A bunch of stuff, loosely organized by theme.

Media

First up, I need to thank Brian Switek, who invited me to comment on Patagotitan for his piece at Smithsonian. I think he did a great job on that, arguably the best of any of the first-day major media outlet pieces. And it didn’t go unnoticed – his article was referenced at both the Washington Post and NPR (and possibly other outlets, those are the two I know of right now). I don’t think my quotes got around because they’re particularly eloquent, BTW, but rather because reporters tend to like point-counterpoint, and I was apparently the most visible counterpoint. They probably would have done the same if I’d been talking complete nonsense (which, to be fair, some people may think I was).

Paleobiology vs Records

The most commonly reproduced quote of mine is this one, originally from Brian’s piece:

I think it would be more accurate to say that Argentinosaurus, Puertasaurus and Patagotitan are so similar in size that it is impossible for now to say which one was the largest.

That may seem at odds with the, “Well, actually…[pushes glasses up nose]…Argentinosaurus was still biggest” tack I’ve taken both in my post yesterday and on Facebook. So let me elaborate a little.

There is a minor, boring point, which is that when I gave Brian that quote, I’d seen the Patagotitan paper, but not the Electronic Supplementary Materials (ESM), so I knew that Patagotitan was about the same size as the other two (and had known for a while), but I hadn’t had a chance to actually run the numbers.

The much more interesting point is that the size differences between Argentinosaurus, Puertasaurus, and Patagotitan are astonishingly small. The difference between a 2.5m femur and a 2.4m one is negligible, ditto for vertebrae with centra 59cm and 60cm in diameter. OMNH 1331, the biggest centrum bit from the giant Oklahoma apatosaur, had an intact max diameter of 49cm, making it 26% larger in linear terms than the next-largest apatosaur. The centra of these giant South American titanosaurs are more than 20% bigger yet than OMNH 1331, just in linear terms. That’s crazy.

It’s also crazy that these three in particular – Argentinosaurus, Puertasaurus, and Patagotitan – are so similar in size. Dinosaur developmental programs were ‘messy’ compared to those of mammals, both in having weird timings for things like onset of reproduction, and in varying a lot among closely related taxa. Furthermore, sauropod population dynamics should have been highly skewed toward juveniles and subadults. So is the near-equality in size among Argentinosaurus, Puertasaurus, and Patagotitan just a coincidence, or does it mean that something weird was going on? There’s really no third option. I mean, even if some kind of internal (biomechanical or physiological) or external (ecological, food or predation) constraint forced those three to the same adult body size, it’s weird then that we’re finding only or at least mostly near-max-size adults. (If the available specimens of these three aren’t near-max-size, then any hypothesis that they’re forced to the same size by constraints is out the window, and we’re back to coincidence.)

BUT

With all that said, the title of “world’s largest dinosaur” is not handed out for effort expended, number of specimens collected, skeletal completeness, ontogenetic speculation, or anything other than “the dinosaur with the largest measured elements”. And that is currently Argentinosaurus. So although for any kind of paleobiological consideration we can currently consider Argentinosaurus, Puertasaurus, and Patagotitan to all be about the same size – and Alamosaurus, Paralititan, Notocolossus, and probably others I’ve forgotten should be in this conversation – anyone wanting to dethrone Argentinosaurus needs to actually show up with bigger elements.

So, if you’re interested in paleobiology, it’s fascinating and frankly kind of unnerving that so many of these giant titanosaurs were within a hand-span of each other in terms of size. Patagotitan is one more on the pile – and, as I said yesterday, exciting because it’s so complete.

But if you want to know who holds the crown, it’s still Argentinosaurus.

Humeri

In a comment on the last post, Andrea Cau made an excellent point that I am just going to copy here entire:

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.

That made me want to start a list of the longest sauropod humeri. Here goes – if I missed anyone or put down a figure incorrectly, I’m sure you’ll let me know in the comments.

  • Giraffatitan: 213cm
  • Brachiosaurus: 203cm
  • Ruyangosaurus: 190cm (estimated from 135cm partial)
  • Turiasaurus: 179cm
  • Notocolossus: 176cm
  • Paralititan: 169cm
  • Patagotitan: 167.5cm
  • Dreadnoughtus: 160cm
  • Futlognkosaurus: 156cm

Admittedly the Patagotitan humerus is from a paratype and not from the largest individual, but that is true for some others on the list, including Giraffatitan. And we have no humeri from Argentinosaurus, Puertasaurus, and some other giants.

Dorsal Vertebrae

A couple of further thoughts on how the dorsal vertebrae of Patagotitan compare to those of Argentinosaurus. First, now that I’ve had some time to think about it, I have a hard time seeing how the dorsal polygon method used by Carballido et al. in the Patagotitan paper has any biological meaning. In their example figure, the polygon around the Puertasaurus vertebra is mostly full of bone, and the one around Patagotitan has a lot of empty space. It’s easy to imagine an alternative metric, like “area of the minimum polygon actually filled by bone”, that would lead to a different ‘winner’. But that wouldn’t mean much, either.

Something that probably does have a real and important biomechanical meaning is the surface area of the articular face of the centrum, because that’s the area of bone that has to bear the compressive load, which is directly related to the animal’s mass. The biggest Patagotitan centrum is that of MPEF-PV 3400/5, which is at least a local maximum since has smaller centra both ahead and behind. The posterior face measures 59cm wide by 42.5cm tall. Abstracted as an ellipse, which may not be perfectly accurate, those measurements give a surface area of (pi)(29.5)(21.25)=1970 cm^2. For Argentinosaurus, the largest complete centrum has a posterior face measuring 60cm wide by 47cm tall (Bonaparte and Coria 1993: p. 5), giving an elliptical surface area of (pi)(30)(23.5)=2210 cm^2. (I’d use hi-res images of the centra to measure the actual surface areas if I could, but AFAIK those images either don’t exist or at least have not yet been made public, for either taxon.) So although the Argentinosaurus dorsal seems like it is only a bit bigger in linear terms, it’s 12% larger in surface area, and that might actually be a meaningful difference.

Cervical Vertebrae

One thing I haven’t commented on yet – Patagotitan is the newest member of the “world’s longest vertebrae” club. The longest Patagotitan cervical, MPEF-PV 3400/3, is listed in the ESM as having a centrum length of 120cm, but it’s also listed as incomplete. In the skeletal recon in the paper, the centrum is colored in as present, but the neural spine is missing. So is the centrum complete in terms of length? I don’t think it’s clear right now.

Anyway, here’s the current rundown of the longest cervical centra of sauropods (and therefore, the longest vertebrae among animals):

  • BYU 9024, possibly referable to Supersaurus or Barosaurus: 137cm
  • Price River 2 titanosauriform: 129cm
  • OMNH 53062, Sauroposeidon holotype: 125cm
  • KLR1508-77-2, Ruyangosaurus giganteus referred specimen: 124cm
  • MPEF-PV 3400/3, Patagotitan holotype: 120cm (+?)
  • MPM 10002, Puertasaurus holotype: 118cm

You may be surprised to see the Price River 2 cervical in there. It was reported in an SVP abstract a few years ago (I’ll dig up that ref and update this post), and Mike and I saw it last year on the Sauropocalypse. We measured the centrum at 129cm, making it just a bit longer than the longest centrum of Sauroposeidon, and therefore the second-longest vertebra of anything ever.

Aside – I’m probably getting a reputation as a big ole meanie when it comes to debunking “world’s largest dinosaur” claims. If I’m willing to take the lead in kicking my own dinosaur down the ladder, don’t expect me to be kind to yours. I follow where the numbers lead.

Now, here’s an interesting thing – now that Sauroposeidon is coming out as a basal titanosaur, rather than a brachiosaur, it might not have been a skinny freak. The 120cm cervical of Patagotitan makes the 125cm cervical of Sauroposeidon and the 129cm cervical from Price River 2 look even more tantalizing. Maybe it’s super-giant sauropods all the way down.

“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

LACM dino camp 3 - Mamenchisaurus and Triceratops 1

Last night London and I spent the night in the Natural History Museum of Los Angeles County (LACM), as part of the Camp Dino overnight adventure. So we got lots of time to roam the exhibit halls when they were–very atypically–almost empty. Above are the museum’s mounted Triceratops–or one of them, anyway–and mounted cast of the Mamenchisaurus hochuanensis holotype, presented in glorious not-stygian-darkness (if you went through the old dino hall, pre-renovation, you know what I mean).

LACM dino camp 1 - dueling dinos

We got there early and had time to roam around the museum grounds in Exposition Park. The darned-near-life-size bronze dinos out front are a minor LA landmark.

LACM dino camp 2 - fountain

The rose garden was already closed, but we walked by anyway, and caught this rainbow in the big fountain.

LACM dino camp 4  - Mamenchisaurus and Triceratops 2After we checked in we had a little time to roam the museum on our own. I’ve been meaning to blog about how much I love the renovated dinosaur halls. The bases are cleverly designed to prohibit people touching the skeletons without putting railings or more than minimal glass in the way, and you can walk all the way around the mounted skeletons and look down on them from the mezzanine–none of that People’s Gloriously Efficient Cattle Chute of Compulsory Dinosaur Appreciation business. Signage is discreet and informative, and so are the handful of interactive gizmos. London and I spent a few minutes using a big touch-screen with a slider that controlled continental drift from the Triassic to the present–a nice example of using technology to add value to an exhibit without taking away from the real stuff that’s on display. There are even a few places to sit and just take it all in. That’s pretty much everything I want in a dinosaur hall.

Also, check out the jumbotron on the left in the above photo. It was running a (blessedly) narration-free video on how fossils are found, collected, prepared, mounted, and studied, on about a five-minute loop. Lots of pretty pictures. Including this next one.

LACM dino camp 5 - big ilium photo

There are a couple of levels of perspective distortion going on here, both in the original photo and in my photo of that photo projected on the jumbotron. Still, I feel confident positing that that is one goldurned big ilium. I’m not going to claim it’s the biggest bone I’ve ever seen–that rarely ends well–but sheesh, it’s gotta be pretty freakin’ big. And apparently a brachiosaurid, or close to it. Never mind, it’s almost certainly an upside-down Triceratops skull. Thanks to Adam Yates for the catch. I will now diminish, and go into the West.

LACM dino camp 6 - ceratopsian skulls

Triceratops, Styracosaurus, and Einiosaurus–collect the whole set!

LACM dino camp 7 - tyrants

Of course, the centerpiece of the second dinosaur hall–and how great is it that there are two!?–is the T. rex trio: baby, juvenile (out of frame to the right), and subadult. Yes, subadult: the “big” one is not as big as the really big rexes, and from the second floor you can see unfused neural arches in some of the caudal vertebrae (many thanks to Ashley Fragomeni for pointing those out to me on a previous visit).

LACM dino camp 8 - baby rex

Awwwww! C’mere, little fella!

LACM dino camp 9 - pneumatic diplodocid caudals

Still, this ain’t Vulgar Overstudied Theropod Picture of the Week. Here are some sweet pneumatic diplodocid caudals in the big wall o’ fossils (visible behind Mamenchisaurus in the overhead photo above). The greenish color is legit–in the Dino Lab on the second floor, they’re prepping a bunch of sauropod elements that look like they were carved out of jade.

Sculpey allosaur claws

Sudden violent topic shift, the reason for which will be become clear shortly: London and I have been sculpting weapons of mass predation in our spare time. In some of the photos you may be able to see his necklace, which has a shark tooth he sculpted himself. Here are a couple of allosaur claws I made–more on those another time.

LACM dino camp 10  - molding and casting

The point is, enthusiasm for DIY fossils is running very high at Casa Wedel, so London’s favorite activity of the evening was molding and casting. Everyone got to make a press mold using a small theropod tooth, a trilobite, or a Velociraptor claw. Most of the kids I overheard opted for the tooth, but London went straight for the claw.

LACM dino camp 11 - raptor claw mold

Ready for plaster! Everyone got to pick up their cast at breakfast this morning, with instructions to let them cure until this evening. All went well, so I’ll spare you a photo of this same shape in reverse.

LACM dino camp 12 - Camp Wedel in the African bush

We were split into three tribes of maybe 30-40 people each, and each tribe bedded down in a different hall. The T. rex and Raptor tribes got the North American wildlife halls, but our Triceratops tribe got the African wildlife hall, which as a place to sleep is about 900 times cooler. Someone had already claimed the lions when we got there, so London picked hyenas as our totem animals.

LACM dino camp 13 - London with ammonite

Lights out was at 10:30 PM, and the lights came back on at 7:00 this morning. Breakfast was out from 7:15 to 8:00, and then we had the museum to ourselves until the public came in at 9:30. So I got a lot of uncluttered photos of stuff I don’t usually get to photograph, like this ammonite. Everyone should have one of these.

LACM dino camp 14 - Wedel boys with Carnotaurus

London’s favorite dino in the museum is Carnotaurus. It’s sufficiently weird that I can respect that choice.

LACM dino camp 15 - London with rexes

Not that there’s anything wrong with the old standards, especially when they’re presented as cleanly and innovatively as they are here.

LACM dino camp 16 - Matt with Argentinosaurus

Finally, the LACM has a no tripod policy, and if they see you trying to carry one in they will make you take it back to your car. At least during normal business hours. But no one searched my backpack when we went in last night, and I put that sucker to some good use. Including getting my first non-bigfoot picture of the cast Argentinosaurus dorsal. It was a little deja-vu-ey after just spending so much time with the giant Oklahoma Apatosaurus–elements of the two animals really are very comparable in size.

If you’re in the LA area and interested in spending a night at the museum–or at the tar pits!–check out the “Overnight Adventures” page on the museum’s website. Cost is $50 per person for members or $55 for non-members, and worth every penny IMHO. It’s one of those things I wish we’d done years ago.

[This is a guest post by frequent commenter Heinrich Mallison.  Heinrich is maybe best known to SV-POW! readers for his work on digital modelling of sauropodomorphs, though that may change now that his paper on sauropod rearing mechanics is out.  Read on …]

Maybe this post should have been titled “How sauropods breathed, ate, and farted”. Or maybe not. But breathing, eating and fermenting the food will play an important role.

Last week held a special pleasure for me. I spent it in New York, digitizing sauropods bones in the American Museum of Natural History’s Big Bone Room. Treasure trove that this room is, the museum still held something even better: the opening of a new special exhibit titled The World’s Largest Dinosaurs. While all such exhibits are of general interest to me, this one is special. Mark Norell, famous palaeontologist and curator at the AMNH, had a co-curator for this exhibit, Martin Sander of Bonn University, who is the head and speaker of the German Research Foundation Research Unit FOR 533 “Sauropod Biology”. As a member of FOR 533, and having received funding for both my PhD work and my first post-doc project, I am obviously somewhat biased, so please take this into account when you read this report.

The exhibition does not show a large amount of sauropods material. Not that it wouldn’t make for a nice exhibit, as the AMNH’s Hall of Saurischian Dinosaurs doesn’t really have that many sauropods (one Apatosaurus mount, to be exact, with a mashed up Barosaurus vertebral column half-hidden away and a wonderful but obviously depressed “prosauropod”, my old friend Plateosaurus, thrown in to make up a bit for the many, many stinkin’ theropod specimens). But instead of showcasing some of the usually hidden-away bones of the AMNH collection (and believe me, there is some wonderful stuff there), it rather focuses on those parts of the animal that are usually missing: the soft tissues. “How did sauropods get so big?”, or, reversing the question: “Why did and does no other group of terrestrial vertebrates reach such gigantic body sizes?” These were the questions our research group has been busily investigating for the last six years, and the answers to these question are what the exhibit now tries to communicate to the public. And it does so quite successfully!

The centerpiece of the AMNH exhibit: the belly of Mama Mamenchisaurus.

The centrepiece is a full-sized, fleshed out model of a sauropod (Mamenchisaurus hochuanensis), but on one side the skin and superficial musculature has been cut away. The visitor can see the neck vertebrae, the trachea, the carotid artery, and the ribcage. And the ribcage is also a projection area, on which a video is played that shows the internal organs and how they work.

With a voice-over that explains the actions in simple terms, the principle of the avian-style unidirectional lung and the air sacs is explained (albeit with a small error, as lung physiologist and FOR 533 member Steve Perry was quick to point out – the AMNH has promised to fix things), as well as the basic principles of sauropod reproduction (high number of offspring). Many things are not said or shown here, which is a good thing as it allows for the normal short attention span of the average museum visitor for one piece of exhibit. Instead, interesting stuff like how much fodder a sauropod needed per day (or even per hour), a comparison of a sauropod’s and an elephant’s heart, and of a giraffe’s and a sauropod’s neck vertebra (wow, how light the sauropod one is!) are explored at small science stations spread around the room. I won’t go into a detailed description here, you can find that elsewhere on the web. The AMNH did a blogger’s preview a while ago, and invited the press for a press conference and walk-through of the exhibit with the chance to interview the scientists present on Wednesday, so much info has already been plastered all over the web. Instead, I’ll just show you some pics and talk a bit about the concept of the exhibition, and how various issues were handled that can make or break a show.

One thing is how to catch the attention of visitors and direct it to the content of the exhibit. You don’t want people just going “aw, sh*t! That is one HUGE bone/animal!” and wandering off into the next room. If you want to educate them (and that, may I remind you, is the central purpose of a museum exhibit), you need to get them interested in stuff. Get them to read texts, look at stuff (not just let their eyes wander across it for a few seconds), try to get their brains going. The sauropod exhibit manages this by, first of all, being behind a closed door you can’t see through. Usually, the AMNH halls are accessible either through an open doorway, or in a few cases through glass doors. Secondly, the exhibit, especially the rather confined area you enter first, is dark. Very dark. Again a marked contrast to the AMNH’s usually well-lit halls. Just a few plants greet the visitor, and it takes a second to adjust to the dark – enough time to look around a bit and notice the neck and head of Argentinosaurus (fleshed out model) above.

My esteemed colleague Vivian Allen from Royal Veterinary College London going "Aw, sh*t! That is one HUGE sauropod!"

Next, the visitor is channeled along, with only a very few specimens to catch his attention. Well done, because these few pieces (sauropod leg, Komodo dragon skeleton, human skeleton, etc.) focus on getting the main message across (sauropods = way larger than everything else), aided by the largest animals (or their silhouettes) or various groups painted on the wall. Only once the message has been driven home, as I could detect from the comments I overheard, are the visitors released into the main area that contains the sauropod model and the various detail exhibits around it.

The next thing is giving people time to check things out. If you herd them too much, they will get driven along by the masses. That’s why the larger, opener area around the sauropod model and the smaller bits around it works so well: people can sit down to see the projected videos on the sauropod belly, or they can drift around from one specimen or science station to the next.

The stations are not just glass cabinets with some bones in them. Instead, at many of them you can DO things. One allows you to measure either an adult or baby sauropod femur or your own, and then calculate how heavy a sauropod of that size was. At another you can pump a sauropod’s and an elephant’s lung. One I liked very much simply had an unpainted sauropod model, and two sets each (adult and children height) of oculars. One showed a colorful “show-off” version, the other a “camouflage” one. “Which one is true? We don’t know!” is how I’d paraphrase the text that goes with it. One that innocently hides in the corner is among the most impressive: a 5 ½ ft cube (1.7 m, for the civilized) made from Plexiglas filled with sauropod food. A serving sufficient for one day! On it, also, the various plant groups available in the Mesozoic were rated for various factors, getting an easily understood rating in stars. That’s another big thing: make things easily understandable, visualize them!

Yummy! 100% Recommended Daily Value for your average sauropod.

With all these things well done, there remains only one more thing: make things fun for kids! And the AMNH did just that by adding a kids’ dinosaur dig. OK, it is one of those cheesy things where you use brushes and stuff to brush sand off fossils (cast), but it was done well enough that kids lined up like there was no tomorrow.

Overall, the exhibit gets two big thumbs up from me. If you make it to NY while it is on, or to any of its future stations, go see it! However, as FOR 533 member Steve Perry was quick to point out: if you’re in it only for the size, you’ll be disappointed! Aside from a few isolated bones, not much of the largest dinosaurs (Argentinosaurus and Amphicoelias) is to be seen in bone. It is the biological details that matter!  But don’t get me started about the tail musculature, especially the caudofemoralis, of the big model.

And then, there is the other thing about it that is closely tied to shameless self-promotion: the AMNH did not produce a catalogue or anything similar. Instead, the latest book from the “Life of the Past” series (Editor: James Farlow) of Indiana University Press was presented at the press conference. The lucky reporters all even got a free copy! The title is Biology of the Sauropod Dinosaurs: Understanding the Life of Giants, edited by N. Klein, K. Remes, C. T. Gee and P. M. Sander. And by now, I am sure, you have figured out who the authors are … It is intended to be a summary of the research findings of the first (and part of the second) funding period of FOR 533, and yours truly has two chapters in it. The first doesn’t really give much new information; most is already contained in my two papers here and here. The second, however, presents novel research that didn’t make it into the AMNH exhibit. But hey, why spoil the surprise – go and buy our book!) Overall, it is quite a technical book, so laypeople beware, but we did try to make the research as accessible as possible while retaining a high standard. For the even more technically minded there is the summary of our research group’s work (which cost the DFG ~€6.000.000) to be found in Sander et al. 2010. However, reading that paper is not half as much fun as the book, or the exhibit.

References

Dorsal vertebrae from Argentinosaurus (center) and Supersaurus (either side). The vert on the left is the holotype of Ultrasauros, and the one on the right is the holotype of Dystylosaurus, but both of those taxa have been sunk into Supersaurus. Found on teh intert00bz.

As often happens here, a comment thread got to be more interesting than the original post and ended up deserving a post of its own. In this case, I’m talking about the thread following the recent Mamenchisaurus tail club post, which got into some interesting territory regarding mass estimates for the largest sauropods. This post was inspired by a couple of comments in particular.

Zach Armstrong wrote:

I don’t trust Mazzetta et al.’s (2004) estimate, because it is based off of logarithmic-based regression analyses of certain bone lengths, which a recent paper by Packard et al. (2009) have shown to overestimate the mass by as much as 100 percent! This would mean the estimate of 73 tonnes given my Mazzetta would be reduced to 36 tonnes.

To which Mike replied:

Zach, Mazzetta et al. used a variety of different techniques in arriving at their Argentinosaurus mass estimate, cross-checked them against each other and tested their lines for quality of fit. I am not saying their work is perfect (whose is?) but I would certainly not write it off as readily as you seem to have.

Weeeeell…Mazzetta et al. did use a variety of measurements to make their mass estimates, but they did it in a way that hardly puts them above criticism. First, their estimates are based on limb-bone allometry, which is known to have fairly low accuracy and precision (like, often off by a factor of 2, as Zach noted in his comment). Second, the “raw data” for their allometric equation consists of volumetric mass estimates. So their primary estimation method was calibrated against…more estimates. Maybe I’m just lazy, but I would have skipped the second step and just used volumetric methods throughout. Still, I can see the logic in it for critters like Argentinosaurus where we have limb bones but no real idea of the overall form or proportions of the entire animal.

Anyway, the accuracy of their allometric estimates is intertwingled with their volumetric results, so if their volumetric estimates are off…. The volumetric estimates used a specific gravity of 0.95, which to me is unrealistically high. Taking into account the skeletal pneumaticity alone would lower that to 0.85 or 0.8, and if the critter had air sacs comparable to those of birds, 0.75 or even 0.7 is not beyond the bounds of possibility (as discussed here and also covered by Zach in his comment).

Now, Mazzetta et al. (2004) were not ignorant of the potential effects of pneumaticity. Here’s  what they wrote about density (p. 5):

The values from Christiansen (1997) were recalculated using a slightly higher overall density (950 kg/m^3), as the 900 kg/m^3 used in that paper may be slightly too low. Most neosauropods have extensively pneumatised vertebrae, particularly the cervicals, which would tend to lower overall density. However, these animals are also very large, implying a proportionally greater amount of skeletal tissue (Christiansen, 2002), particularly appendicular skeletal tissue, and consequently, they should have had a higher overall density.

This is pretty interesting: they are arguing that the positive allometry of skeletal mass as a fraction of body mass–which is well documented in extant critters–would offset the mass reduction from pneumaticity in animals as big as sauropods. I haven’t given that enough thought, and I definitely need to. My guess–and it is a guess–is that the effects of skeletal allometry were not enough to undo the lightening imposed by both PSP (~10%) and pulmonary air sacs (another ~10%, separate from the lungs), but I haven’t done any math on this yet. Fodder for another post, I reckon.

Getting back to Mazzetta et al., some of the volumes themselves strike me as too high, like ~41,500 liters for HM SII. That’s a LOT more voluminous than Greg Paul, Don Henderson, or Mike found for the same critter. The 16 metric ton Diplodocus and 20.6 metric ton Apatosaurus used by Mazzetta et al. are also outside the bounds of other recent and careful estimates. Not necessarily wrong, but definitely at the upper end of the current spectrum.

Mazzetta et al. got a mass estimate of 73,000 kg for Argentinosaurus, but (1) they used a density that I think is probably too high even if skeletal allometry is considered, (2) at least some of the volumetric mass estimates that form the “data” for the limb-bone regressions are probably too high, and (3) even if those problems were dealt with, there is still the general untrustworthiness of limb-bone regression as a mass estimation technique. 1 and 2, if fixed to my satisfaction, would tend to push the estimated mass of Argentinosaurus down, perhaps significantly (the effect of 3 is, if not unknowable, at least unknown to me). Given that, Zach’s ~52 metric ton estimate for Argentinosaurus is very defensible. (Probably worth remembering that I am a sparse-wing fanatic, though.)

None of this means that Mazzetta et al. (2004) were sloppy or that their estimate is wrong. Indeed, one of the reasons that we can have such a deep discussion of these points is that every link in their chain is so well documented. And there is room for honest disagreement in areas where the fossils don’t constrain things as much as we’d like. You cannot simply take a skeleton, even a complete one, and get a single whole-body volume. The body masses of wild animals often fluctuate by a third over the course of a single year, which pretty well buries any hope of getting precise estimates based on skeletons alone. And no one knows how dense–or sparse–sauropods were. I haven’t actually done any math to gauge the competing effects of skeletal allometry on one hand and PSP and air sacs on the other–and, AFAIK, no one else has either (Mazzetta et al. were guessing about pneumaticity as much as I’m guessing about skeletal allometry). Finally, Argentinosaurus is known from a handful of vertebrae and a handful of limb bones and that’s all, at least for now. If we can’t get a single body volume even when we have a complete skeleton, we have to get real about how precise we can be in cases where we have far less material.

The upshot is not that Argentinosaurus massed 73 metric tons or 52 or any other specific number. As usual, the two-part take home message is that (1) mass estimates of sauropods are inherently imprecise, so all we can do is make our assumptions as clear as possible, and (2) even the biggest sauropods might have been smaller than you think. ;-)

Reference

Mazzetta, G.V., Christiansen, P., and Farina, R.A. 2004. Giants and bizarres: body size of some southern South American Cretaceous dinosaurs. Historical Biology 2004:1-13.

So I finally got to see the Discovery Channel’s new series, Clash of the Dinosaurs. The show follows the common Discovery Channel MO of cutting between CGI critters and talking heads. I’m one of the talking heads, and I get a lot of air time, and I suppose I should be happy about that. But I’m not, for reasons I’ll explain.

I need to preface what follows by saying that I thought the other talking heads did a great job. My experience suggests that the scientific problems with the series didn’t originate with the scientists, infrasound weapons excepted. Tom Holtz–another of the talking heads, and a good one–nailed it on the DML:

For those going to watch the show, a warning:
The documentarians often take anything that any of the talking heads speculated about, and transformed these into declarative statements of fact. In some cases this is particularly egregious, because I strongly disagree with some of these statements and believe the facts are against some of these (say, about tyrannosaurid cranial kinesis…) and they present these as facts rather than suppositions.

Dangerous

In the fall of 2008 the folks  at Dangerous Ltd, a London-based film production company, asked me if I’d be interested in being part of a new documentary project, which had the working title “Dino Body” (this isn’t a trade secret or anything, that title was on the Dangerous webpage for months). The grand idea was to show how much we’ve learned about how dinosaurs actually lived.

Now, this is something I care about a lot. In the past couple of decades we’ve learned about the physiology, diets, nesting habits, growth rates, and social lives of dinosaurs, in unprecedented detail. Things no one predicted and that I would have bet heavily against, like burrowing dinosaurs, four-winged raptors, and comparative studies of dinosaur and pterosaur genomes, are backed by solid evidence. We are in a golden age of dinosaur paleobiology, and new discoveries, even new kinds of discoveries, are stacking up faster than I can really keep up. So it would be a great time to bring all this new evidence to the public.

In the late 2008 and early 2009 I spent a LOT of time with the people at Dangerous Pictures, going over all kinds of questions about dinosaur biology. I sent them papers, links to blog posts, diagrams, you name it. They seemed really keen to get the science right, and I was hopeful that we’d get a dinosaur documentary that wasn’t overly speculative sensationalized BS.

Sadly, that hope was to be mercilessly crushed.

Deja vu

The series has some obvious faults. It is incredibly repetitive, to the point that I found it hard to watch for any length of time without my attention wandering. Not just the CGI clips, but the narration as well. You’ll learn in 30 seconds why females tend to be choosier about mates than males (eggs are more expensive than sperm), and spend the next 15 minutes having that slowly beaten in your brain using as much empty verbiage as possible. Ditto every other fact on the show.

More galling are the places where animation is cleverly cut with talking head bits so that we end up describing things that were never in the script. I explained on camera about the unavoidably high mortality among juvenile sauropods, and how groups of Deinonychus could probably pick off the baby sauropods like popcorn. I had been speaking of hatchlings, but my words are cut together with a scene–which you’ll see about 15,000 times–of three Deinonychus taking down an elephant-sized subadult Sauroposeidon. In the real world, it would have pulped them. In the dramatically-lit world of Clash of the Dinosaurs, the three raptors inflict a handful of very shallow flesh wounds with their laughably tiny claws and the Sauroposeidon expires theatrically for no visible reason.

(If they really wanted to impress the audience with the implacability of Mesozoic death, they would have shown the three raptors mowing down a field of newly-hatched babies like so much wheat…)

I spent a long time explaining the evidence that sauropods buried their eggs, and at their request I mocked up diagrams showing the possible proportions of a hatchling Sauroposeidon. So naturally the program shows a mother abandoning her eggs in an exposed nest, and then a few minutes later, hatchlings that are perfect miniatures of the adults struggling up out of the ground. I guess they cut the scene in which the Sand Fairy buried the eggs, and lacked the budget to perform the simple morph of the digital model that would have made the babies look like babies, instead of ponderous adults emerging from the Sarlacc pit.

Some may complain that I am picking nits. But what the heck is the point of bringing on scientific advisors if you’re then going to ignore the stuff they tell you? Why not just make the crap up out of the whole cloth? In fact, there is far too much of that in the show. There is no evidence that Quetzalcoatlus could see dinosaur pee with its ultraviolet vision, or that a herd of hadrosaurs could knock over a predator with their concentrated infrasound blasts. Sorry, paleontologists, you’ll be fielding questions about these newly invented “facts” for the next decade at least.

It’s like I had this great working relationship with the researchers, and they were really curious and careful, and we went to great lengths to do the best work we could, and then somewhere in between my filming back in February and the airing of the completed show, all of our diligent work was flushed right down the crapper, and a fresh script was written by a hyperactive child whose only prior preparation was reading Giant-Size X-Men and getting hit on the head a few times.

Do I sound too harsh? I’m just getting started. Let me tell you about the sacral expansion in sauropods.

Back in the Back in the Day

In many sauropods and stegosaurs and a few other archosaurs, the neural canal (the bony tube that houses the spinal cord) is massively enlarged in the sacral vertebrae. This is the origin of the goofy idea that big dinosaurs had a “second brain” back there to control their hind end, because the real brain up front was (supposedly) just too darn tiny and remote. The researchers at Dangerous asked me about this sacral enlargement, and this is what I told them (quoted from an e-mail I sent November 25, 2008):

The sacro-lumbar expansion is possibly the most misunderstood thing in sauropod biology. First, there are two separate things that have been referred to as sacro-lumbar expansions. The first is the slight swelling of the spinal cord in that region in almost all vertebrates, including humans, to accomodate the neurons that help run the hind limbs (you also have a swelling in the spinal cord at the base of your neck to help run your arms). Contrary to popular belief, a lot of your stereotyped actions require little direct involvement from the brain and are instead controlled by the spinal cord. When you walk, for example, most of the motor control is handled by the spinal cord, and your brain only steps in when you have to actually worry about where to place your feet–when you step over a puddle, for example. So there would be nothing remarkable about sauropods using their spinal cords to drive many of their limb movements, this is something that pretty much all vertebrates do, it’s just not widely known to the public. [Aside: this is true. Also, I have heard it claimed that sauropods could not have reared because their brains were too small to coordinate such an action. This was claimed by a non-biologist who evidently doesn’t know how the nervous system works.]

The other sacro-lumbar expansion really is an expansion, but it’s not unique to sauropods and it has nothing to do with running the hind limbs. Most birds have a very large expansion of the spinal cord in the sacro-lumbar region called the glycogen body. As the name implies, it stores energy-rich glycogen, but the function of the glycogen body is very poorly understood. It has been hypothesized to be an accessory organ of balance, or a reservoir of compounds to support the growth and maintenance of the nervous system. Since we don’t even know what it does in birds, we’re straight out of luck when it comes to figuring out what it did in sauropods. Here’s a brief overview:
http://www.innerbird.com/other_special_features/hips/other_features_hips.html

Here’s an explanatory diagram I sent with the message:

This business about the glycogen body caused some consternation and dithering in the production process. They wanted to bring up the second brain because it’s so entrenched in the popular consciousness (i.e., bad dinosaur books), but they were unhappy that the real explanation turned out to be so unsatisfying (“We don’t know what it does, but not that!”). In the end, we did discuss it briefly on camera. I said something like, “There was this old idea that the sacral expansion functioned as a second brain to control the hindlimbs and tail. But in fact, it almost certainly contained a glycogen body, like the sacral expansions of birds. Trouble is, nobody knows exactly what the glycogen bodies of birds do.”

Somebody in the editing room neatly sidestepped the mystery of the glycogen body by cutting that bit down, so what I am shown saying in the program is this, “The sacral expansion functioned as a second brain to control the hindlimbs and tail.” I’m paraphrasing because I don’t have a DVR, but that’s basically it. (Update: my memory was pretty good. Here’s the interview transcript.)

Do you see, do you understand, what they did there? I was explaining why an old idea was WRONG and they cut away the frame and left me presenting the discredited idea like it’s hot new science. How freaking unethical is that?

So. I don’t know if the decision to turn my words around 180 degrees was a mistake made by an individual editor, or if it was approved from someplace higher up the line. I aim to find out. Until I do, I’m boycotting Dangerous Ltd, and I encourage you to do likewise.

The Final Insult

Oh, and they spelled my name wrong, throughout. And also mispelled Sauroposeidon in one of the quiz bits at commercial time. “What does Sauroposeiden mean?” It means you don’t know the Greek pantheon, sauropods, or basic spellchecking, dumbasses.

Science journalism FAIL.

UPDATE, January 27, 2010

This is so perfect that it hurts. For “Science Channel” feel free to substitute any of the ignotainment feeds operated by Discovery Communications.

A quick follow-up on Darren’s recent post: the reconstructed Argentinosaurus dorsal in the photo he used seems to be based on the anterior dorsal of the holotype — at the least, the proportions and most of the features are the same — so we can get some more information by looking at the figure of the same element in the description of Bonaparte and Coria (1993). Here it is:

fig. 2 — anterior dorsal vertebra of Argentinosaurus

This shows the details better than the photo, though admittedly it’s rather less spectacular. But what’s most noticable, to me at least, is that the centrum and the lower part of the neural arch is completely missing … which means that the “hypantrum” of the reconstructed vertebra in the photo that Darren used is pretty much a complete fiction. Or let’s be more charitable and say “involves a certain amount of interpretation”.

So! What’s the story? The dorsal figured here is the one that Bonaparte and Coria considered to be ?first, but the ?second and ?third (and more posterior dorsals) are also preserved — and more fully, at least in the relevant area. The ?second dorsal, shown in their figure 3, is not illustrated in anterior view, but the ?third is shown in their figure 4:

fig. 4 — ?third dorsal vertebra of Argentinosaurus

So now we can see what we came here for: the distinctly ventrolaterally sloping borders of the triangular hollow below the prezygapophyses. But is it a hypantrum? Well, the purpose of a hypantrum is to accept the hyposphene of the vertebra in front: but if this vertebra’s alleged hypantrum were filled by a hyposphene, its neural canal would be almost completely blocked off. So maybe not. And indeed the ?second dorsal of the Argentinosaurus type specimen, figured by B&C93 in posterior view as fig. 3A, doesn’t seem to have anything resembling a hyposphene. So that supports Salgado and Martínez’s (1993) assertion that the “hyposphenes” of Argentinosaurus are in fact just big old centropostzygapophyseal laminae. (Salgado and Bonaparte 2007 cited and reaffirmed this reidentification, but noted that the posterior dorsals of Big-A do seem to have big hyposphenes and hypantra. Unfortunately these don’t seem to be figured in any of the papers we’ve cited here, so who can say?)

At this point, I am going to stop (A) posting all the figures from Bonaparte and Coria 1993, and (B) pontificating … at least until I’ve read Apesteguía (2005) which — for shame — I haven’t, yet. Well, it’s a truly frightening piece of work.

References are the same as for Darren’s post.