Jaguar vs Armadillosuchus

[Deleted]

Nov 27, 2013 20:40:59 GMT -5 Dinopithecus said:

So I ask you for evidence that it had low metabolism and now you ask me for evidence that it didn't (I think there's a term for that, I think it's some sort of fallacy).

Well, it's not exactly evidence, but many people have claimed notosuchians (like Armadillosuchus) to have some sort of endothermic metabolism (I will try to ask some people later to see if there is in fact some sort of study on it).

I just get this really extreme impression that it was at least somewhat endothermic judging from just looking at it and its supposed lifestyle (really good hunch, just not much evidence).

I already said that I have no evidence except that all living reptiles including the related crocodilians are cold-blooded. You are making a much bolder claim by saying that armadillosuchus would be warm-blooded when all its close relatives are not. Why should your claim be more credible without evidence?

Now I have heard studies about possible endothermy in very early archosaurs. Most come down to erect posture and the fact that living crocodiles have a four chambered heart and that because of this crocodiles lost endothermy through evolution. However crocodiles and other extinct relatives still have bone structures more like other reptiles then mammals, birds or dinosaurs, and erect posture isnt necessarily an indicator of high metabolic rates since chameleons have erect postures and are ectotherms. Its also possible that notosuchia lost endothermy by the time it evolved.

But even if its endothermic it is not going to change the fact that armadillosuchus was probably a slow animal with a cumbersome shell that may have lived a digging lifestyle much like a modern day armadillo. Those animals are considered endotherms but they are not very agile or maneuverable. So its basically like a jaguar against a equal-sized armadillo with sharp teeth. I would not favor the armadillo.

Nov 28, 2013 11:27:39 GMT -5 Cr1TiKaL said:

While I do find it hard for the armadillosuchus to kill the jaguar, I also see the opposite. So it's a tie I guess.

jaguars can bite clean through turtle shells. www.youtube.com/watch?v=J_TIl3gclxE

Plus they can easily pierce through caiman skulls which are similar to armadillosuchus and they can also bite through armadillo hide as well as possibly having killed large glyptotheriums with skull bites. The jaguar is obviously not going to attack the body but instead focus on the skull and neck.

[Dinopithecus]

Alright I've already shown that it's supposed "close relatives" (living crocodilians) are not closely related to Armadillosuchus at all (and some people have made the claim notosuchians were somewhat more endothermic to have an active terrestrial lifestyle). I'm not making the bolder claim at all.


Anyway, someone found this for me

This is the best data I could find:

Coulson et al. (1989) and Markwick (1998) found that the metabolic rate is a function of size and temperature, with the lower metabolic rates corresponding to larger animals and colder tempera- tures. This size-based differential response to thermal changes is a direct consequence of ectothermy and the lack of an internal source of energy. Ectotherms gain and lose heat as a function of their heat capacity and the surface area across which heat is gained or lost to the environment (Markwick, 1998). This could be used to infer physio- logical aspects of the large Notosuchia such as baurusuchids and sphagesaurids, and Sebecia such as the peirosaurids from the Late Cretaceous. As an individual grows larger, the greater its body surface area becomes, hence, the more heat or energy is required to raise its body temperature, and the longer it takes to lose heat. This inertial homeothermy has been used to suggest that very large ectotherms would have been able to maintain sufficient body temperatures during cold periods by virtue of thermal inertia. Seymour et al. (2004) even suggest that extant and fossil crocodylians could be homeother- mic animals, a primitive ancestral trait among archosaurs. Then, baurusuchids, peirosaurids and sphagesaurids would have been able to wander large distances, withstanding the heat and low humidity, as active predators in a harsh environment (Vasconcellos, 2006).

www.researchgate.net/publication/223556161_Climate's_role_in_the_distribution_of_the_Cretaceous_terrestrial_Crocodyliformes_throughout_Gondwana/file/504635166074da5cb0.pdf
They use a size and temperature related rule for crocodilian metabolism.

I'm guessing it means they were more ectothermic (contrary to what IMO its anatomy and lifestyle suggested), so I guess then I would slightly favor the jaguar (sort of depending on where they are). Though, I sort of got the impression they think sphagesaurids and modern crocodilians were comparable...

[Deleted]

^ In all honesty I dont even know why endothermy is even such an important factor here. I mean armadillos are endotherms yet they are pretty sluggish compared to a jaguar due to their carapace and digging lifestyle. Even if it was an endotherm I dont see armadillosuchus being very quick or maneuverable enough to counter a jaguar once it gets a hold of its head from the side.

[batcheno]

Probably the armadillosuchus because it has very hard bones