Giant Oklahoma Apatosaurus mount, from above
February 27, 2016
Here’s the “Clash of the Titans” exhibit at the Sam Noble Oklahoma Museum of Natural History, featuring the reconstructed skeletons of the giant Oklahoma Apatosaurus – which I guess should now be called the giant Oklahoma apatosaurine until someone sorts out its phylogenetic position – and the darn-near-T. rex-sized Saurophaganax maximus, which may be Allosaurus maximus depending on who you’re reading.
Now, I love this exhibit in both concept and execution. But one thing that is more obvious in this view from the upper level balcony is that despite its impressive weaponry, a lone 3-to-5 ton Saurophaganax had an Arctic ice cap’s chance in the Anthropocene of taking down a healthy 30-meter, 40-50 ton apatosaur (which is to say, none). I like to imagine that in the photo above, the apatosaur is laughing at the pathetically tiny theropod and its delusions of grandeur.
In this shot from behind, you get a better look at the baby apatosaur standing under the big one, and it hints at a far more likely target for Saurophaganax and other large Morrison theropods: sauropods that were not fully-grown, which was almost all of them. I am hip to the fact that golden eagles kill deer, and some lions will attack elephants – as Cookie Monster says, “Sometime food, not anytime food” – but not only were smaller sauropods easier prey, they were far more numerous given the inevitable population structure of animals that started reproducing at a young age and made more eggs the bigger they got (as essentially all egg-laying animals do).
In fact, as discussed in our recent paper on dinosaur ontogeny (Hone et al. 2016), there may have been times when the number of fully-grown sauropods in a given population was zero, and the species was maintained by reproducing juveniles. The giant Oklahoma apatosaurine is a unique specimen today – by far the largest apatosaurine we have fossils of – but it may also have been an anomaly in its own time, the rare individual that made it through the survivorship gauntlet to something approaching full size.
Amazingly enough, there is evidence that even it was not fully mature, but that’s a discussion for another day. Parting shot:
Sauropod Vertebra Picture of the Week 
February 27, 2016 at 10:57 am
While this is true that probably most known sauropods are not mature, it should be remembered that some specimens were in fact fully grown; e.g. Curry (1999) described an EFS in a 25 m long Apatosaurus (or just apatosaurine?). So some apatosaurines could be smaller than the Oklahoma giant and yet already reached their maximum size.
This argues against the hypothesis of indeterminate growth in sauropods (Curry 1999, Skawiński and Tałanda 2014), even though it was cited in literature quite recently (Delfino and Sánchez-Villagra 2010).
February 27, 2016 at 2:39 pm
So some apatosaurines could be smaller than the Oklahoma giant and yet already reached their maximum size.
Yes, that’s a good point. And it’s worth pointing out that the AMNH 5761 Camarasaurus supremus individuals are bigger than almost all other Camarasaurus for which we have fossils, but they are skeletally immature (AMNH 5761 is a composite of 4 morphologically consistent and roughly equal-sized individuals from a single locality). That’s based on the incompletely-fused sacrum recovered for one of them, on the mostly-unfused cervical ribs in Series II and III (Osborn and Mook 1921). So Apatosaurus is not the only Morrison sauropod for which we have evidence of individuals* that were (1) significantly larger than the average, despite being (2) less skeletally mature than the average.
* And possibly species.
That maybe shouldn’t be surprising, given that animals from different populations of the same species today can vary fairly widely in average adult body size – Homo sapiens included! And also given that our current understanding of Morrison biostratigraphy does not let us rule out the possibility that some of these critters might have been ancestral to others in the true anagenetic sense.
And, as always, we have essentially no handle on variation, and as yet no independent lines of evidence to separate potentially informative interspecific characters from intraspecific variation. But it’s interesting that even our small sample sizes of sauropods have captured so much ontogenetic wackiness already. Either we got really (un)lucky with our first 150 years of collecting, or sauropods were full-tilt weirdos.
February 27, 2016 at 2:57 pm
And let’s not forget the flip side: there aren’t any Allosaurus or Torvosaurus specimens studied yet with an EFS. (Although Saurophaganx may: it hasn’t been sectioned yet.)
February 27, 2016 at 3:02 pm
Yep, strong point. Most of what I know about Allosaurus histo has to do with ontogeny in juveniles. How hard have people looked for an EFS, in terms of sampling even the largest sub-Saurophaganax-size allosaurs?
Tantalizing to think that the allosaur (or torvosaur) equivalent of Amphicoelias fragillimus might be lurking out there somewhere.
February 27, 2016 at 6:03 pm
Correct me if I’m wrong, but isn’t the Epanterias material also immature? I recall reading that it’s neural arches were un-fused, and I know for sure that while the coracoid was recovered it’s scapula was not, which is often used as a sign of immaturity too.
The Epanterias material is probably the biggest allosaur specimen known, so if I’m remembering things right and it was immature too then who knows how big they could get. I don’t usually like using footprints for size-related things, but there are indeed some Jurassic theropod footprints that imply individuals slightly larger than the Epanterias specimen, which would be consistent with the specimen still not being fully mature.
February 27, 2016 at 10:13 pm
Until now, I had no reason to go back to Oklahoma. That museum looks worth the seeing!
February 27, 2016 at 10:23 pm
Maybe the Saurophaganax is just going in for some parasite cleaning?
February 28, 2016 at 1:14 am
So far, the primary work on Allosaurus (Bybee et al. 2006) looked at isolated specimens from Cleveland-Lloyd; their largest femur was 872 mm. There are definitely larger specimens (such as the AMNH mount), but they haven’t been sampled yet.
February 28, 2016 at 10:50 am
Re the Saurophaganax’ chance of a kill: what if its techie was not ‘take prey down there and then” but like a Komodo dragon’s: get in a bite or two then retire and track it from a safe distance, until introduced haemotoxic saliva brings it down through induced septicaemia shock’?
February 28, 2016 at 4:14 pm
I’d considered possible methods of attack for Allosaurus before; what I thought most likely was a series of bite-and-retreat attacks designed to draw a lot of blood. This would continue until the sauropod was close to passing out from blood loss before a serious attempt at killing it would happen.
February 28, 2016 at 4:17 pm
I dunno, Jamie, are we even confident that something as weedy as an allosaur could even penetrate the skin of n adult sauropod?
February 28, 2016 at 7:39 pm
There is some evidence from osteoderms that at least some sauropods had very thick skin, and it makes sense given their size. Given their blood pressure issues, very tight, tough skin, at least on the legs, also makes sense. But given that there are Morrison sauropod bones that are several inches thick that are bitten right through by something big and toothy, at least something roaming around the Morrison had the necessary tools to punch through that skin.
Still, all of the arguments for big Morrison theropods regularly attacking fully-grown sauropods in the 25-ton-and-up range seem like special pleading to me. I don’t doubt that at least a few of the biggest, like Saurophaganax, could get in and deal a nasty bite – nasty both in depth and in possible contamination, as armadillozentih notes. But there are at least two really solid counterarguments that seem to get glossed over or ignored outright:
1. Taking on prey many times your size is risky. A 25-to-50 ton sauropod had many more ways to cripple or kill a 5-ton theropod than vice versa. Yes, we know that some populations of lions are adapted for killing elephants – but we also know that elephants will go out of their way to kill lions, and some of them are pretty darned good at it. And yeah, sauropods were not nearly as smart as elephants – neither were allosaurs as clever as lions, I’ll bet, and when you’re 5 to 10 times as massive as your assailant, you don’t have to be particularly graceful. Even one clumsy misstep may register as a crippling stomp to the predator.
2. Why go to the trouble of attacking the very biggest sauropods when they were the rarest members of the population? Even assuming that max-sized individuals were around – which may not always have been the case, as described in the post – the theropods would have to walk right past a whole boatload of smaller, easier targets to get to them, ignoring winnable fights and achievable calories just to roll the dice in the most dangerous possible encounters.
Now, I’m not saying that Morrison theropods didn’t attack sauropods – pretty obviously they did, as that is most what was around to be eaten. Nor am I saying that they only attacked babies and very young juveniles. Watching the behavior of big predators today, it seems plausible that even half-grown sauropods would have been vulnerable to large theropods – and that may be part of the reason why we find so few of the real titans. I just have a hard time with the idea that a 5-ton theropod would ignore dozens or hundreds of 5-ton, 10-ton, and even 20-ton targets to seek out and take its chances with a 50-tonner.
February 28, 2016 at 9:34 pm
There also the issue of what would it do with it if it killed it. Even assuming a high metabolism in the theropod and an ability to eat rather dodgy meat like hyenas, how is an animal going to eat something 10 times it’s mass before the whole lot turns into decayed slush from flies, beetles, bacteria etc. It’s an absolutely insane situation that they’d target dangerous food items they can’t eat much of, so they don’t get the benefits of getting more food. (And don’t just invoke pack hunting without any evidence, and even if you put that in, this is till a massive mismatch in size / consumption for a whole group of multi-ton animals).
February 29, 2016 at 9:19 am
Dave Hone makes a good point. Do we know what happens to the elephants killed by those aberrant prides of lions, when they manage to bring one down? How much actually gets eaten?
February 29, 2016 at 11:09 am
I imagine most of it (though i don’t know and don’t know if the data even exists). What I have seen suggest decent sized prides (i.e. not 2 or 3 animals but c 6) and primarily targeting younger animals (not necessarily babies but not adults) and coupled with the ?higher metabolism in mammals vs big theropods implying a higher consumption rate you might be looking at total elephant mass at x1-x2 combined lion mass, and you’d struggle to replicate that ratio with even big theropods and a huge sauropod.
February 29, 2016 at 1:32 pm
Something we can’t entirely dismiss, too, is feeding without killing: Greg Paul’s orca-insipred flesh-grazing model.
February 29, 2016 at 4:16 pm
Something we can’t entirely dismiss, too, is feeding without killing: Greg Paul’s orca-insipred flesh-grazing model.
I’ve always wished that model would get more attention, but not because I think it’s particularly likely. In particular, I’d like to see more discussion about the significant differences between the marine orca-rorqual system where it was first observed, and the terrestrial theropod-sauropod system where Paul applied it. Seems to me that at least two things need to be addressed:
1. Rorquals don’t have a lot of appendages for whacking orcas, or firm ground on which to brace themselves for a really devastating hit, and the density of water will blunt whatever tail-whaps they might deliver. Sauropods didn’t have any of those limitations.
2. I’m also curious about the potential for wound infection in marine vs terrestrial settings. If the wounds get infected and the prey animals die, then we’re looking at a Komodo dragon model rather than a ‘pure’ flesh-grazing model. Did anyone track those bitten rorquals to see if they recovered?
February 29, 2016 at 6:41 pm
We might also flip the predation issue around and ask: is there any reason to expect that theropods attempted to predate prey much larger than themselves?
Since the vast majority of living predators feed on things smaller than themselves, and prefer juvenile prey (independent of mass), the null hypothesis would be that theropods ate juveniles of comparatively small size. We should really insist on compelling counter-evidence to conclude otherwise.
Relevant to this question are the living exceptions that make the rule: in the terrestrial realm, one might note that nearly every anecdote about predators taking very large prey involves either cats or raptors*. Birds of prey have the distinct advantage of being able to abort mission and fly away risk-free if the attempt fails. Cats are actually really unusual predators – they are particularly well adapted for killing big prey (and even then, they don’t do it much).
For those of us working on dinosaur biology, I think it is very tempting to imagine that theropods were just as “tough” as cats – that is, well adapted to tumbling fights with big prey. But the reality is that nothing in theropod anatomy suggests they were. Quite the opposite, in fact: You have a group of predators with comparatively stiff bodies, brittle builds and a face-first feeding strategy (those forelimbs, despite claws, can’t reach anything useful). Theropods didn’t even have a fast-recovery locomotor mode – cats can tumble while running at full speed and just bounce back. A bad fall at full tilt for a big theropod would at least mean a comparatively slow recovery to standing position.
As already noted in this thread, the availability of small prey was also enormous in sauropod-dominated landscapes of the Mesozoic, compared to most modern landscapes with large mammals. Since the anatomy of large theropods makes them look like small-prey specialists, and since the availability of small prey was particularly extensive, it seems to me like everything lines up just fine: the best supported conclusion is that the Mesozoic was full of baby slayers and adults were probably more or less immune to predation.
*Yes, I realize that Komodo dragons are also a popular case, but they are highly specialized big-game hunters with few real similarities to theropods other than tooth morphology. That may make them a decent model for prey processing, but probably not prey capture. It is also worth noting that Komodo dragons still mostly eat deer, and (so far as I’m aware) most often juveniles. Since a big timor deer is only 50 kg, and a big dragon is 70 kg, the dragons aren’t actually tackling things that outweigh them on a regular basis.
February 29, 2016 at 6:45 pm
Thanks, Mike, for the reality check. If there was some way on WordPress to star or ‘like’ your comment, I’d be all over it.
March 1, 2016 at 8:40 am
Mike appears to have described the Hone & Rauhut paper (with some additional thoughts on cats). Obviously this is an amazing piece of work ;) but it does seem to still meet a lot of resistance.
March 2, 2016 at 2:52 am
What’s the flesh-grazing model? Take a big bite and swallow it without killing the prey animal?
—
@Michael Habib: Interesting point. I’d noticed that most predators go after prey smaller than themselves, but that lion, cougar, tiger, wolves etc. were exceptions. But these are either cats or pack hunters (or both for lions).
March 2, 2016 at 7:41 am
William: yes.
March 3, 2016 at 5:13 pm
Interesting idea. I think cookiecutter sharks do the same thing, but they are small enough it might be hard for the whale, etc. to hit them.
March 22, 2016 at 4:34 am
I’m not sure that the Komodo model of prey capture is entirely dismissable as an analogue for theropods attacking large prey as it is primarily bleeding caused by their serrated teeth that causes the prey to weaken and die (not septicemia). The key difference between dragons and theropods is that the bleeding is facilitated by the anticoagulating effects of the dragon’s venom. The most recent studies suggest that septicemia is not caused by their bite, but rather by bacteria present in the nasty tropical environment, and septicemia apparently only occassionally accounts for the prey’s death.
https://www.sciencedaily.com/releases/2009/05/090518172650.htm
One could imagine that a large theropod with substantially stronger jaws, longer teeth and long wrenching neck could inflict a significantly deeper wound than a komodo, possibly reaching the massive hose-line arteries and veins that would’ve oxygenated the rear legs and tail of sauropods. Komodos also seem to target the achilles tendon in order to hamstring their prey, crippling it from behind and then eating in through the thighs, anus and belly. And even averaged sized komodos will target full grown asian water buffalo (which can outweigh big komodos by about 3x)…
vs buffalo using dirty tropical mudhole & venom mode: https://www.youtube.com/watch?v=EHB_CM86rgk
vs deer, nasty hamstring snaggle: https://www.youtube.com/watch?v=n6Riq-d4W_o
ouch: https://www.youtube.com/watch?v=XPBiLXp5Uj8
We know from that Edmontosaurus with a healed t-rex calliber bullet wound in it’s tail that at least tyrannosaurs sometimes bit the tails of their prey, which makes sense considering that the m. caudofemoralis longus runs the length of the tail and drives the back legs. So it seems plausible to me that if a predator can get within biting range of the underside of the tail, a deeply lascerating bite could either cause insane bloodloss and/or ‘hamstring’ a large sauropod, and by weakening the back legs potentially cause it to collapse under it’s own massive weight. This may explain some of the caudal defensive adaptations in such as huge flailing whips, spikes and clubs seen in (even large) sauropods…
Conspicuously lacking from this coversation is any discussion of crocodiles and their feeding strategies. Here’s a truly horrifying video of a zebra crossing a river being eviscerated from below by multiple crocodiles converging on it: https://www.youtube.com/watch?v=PuiQUZS8Owc
We also know that massive sauropods had relatively tiny, fragile heads which they would’ve had to lower down to the murky surface of mesozoic rivers and shit filled water holes in order to slurp up fetid parasite-infested mesozoic “water” beverage. Tantilzingly one line of large mesozoic theropods (at least) appears to have taken to the water to become giant pseudo crocodilians. Even i you insist baryonychine spinosaurs jaws were too weak to crush a flimsy sauropod skull (which i think is a bit conservative) at the base of either of the leading current spinosaur phylogenies are a bunch of standard issue megalosaur-line theropods, with a bunch of forms with pretty goddamn ridiculous jaws (by modern animal standards, at least). I can’t help but speculate that there was some intergrade species that had both a semiaquatic lifestyle and nasty jaws that could effortlessly flatten the airfilled brown paper bag that was most sauropods pathetic skulls as they hovered them above the skeezy predator infested river. Imagine: spinosaur-line theropods crouched below the water’s surface like a weird leggy croc-bird chicken monsters, ready to launch upward out of the filthy water to snatch a massive sauropods tiny head as it dips in for a yummy drink. SCRUNCH. An 80 foot animal instantly collapses and a horrendous feeding frenzy ensues as dozens of filthy theropods emerge from the slime of their murder-pool to liberate the wealth of calories stored in the the terrestrial repti-whale.
With regards to lions attacking elephants, iirc there’s only 1 pride known to do that and the hunt often involves a dozen or more lionesses and is only attempted during desparate times: https://www.youtube.com/watch?v=-JVTe9FnAto
If we throw cats out the window as analogues (as we probably should) we still are left with dogs and hyenas, which are arguably better analogues as they are stiffer, adapted for long distance endurance running, and kill their prey with their jaws. Swarms of wolves will bring down large elk and bison which vastly outweigh them using a group bite and pull-down strategy that isn’t altogether different from crocodilian feeding. If indeed the struggle of an animal drew in more predators, one can imagine big groups of hungry theropods converging on a struggling sauropod, all taking bites as they can, eventually bringing the beast down through death by a thousand cuts.
In short i generally agree with Matt that attacking big sauropods was a risky maneuver and probably not what most predatory dinos were doing all the time, but I don’t think that biology always works in terms of strait-forward predator risk assessment vs availability of other calories. Sometimes the numbers game of predator prey interactions is bizarrely skewed by things like environment, anatomical vulnerabilities and sheer predator numbers.
and so, i will leave you with this paper describing a mid sized gecko (Tarentola annularis) mashing a gerbil that’s about the same size as it:
Click to access Crochet_Herpetology_Notes_Volume1_pages58-59.pdf
March 22, 2016 at 8:37 am
Lots of good stuff here, Brian, thanks. In that first video, the problem seems to be that the buffalo is a moron. Even at the start, before it’s injured, it just hangs around where the lizards are, making no attempt to stay our of their way or (better) stomp them into a puddle. I assume what we’re seeing here is thinning of the herd by natural selection.
Am I imagining it, or does the zebra try to eat its own innards?
March 25, 2016 at 6:09 am
I agree that that buffalo is failing to produce the most tactical response to the komodos, but do bear in mind that it’s brain is way way bigger than probably any sauropod’s. I know this may be heresy, but I sorta doubt sauropods were terribly brilliant tacticians.
With regards to the Zebra, i agree that it it appears to nip at it’s hanging innards, though i suspect because it felt something dragging back there & didn’t understand or hadn’t yet realized that it is its own viscera. I hope I never make a similar discovery. I have seen horses reach back and nip like that when they get tangled in something or have a blanket on their back that they don’t want there, or even bite predators in the same way.
I imagine a group of theropods attacking like those crocs from multiple directions might confuse a sauropod and be able to snap at it’s (presumably) soft underbelly in front of the thigh. It would seem that if they made even a small hole in the sac containing the intestines the massive weight might push them out like a hernea, with a result similar to what happened to that zebra…
March 25, 2016 at 8:12 am
… and so a new palaeoart meme was born!
August 10, 2017 at 8:22 pm
[…] a lot among closely related taxa. Furthermore, sauropod population dynamics should have been highly skewed toward juveniles and subadults. So is the near-equality in size among Argentinosaurus, […]