More sketches from Brian Engh

January 19, 2013

BrontomerusRoughWeb From field correspondent Brian Engh:

A Brontomerus on the edge of a jumbled forest of partially knocked over trees. While I won’t be finishing this particular drawing I decided I want to develop this idea a bit further – I think it would be cool to show a group of brontomeri rearing and grazing on the edge of a forest where a lot of the trees are leaning and show signs of heavy grazing, particularly by giants who rear up, bear hug them and rip down their branches. I’m talking tore-up bark around hand-claw height, trees that are growing bent, but then straighten up above max-bronto height, and maybe a constellation of camptosaurs and pterosaurs living around the brontos for food and protection… anyway, just an idea. Any thoughts?

Yeah. I judge it rad. And plausible. I love the heavy texturing on Bronto and the way the background is simple and evocative at the same time. I like the idea of a forest modified by sauropods for their use. I would like to see more plants damaged by sauropods (but still surviving)–and vice versa. For the proposed full version, the camptosaurs will have to be replaced by tenontosaurs, this being the Early Cretaceous. But they’re both ornithopods, so probably no one will know or care.

Anyway, I’m pretty sure Brian wants genuine feedback, and not just predictable gushing from yours truly. The comment field is open.

Bonus Engh sketch: a rearing Miragaia. Rearing Miragaia by Brian Engh

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35 Responses to “More sketches from Brian Engh”

  1. Mike Taylor Says:

    Lots to love about this, but one crucial error (if this is meant to be Brontomerus) — the thighs are tiny! Check again the ventral view of the ilium, and see how forward it projects and how far outwards it flares. That ilium wouldn’t fit inside the sauropod in the drawing.

  2. Matt Wedel Says:

    I wondered about that, but I decided it was fine as-is. Here’s why: the sauropod is not shown in lateral view here, but antero-lateral oblique. That combined with the lateral flare of the preacetabular process of the ilium means that we’re looking basically straight down the preacetabular blade, so it shouldn’t be “sticking out” anywhere in the drawing because it’s pointing right at us.

    Second item is that because of incompleteness we really have no idea how big the ilium was compared to the rest of the animal. In Paco’s version we advised him to make the ilium proportionally large and visually prominent, so that it defined the dorsal margin of the body profile. But (1) we don’t know how tall the sacral neural spines were, and (2) we don’t know how much the dorsal ribs flared out. A taller back profile and a wider gut would help blend the body profile and make the ilium and its associated musculature stand out less.

    Anyway, with those caveats aside, I mostly agree with you, in that I think it is likely that the ilium was more visually prominent. But I think it is at least plausible that it was not, and that’s my usual standard for judging paleoart.

    One point in favor of having the ilium jump out more is that almost all macronarians had wide sacra, which would tend to separate the ilia quite a bit more. Since this is an antero-lateral oblique drawing, that width would tend to shove the hips outward. This one’s a bit narrow in the butt.

  3. Mickey Mortimer Says:

    “I would like to see more plants damaged by sauropods (but still surviving)–and vice versa.”

    So more sauropods damaged by plants (but still surviving)? Perhaps a sauropod with brambles caught around its neck, which is subsequently scratched up. Or one who was stupid enough to wander into a broken branch, leaving it jutting from a bleeding wound like a spear… ;)

  4. Heteromeles Says:

    Unlike an elephant, that sauropod doesn’t look like it’s built like a bulldozer. How does it go about knocking down a tree?
    Would it make sense more sense to show the trees as heavily pruned (google “bad tree pruning” for a lot of examples), but upright?

    One thing I’ve seen in old pictures of Santa Catalina Island (which was heavily overgrazed) were large bare areas with big thickets of prickly pear. The only well-developed trees and shrubs were well inside the cactus rings, out of the range of cattle, sheep, goats, pigs, bison, and mule deer.

    I’d suggest something similar for a Mesozoic landscape, rings of prickly cycads (or similar) with trees in the middle, or, in any case, a landscape of high-lined trees and clumps of plants, outer spiky members guarding inner tall members that eventually shade out the low spiky species if they aren’t pruned back by the grazers.

  5. Matt Wedel Says:

    Unlike an elephant, that sauropod doesn’t look like it’s built like a bulldozer. How does it go about knocking down a tree?

    Well, for starters, many sauropods got into the 10x-the-mass-of-an-elephant range, so I assume they could just lean on them. Or push them down with their feet. Obviously some trees were too big for this sort of abuse–but equally obviously, some weren’t. I suppose the question is, what kinds of trees, if any, would be too tall for easy feeding but still wimpy enough to knock over.

    rings of prickly cycads (or similar) with trees in the middle, or, in any case, a landscape of high-lined trees and clumps of plants, outer spiky members guarding inner tall members that eventually shade out the low spiky species if they aren’t pruned back by the grazers.

    Interesting! Of course, the ring would have to be deep enough to keep the real long-necks from simply reaching over the barrier and having a bite anyway. And cows are wussies–the kind of spiky barrier that will dissuade a cow might not scale well. Does anyone know if this sort of spiky-moat-around-the-good-stuff ever happens in environments with elephants? Also, we have evidence from osteoderms that at least some sauropods were very thick-skinned, over at least parts of their bodies. I am curious whether any vegetative barrier (not made of mature conifers) would dissuade a full-grown Argentinosaurus.

    So more sauropods damaged by plants (but still surviving)? Perhaps a sauropod with brambles caught around its neck, which is subsequently scratched up. Or one who was stupid enough to wander into a broken branch, leaving it jutting from a bleeding wound like a spear… ;)

    Yes! I wrote exactly what I meant. I’m sure that sauropods did stupid things and got hurt from time to time, just as all real animals do, but we hardly ever see this illustrated. To get all All Yesterdays about it, paleoart has a serious dearth of sauropods with healed wounds, sauropods that have been wounded by anything other than theropods, and sauropods that died from anything other than theropods, drought, or drowning (and the last two are mighty rare)–although Bob Nicholls did paint one being struck by lightning, which is a start. I want to see sauropods with stump tails, three-legged sauropods, sauropods that died with their heads caught in trees, and so on.

  6. brian engh Says:

    A major difference to note between the human-altered ecosystem of the Channel Islands in CA and the mesozoic habitats of the Brontomerus is that there are no large predators on the channel islands to keep the herbivores in check. That makes a huge difference in what floral communities that can sustain themselves. CA used to be covered in a diversity of native grasses and shrubs which supported thriving populations of elk, antelope, sheep and grizzly bears (grizzly bears eat mostly vegetation). Throughout CA native plant communities have been ravaged by overgrazing of livestock, which was made possible by destroying the populations of native predators. Amazingly, when wolves were reintroduced to Yellowstone, several species of plant formerly thought to be extinct actually managed to reestablish themselves as the wolves kept the heavy grazers moving. Considering the huge advantage bipedalism gives to distance runners, I imagine mesozoic theropods had herds of herbivores constantly on the move, while the sauropods provided a high set of eyes for the other prey-species living around them (as modern giraffes do). By spying oncoming predators at a greater distance, they could’ve given some of the herd enough advanced warning to escape to safer pastures before the speedier predators could catch them.

    Also, I think mesozoic plant communities wouldn’t have been anywhere near as depressed as what we see in modern man-made overgrazing scenarios because really big animals often have complex nutritive needs. Many of the biggest animals alive today (i’m thinking elephants, whales, crocodiles, large sharks, bears, big cats etc etc) all roam vast areas to exploit a variety of food sources at key times. As a result, each individual food source isn’t under constant pressure, and can thus recover between episodes of it’s exploitation.

    In the doodle above, I was imagining the Brontomerus visiting a particular grove where a particularly tasty kind of tree is growing at a height that they can exploit by rearing (which a giant pelvis may have helped them do). What that tree would be, I don’t know, but considering the lengths elephants (an many other large animals) will go to to collect a particular resource at an optimal time of year, i think its reasonable to speculate that there were special groves that sauropods visited repeatedly in order to get at some tasty food source.

    Also atmospheric C02 was way higher in the mesozoic, which would’ve meant substantially faster plant growth rates… So again modern man-made overgrazing habitats don’t quite make a good analogue for the ecology of the mesozoic.

    I appreciate the note on the hip width… i’ll dig up some more reference of camarasaur skeletons from the front.

  7. Mike Taylor Says:

    Three-legged sauropods? How does that work? What kind of accident could rip a leg right off a sauropods? Do we ever see three-legged elephants?

  8. Mike Taylor Says:

    Brian mentioned in passing: “Considering the huge advantage bipedalism gives to distance runners …”

    I’d not heard about this. Is it a well-known thing? Thinking about three species that make good distance runners, ostriches and humans are bipedal, but dogs are not. (And I suspect humans are not intrinsically anywhere near such good distance runners as the other two — it may be that only the best of us are, and that’s because one tendency we do have as a species is pushing ourselves as far as possible in one direction or another.)

  9. Matt Wedel Says:

    Three-legged sauropods? How does that work? What kind of accident could rip a leg right off a sauropod?

    Possibly a very minor one, on an absolute scale, if it happened when the sauropod was a baby. Or maybe no accident at all, if it was a congenital defect. Certainly a three-legged baby sauropod would be at a disadvantage growing up, but that doesn’t mean it never happened. Turtles–which, admittedly, have fewer body support issues than sauropods–have been caught in the wild, alive and apparently healthy, with three legs, two legs, one leg, no lower jaw… I’ve seen plenty of three-legged dogs, but those get help with food so probably don’t count.

    Do we ever see three-legged elephants?

    Beats me. Maybe Darren will pipe up. Still, sauropods were around for about 150 million years and globally distributed for most of that time. I think it’s less reasonable to suppose that there were no three-legged sauropods, than to suppose that there were at least a few.

    Brian mentioned in passing: “Considering the huge advantage bipedalism gives to distance runners …”

    I’d not heard about this. Is it a well-known thing?

    Yep. Read on.

    And I suspect humans are not intrinsically anywhere near such good distance runners as the other two

    You suspect wrong. We are not such good sprinters, but we are better distance runners than just about anything else on the planet. From page 2 of this popular article:

    A deer and a decently fit man, Lieberman discovered, trot at almost an identical pace, but in order to accelerate, a deer goes anaerobic, while the man remains in an oxygenated jogging zone. The same is true for horses, antelopes, and a slew of other four-legged creatures. Since animals can run anaerobically only in short bursts before they must slow down to recover, a human in pursuit may have the final advantage. And because quadrupeds can’t pant while they run, they also quickly overheat. To run down dinner, Lieberman realized, might simply have been a matter of spurring the poor beast into a sprint enough times to make it collapse from hyperthermia.

    Whatever one thinks of the “endurance running” hypothesis, which holds that Homo sapiens is adapted to run prey to death and that this was a primary driver of our morphology of the past few million years, the fact is that humans can and do run prey to exhaustion whether we’re adapted for it or not. There is a great description of how Kalahari bushmen do this here.

    Anyway, back to bipedality: most quadrupeds are forced to sync their breathing with their running, since their guts are getting squeezed in each ‘gathered’ phase of the gait and stretched in each ‘extended’ phase. Bipedality frees us from that constraint.

    Embarrassingly, I don’t know if running birds sync their breathing or not. My guess is no, but I’ll see if I can get Darren to drop in and give us the skinny. If anyone else knows the answer, feel free to chime in!

  10. Darren Naish Says:

    As Matt says, three-legged individuals of normally quadrupedal species show up all over the place and apparently get by ok (incidentally, some birds can also survive ok with one leg. I base this on a one-legged Great crested grebe I once observed in normal pursuit of a fish).

    Three-legged elephants? It’s a sad fact that elephants are frequent victims of landmines – seriously, this is well known and a cause of major concern in some parts of the world. So, lots of three-legged elephants about in the modern world (use google: I just searched for ‘land mine elephant three legs’). Given that landmines were not a persistent feature throughout geological time, I don’t know if three-leggedness was caused in the elephants of the past. You might imagine that megapredators like big creodonts and such were occasionally capable of wrenching the leg off a young elephant, but I’m speculating. Are there instances in the modern world that don’t involve landmines and result in an elephant losing a leg? There’s snares: many animals lose legs this way (a 3-legged Sumatran tiger was photographed in 2007) but, again, they weren’t present in the distant past. One three-legged elephant – actually, an individual called Sama later kitted out with a prosthetic limb – was suspected by some zoo-keepers of being born three-legged, so there’s always the possibility of natural deformity.

    I’ll try and answer on the bird later, gotta disappear for now.

  11. eotyrannus Says:

    Oh – on plants and anti-sauropod adaptations, it’s at least plausible that some Mesozoic plants evolved impressive defensive adaptations that we haven’t yet discovered. New Zealand has many plants that divaricate – they grow a sort of woody ‘cage’ around the foliage that makes it hard for herbivores (in this case, moa) to get to the greenery. Imagine a giant, souped-up, anti-sauropod divaricating woody plant – it could look incredible!

    On Madagascar, giant spiny burrs seem to have co-evolved with elephant birds – again, could there have been Mesozoic burrs that took advantage of sauropods? Adhesive plants in the modern world are sometimes so good at sticking to animals that they smother and even kill birds. I doubt a sauropod would ever be in such trouble (feathers are part of the issue there), but the idea of a Mesozoic dinosaur covered in the adhesive parts of some plants might be fun to explore.

  12. Mike Taylor Says:

    Lots of interesting stuff here, thanks everyone.

    So how do dogs do so well at endurance running?

  13. Tommy Leung Says:

    On plants and anti-herbivore adaptations – how about some ants? There are many modern examples of plants having ants serving as bodyguards (and other roles), and the fossil record for ants goes back to at least Cretaceous (?). I think the face of a sauropod being swarmed by ants (or some other social insect) would make for a rather interesting image…

  14. Heteromeles Says:

    @Brian: I do happen to know a bit about the Channel Islands, having done some of my graduate work out there and worked out there afterwards. I picked it because it’s a real clear example of a pattern seen elsewhere, at least in California, of taller plants using more impenetrable plants as nurses. I was lucky enough to be on Catalina after they took the goats off, so I got to document how the cactus rings were starting to break down under shading. Those rings are mostly gone now, which is actually too bad. The 2007 fire burned much of the old chaparral, and the deer on the island are killing the resprouts, turning what used to be chaparral into grassland. They could use a lot more cactus out there.

    The reason I chose that comparison is that the biggest sauropods are far larger than their dinosaur predators, so it’s unclear that their browsing would be controlled by predation. While it’s pretty clear that conifers can grow taller than any sauropod can reach, eventually, the only good mechanism I’ve seen from growing seedling conifers is to give them a refuge from browsing, either with rocks or from a nurse plant that would repel browsers. The equivalent of a cactus ring would seem to work. While modern cycads like Encephalartos ferox are too small to work, I don’t know the full range of Mesozoic prickliness.

    In any case, to get back to the original question: how does a sauropod break a tree down? The problem is that most sauropod weight (guts, neck, tail) isn’t in a place where it can easily push, and many of the force-transmitting bones in their spine are hollow, which is great for weight saving and load bearing, but not necessarily great for pushing, which generally means a compressive force at an angle to the normal weight bearing direction.

    Elephants are well-built for pushing, because they have heavy skulls, solid bones and spines, and four legs behind that can push in a line. If they are bulldozers, a sauropod might be better characterized as a passenger jet. The plane is bigger than a bulldozer, but structurally, it is poorly designed for pushing. Weight alone is insufficient. Or if that comparison bugs you, think bull moose vs. giraffe.

    Yes, sauropod legs and ribs are tough, but again, how would a sauropod use them to knock down a tree?

  15. Duane Says:

    I like the idea of spiky cycads providing a protective barrier for seedling trees- in fact I see a similar process at work in my own backyard with weeds finding a sanctuary under my rose bushes.

    “The reason I chose that comparison is that the biggest sauropods are far larger than their dinosaur predators, so it’s unclear that their browsing would be controlled by predation.”

    Predators don’t have to actively predate in order to compel herbivores to move on. It’s quite possible that even large adult sauropods, after surviving theropod attacks while growing up, would not be comfortable with abundant theropods roaming about. And if some theropods were “flesh grazers” they would have done the trick as well. The diverse and large ectoparasites coming to light might also have proved a deterrent to sauropods over-browsing a particular area. One can easily imagine the mountain of flesh a sauropod represented would have acted as a beacon to local parasites, also keeping them moving.

    And I feel the idea of sauropods breaking down trees has been overstated. As any logger will tell you logging is a dangerous business. And completing the task safely requires a bit of intelligence and foresight as well- perhaps beyond the scope of a sauropods brain power. I can easily imagine the long, vulnerable neck of sauropods getting caught up in snags, branches and other
    stuff in the fall. On a more gory note what if only the top of tree was pushed over and the sauropod impaled its gut on the stump. No doubt tree felling occurred, especially by the largest sauropods and during extreme food shortages. but I feel browsing ratites, moas, camels, and giraffes offer a better analogy for sauropod browsing methods than elephants.

  16. Matt Wedel Says:

    I am really surprised at all scepticism regarding sauropods pushing down trees.

    Elephants are well-built for pushing, because they have heavy skulls, solid bones and spines, and four legs behind that can push in a line.

    Yeah, and sauropods weighed 10 times as much, some almost 20 times as much, and had strong limbs and big sternal plates. Are you seriously suggesting that elephants’ foreheads make them better tree-pusher-downers than animals 10x bigger? That is one hell of a power-up. I submit that any tree an elephant can knock down, a big brachiosaur or apatosaur could have knocked down, and then some.

    Also, animals engage in activities that they seem to us to be poorly designed for all the time. See: goats in trees, elephants swimming far out to sea, snapping turtles making mile-long overland hikes to lay their eggs, etc. And I don’t even think sauropods were poorly designed for pushing over trees.

    As any logger will tell you logging is a dangerous business. And completing the task safely requires a bit of intelligence and foresight as well- perhaps beyond the scope of a sauropods brain power. I can easily imagine the long, vulnerable neck of sauropods getting caught up in snags, branches and other
    stuff in the fall. On a more gory note what if only the top of tree was pushed over and the sauropod impaled its gut on the stump.

    Yes, exactly! Tree-felling is dangerous, and sauropods were, by any reasonable mammalian standard, pretty stupid. I’ll bet they got into trouble all the time when their tiny brains and huge bellies decided that obvious food outweighed not-so-obvious danger. Just as giraffes get caught in trees and beavers get crushed by the very trees they felled. These things happen, commonly enough to be well-known to natural historians, but infrequently enough that they don’t dissuade giraffes and beavers from pursuing their sometimes risky behaviors. I expect the same to have been true of sauropods.

    No doubt tree felling occurred, especially by the largest sauropods and during extreme food shortages. but I feel browsing ratites, moas, camels, and giraffes offer a better analogy for sauropod browsing methods than elephants.

    We-ell. I was all set up to agree with this wholeheartedly. And I do agree that sauropods were primarily browsers. But ratites, camels, and giraffes don’t have the option of pushing down trees. If they did have that option, we might see different behaviors from them. Sauropods did have that option, and it seems extremely unlikely that they didn’t make use of it. Whether is was a big component of their behavioral repertoire, or just something they did on occasion, is probably unknowable.

    But the larger point is that paleoart that sticks to stuff we can be 100% certain about is doomed, because we can’t be 100% certain about enough stuff to even make a life restoration, let alone an environmental scene, and worse, it’s boring. I’m not making a scientific case that knocking trees over was the primary mode of getting at leaves for sauropods. I’m making the artistic case that big sauropods knocking down trees when they could is sufficiently plausible to be worth exploring.

  17. brian engh Says:

    I basically live in a redwood forest, and my family owns property in the western sierras and conifers of all sizes fall down all the time without sauropods (or any other large animals) pushing on them. Also, I wasn’t suggesting that sauropods were even intentionally pushing trees over (although i do think it’s possible they did) – I was suggesting that in the act of rearing up on their hind legs and using their front claws to hook into the trunk (which brontomerus may have been particularly suited to do with such a huge, load-bearing pelvis and thighs), they would’ve caused some trees to lean and some to fall, especially if there were particular groves they visited regularly.

    As for the argument that sauropod’s weight wasn’t in the right place for knocking trees down; neither is mine, but I’ve shoved and/or kicked over trees in the 15 to 20 foot range with weak root systems or partially rotted/bug eaten trunks more than once. Some trees are wonky, and if you push against them with your hands you can feel your force pushing forward from your hips and shaking the tree. And I’m weak as hell compared to anything from the mesozoic.

    And again I reiterate my objection to the idea that giant sauropods resulted in completely depressed plant populations anything like what we see in human altered landscapes where predators have been removed and ungulate populations have exploded. Giant sauropods were the rarity, the fossil evidence seems to indicate that most sauropods never made it to full size… and i suspect predation had a lot to do with that. Also I doubt the big sauropods would have bothered much with browsing down young seedlings (as the deer on Catalina did), while virtually anything that was feeding that close to the ground in the mesozoic was in constant threat from a myriad of ridiculously awesome predators. I seriously doubt if there were even a couple Concavenator on Catalina there would be a deer problem.

    Also, considering how much growth big theropods (especially tyrannosaurids) were putting on during their prime growth phases, they had to have been eating CONSTANTLY, and probably covering crazy distances in the process.

  18. Duane Says:

    Great discussion points above from Engh and Wedel.

    I am not at odds with sauropods toppling over trees, the largest ones most likely did just moving about- and I can see how some sauropods like Brontomerus/Apatosaurus may have indeed knocked over trees habitually based on their robust builds. What I am at odds with is the recurrent assumption- which you can find in any number of popular dino texts- that dino herbivores, especially sauropods, always had a more profound impact on vegetation than modern mammal communities- through their grazing, habitat modification etc. I don’t think that this is a given more or less and the question should be tested.

    And back to the elephant question. I believe elephants are ultimately greater habitat modifiers than sauropods not because they topple trees, but because they girdle them by bark stripping with tusks/chewing through the living outer bark tissue of trees. In this manner the size of tree an elephant can kill is essentially limitless. Sauropods, at least from what we know from the finite element analysis of diplodocus skulls, do not so far appear to have targeted the bark the way elephants do.

    Not trying to just advertise my blog but the discussions above also prompted me to sketch an unfortunate “crown of thorns” Saltasaurus that got its neck tangled in a tree it was toppling. Check it out here at http://antediluviansalad.blogspot.com/2013/01/crown-of-thorns-saltasaurus.html

    BTW I do love the pic above- paleoart is inherently speculative!!!

  19. Matt Wedel Says:

    Duane, I’m pretty much in agreement with all of that. Especially:

    What I am at odds with is the recurrent assumption- which you can find in any number of popular dino texts- that dino herbivores, especially sauropods, always had a more profound impact on vegetation than modern mammal communities- through their grazing, habitat modification etc. I don’t think that this is a given more or less and the question should be tested.

    Yes. Quite. On one hand, we have lots of multiton herbivores, pretty much everywhere all the time for the entire Mesozoic. On the other hand, we have: multiton carnivores putting pressure on those herbivores; herbivores with very different life history strategies and population structures than we get with big mammals; and–as you point out–lots of differences in food-gathering strategies. I don’t think it’s a call we make a priori. Even the things we’d need to figure it out are unknowns.

    Take sauropod populations–were they most often in big groups, small groups, solitary but coming together at times? Dominated by youngsters with a few subadults and extremely rare adults? Territorial, moving around with a home range, migrating over long distances?

    And, of course, not all sauropods did things the same way. Sauropoda was big, diverse clade that lasted for a long time. I look at the differences in habitat preference, gregariousness, and so on among extant mammals–even quite closely related ones like big cats, or rhinos–and wonder how they scale out over a globally-distributed clade that persists for 150 million years.

    Frankly, as a scientist the number of those things that we don’t know and probably will never know often bums me out. But I was a dinosaur-lover before I was a scientist. For that kid who grew up reading dinosaur books, watching Nature and Wild America and the various Attenborough series on PBS, and catching turtles and snakes down at the creek, all that unknowable history glitters with possibility. So I relish these little speculative thought-experiments. They let me get my mental boots muddy, and keep me alert to the wonder and unpredictability of the living world.

    Also: your Saltasaurus drawing is excellent, and with your permission I’d like to write a post about it. May I?

  20. Duane Says:

    By all means go right ahead Matt I’d be honored!

  21. Mike Taylor Says:

    “Even the things we’d need to figure it out are unknowns.”

    But at least we know that the unknowns are unknown.

  22. Heteromeles Says:

    Yes, I’m going to stick to my guns. Try comparing a Boeing 747 with a bulldozer. The 747 is much heavier, but it is much more fragile. While airplanes moving at high speed cause a lot of damage, at low speed, they are a fire risk, not something that bulldozes over trees.

    If we’re talking stomping a sapling, sure. Even I can do that. If we’re talking Brachiosaur vs. full-sized redwood (just to be silly, and remembering that full-sized redwoods are in the 75-100 m tall range), the Brachiosaur loses handily. It would cripple itself trying.

    Give an elephant enough time, though, and that tree is coming down, because as Duane points out, the elephant has the tools to girdle the tree, whereas all the brachiosaur can do is lean on it.

    The critical point is that weight doesn’t particularly matter. It’s how that weight can be used to put force on a point or surface. That’s trickier for a sauropod than for an elephant.

    While this is petty, if you don’t get the idea that structure matters, one way to understand it intuitively is to strip down and try to give a cat a cold shower. The cat can’t kill you, and you outweigh the cat by 10x or more, but I have a pretty good guess about which of you will be controlling the situation, once the water comes on…

  23. eotyrannus Says:

    Heteromeles: you’re underestimating sauropods. They are not more fragile than elephants, but (in many, maybe all, cases) with stouter bones, bigger muscles and chunkier bodies. They have tools too: the big and often deep thumb claws of some groups (notably diplodocoids) have often been suggested as having played a role in damaging plant tissue of some sort. Maybe they could tear and rip with these organs.

  24. LeeB Says:

    Also when considering whether dinosaurs had more effect on the vegetation and especially trees than mammals did it is worth bearing in mind that mammals probably influenced vegetation much more even 20000 years ago.
    When multi ton mega-mammals occurred on most continents forests probably looked a lot more open than those we are used to.
    And their browsing (along with the ready availability of nutrients in their dung) probably led to the occurrence of Mammoth Steppe where taiga or tundra occurs today.
    And even large birds can effect the vegetation; Moa in New Zealand have led to the presence of divaricating dranches on trees and shrubs, and the trees change their leaf form and branching mode when they get above the browsing height limit of Moa.

    So I would expect both dinosaurs and mammals to have had major effects on vegetation striucture and occurrence.

    LeeB.

  25. Heteromeles Says:

    Chunkier bodies, yes. I agree on that. Chunkier limb bones. Yes, I agree on that too.

    Spinal columns, though, that’s where it gets weird for sauropods. Since I’m learning a new tai chi set (with my significant other), I’m getting another great lesson in how much the spine matters in transmitting force. With an elephant, there’s great transmission from all four legs to the trunk, because it’s solid all the way.

    Problem is, if you start cutting weight with those air sacs, how well do the vertebrae actually transmit force up and down the spine? If they do not do a great job of transmitting force up and down the line of the spine(and that’s the point I’m making), then most of the weight advantage for sauropods goes away. They can apply some of the force of one or two legs at a time.

    That’s the critical question of asking: HOW do sauropods knock down trees? It’s not about weight, it’s about applying force at a point, in a direction that will take down a tree. I think it’s great that we’re talking about thumb claws, but again, how can a sauropod apply force to a tree? Are we talking about it standing on its hind legs and giving the tree a left hook with a foreclaw? that’s certainly not applying the full weight of its body to the target. Are we talking about applying the force of one leg at a time to a tree. Maybe it can apply some of the weight of its upper body, if it can rear and bring both forefeet down. That’s very different than what elephants can do.

  26. Matt Wedel Says:

    Problem is, if you start cutting weight with those air sacs, how well do the vertebrae actually transmit force up and down the spine? If they do not do a great job of transmitting force up and down the line of the spine(and that’s the point I’m making), then most of the weight advantage for sauropods goes away.

    Are you freakin’ kidding me? If your argument comes down to “sauropod vertebrae couldn’t transmit force because they were hollow, and elephant spines and skulls can because they are solid”, then you are going to lose.

    First of all, there is zero evidence that being filled with air compromises a bone’s ability to absorb or transmit force. Look at this bighorn sheep horncore, which is totally pneumatic. As are the foreheads and horncores of bison and loads of other critters that use their horns in combat.

    Second, elephant foreheads are just as pneumatic as sauropod vertebrae. See this image and this one.

    So, in the sense you’re talking about:

    With an elephant, there’s great transmission from all four legs to the trunk, because it’s solid all the way.

    No, it’s not. And it’s not solid right at the point where the force is applied to the tree.

    That’s the critical question of asking: HOW do sauropods knock down trees? It’s not about weight, it’s about applying force at a point, in a direction that will take down a tree.

    Right. You’ve been talking about elephants pushing trees with their heads (or with their tusks, which amounts to the same thing–the tusks are rooted in the highly pneumatic skull). I’ve been talking about sauropods leaning on trees with their great big bodies, or stomping them with their feet. The sternal plates of something like Giraffatitan are huge, and a lot thicker than the cortical bone on the front of an elephant skull, and the body weighs 5-10 times as much. I don’t get how a static push from a 5-ton elephant’s forehead through bone a centimeter thick is better than a static push from a 30-ton sauropod’s torso through bone several times thicker.

    I think it’s great that we’re talking about thumb claws, but again, how can a sauropod apply force to a tree? Are we talking about it standing on its hind legs and giving the tree a left hook with a foreclaw?

    Whoa, hoss. Darren brought up claws in the context of damaging plant parts, not pushing them over, because you wrote,

    Give an elephant enough time, though, and that tree is coming down, because as Duane points out, the elephant has the tools to girdle the tree.

    Well, yes. The elephant can girdle the tree, and wait for it to die, and come back weeks or months later and push the dead tree down. Similarly, a sauropod could probably girdle a tree with its claws, wait for it to die, and come back later to knock it down. That’s a very different scenario than knocking a live tree over with main force.

    Maybe it can apply some of the weight of its upper body, if it can rear and bring both forefeet down. That’s very different than what elephants can do.

    Uh, duh! That is one of several possible scenarios for sauropods knocking trees down, and of course it’s different than what elephants do, because sauropods are not elephants. An elephant doesn’t have the option of using sauropod-sized torsos and limbs to push trees over, or stomp them until they give.

    So I repeat: I cannot understand the basis for your argument that an elephant is better than a much larger sauropod at bringing trees down. On sheer physical grounds it seems terribly unlikely, your anatomical reasoning vis-a-vis “solidity” is flatly incorrect, and you seem waaaay more certain than I think you have any right to be.

    But feel free to prove me wrong.

  27. Mike Taylor Says:

    A big *thank you* to Matt, there, for making all the points I was wearily preparing to make, until I saw that he’d already done it.

  28. Heteromeles Says:

    Thank you too from me, Matt. My question was “how do sauropods push down trees, You’re answer is great, and it makes more sense than talking about how something is huge, therefore it can do anything it damn well wants with that weight.

    It may not be obvious, but I don’t look at sauropod skeletons all day, so that’s why I was asking. Most of what I see are beautiful pictures of very open vertebrae, all which seem highly evolved as cantilevered supports, but not at all well designed to take tonnes of compression in various different directions. I’ve also suffered through enough back and neck problems in the last year to have a subjective and painful understanding of what happens when you put a lot of force on a complex set of joints that aren’t properly aligned to take that force.

    Again, thank you.

  29. Matt Wedel Says:

    Thanks for the kind words. Sorry I got a bit heated there.

  30. Vertebrat Says:

    [takes cover from anti-elephant fire] Uh, about the ecological impact thing…

    Sauropods might not have an outsized impact per species, or per biomass, or per food consumed. But they come in very large pieces, which means their ecological impact does too.

    One sauropod could knock down a few trees or strip the pinnae off a great many ferns. (Isn’t that what would happen if they applied the leaf-stripping feeding style? Imagine the resulting fields of naked petioles.) A herd of them… Fifty 20-ton sauropods is 1000 tons of biomass, so they should have ecological impact comparable to 1000 tons of some other animal. That’s a thousand bison. Thirty thousand goats. Five million rats. Half a billion locusts. A trillion mosquitoes.

    They’d do more than damage a few trees.

    Big things are dramatic, and one of the few things bigger than a sauropod is its ecological footprint. There should be more art about this.

    (Actually the locusts have more impact, because they eat their own weight daily, thanks to sublinear scaling and inefficient digestion and crazy insect metabolisms.)

  31. Mike Taylor Says:

    Vertebrat, I was getting ready to contradict you all the way till your last, parenthetical, comment, when you did the job for me :-)

    As you say, large animals have a slower mass-specific metabolic rate than small animals. As McNeill Alexander memorably put it, you’ll won’t keep as warm sleeping next to a 500 kg cow as will next to twenty thousand 25 g mice. So other things being equal, a 50-tonne sauropod will eat rather less food then ten 5-tonne elephants (though of course much more than a single elephant).

    How does Basal Metabolic Rate scale with body mass, you ask? Amazingly, this has yet to be determined! Some studies have found, or maybe just assumed, that BMR is proportional to mass ^ (2/3); others have found or assumed mass ^ (3/4). If I recall correctly, there are theoretical reasons for preferring one or the other these. Experimental results (weigh the animal, measure oxygen consumption) have also given differing results.

    Anyway, if we pick an exponent between 2/3 and 3/4 — say 0.7, which is roughly their geometric mean, sqrt(2/3 * 3/4) — then we’d concude that our 50-tonne sauropod, which weight ten times as much as our 5-tonne elephant, would have a total energy budget 10^0.7 times that of the elephant. That is conveniently about five times as much, or about half of what you’d expect from simple linear scaling.

  32. Vertebrat Says:

    So a 20-ton sauropod is nine 900-kg bison, 95 30-kg goats, 3000 200-g rats, 80000 2-g locusts, or 16M 1-mg mosquitoes. The herd of 50 is 440 bison, 5000 goats (140 tons), 150k rats (30 tons), 4M locusts (8 tons), or 800M mosquitoes (only 800 kg). That’s somewhat less impressive.

    On the plus side, it does make large populations (and large herds) more plausible. A population of only 500,000 20-ton sauropods is ten million tons, which is a lot – more than the peak biomass of North American bison, when they occupied a significant part of the continent, more than the pre-whaling biomass of many whales, and close to that of the historical 3M African elephants. Even the worldwide biomass of humans (or cattle or Antarctic krill) is only 350M tons.

    But we should rate ecological impact by metabolism directly. Scaling metabolism from a 500-kg 1-hp horse (this might be low; horses eat something like 20 Mcal/day = 1 kW), one 20 t sauropod is 10 kW. That’s 1000 100-W humans, or two billion 5-µW fruit flies. The herd of fifty is 500 kW; the population of 500,000 is 5 GW, or 500M humans or 7M horses.

    Hmm, the cost of walking also scales as mass^0.7.

  33. Vertebrat Says:

    Er, 100 humans, and 50M. Unless there are 10-watt humans now. I am a dim bulb.


  34. […] out with Brian Engh and some of his friends in LA. You may remember Brian from this, this, this, this, and, most notoriously, this. We got to drawing dinosaurs, […]

  35. Bryan Riolo Says:

    Heteromeles:

    “Yes, sauropod legs and ribs are tough, but again, how would a sauropod use them to knock down a tree?”

    Very easily. I posted a sketch of sauropods doing that on deviantART. If you want, I’ll link it up.


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