didn't have many more than that, Opisthocoelicaudia preserves 35 and probably doesn't have many more, Dreadnoughtus here preserved 33 last I counted and is missing a handful, and Alamosaurus preserves 30 but had at least a couple more. Malawisaurus preserved 35 but is missing many caudals, around 50 would probably be more likely. [Added on: the Patagotitan mount has 65 caudals, which isn't an unreasonable number]
A thing to note is that even thought caudal number changes the tails aren't getting significantly longer, the caudals are just becoming smaller and more numerous. Except in the Rincon titanosaur I'm not sure about their proportions but 65 caudals is a very large number compared to 40.
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Aside from the (unpublished) Rincon titanosaur, titanosaurs are generally considered to have fewer vertebrae than in any other sauropod group. Typical sauropod vertebra counts are in the 40s or 50s (Shunosaurus: 44; Camarasaurus: 53), whereas titanosaurs are generally considered to have had no more than around 40.
Tangvayosaurus doesn't have a complete tail that I'm aware of. According to the original description, only 38 caudal vertebrae are preserved--and it's apparently only missing a few anteriormost and posteriormost caudals. It also isn't a titanosaur sensu stricto, so a caudal count on par with the 53 caudals of Camarasaurus would seem reasonable. The Epachthosaurus specimen UNPSJB-PV 920 only preserves 29.
The posteriormost preserved caudals of Epachthosaurus, Opisthocoelicaudia, Dreadnoughtus, and Alamosaurus are all very small and lack well-developed neural spines or anything, and are from around Cd30. The Patagotitan mount doesn't reach this condition until around caudal 60, well exceeding the number of "middle" caudals found in any sauropod, and even worse considering the apomorphically short tails of most titanosaurs!
The FMNH Patagotitan cast has 70 caudals, unless I miscounted last time I was there. This exceeds the alleged count in the Rincon titanosaur, and far exceeds the known or likely caudal count in every other sauropod except diplodocoids.
Finally, the translation I've read of the first Calvo et al. abstract describing the Rincon titanosaur makes it sound like the caudal count is uncertain ("We anticipate the total number of caudal vertebrae was 65"). Even if it did have 65 caudals, this number is clearly an apomorphic increase relative to the ~50 caudals of non-titanosaur sauropods and the ~40 caudals estimated for other titanosaurs, and in the absence of clear evidence of its phylogenetic position (the second abstract merely says it had similar proportions to Futalognkosaurus) there's no reason to give the same caudal increase to any other titanosaur.
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The posteriormost caudal preserved in Dreadnoughtus is only small in height compared to the others but the centrum length is as high as in the middle caudals, longer than some if we exclude the totallity of the articular surface. The Patagotitan mount has 65 caudals; the same as the rincón titanosaur; it's easy to count them using the top view of the mount that appears in the supplementary materials of Carballido et al 2017.
The last caudal preserved of Patagotitan is labeled as caudal 44, of which supossedly 21 are missing; and 23 preserved. The only huge gap is between caudal 8 and caudal 19; even if we asumed the caudal 19 was really a caudal 9, (something that I consider imposible since the people that wrote that paper are not idiots, we are talking about J.L.Carballido ; and Salgado is a coauthor of the Rincón titanosaur abstract and thus has better access to data than we have); the caudal labeled as cd44 would still be cd 33 and is 28 cm long, which is cery close to the average length of the centra of the preserved caudals (28.5 cm, you can do the math with the data in the SM); in fact it would again be longer than some middle caudals; for example the cd 8 is 26.5 cm long; the one labeled as cd 22 is 26 cm long, etc. So all Patagotitan preserved caudals are about the same length; and the functional length is in all about 70% the total length of the centra including the articular surface going by the figures, so it is not true that the middle increse the tail length more than the other preserved caudals.
Finally, the abstract of the Rincón titanosaur is in spanish which is my birth language and thus I don't need to use translations. The phrase written is "Podemos anticipar que el número de caudales is 65" which means that they can announce that the number of caudals is that; it's not an estimation. The only parts missing are the hindlimbs and one forelimb as they say in the abstract; not only this but the measurements of the vertebral column of the animal were also given in this Futalognkosaurus abstract ; so we know it was close to 50% of the length of the body too. Therefore at least a titanosaurian taxon evolved a long tail; and is potentially related to Patagotitan; and if it really was close to Futalognkosaurus, then you wouldn't need to look any further because Patagotitan is recovered as a lognkosaur in both Carballido et al 2017 and the latest iteration of Mannion's matrix (The newer Mendozasaurus' osteology, Gonzalez et al 2018).
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11 years later, we still don't have a detailed detailed description of Futalognkosaurus or ANY description on the exceptionally complete "Rioncon titanosaur".
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Dreadnoughtus's 32nd caudal is only around 75% the length of its mid-caudals, so it is, in fact, shorter (similarly to Camarasaurus), but my point was that the diameter of the centrum and height of the neural arch are much reduced, clearly indicating that the tail is coming to an end (I'd say there are only around a dozen more caudals from the tip of the tail not preserved in Dreadnoughtus).
I have had ample opportunity to personally observe the Patagotitan mount in the Field Museum, it has 70 caudals. I was specifically referring to the mount (as ijreid had referred to the mount), though you seem to be right that Fig. S5 of Carballido et al. 2017 has only 65.
Note that 'Cd8' and 'Cd44' are from different individuals ('Cd8' is from the holotype, and 'Cd44' is from the slightly larger main paratype), and because the material was found as a disarticulated bone bed, I don't think we can be entirely sure that 'Cd44' is from the same individual as 'Cd22' either.
I only had access to the English translation of the Rincon titanosaur abstract, so thank you for clearing that up. My other point remains, that we don't know if the Rincón titanosaur is related to Futalognkosaurus. The second abstract doesn't provide any meaningful evidence for their use of the Rincón titanosaur as a basis for comparison for Futalognkosaurus. Even if it had demonstrated that, we still wouldn't know if the long tail is an autapomorphy of the Rincón titanosaur or if it was widespread among lognkosaurs.
Ultimately, the claim of a 65-vertebra tail in Patagotitan is dependent on two sources of unpublished information: the morphology of the caudal vertebrae of Patagotitan not figured, and the morphology of the undescribed nearly complete Rincón titanosaur. As it would be a radical departure from the previously inferred morphology in titanosaurs, I don't find the available evidence convincing.
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As I said above, elongating a tail isn't just adding vertebrae, it's also adding more _large_ vertebrae. Diplodocids not only have 70-80 caudals, they have a lot of "mid-caudals" that really stretch the length of the tail. That isn't known in any reasonably complete published titanosaur tail, and while the Patagotitan mount does this, it's probably wrong.
As you yourself note, most of the complete (or largely complete) known titanosaur tails suggest 50 caudals or less, and even when the caudal count is increased in Tangvayosaurus it doesn't add appreciably to the length of the tail (seen here: en.wikipedia.org/wiki/Tangvayo… ). I
That means Patagotitan would require extraordinary evidence to support a radical departure in tail anatomy from other titanosaurs, and so far it just isn't there.
Of course there isn't an articulated Patagotitan tail, we have to composite two different specimens (which are mostly not figured) that consist of disarticulated and missing caudals, which means the position of those vertebrae need to be carefully justified. So what is the authors' justification for how they assign the disarticulated vertebrae into a sequence? That's in the supplemental data (section 1.5, page 24) where unfortunately they simply don't explain it with any detailed morphological description or images. Instead, it's simply stated that "they compared" the serial changes to Alamosaurus (which is not at all closely related to Patagotitan) and the undescribed Rincon titanosaur, which is undescribed and hence we have no clue what titanosaurs it is related to, what the transitional series looks like, or what about it supposedly justifies the assignments in Patagotitan. There's literally no useful information there.
A couple paragraphs down in the same section, they authors go on to explain that why they assign the position of the MPEF-PV 3399 "mid and posterior caudals" so far back in the series (which is the entire crux of this "long tail" claim) and astonishingly justify it based on _Apatosaurus_ and (once again) the undescribed Rincon titanosaur. This is even worse than the previous attempt - no one should be using a diplodocid to reconstruct the position of titanosaur tail vertebrae without extensive morphological justification, of which once again there is none. They are making extraordinary claims, and there's literally nothing in the supplemental data to support it.
But based on this arm-waving they explicitly label the mid-caudals of MPEF-PV 3399 numbers 19-30 and 36-44 (Table S4), and since their supposed caudal 44 is clearly not near the end of the series, suppl section 1.5 points out that the tail must be significantly longer than this. That's the hocus pocus of this claim - since they've now stretched the 3399 designations all the way to caudal 44 then of course well more than 50 vertebrae would be there (and the more anterior midcaudals no longer decrease at a normal rate).
Why am I skeptical of the assignments in table S4? Aside from the fact that no published titanosaur tail looks like this, that they don't figure the relevant caudals, and they never justify their assignments with actual descriptions of the series, when you scale the couple of holotype caudals they do figure (Fig 2.) and use their assignments the neural spines are decreasing rapidly in height - that is, too rapidly for the late assigned midcaudals, and just like every other known titanosaur anterior caudal series.
Interestingly, back in supplemental section 1.5, paragraph 3 they say something different: that the first of the midcaudals is "around 15", which contradicts table S4 (where the first in the sequence is 19). 15 is much more plausible (I'd guess maybe 14), and if you also bumped the second part of that distal 3399 series up (so it doesn't skip from five vertebrae) you'd end up with a tail that looks like basically any other middle of the road titanosaur caudal series in length, and with the 3399 caudals now ending around 39, you would only expect ~50 caudals in the series.
So until evidence is published that would support the mounts weird stretch-job interpretation, everyone should be skeptical.
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It's frustrating when published reconstructions are either, wrong, or in the case of Patagotitan, questionable. I created the scale chart for the Patagotitan Wikipedia entry, using the figure in the description as a starting point. I could tell it was off, but there is a fine line between correcting something and what could be considered 'original research'. (I made a few minor adjustments to better emulate the mounted skeleton.) It leaves you in a difficult position of either being misleading regarding the published science or showing something that isn't correct/accurate but 'verifiable'.
I find it strange that in the main paper the authors show a low fidelity illustration and in the supplementary, they have a more precise (at least in terms of bone rendering) 3d reconstruction which they use for the mass estimation. They didn't think however to show it in an orthographic side view, which would have been helpful.
I look forward to your take on it.
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Thanks Steve. I don't want to sound too down on the authors - this was a pretty fast publication time so I understand why not everything is figured, and there's plenty of other stuff to like about the paper. But yes, the "long tail" thing is unfortunate (also, it's been done before, e.g. "Seismosaurus", Ruyangosaurus), especially since it's already creating a paleoart meme for Patagotitan and Argentinosaurus.
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I think only you can answer that?
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I am so glad you're back...
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I wasn't so much gone as I was doing skeletals I can't post until an embargo is lifted. I probably did as most skeletals last year than almost any other year. 2019 should see a small avalanche of stuff posted!
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Yaay!
It feels like Christmas every one of these comes out...
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What matters is that it could completely flatten someones car with a single stomp
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