Purussaurus brasiliensis vs. Dunkleosteus terrelli

[dinosauria101]

Purussaurus brasiliensis
Purussaurus is an extinct genus of giant caiman that lived in South America during the Miocene epoch, 8 million years ago. It is known from skull material found in the Brazilian, Colombian and Peruvian Amazonia, and northern Venezuela. The skull length of the largest known individual of the type species, P. brasiliensis is 1,453 millimetres (57.2 in). It has been estimated that P. brasiliensis reached about 10.3 metres (34 ft) in length, weighing about 5.16 metric tons (5.69 short tons). Another estimate gave a larger size of 12.5 metres (41 ft) in length and 8.4 metric tons (9.3 short tons) in weight, with a mean daily food intake of 40.6 kilograms (90 lb). Bite force has been estimated to be around 69,000 N (around 7 metric tons-force).. Two other extinct crocodilians, Sarcosuchus and Deinosuchus, have similar proportions, but both are geologically much older, dating from the Early and Late Cretaceous, respectively, and another from the Miocene of India, Rhamphosuchus, is estimated to be slightly smaller, though assumed to have been proportioned like a gharial. During the summer of 2005, a Franco-Peruvian expedition (the Fitzcarrald expedition) found new fossils of Purussaurus in the Peruvian Amazon (600 km from Lima).


Dunkleosteus terrelli
Dunkleosteus is a genus of prehistoric fish, one of the largest arthrodire placoderms ever to have lived, existing during the Late Devonian period, about 380-360 million years ago. This hunter, measuring up to 9 metres (29 ft) and weighing 3.6 tonnes (4.0 short tons), was a hypercarnivorous apex predator. Few other placoderms, save, perhaps, its contemporary, Titanichthys, rivaled Dunkleosteus in size. Due to its heavily armoured nature, Dunkleosteus was likely a relatively slow, but powerful, swimmer. It is thought to have dwelled in diverse zones of inshore waters. Fossilization tends to have preserved only the especially armoured frontal sections of specimens, and thus it is uncertain what exactly the hind sections of this ancient fish were like. nstead of teeth, Dunkleosteus possessed two pairs of sharp bony plates which formed a beak-like structure. After studying a biomechanical model of the fish's jaws, scientists at the Field Museum of Natural History and the University of Chicago concluded that Dunkleosteus had the second most powerful bite of any fish (the giant Megalodon being the strongest). Dunkleosteus could concentrate a pressure of up to 8,000 pounds per square inch (55 MPa) at the tip of its mouth, placing Dunkleosteus in the same league as Tyrannosaurus rex and modern crocodiles as having the most powerful known bite. Dunkleosteus could open its mouth in one-fiftieth of a second, which would have caused a powerful suction that pulled the prey into its mouth, a food-capture technique used by many fish today.

Credit to Wikipedia

[dinosauria101]

This has now been edited to something else!

[jhg]

I thought Dunkleosteus was only 1 tonne. This is just another breakfast for Purussaurus.

[dinosauria101]

Apparently, scaling up from a great white gets a 6-7 tons animal (forgot to add that in the OP)
The reason I favor Purussaurus is due to much wider gape and skull size

[elosha11]

^Yes, given Dunk's relatively small gape and suction motion, I wonder if it wasn't seeking much smaller prey base than what is frequently imagined. However, it must have had some evolutionary need for its heavy armor. I wonder if it was a fish that was combative with its own species, as I don't really know of any other creature at the time that could have threatened it (I could be wrong there, I'm not going to claim I'm an expert at the Devion time period). It seems like it would be way too long ago for giant mosasaurs, pliosaurs, or sharks that could have threatened it. I don't think even predatory Icthyosaurs lived that far back, although again I could be wrong. I guess Titanichthys could be a rival, but wasn't that fish substantially smaller (although still quite massive)?

If we assume the heavy frontal armor was for intraspecific confrontations, we might assume Dunkleosteus was a seasoned combatant, at least in fighting its own kind. But again, despite its size, armor, and power of its bite, it's relatively small gape and correspondingly small gape volume (relative to Purussaurus) might ultimately doom the fish. It could certainly cause nasty injuries to the croc, its powerful bladelike jaws/teeth could pierce the croc's armor quite easily and cut quite deeply. But unless it got an extremely lucky bite and was able to pierce the croc's heart or brain (pretty slim chance of that), it would likely do nasty, but relatively small and non-fatal injuries. Whereas the croc, if it could figure out to bite the less protected middle and back end, would do devastating damage with its own very powerful and massive bite. And it also looks like Purussaurus was the heavier and larger of the two animals, another significant advantage. Purusssaurus is probably my current pick for the most formidable crocodilian that has ever lived. It's more robust and with larger jaws than other giant prehistoric crocodilians. My only question is how aggressive it was. It's classifed as a caiman, and caiman's today, even the biggest ones such as the black caiman, are not considered as aggressive or as formidable as sw or nile crocs.

Interesting match up, but I'd give it to the croc 8/10 in a fight to the death. I will say that if the fish could get in some quick and painful bites and the croc couldn't figure out how to get past the frontal armor, the fish could drive away the croc or maybe even dominate interactions with it. Or of course, vice-versa, the croc might drive away, (but not kill) the fish.

[dinosauria101]

Jun 28, 2019 11:07:52 GMT 5 elosha11 said:

Interesting match up, but I'd give it to the croc 8/10 in a fight to the death. I will say that if the fish could get in some quick and painful bites and the croc couldn't figure out how to get past the frontal armor, the fish could drive away the croc or maybe even dominate interactions with it. Or of course, vice-versa, the croc might drive away, (but not kill) the fish.

Well the thing is, that shearing bite is extremely efficient at cutting chunks out from an opponent. And we've got little actual evidence to back the slow Dunkleosteus theory, so it'd probably be best to assume similar speed for both.
Your post was so long I need more than 1 post to reply to it fully

[dinosauria101]

Jun 28, 2019 11:07:52 GMT 5 elosha11 said:

^Yes, given Dunk's relatively small gape and suction motion, I wonder if it wasn't seeking much smaller prey base than what is frequently imagined. However, it must have had some evolutionary need for its heavy armor. I wonder if it was a fish that was combative with its own species, as I don't really know of any other creature at the time that could have threatened it (I could be wrong there, I'm not going to claim I'm an expert at the Devion time period). It seems like it would be way too long ago for giant mosasaurs, pliosaurs, or sharks that could have threatened it. I don't think even predatory Icthyosaurs lived that far back, although again I could be wrong. I guess Titanichthys could be a rival, but wasn't that fish substantially smaller (although still quite massive)?

If we assume the heavy frontal armor was for intraspecific confrontations, we might assume Dunkleosteus was a seasoned combatant, at least in fighting its own kind. But again, despite its size, armor, and power of its bite, it's relatively small gape and correspondingly small gape volume (relative to Purussaurus) might ultimately doom the fish. It could certainly cause nasty injuries to the croc, its powerful bladelike jaws/teeth could pierce the croc's armor quite easily and cut quite deeply. But unless it got an extremely lucky bite and was able to pierce the croc's heart or brain (pretty slim chance of that), it would likely do nasty, but relatively small and non-fatal injuries. Whereas the croc, if it could figure out to bite the less protected middle and back end, would do devastating damage with its own very powerful and massive bite. And it also looks like Purussaurus was the heavier and larger of the two animals, another significant advantage. Purusssaurus is probably my current pick for the most formidable crocodilian that has ever lived. It's more robust and with larger jaws than other giant prehistoric crocodilians. My only question is how aggressive it was. It's classifed as a caiman, and caiman's today, even the biggest ones such as the black caiman, are not considered as aggressive or as formidable as sw or nile crocs.

And now for the second reply

I do agree the armor seems to be a plausible defense mechanism against other species or intraspecific comptetition; however there were no ichthyosaurs, pliosaurs, or anything of the like back then, and Titanichthys seems to be a good deal smaller and less well armed than Dunkleosteus, so I think that 1st theory for intraspecific conflict holds up well.
About their bites, I think assuming equal skull size it's pretty even. The fish's bite would potentially be able to shear off limbs, even! However, in the end, I think I'd favor Purussaurus about 7/10 due to size advantage, larger skull, better durability, and known for sure to be a competent fighter.

[elosha11]

How do we know "for sure" Purussaurus was a competent (and by that I assume you mean good, rather than just average) fighter? It's supposed to be a prehistoric caiman. In general, modern day caimans seem less aggressive and less adept at fighting than similar sized crocs. Crocs of the same size, (particularly sw and nile crocs) dominate comparable sized caimans when they are together. Physically speaking, Purussaurus might be the most impressive of known prehistoric crocodilians and is more comparatively bulky than modern day caimans. But we don't know if it had similar less aggressive behaviors, such as modern caimans, or was more dominant like today's largest crocs.

I still agree that the caiman wins, but mainly because I don't think the fish's gape/bite volume would allow it to inflict great enough damage. I agree it might be able to bite of the caiman's leg, but we know crocodilians readily survive such injuries by modern examples.

[dinosauria101]

Well, I think it would probably have been a good fighter on the principle that it was the largest and most predatory crocodilian in its environment (coexisting with the gharial Gryposuchus and the planktivorous Mourasuchus); similar to the case with saltwater crocodiles being the most aggressive where they coexist with gharials (solely piscivorous) and false gharials (mostly but not exclusively piscivorous).
And also about Dunkleosteus' speed, I found this quote from Wikipedia. Looks like it could have been sharklike in behavior:

Mainly the armoured frontal sections of specimens have been fossilized, and consequently the appearance of the other portions of the fish is mostly unknown.[10] In fact, only about 5% of Dunkleosteus specimens have more than a quarter of their skeleton preserved.[11] Because of this, many reconstructions of the hindquarters are often based on smaller arthrodires, such as Coccosteus, which had preserved hind sections. However, an exceptionally preserved specimen of D. terrelli preserves ceratotrichia in a pectoral fin, implying that the fin morphology of placoderms was much more variable than previously thought, and was heavily influenced by locomotory requirements. This knowledge, coupled with the knowledge that fish morphology is more heavily influenced by feeding niche than phylogeny, allowed a 2017 study to infer the body shape of D. terrelli. This new reconstruction gives D. terrelli a much more shark-like profile, including a strong anterior lobe on its tail, in contrast to reconstructions based on other placoderms.
Citation: peerj.com/articles/4081

Moreover, I agree with you there as well about the fishes bite; we've seen what modern crocodilians can survive, so a few shearing bites on an 8 ton behemoth shouldn't be an instakill. However, as you say, it's often a good idea to look at things from the winner's perspective, and that's what I think would happen on the caiman's viewpoint

[all]

This is a mismatch. The size of crocodile is more than double. He is not only larger he is also very powerful as well. of course he is going to win

However pound per pound its 50/50 I might even give slight edge to dunkleosteus.

[dinosauria101]

all

Yes, with 2 ton DUnkleosteus, this is a mismatch. But we do have a study suggesting otherwise, so this likely depends on the estimate

[all]

Some info on dukleosteus suggest its 10 meters in length other say only 6 meters.  6 meters would be about half of purussarurus's length

If you take 10 meter DT then it has arealistic chance if it would weigh slightly above 4 tons not little bit below. and PB weigh 5 tons

Under those circumstances I would give it 50/50

If however DT is only 6 meters then it has no realistic chance. Nonetheless pound per pound I give the edge to DT. If it is only 6 meters it makes his bite force all the more impressive from pound per pound point of view. a 6 meter crock has a very impressive bite force of 7700 lbs per square inch. But DT has bite force of 11000 lbs per square inch. Crocodile's teeth are relatively blunt. So increase on the blade-tip is not going to be that large. Increase on blade-tip of DT gets it to 80000 lbs per square inch.

Of course all this does not matter if weight difference is as huge as it would be between 6 meter and 12 meter animal. So Purussaurus wins easily. Pound per pound however this would be a different story.

[Infinity Blade]

It seems like it would be way too long ago for giant mosasaurs, pliosaurs, or sharks that could have threatened it. I don't think even predatory Icthyosaurs lived that far back, although again I could be wrong.

You’re absolutely right. Reptiles didn’t even exist when Dunkleosteus was extant, let alone any of the marine taxa you mentioned (they lived in a completely different era). Sharks were around but I’m not aware of any large macropredatory examples that existed this far back.

[all]

I know that there were small sharks I' m not sure about the large ones. One possible answer to why dunkleosteus needed the armor  is so they could be protected from each other since they were cannibals. However I don't know if that was on occasion or was it a norm.