National Geographic

Dinosaur Reproduction, Not Ancient Gravity, Allowed Super-Sized Sauropods to Evolve

Why was Supersaurus so big? This impressive, 100-foot-plus sauropod was one of the largest creatures to ever walk the Earth – far larger than any terrestrial animal alive today. What could account for such superlative size? Baseball player Jose Canseco offered his own hypothesis on Twitter a few days ago.

After promising to share some of his thoughts on gravity, Canseco cemented his reputation for weird tweets by outlining his thoughts about why there’s nothing quite so big as Supersaurus around anymore:

Plenty of bloggers picked up on the armchair speculation, and science communication star Bill Nye even chimed in. But there was something totally missing from the various responses – science.

Writers with time to kill picked out Canseco as an easy target worth a bit of ridicule, but neglected to explain why the sports star was wrong. Snark is easier than substance. That’s a shame, especially given the growing amount of literature about why dinosaurs – and sauropods in particular – got to be so mind-bogglingly enormous.

Canseco didn’t have all his facts straight. No dinosaur ever grew to be 200 tons in weight. Yet his off-the-cuff comments about gravity aren’t so unusual as they might initially seem. Researchers have at least considered the speculative idea. In a 2011 paper on sauropod gigantism, paleontologist P. Martin Sander and coauthors briefly debunked the proposal that Jurassic gravity was weaker. Sauropods didn’t grow so large because of reduced gravity, greater oxygen content in the prehistoric atmosphere, or because of an overabundance of food, the paleontologists concluded. More subtle factors accounted for big body size. A characteristic the dinosaurs shared with birds and the way sauropods reproduced made their Mesozoic growth spurt possible.

Before getting to the oddities of sauropod biology, though, let’s dispense with the idea that there was something about Earth’s environment that drove dinosaurs to gargantuan sizes. My friend and fellow science writer Matthew Francis covers the gravity angle over at his blog – there’s no evidence that the Earth’s gravity was weaker during the heyday of the dinosaurs. Even as continents shifted around, the Earth’s gravity didn’t change. Canseco’s idea of “nimble” dinosaurs sprinting around in low gravity isn’t grounded on any actual evidence. (Canseco didn’t consider what would happen to all the smaller dinosaurs that lived during the same time as Supersaurus. I can’t help but imagine Stegosaurus happily leaping and bounding over Jurassic plains in reduced gravity.)

And there’s no reason to think that giant dinosaurs got an assist from higher oxygen levels, either. Even though Canseco didn’t bring up this idea, some of his fans did in response to his ancient gravity tweets. The idea goes back to the connection between increased oxygen and the evolution of giant insects during the Carboniferous, over 300 million years ago. While oxygen composes about 20% of the air we breathe now, Carboniferous air contained about 30% oxygen. This boost is connected to better breathing efficiency among ancient insects and arthropods, which allowed the invertebrates to grow larger.

Some paleontologists speculated that oxygen might be behind the evolution of huge dinosaurs, too, but the hypothesis has been totally undermined by evidence from the geological record and dinosaur anatomy. Geochemical evidence has shown that Jurassic and Cretaceous air contained about as much oxygen as today, if not a little less. More than that, the dinosaurs did not need increased oxygen to adequately nourish their bodies.

As part of their respiratory system, sauropods had a complex network of air sacs that gave them two advantages. Not only did the air sacs allow the dinosaurs to breathe more efficiently – more like birds than mammals – but the soft tissues invaded bone to make the skeletons of these dinosaurs lighter without sacrificing strength. Indeed, even at around 100 feet long, Supersaurus has been estimated to weigh in between 35 and 40 tons. That’s quite hefty in absolute terms, but consider that the largest African elephant on record weighed about 12 tons, and the extinction rhino Paraceratherium – about 26 feet long and 16 feet tall at the shoulder – weighed about 18 tons. You’d think a dinosaur about four times as long as Paraceratherium would be much heavier – 72 tons or more – but Supersaurus and similar dinosaurs were relatively light.  Air sacs allowed sauropods to escape some of the physical constraints that have limited the evolution of mammal body size over the past 66 million years.

Sauropod neck length, presented to scale with the necks of other organisms (at left). From Taylor and Wedel, 2013.

Sauropod neck length, presented to scale with the necks of other organisms (at left). From Taylor and Wedel, 2013.

Sauropod experts Michael Taylor and Mathew Wedel just published a paper outlining how these air sacs, and other biological features, allowed sauropods to evolve extravagantly-long necks. While just part of the whole animal, the long necks of sauropods greatly contributed to the overall size of these dinosaurs. Indeed, Taylor and Wedel estimate, the neck of Supersaurus probably stretched about 50 feet long, nearly half the animal’s entire length. The ability of this dinosaur, and other sauropods, to support such a long neck relied on several different features.

Compared to a giraffe, sauropods had a more stable, sturdy body that was better able to support ridiculously long necks and tails. But an even more critical feature was that sauropod had small heads. Unlike big mammals – which typically have big, heavy heads set with large teeth necessary for chewing – sauropods had tiny skulls with teeth that could only grip and crop food. Sauropods couldn’t chew, and instead relied on some other mechanism in their guts to totally break down food. Mammals have to balance neck length with having heavy heads, while sauropods avoided this problem by getting around chewing. (Although exactly how these dinosaurs processed the massive amounts of plant food they needed is a mystery.)

Furthermore, indentations and pockets in sauropod neck bones show that these dinosaurs had a bird-like air sac system – soft tissues that eliminated some of the mechanical and physiological problems of breathing with an extra-long neck. For example, sauropods undoubtedly breathed through their trachea like other vertebrates, and this structure faces certain physical constraints. In a long, narrow trachea, Taylor and Wedel point out, it’s difficult for an animal to inhale quickly. But to widen an elongated windpipe creates the problem of “tracheal dead space”, in which previously used air may be re-inhaled with each new breath and therefore cut breathing efficiency. Birds are able to eliminate such dead space by virtue of their air sacs, and so it’s likely that the same held true for sauropods. The posture, diet, physiology, and air sac systems of sauropods removed evolutionary pathways that have blocked mammals from attaining truly long necks.

Of course, not all sauropods were giants. Some of the smallest were between 13 and 17 feet long, including dwarfed varieties that evolved on islands (such as Magyarosaurus). Understanding why sauropods evolved such insanely long necks is part of the key to understanding why they loomed so large over the Mesozoic landscape, but it’s not the entire story. In fact, the reason sauropods could attain such large sizes has just as much to do with reproduction as skeletal architecture and specialized soft tissues.

The biggest dinosaurs started off very, very small. Sauropod mothers laid clutches about 10 eggs at a time in small nests, and the embryonic dinosaurs developed in eggs about the size of a large grapefruit. Once they hatched, these little dinosaurs grew at an absolutely fantastic rate. Based upon sprawling nesting grounds where many sauropods came to lay their eggs, these dinosaurs might have had a reproductive strategy similar to extant sea turtles. Rather than investing a great deal of energy into one or two offspring that required a great deal of care, sauropods regularly flooded the environment with clutches of offspring that were probably on their own from the very start. As suggested by paleontologists Christine Janis and Matthew Carrano in 1992, and more recently supported by a study conducted by Jan Werner and Eva Maria Griebeler, this way of reproducing may have removed constraints that keep mammals relatively small by comparison.

Elephants, giraffes, and other large mammals reproduce in a different way. Big mammals usually carry a single offspring internally for a long period of time, and the need for protection and milk means that mammalian youngsters continue to be an energy drain after birth. The costs of carrying and caring for a single, large baby are staggering, and long pregnancies run the risk of potentially fatal complications. All these factors conspire to create a reproductive threshold that mammals just can’t cross. For mammals to get much larger, they would have to carry young for longer and likely provide increased parental care. The extinct Paraceratherium and steppe mammoth, two of the largest land mammals ever, might represent how large it’s possible for mammals to get without fundamentally changing the way large mammals reproduce.

By externalizing birth and development, sauropods and other dinosaurs were able to sidestep the costs and risks that constrain mammal size. For dinosaurs, mechanical and other biological constraints might have prevented them from becoming even larger – the amount of time it would take for nerve impulses to travel to a 100-foot-long dinosaur’s brain for example. The fact that all the genera that are contenders for the “largest dinosaur of all time” title – including Argentinosaurus, Supersaurus, and Diplodocus – top out around 100 to 110 feet in length might indicate that these dinosaurs were reaching the anatomical ceiling of how large it was possible for them to get.

But let’s be clear about sauropod size. Biological quirks such as air sacs and laying lots of little eggs allowed sauropods to grow to large size, but these features did not drive dinosaur inflation. There were titanic dinosaurs as well as tiny ones. Dinosaurs did not experience the same barriers as mammals, and therefore evolved a greater range of body sizes. The evolutionary driving forces behind the evolution of truly huge body size are not clear, and likely differed from one group of dinosaurs to the next. Paleontologists have determined the features that made it possible for a creature as spectacular as Supersaurus to exist, but the reason why the dinosaur’s lineage ended up pushing biological boundaries of body size are still unknown.

Will creatures the size of Supersaurus ever walk the Earth again? Perhaps. Paleontologists have now outlined some of the major features that allowed huge body sizes to evolve. An egg-laying quadruped with a sturdy torso and some sort of efficient breathing system would be a good candidate. Sadly, though, there’s nothing alive today that quite fits that description. Mammals certainly don’t, and, as Taylor and Wedel pointed out in their study, the evolutionary pathways presently open to birds are limited by their bipedal posture. If anything on the scale of Supersaurus is going to evolve again, it’s many millions of years off.

Animal life was evolving for over 380 million years before the origin of sauropods, and there hasn’t been anything so wonderful as Supersaurus and Diplodocus in the last 66 million years. Maybe the behemoths will end up being a rare, contingent product of evolutionary unfolding that will never be matched. Still, thanks to the wonderfully rich fossil record, we can imagine the heyday of giants as we admire what remains of enormous dinosaurs.

References:

Sander, P., Christian, A., Clauss, M., Fechner, R., Gee, C., Griebeler, E. Gunga, H., Hummel, J., Mallison, H., Perry, S., Preuschoft, H., Rauhut, O., Remes, K., Tütken, T., Wings, O., Witzel, U. 2011. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews. 86, 1: 117-155. 10.1111/j.1469-185X.2010.00137.x

Taylor, M., Wedel, M. 2013. Why sauropods had long necks; and why giraffes have short necks. PeerJ: e36 http://dx.doi.org/10.7717/peerj.36

Werner, J., Griebeler, E. 2011. Reproductive biology and its impact on body size: Comparative analysis of mammalian, avian and dinosaurian reproduction. PLoS One. 6, 12: e28442. 10.1371/journal.pone.0028442

There are 37 Comments. Add Yours.

  1. Mike Taylor
    February 25, 2013

    Hi, Brian, thanks for the coverage!

    Just a few points to clarify …

    1. “No dinosaur ever grew to be 200 tons in weight.”

    To be precise, we have no compelling evidence that any dinosaur reached 200 tonnes — nor for that matter conclusive evidence of even 100 tonnes. But there are legitimate tantalising hints — lost and destroyed partial fossils — of sauropods that could conceivably have got that heavy. I wouldn’t rule it out.

    2. “Although exactly how these dinosaurs processed the massive amounts of plant food they needed is a mystery.”

    Well, not really. Seems to be simple hind-gut fermantation. With a saropod-sized torso, you retain ingesta for three days, which is as long as it takes to extract all the nutrients, whatever the particle size. For a big sauropod, chewing the food would simply be a waste of time — it wouldn’t get any more out of it.

    3. “the genera that are contenders for the “largest dinosaur of all time” title — including Argentinosaurus, Supersaurus, and Diplodocus — top out around 100 to 110 feet in length.”

    I’d lay good money that a complete adult Supersaurus skeleton would come out longer than that. Remember we’re talking about the neck along reaching 15 m, or about fifty feet.

    Hope this is helpful.

  2. Nicole
    February 25, 2013

    Great article! What about the possible effect of water– is there any evidence that these were water/swamp animals that kept most of their body underwater and used their long necks to reach the shore without predators reaching them? Was there possibly more of this type of environment around?

    [Nicole: Thanks for the kind words and your comment.

    Sauropods were entirely terrestrial animals. Even though old, inaccurate restorations used to show these dinosaurs up to their heads in water, we now know that dinosaurs such as Supersaurus lived entirely on land. In fact, that system of air sacs that they needed to breathe would have made sauropods relatively unstable in water, so they wouldn't have been able to just hang out in swamps (not to mention the problem of finding swamps of just the right depth!). For more, see this post I wrote for the Dinosaur Tracking blog - Brian Switek.]

  3. Jim
    February 25, 2013

    How did these giant beasts mate?

    [Jim - I wrote an overview of just that subject for Smithsonian a few years ago. I hope it helps. - Brian Switek]

  4. Bruce T.
    February 25, 2013

    Once when I was riding over to some friends’ house in Dublin CA, with some other friends, this candy apple red Jaguar roadster erratically veered into our lane on Route 680, nearly shoving us off the road. Fortunately my friend was a good driver, saved the day and our lives by quickly regaining control of his fishtailing station wagon. I noted the vanity license plate which read MR 40 40 on the rapidly disappearing sports car. That was the nickname of the steroidal Oakland Athletics slugger. He got the name because he was the first player to ever get 40 home runs and to steal 40 bases. He was always kind of a weird-o even in his early days at Oakland. I was at Canseco’s last game when he was suddenly traded after the middle of, I think, the first inning. Glad to see he’s keeping busy with Twitter. And that there’s a paleontology connection, however strained. Also, nice explanation of the science involved.

  5. Davros
    February 26, 2013

    Really interesting article!

    I’m not sure I buy the reproductive limitation on mammal size. Blue whales reach a maximum of about 110 feet and regularly make it to about 100 feet. Fin whales get to about 90 feet. If the costs of reproduction limit mammals size, surely it should limit maximum size in whales.

    Maybe it’s not the investment in offspring that limits terrestrial mammal size, but carrying that amount of mass internally. Dinosaurs, assuming they invest a similar total amount in young for a given body size, could get around the problem by laying several clutches. More of a fish strategy than a turtle strategy.

  6. Aaron
    February 26, 2013

    very interesting. but isn’t foraging range an important limitation on size as well. there is many examples of dwarfs in the fossil record like elephants and mammoths when their ranges were limited on small islands.

    This is just speculation, but maybe sauropods were so successful in the Jurassic becasuse there was larger land masses to support them. Does that sound reasonable?

    [Thanks for the idea, Aaron. Sauropods lived during the break-up of the continents that once made up Pangaea. Some of the largest - such as Argentinosaurus - were some of the last. The separation of the continents runs counter to the larger landmass=larger bodies idea. - BS]

  7. JMW
    February 26, 2013

    Lower gravity…of course! That explains all those “flying stegosaur” drawings from the late 19th and early 20th centuries!

    How could we have been so blind?

  8. Austin
    February 26, 2013

    I knew the gravity hypothesis was a bunch of hooey, but it’s still nice to see it officially refuted. I always thought there was more oxygen back then, though–so I learned something new about that as well.

    And in other news, Jose Canseco is a weirdo. Or he has a really great sense of humor, and doesn’t mind if everyone thinks he’s a weirdo.

    Also, not to be *that guy*, but:

    “…the extinction rhino Paraceratherium – about 26 feet long and 16 feet tall at the shoulder – weighed about 18 tons. You’d like a dinosaur about four times as long as Paraceratherium…”

    We all make mistakes.

  9. Christopher
    February 26, 2013

    What about the issues of blood pressure, nimbleness, and the flying pterosaurs? I feel like a lot of what Canseco actually asked/said got skipped over in this piece . . ..

  10. Brian Switek
    February 26, 2013

    Christopher: Blood pressure, how pterosaurs flew, and “nimbleness” (whatever that means) are all separate issues. Canseco was using his impressions about these topics to argue backwards that gravity must have been lower.

    As I established at the outset, and as Matthew Francis details in his post, there’s no evidence whatsoever that ancient gravity was different. So Canseco’s arguments totally fall apart – I don’t need to write a textbook countering each of his tweets. I chose to point out that there’s no difference between ancient and modern gravity, and, from there, tackle what we actually know about why dinosaurs got to be so much larger than any mammal. Since Canseco was totally wrong about ancient gravity being different, there was no point in addressing each of his tweets separately.

  11. David Esker
    February 26, 2013

    “What about the issues of blood pressure, nimbleness, and the flying pterosaurs? I feel like a lot of what Canseco actually asked/said got skipped over in this piece . . ..”
    Great point Christopher!

    In science we are suppose to ask questions about our reality so as to start us on the path to discovery. How the dinosaurs grew so large is certainly a legitimate scientific question. Yet the know-it-alls do not know the answer. How embarrassing. So they give one silly explanation after another so as to divert the public’s attention away from the fact they that they do not have a clue. As Chris clarifies, the large dinosaurs is just one of many scientific paradoxes that these ‘experts’ continue to sidestep on their way to their retirement.

    These science paradoxes were solved and posted on the internet over seven years ago. For seven years DinosaurTheory.com has been the number one science website on the internet. And because DinosaurTheory.com is outstanding science it will probably continue being number one indefinitely. Science is changing in a big way, but you will not hear about this from these know-it-alls; they have nothing to gain by admitting that they are wrong. Read DinosaurTheory.com and rediscovery your love for science.

    • Mike Taylor
      February 27, 2013

      How the dinosaurs grew so large is certainly a legitimate scientific question. Yet the know-it-alls do not know the answer.

      As a matter of fact, yes, we do. The best overview is found in Sander et al. 2010, “Biology of the sauropod dinosaurs: the evolution of
      gigantism”. Happily, it’s open access, so anyone who cares to understand can get it freely from here.

  12. Austin
    February 27, 2013

    “So they give one silly explanation after another so as to divert the public’s attention away from the fact they that they do not have a clue. As Chris clarifies, the large dinosaurs is just one of many scientific paradoxes that these ‘experts’ continue to sidestep on their way to their retirement.”

    So they “sidestep” this issue… aside from writing about it, studying it, and explaining it?

  13. David Esker
    February 27, 2013

    Hi Mike. You start off with the statement “As a matter of fact…” and then you give a link to a paper presenting a dumb hypothesis: long necks produced gigantism. Mike, a hypothesis is not a fact, not even close. Your claim that this solves the paradox of how the dinosaurs grew so large does not even qualify as being ridicules. It’s just stupid. Sorry dude, but if you want to actually contribute to science then you need to develop your thinking skills rather than just play follow the leader.

    “Unthinking respect for authority is the greatest enemy of truth.” Albert Einstein

    • Mike Taylor
      February 28, 2013

      “Sorry dude, but if you want to actually contribute to science then you need to develop your thinking skills rather than just play follow the leader.”

      Well, I don’t wish to seem arrogant, but in this field I am one of the leaders. See my publications (all free to read) here.

      I am afraid your “theory” proposes left-field solutions to problems that are already well understood.

      And with that, I will leave the last word to you, as I doubt there is much point in prolonging this discussion.

  14. Jordan
    March 1, 2013

    I really enjoyed reading this article. It was my first time coming to this site. I will have to look for more things you have written. Very interesting

  15. Adrian D. Thysse
    March 1, 2013

    Great article. I have strayed from reading your blog regularly in the last few years…my loss.

  16. BJ Nicholls
    March 1, 2013

    Kudos to Jose Canseco for having an the science curiosity to think about interesting questions. And to Brian and Matthew for respecting curiosity by providing considerate scientific answers.

  17. Mark Robinson
    March 1, 2013

    @David Esker
    Please direct me to your peer-reviewed paper(s) where you delineate the actual evidence for your hypothesis that the Mesozoic atmosphere was substantially “thicker” than today.

    Making something up is not doing science no matter how neatly it might resolve whatever problems you think exist. You could make it science by looking for evidence both in support *and* against your idea, than (and this is important) publishing it so that other scientists can review the evidence for themselves.

    You should consider getting in contact with Brian J. Ford. He shares your methodology.

  18. Jaideep
    March 7, 2013

    Now looking at my pet cockatoo in whole new light. Great article! We can say now sauropods have been up against gravity ever since. I also wonder why there haven’t been any walking-type (like modern hippos) life form of similar gigantism in our oceans; you know with all the water to support such a gait?

  19. Stephen Hurrell
    March 8, 2013

    Interesting article. Can I check a few references please? When you say that “In a 2011 paper on sauropod gigantism, paleontologist P. Martin Sander and coauthors briefly debunked the proposal that Jurassic gravity was weaker.” Are you talking about the sections that say:
    “Gravity also limits body size, and the current gravity constant of 0.981 ms−2 has been proposed to limit body size to 20 t (Economos, 1981) based on a mass estimate for the largest land mammal ever, Paraceratherium (also known as Indricotherium). However, sauropods were much heavier than the largest land mammals, and G¨unther et al. (2002) suggested the upper limit for terrestrial organisms due to gravitational forces to be at least 75 t. Similarly, Hokkanen (1986) calculated that bone strength and muscle forces only become limiting to terrestrial animal size at masses in excess of 100 t.”

    “(1) Physical boundary conditions
    Although gravity is of overriding importance in determining the bauplan of an organism, we have to assume that there were no secular variations in Earth’s gravity in the Phanerozoic geologic past (Economos, 1981).”

    [Yes. That's it. - Brian]

    All the best

    Stephen

  20. Stephen Hurrell
    March 13, 2013

    Thanks for confirming those references. I briefly discussed Hokkanen’s 1985 paper in my 2012 paper about ancient gravity and highlighted how he had also calculated the athletic ability of the largest animal to be so low that, “a mass 10^6 kg allows a running speed of 6 km/h – a man could walk and overtake”. I can’t think of any modern paleontologists that argue that the sauropods were this unathletic. Do you know of any? Your suggestion of air sacs invading the bones to “make the skeletons of these dinosaurs lighter without sacrificing strength” overcomes this objection of low athletic ability but I calculate we would need to reduce sauropods weight by about 50% to explain their large size. This seems a very large void space to account for. How large are the air sacs you are suggesting? But air sacs may only be part of the answer and as you suggest, perhaps a combination of “air sacs and laying lots of little eggs allowed sauropods to grow to large size”.

    Also my memory of Economos’s 1981 paper (I can’t find my copy unfortunately) is that he simply assumed that the limit to mammal size must be the largest mammal ever found without outlining why the mammals of today are smaller. Mammals’ size is very interesting. Have you considered writing an article about this? It always seems such a neglected area.

    Hopefully many of your thoughts about large size will become clearer when I get hold of a copy of your new book, My Beloved Brontosaurus.

    All the best.

    Stephen

  21. Herman Diaz
    March 31, 2013

    Good summary overall (as usual). There are 3 things that stood out to me, though.

    “Although exactly how these dinosaurs processed the massive amounts of plant food they needed is a mystery.”

    Based on what I’ve read (although I might’ve missed something newer), the same way prosauropods did (“Once the food was past the mouth, grinding likely took place via gastroliths — which have been found in association with prosauropod skeletons — and by stomach fermention, to judge from their barrel—shaped torsos”: http://www.amazon.com/Dinosaurs-Concise-David-E-Fastovsky/dp/0521282373/ref=la_B001IQZAB4_1_1?ie=UTF8&qid=1364756913&sr=1-1 ).

    “Sauropod mothers laid clutches about 10 eggs at a time in small nests, and the embryonic dinosaurs developed in eggs about the size of a large grapefruit.”

    Again, based on what I’ve read, they laid “clusters of 15—34 linearly paired eggs” (Same book).

    “The fact that all the genera that are contenders for the “largest dinosaur of all time” title – including Argentinosaurus, Supersaurus, and Diplodocus – top out around 100 to 110 feet in length might indicate that these dinosaurs were reaching the anatomical ceiling of how large it was possible for them to get.”

    Again, based on what I’ve read, the largest sauropods are estimated to have reached “40 m from the tip of the snout to the tip of the tail” (Same book).

  22. David Esker
    September 17, 2013

    There are many examples of in the history of science where a new unusual perspective eventually won out as being the correct solution to a science puzzle. Copernicus’ idea that the Earth revolves around the Sun, Darwin’s idea that humans and other species evolved from other species, and Einstein’s idea and mass and time changes as an object travels at speeds that are close to the speed of light. When we look back with the wisdom of hindsight we observe that in nearly every case the initial ideas of the science community were hardly distinguishable from the ideas of the other crackpots. It is not surprising that the science community would like everyone to believe the myth of them being perfect and all knowing rather than remember all of their mistakes and folly.

    The large size of dinosaurs and pterosaurs is a scientific paradox. Galileo’s Square-Cube Law clarifies how size matters and once we understand this we recognize that the exceptional size of the dinosaurs is a paradox that cannot be dismissed. In 1986, the paleontology community contracted the best aerodynamic experts to build them a flying radio control pterosaur so that they could justify their claim that they understand how the pterosaurs flew. Even with considerable cheating, they could not get this ‘animal’ to fly. And because of the laws of aerodynamics, they never will. Thus we are at a point where people must either yield to the evidence of there being a scientific paradox or forfeit their claim to being a scientist.

    Some proposed solutions to this scientific paradox really are stupid. By stupid I mean that it hardly takes any effort to identify both the flaws in the reasoning and the contradicting evidence. Yet the science community can take no pleasure in mocking these ideas when their own ad hoc ideas are no different. In their effort to dismiss the large dinosaur paradox, the ad hoc solutions that some scientists have proposed are so stupid that these ‘scientists’ have no business laughing at anyone but themselves.

    Despite what the leaders of the paleontology community might say about wanting to advance science, they have a very strong motivation for censoring any new ideas that might solve this puzzle. The reality is that if someone outside of paleontology solves this problem the leaders of the paleontology community lose everything… prestige, grant money, possibly their careers, everything.

    Based on the assumption that my ideas have been censored, one commenter has attempted to dismiss my ideas my implying that my ideas have not passed peer review. His assumption is incorrect and extremely misleading. My writings and presentations on topics related to the large dinosaur paradox have been peer reviewed and accepted by over two dozen scientific educational committees around the country.

    I think the paleontology community needs to acknowledge the evidence of this science paradox and their inability to solve this problem on their own. They need to listen to scientists outside of their discipline; scientists that can help them. Otherwise they will be the ones who will be dismissed as the propagators of pseudoscience, and in fact that is what is already happening.

    • Mike Taylor
      September 17, 2013

      We listen to scientists outside of our own discipline all the time. We publish collaborative papers alongside zoologists, flight dynamicists and more. Among our ranks are some of the world’s leading biomechanics experts. People like John Hutchinson don’t get that level of respect just because they’ve demanded it, but because they’ve proved they’re worth it with decades of top-quality, careful, detailed work.

      Please don’t waste your time in thinking you’ve thought of something that John and his colleagues have missed. You haven’t.

  23. Harrison Pakenham
    September 22, 2013

    “Just so stories”. A lack of real evidence makes many theories plausible or at least debatable.

  24. David Esker
    October 5, 2013

    Hi Mike,

    Since you are now telling me that John Hutchinson can do a better job than you in answering my questions, I sent him the following email.

    Hi John,

    Your name has come up in the comment section of the National Geographic Phenomena blog. The discussion began with baseball player Jose Canseco questioning how the dinosaurs grew so large and from there it evolved into a debate as to whether the exceptionally large dinosaurs and pterosaurs give evidence to there being a scientific paradox. In defending his position that the large dinosaurs and pterosaurs do not present a scientific paradox, Mike Taylor first informed me that he is one of the leading experts in this field but now he is indicating that you are really the top guy with all the answers.

    Please take a moment to read comments so as to get up to speed on the discussion. Once you are ready I then have a new question for you and Mike.

    One of my science class labs is called Weighing Dinosaurs. It is a wonderful lab for students where by submerging authenticated dinosaur models in water my students are able first to determine the mass of the displaced water using Archimedes Principles and then scale this value up so as to determine the mass of a full size dinosaur. When using models of present day animals and models of the smaller dinosaurs the results are right on target, as every good scientist would expect. Yet oddly enough the experiment gives much higher values than the estimates that most paleontologists give for the mass of the larger dinosaurs. Within the last few years some paleontologists have lowered their mass estimates of the Brachiosaurus down to being a mere 23 tons, while the results of this experiment place the mass of the Brachiosaurus in the ballpark of 87 to 97 tons. Would you like to explain to me how the estimates from these paleontologists could be so far off from the experimental results?

    Clearly, not being able to explain how the exceptionally large and massive dinosaurs were able to walk about on the land is an embarrassing problem for paleontologists, but fudging the numbers so as to avoid the problem is not something to be proud of.

    Fudging of the mass of the largest dinosaurs is just one of many examples I could give to illustrate how paleontologists are dodging the facts; and this resistance to accepting evidence is eroding the credibility of science. As a physicist, I feel that I speak for all good scientists when I state that this ‘could not care less about the facts’ culture of the paleontology community is an embarrassment to science. Since you are currently a recognized leader within the paleontology community I would like to hear from you how you plan to address this problem.

    David Esker

  25. Mike Taylor
    October 6, 2013

    David,

    Regarding changing mass estimates for Giraffatitan (= “Brachiosaurus” brancai), see page 375 and Table 2 of my 2010 paper on this history of sauropod palaeontology:
    http://www.miketaylor.org.uk/dino/pubs/taylor2010/Taylor2010-sauropod-history.pdf

  26. David Esker
    October 8, 2013

    Hi Mike,

    Thank you for sending me a link to your publication Sauropod dinosaur research: a historical review. You did a fine job of summarizing the historical changes in the perspectives regarding these large dinosaurs. I also like the fact that you included the table of results from different researchers regarding their mass estimates for Brachiosaurus.

    Regarding the mass estimates of the Brachiosaurus I must wonder does it really take a doctoral degree in paleontology to produce a reasonably precise estimate of this animal’s mass, and how is it that these estimates are all over the place?

    It appears that Colbert was the first to actually conduct an actual experiment and in doing so he produced the estimate of the Brachiosaurus having a mass of 78 tons. By using the Archimedes Principle method, my students get either 87 or 97 tons depending on which model is used. Since the mass of adult animals can vary, I am fine with these numbers all being in the same ballpark.

    But then you guys cannot seem to leave well enough alone. The limb-bone allometry method has about as much credibility as the proposed foot print method and so these numbers should be thrown out. The same goes for the computer modeling. I fail to see how computer modeling can serve any purpose other than confusing the public. The use of computers is often associated with producing greater precision in making calculations, but in this case in inclusion of computers actually decreases the precision because you are using the computers to make models of the models. I am not sure how your graphic double integration method differs from the computer models. If you are interested in a further review of your work, I am a physicist and so unlike many of your associates I can do the math and I would not mind taking a look at it.

    The problem that I am seeing here is the many opportunities for the researcher’s bias perspective to be inserted into the process so as to produce the desired outcome. The saurpods were not just incredibly large terrestrial animals; they were incredibly massive terrestrial animals. Explaining how these massive animals were able to walk around on the earth remains a perplexing problem for the paleontology community. Hence the idea of fudging the mass numbers to be much lower will more likely come with approval rather than resistance from your fellow paleontologists. However by giving their approval to these fudged mass estimates the paleontology community has lost much of its credibility.

    As I said before, the paradox of how these animals grew so large is only one of several puzzles concerning the Mesozoic era. Instead of fudging numbers and/or sweeping facts under the rug, you need to open up your minds to the possibility that you might have missed something, something big.

    David Esker

  27. Mike Taylor
    October 8, 2013

    Hi, David. Colbert used models that were both incorrectly shaped and too large — see for example Paul’s (1997) Dinofest paper. Alexander followed this error by using the BMNH models, which are not scientifically accurate. I imagine your students are falling into the same trap.

    I agree that estimating body mass by regression lines on a mass-vs-limb-dimensions plot is a poor method, since it brings in additional presuppositions. In particular, the Russell et al. estimate is plainly very wrong.

    Computer modelling is in some respects superior to physical modelling for two reasons. First, the models can easily be tweaked, e.g. to see how mass varies under different body-fat assumptions. Second, they can be automatically constructed from measurements taken by laser directly from mounted skeletons.

    Graphic Double Integration would seem very primitive compared with the other methods, but works surprisingly well. In the only published study that compares the accuracy of various methods on extant animals of known mass, Hurlburt (1999) found that GDI estimates were sometimes off by as much as 20%, but that allometric estimates were much worse, with several off by 90-100% and one off by more than 800%. GDI estimates were not only closer to the right answers, they also varied much less than allometric methods.

    For more, see Matt’s SV-POW! post.

    I can tell you that I am certainly not fudging the numbers downwards. If anything, me personal inclination is to want them to be higher. I don’t see why crappy whales should get to be the biggest animals ever.

  28. David Esker
    October 10, 2013

    Hi Mike,

    So you are claiming that Colbert, Alexander, and my results are all wrong because every one of the different authenticated Brachiosaurus models that we used were wrong.

    I do not think so or at least they cannot be off to the degree that you are claiming. My hunch is that the creation of each one of these popular lines of dinosaur models such as Carnegie, Schleich, Papo museum and others required the input of several paleontologists and biologists. Then after being placed in the gift shops of museums the commercial success of these dinosaurs models largely depended on the approval of most paleontologists. Since the form of these dinosaurs is a matter of speculation you have a right to your opinion. But by suggesting that these dinosaurs were three or four times thinner you are way out on your own in taking an extremist position. As a non paleontologist, I just want to say that to me many of these accepted dinosaur models already look too thin. For many of these dinosaur species, the models have too thin of a torso and so the skin has to be stretched out in an unnatural way to accommodate the ischium and pubis bones extending from the hips. While not fully to my liking, I am still willing to accept the consensus of the paleontology community that based on their understanding of biology and the fossil evidence that these experts have properly determined size and shape of these dinosaurs. Can you not do the same?

    Once we have a reasonable agreement on the size and shape of these animals the only other important variable necessary for determining the mass is the overall density of these dinosaurs. The vast majority of land animals have a density very close to the density of water. What argument can you present that dinosaurs could have had a different density? More important, what evidence could you present that might indicate that the dinosaurs may have had a lower density so as to support your low mass estimate?

    Pick any authenticated Brachiosaurus model that you want. Use Archimedes Principles to accurately determine its volume. Multiply this by your corrected density if it is not 1g/cm3. Scale this value up to size and you have the mass of your Brachiosaurs. That’s really all there is to it. I have worked this experiment with two different models of Brachiosaurus, and my guess is that if you were to purchase all of these various models and run this experiment that all of the results would fall in the range of 60 to 100 tons.

    Coming up with a reasonably accurate estimate of the mass of these dinosaurs isn’t that hard. The real problem is when the results are not what people want. Then people often respond by refusing to accept the results. You talk about having the ability to tweak a process as being a good thing. It is not. People tend to be incredibly resistant to changes in their beliefs. Often times, as it is in this case, the evidence is right there in front of us but we do not like what it is saying and so we try to push it to the side. Ignoring the evidence serves no purpose other than holding back the advancement of science. Dinosaurs were incredible large massive terrestrial animals. Let’s at least acknowledge that it is odd that these animals were able to grow so large.

    David Esker

    • Mike Taylor
      October 10, 2013

      “So you are claiming that Colbert, Alexander, and my results are all wrong because every one of the different authenticated Brachiosaurus models that we used were wrong.”

      Yes. Alexander would agree with that assessment; so would Colbert, before he died. You’re talking about work done in the 1960s and 1980s. It’s been superseded.

      “I am still willing to accept the consensus of the paleontology community that based on their understanding of biology and the fossil evidence that these experts have properly determined size and shape of these dinosaurs. Can you not do the same?”

      The consensus of palaeontologists is that these models are not scientifically accurate, and that they are badly scaled.

  29. Staten-John
    October 10, 2013

    David,
    I agree with your analysis. Aside from sauropods:

    The African elephant spends 16-20 hours a day gathering food. If Indricotherium could exist today, how many hours a day would it need to gather food?

    Some things are obvious but once folks dig in their heels, there’s no changing their minds.
    Good luck!

  30. David Esker
    October 12, 2013

    Hi Mike,

    I think that we are starting to go in circles.

    You are claiming that Colbert and Alexander’s mass estimates should be thrown out because they used inaccurate obese Brachiosaur models. I am not sure what Brachiosaurus models Colbert and Alexander used but nevertheless your assertion does not make sense. Using Archimedes Principles, I, my students, or really just about anyone can use any of the currently available authenticated Brachiosaurus models – Carnegie, Schleich, Papo and so on – and the experiment will indicate that the mass of a Brachiosaurus is actually even higher than the values given by Colbert and Alexander.

    Regarding the scaling of these models, it is not rocket science to compare the length of the model to the stated or measured lengths of the skeletons to get the scaling. For example, there appears to be some confusion over whether the Carnegie Brachiosaurs model is a 50 or a 40 scale. To end this confusion we simply do a comparison of the measurements and this comparison shows that the Carnegie model is indeed a 50 scale.

    I have to wonder what kind of freakishly starved-looking model you would have to create so as to achieve a mass estimate that is three or four times less than the mass estimates produced by the currently popular authenticated Brachiosaurus models. Such a creation could not be brought out for presentation to the public as being representative of a Brachiosaurus without it being severely criticized by biologists, zoologists, and your fellow paleontologists as being an abomination.

    It is understandable that the paleontology community would like to see very low mass estimates for all of the larger dinosaurs. Very low mass estimates help to get the paleontology community off the hook for not being able to explain how these terrestrial animals grew so large. Nevertheless the scientific evidence indicates that your mass estimate for the Brachiosaurus is not even close to being accurate.

    At this point it appears that we have each hit all the major points of this debate such that we are now beginning to repeat ourselves. Therefore I would like to make this my last entry. It appears to me that we are just going to have to agree that we disagree. I thank you for the discussion.

    David Esker

  31. Mike Taylor
    October 14, 2013

    You’re right, we’re going in circles. Read the literature for more information.

  32. Hit Shed
    January 1, 2014

    The answer to all this can probably be solved by a Paleobotanist. How big were the ancient trees that are close relatives to some of today’s trees? In other words: How big was the ancient Redwood compared to today’s Redwood. This may be some research that would help…

  33. Gianni
    March 30, 2014

    I wonder how carnivorous dinosaurs got that big since carnivorous mammals never got much over 1 ton despite potential preys with the sizes of tryceratops (like brontotherium/elasmotherium/elephants) or even medium sized sauropods (like paraceratherium).

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