Talk:Sarcosuchus

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Hi, and thanks for your contributions Mokele... but I wondered if you have a reference for that ectothermic animals can't develop muscles through exercise bit ... the article I ripped it from is non-technical, but if you're right I wonder why perfectly good scientists are taking their bite bar tests into the wild... [1]. And the lifespan reference was to the period the crocs keep growing, not their total lifespan: the growth rate in most modern crocs slows down dramatically after about 10 years, while it seems the gigantic breeds sustained a high rate of growth for a longer time... but if it caused confusion, it should be clarified. 68.81.231.127 10:30, 15 Jan 2005 (UTC)

The reference for the exercise physiology and lack of benefits of conditioning is "Effects of endurance training and captivity on activity metabolism of lizards", Garland et al. Am J Physiol Regul Integr Comp Physiol.1987; 252: 450-456. In this particular study, 2 groups of non-specialized agamid lizards were kept, one was exercised regularly, the other not. To quote from the abstract, "It is concluded that the adaptive response to endurance training, typical of mammals, does not generally occur in lizards. Moreover, levels of chronic activity that would elicit adaptive responses in mammals may be excessive for lizards and may induce pathological effects in joints and skeletal muscle."

As for why wild specimens are used, there are many reasons. First and foremost is that captivity is an un-natural state, and measurements may be skewed by things such as minor nutritional deficiencies. Additionally, many captive crocs have jaw deformities (nutrition has been implicated in this, as have several other aspects of captive care, but there's no even moderately strong consensus on it yet) which could skew tests. Furthermore, captive collections have only a limited number of crocs, often clutchmates or only from a narrow range of species and localities. Wild collection allows more diverse data gathering, reducing potentially confounding hidden variables. Plus, any excuse for fieldwork is a good one. ;-)

I also question the accuracy of the study in question, for two reasons. First, because it concludes that bite power is proportional to size. However, muscle power (including jaw muscles) is proportional to the cross-sectional area of the muscle, and, when scaling up or down in size, cross-sectional areas increase to the square of linear dimensions. Thus, if you double an animal's size, bite power should increase 4-fold, not 2-fold. However, this relationship was probably obscured by the data scatter caused by innate inter-individual variation. Also, the study in question used data from a variety of species. Obviously, a 4 foot gator will have a differnt bite pressure than a 4 foot gharial, due to differnt sizes of muscles, and different locations of muscle attachment in the species. A more accurate study would have relied exclusively on gharials (or had 3 parralell studies for gharials, false gharials and african slender snouts) and studied bite pressures from everything from hatchling to adult in large numbers, then compared differences in skull morphology. I suspect the results would have been much different.

In terms of lifespan, the comment I removed seemed to indicate that Sarcosuchus' lifespan as a whole (not just until adulthood) was significantly longer than most modern crocodilians, which does not seem to be the case. But you're right, it should be clarified. --User:Mokele

Well, it's a popular article about a scientific study not a technical paper — I'd expect errors in translation. 2,000 kg vs. 8,000 kg may be a bit high for a strict linear scaling, anyway. And have you seen the skull of S. imperator or a diagram? It's not a gharial snout, by any means. It seems to be an intermediate design between the narrow piscivores and the broad generalists.... though even the wide-mouthed C. niloticus eats more fish than anything else. The most interesting bit, which I forgot to include the first time, is that the juvenile snout is gharially slender — but it expands considerably upon maturity. I added the counter argument from Sereno's paper, and a bit more detail on classification. The whole thing really needs a copyedit, but that will have to wait for a bit. 68.81.231.127 18:37, 16 Jan 2005 (UTC)

I've read the paper, yes, but I'm unconvinced of routine large terrestrial prey, mostly because the local fish fauna included a hefty number of 6 foot long, 200 lb lobe-fins (roughly similar to the australian lungfish (Neoceratodus) in form), complete with osteoderms. I feel that, given the narrowness of the snout of both adults and juveniles, that the adult 'bulking up' is an adaptation to deal with these larger fish rather than terrestrial prey.

I agree that it's not a technical paper, but at the same time, I feel it's necessary to prevent a balanced view of the controversy surrounding this animal's feeding habits. Personally, I'm skeptical (as you can no doubt tell), mostly because of the skull shape and local sarcopterygian fauna, but I will admit that the grandiose publicity surrounding it has made me more suspicious that I otherwise would be. I feel that the most likely truth is that it's diet was primarily fish, only intermittently suplemented with smaller species of dinosaurs, as well as juveniles and carrion. Given the incredibly broad skulls of other giant crocs such as Purrasurus and Deinosuchus, I believe we can still reasonably make the link between very broad skulls being necessary for tackling large prey.

There's also the issue of bending stresses. I haven't done any biomech analysis of the skull myself, but I know that bending stress and buckling stress do not scale linearly; a large organism can't have as thin of a snout as a smaller one.

Another issue that I feel corroborates my views is the dorsoventral compression of S. imperator's snout. Such compression/reduction is needed to reduce resistance when flicking the head sideways underwater (the usual means by which crocs catch fish, as I'm sure you know). It's present in all modern crocs that are obligate piscivores (or nearly so), while "big-game hunter" crocodilians have much deeper heads.

On a totally tangential note, I noted you re-did the taxonomy. I've been meaning to learn more about the phylogeny and fossils of a broader selection of extinct croc taxa, and was wondering if you could recommend any particular papers or books on the topic? user:Mokele

Oh, I'm skeptical too... but I find the argument at least plausible, if not probable. Without something more conclusive like preserved stomach contents or tooth marks, it's just speculation. I agree that the fish-eating hypothesis should have more weight... but the article needs a reference for that opinion. (Sereno's was easier to add because I had a copy on hand.) You don't have to know of one offhand, do you?

I don't know much about biomechanics, but I'm always a little skeptical without practical tests, which is hard in extinct species. And the snap-thing isn't necessarily conclusive: C. niloticus does it too. I'd be interested to see a more depth analysis... while gigantic, sauropods have tiny necks and heads. If a croc snagged a drinking titanosaur, it might be able to kill it instantly, or at least hold on until it died and then munch on the body. But even if true, it would be opportunistic, and not the mainstay of its diet.

I'm surprised you haven't commented on Suchomimus. The comment about them fighting is absurd — even if their snouts were broader carnivores aren't MAD :). But it is in half the articles, so it needs to be mentioned. I really need to tone it down a bit more, though.

I expanded the classification mostly because the taxobox conflicted with the rest of the article... rather than force a triangular cladogram into the square hole of the Linnean taxobox, I used the old classification used in the Crocodylia article, and that just needed an explanation. I kept it general... is Deinosuchus an alligator or a croc? I'm not an expert (I'm sure you know far more about general crocodile classification and physiology than I do), but I suppose any look into ancient crocs is going to start with Benton & Clark 1988. They revised it later (1993?) with more characteristics, but the result was garbage... too many homoplasies. One of these days I'll read Schwimmer's book on Deinosuchus, and I've also heard good things about Hua's Ancient Marine Reptiles, but it's pricey.

When I get around to prettying up some of my less than brilliant prose and fixing some typos (philowhat?), I'll consolidate the argument as well... I think we've covered all the major points, but right now it reads more like a back and forth debate than an encyclopedia article :). 68.81.231.127 02:15, 17 Jan 2005 (UTC)

• I was thinking that this page really should be named Sarcosuchus and not SuperCroc. SuperCroc was just a tagline for the National Geographic special, while the actual article deals with the animal. I think it would make more sense to have the redirect be for SuperCroc and not Sarcosuchus Jura 17:29, 12 April 2006 (UTC)

I agree. SuperCroc just sounds like a dumb "common name" invented to hype up the TV special. I'll go ahead and move the page to Sarcosuchus.Dinoguy2 21:23, 12 April 2006 (UTC)