Tuesday, April 3, 2012

No, dinosaurs were not aquatic.

So, as some of you might have heard, a very questionable news item hit the BBC this morning.  In short, they did a news release on the claim by a rather odd individual that all large dinosaurs were semi-aquatic.  I could go on for pages about how many things are wrong with the "research" in question (which isn't actually research because no evidence or data are provided) or the fact that it was given a feeling of legitimacy by the BBC.  I'd just be repeating my colleagues, though, because they have taken care of it nicely here, here, and here.

Now, I'll be honest - I still think that this may have been an elaborate April Fool's Day prank, and others have suggested this as well.  Even if that is true, however, it managed to dupe the BBC, which is pretty scary.

The individual who was interviewed on the program, Brian J. Ford, has a website where he discusses the supposed merits of aquatic dinosaurs, etc.  I was just going to laugh and blow the whole thing off, but it occurs to me that his supposedly "difficult" questions might actually pose some interest to readers.  So, here is my quick debunking of his list.  Enjoy.




"a) How dinosaur limbs could otherwise have borne such weight 
(up to 100 tonnes)"

-- Short answer: easily.  Longer answer: bone is much stronger in axial compression than in bending or torsion.  Sauropods, in particular, had columnar limbs, so the bones were loaded almost purely in axial compression.  Their long bones were also almost solid compact bone at midshaft.  The failure stress of compact bone in axial compression is 170 GPa, which for comparison, is nearly 5x the compressive failure stress for concrete.  Not only could sauropod limbs support their weight, not a single sauropod known to date was at the mechanical limit for the group.  It's also worth noting that the 100 tonnes estimate is pretty outrageous.  Mike Taylor (an expert on sauropods, specifically) estimates Giraffatitan to have weighed in at 23 short tons in life.  That is among the largest known sauropods.  So it's a bit puzzling where the other 80+ short tons are coming from.  Perhaps sauropods were composed largely of metal.

"b) Why they would expend such a large amount of metabolic energy holding tails erect 
(There are no tail drag marks in the fossil footprints; there are for crocodiles)"

--"Why" is presumably because of mobility and balance.  What I think he really means is "how", to which the answer is that holding tails erect is not very energetically expensive when much of the weight support is done by tension.  Besides, plenty of animals hold parts of their body upright for long periods of time.  We hold our entire trunk, upper limbs, head and neck erect.

"c) How they maintained their steady body temperature without the cushion of a huge body of warm water (Isotope analysis shows they maintained a constant body temperature and no reptiles evolved a mechanism to do so)"

--Vertebrate animals are mostly water to begin with; large animals have naturally high thermal inertia as a result (this leads to the possibility of so-called "gigantohomeothermy" for very large ectothermic, organisms).  Even more damning, however, is that Ford has forgotten basic physics here: unless the water was the temperature of the animals, or greater, they would lose heat over time while submerged.  Given that homeoendothermic animals (i.e. "warm-blooded") can be 90+ degrees or more resting temperature, that is some awfully hot water.  Oh, and "reptiles" have evolved endothermy at least twice (see: mammals and birds - the latter, being dinosaurs, likely inherited some endothermic traits from the very sorts of animals Ford implies could not possibly have been truly endothermic).

"d) Why the abundant fossil footprint are proportionately comparable 
(They'd have sunk up to the armpits were they standing on dry land)"

--The depth to which an animal sinks is a product of the shear imposed on the substrate, not simply total mass.  This depends on the stress on each foot, as well as duty factors and substrate conditions.  In short, there is no reason to think that a large dinosaur would sink appreciably deep on dry land.  Elephants, for example, do not leave footprints much deeper than those of humans.

"e) Why they claim that Spinosaurus - and a host of similar dinosaurs! - simply dipped their heads beneath the waves (Their snout glands are like those of crocodiles; clearly they spent most of their lives in water)"

--"Host" here is about three or four, depending on who you ask.  In short, while spinosaurids have cranial features associated with aquatic feeding, the postcrania typically lack any major aquatic adaptations.  Hence, the current best conclusion is that they hunted from the shoreline.

19 comments:

  1. Mammals are not reptiles, as Reptilia is defined as the most recent common ancestor of >insert living reptile species< and all of its descendants, and synapsids diverged before that. Pedant Man away!!!!

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  2. Ah, but that's not the only definition of Reptilia out there, and it's not the one that the illustrious Mr Ford was using. He seems to have been using the more classic, ecological version, in which scaly ectotherms are and were reptiles. By that usage, early synapsids count, and thus so do mammals.

    Of course the real problem here is that "Reptilia" is really just a slow motion train wreck of a phylogenetic group, which so many potential definitions out there I can't keep them all straight. I prefer the same one you do, when pushed, but I don't think it's the one in question.

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  3. Has another phylogenetic definition of Reptilia been published? The four I know of (Gauthier et al., 1988; Gauthier et al., 2004; Reisz, 2004; Kischlat and Timm, 2006) are all equivalent variations of the crown clade.

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  4. Yes, there have been a few, but I don't think most have stuck.

    See: http://sysbio.oxfordjournals.org/content/53/5/815.full

    And, of course, what is in Reptilia changes, even if the definition is kept constant, because things keep moving in and out of diapsida etc as new analyses are published. So far as I know, all of the recent versions do exclude Synapsids from Reptilia, but the colloquial usage of the term is less clear. Obviously neither you nor I tend to be into colloquial usages, but the source I was referring to (Ford) does, sad to say.

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  5. This article claims large pterosaurs would not have been able to fly in todays world:

    http://www.dinosaurtheory.com/flight.html

    What are your thoughts?

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    1. Ah, yes, David Esker's site. To be frank, David has no idea what he is doing. I actually tried to chat with him about it at one point, but he turns out to be rather hard to talk to (he's remarkably aggressive and abrasive). He and I had a little "debate" on the NatGeo news site at one point.

      It would take forever to debunk everything in that website, because practically everything on it is inaccurate, but here are a few highlights:

      1) Esker tries to get the mass of an azhdarchid pterosaur by isometrically scaling a swan. This is nowhere close to a good shape match (swans have short wings and large torsos), and yields a super-massive pterosaur.

      2) He tries to derive available power by literally calculating in terms of horse masses and assuming that "horse power" is literally the power of one equid. Actually, a horsepower is 745.7 watts, and there are already good estimates of vertebrate muscle power production in the literature. The estimates of available power on that site are completely nonsensical (for example, the anaerobic muscle of quail produces about 390 Watts/kg. So just two kg of quail grade muscle would be more power than 1 horsepower).

      3) It should be apparent that the estimates aren't working when the results for living species don't make sense. He gets marginal results for a few living animals that are nowhere near marginal flyers, and tries to play it off with things like "they don't like to fly in the rain" and other such nonsense. That ignores the fact that a flying animal with only 1.1 to 1.2 times the power output required to fly would be unable to climb in altitude effectively. The reality, of course, is that his equations just aren't correct. If you have a particular one in mind I'm happy to show you where the derivation failed.

      4) He doesn't understand launch at all. It is not wing driven in large vertebrate flyers.

      5) Most troubling, Esker insists that before he derived these critical equations, educators did not know how flight worked. This is hubris of the highest caliber. Not only are his equations incorrect in many places, but the correct equations for these same problems were derived back in the 1920's - that many individuals cannot explain flight mechanics effectively has nothing to do with a fundamental lack of knowledge among aerodynamicists.

      6) His solution is an atmosphere 3/4 the density of water. There are so many things wrong with this it boggles my mind. Not the least that it would kill most animal life (and most of the plants, too). Plus it'd show up in the geological record big time (and doesn't).

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    2. Thanks again to Alex for the question; I hope that the little rant above is useful!

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  6. As an aside, readers will note that my comment reply to Alex above may seem rather snide and aggressive. I just want to clarify that this is not because he is wrong, or anything to do with credentials. Those things don't bother me (if it's wrong I'll correct when reasonable, but I'm wrong plenty often myself). I took a forceful tone because David Esker has been extremely condescending and arrogant to me, Mark Witton, and others. As such, I no longer feel the need to be as polite in return as I would usually be.

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  7. Oh, and when I said "he is wrong" above, I mean David Esker, of course, not Alex. Sorry for the poor grammar. Sheesh, not an on-day for me...

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    1. Oh, ok thank you. Im just a layman but mr eskers "solution" of an atmosphere that is almost as thick as water really did seem quite extreme and implausible to me but I just wanted to be sure.

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    2. Mr Habib. I have read many of your articles, and those by Witton et al. I have studied bird-flight and I have flown model aircraft all my life. I can tell you in words of one syllable that Quetzalcoatlus, as specified by palaeontologists, could not even glide in our present atmosphere, let alone take off or climb. David Esker is also right that aerodynamicists don't always know what they are talking about - in certain areas. I know how lost they get as soon a Reynolds numbers come down, because it is not part of their training.

      To the man on the street, a Boeing 747 lifts off at 150mph. A Ferrari can travel much faster than that. So why can't a Ferrari tow a 747 into the air? I'll bet you could produce some formuale to prove it could, but reality tells us all it just can't be done.

      The four-point launch theory is frankly pathetic. If Quetzelcoatlus could launch to even half its stall speed with a single jump, it still has huge wings to unfurl (against the air flow) before it could even start a downstroke. It would be flat on its face before it even got half way. I think you have a long way to go to beat David Esker. His simple thick atmosphere theory is Occams Razor writ large and I think it should be researched, not belittled as you have done. In my 50 years of flying all shapes and sizes of models, I could tell just by looking at it whether a particular machine could glide or plummet. How do you know the thick atmsophere is wrong?

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    3. Oh, and your sweeping generalisation:

      6) His solution is an atmosphere 3/4 the density of water. There are so many things wrong with this it boggles my mind. Not the least that it would kill most animal life (and most of the plants, too). Plus it'd show up in the geological record big time (and doesn't).

      Let's see some expansion. Why couldn't animal life exist? How would it show up in geological records? What does 'boggle the mind' mean in scientific terms?

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  8. Even if that is true, however, it managed to dupe the BBC, which is pretty scary.

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  9. I wanted to see what comments you got. Nice blog by the way.

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  10. There are no tail drag marks in the fossil footprints; there are for crocodiles.

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  11. Ah, yes, David Esker's site. To be frank, David has no idea what he is doing.

    Come on Mr Habib - apart from talking like a severe non-scientist, I have yet to see anything from you that remotely approaches the detail and credibility of David Esker's site.
    1. How do you explain that Quetzalcoatlus clearly cannot fly in our atmosphere. No waffle - it just can't.
    2. If the thick atmosphere (lets call it a hypothesis for now) is wrong - what would you be looking for under paleoclimatology to show that it is wrong. Has anyone done a study on it?
    3. I just don't like the way you belittle someone in a scientific blog. It doesn't matter whether you love him or hate him, just concentrate on what he is saying.
    4. Have you done the maths for a Q. to fly in a heavy atmosphere? I have and it flies a treat. It doesn't even need 3/4 of the density of water - it is nearer half.

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  12. Mike Habib,
    If you get to read this I challenge you to provide the maths behind your outrageous claims that Quetzalcoatlus Northropi could fly at 80mph; could fly for 12,000 miles non stop (literally); could reach 15,00 ft altitude and yet had a body about the same size as a Labrador dog: a shoulder to hip measurement of less than 2 feet to hold the muscle mass to flap a 34ft wing.
    Habib, unless you can provide some maths for the above, I place you as a charlatan and a snake-oil salesman. You are one of those so called 'scientists' who invent facts to fit the answers they have already decided they want. Shame on you. Give me the maths behind these outrageous claims above or withdraw them. Put up - or shut up!
    Phil Parsons

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  13. Phil Parsons,
    I'm not sure you quite understand how Occam's Razor works. One way to think about it is to accept the explanation that requires the smallest number of magic wands. Even if we accept your contention that Quetzalcoatlus couldn't fly, that's only one wand. Esker's explanation requires one wand to somehow make the atmosphere almost 12 times as dense as that of Venus, a second to somehow make animals survive under what would have to be vastly different conditions than those known to be capable of supporting life, a third to make that atmosphere leave no traces in the formation of minerals, a fourth to make it leave no traces in the anatomy of these presumably very different animals (aside from the flight of the Quetzalcoatlus), and a fifth to somehow make that atmosphere disappear. There are probably many more, but it is already clear that five is more than one. Occam's razor is not on your side this time.

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