Largest crocodilians ever ?

[theropod]

Vastly is a little much, but yes, being similar in lenght it is somewhat wider and more rounded. But the robusticity of the skull doesn’t necessarily relate to the robusticity of the body.
Its possible that these two had bodies of similar rubusticity, despite Purussaurus having the more massive skull. Besides, differences in the skull-to-body-lenght proportions of these two are almost certain, and saying anything about their respective body sizes merely from skull built without knowing those variables is premature.

Not sure how many specimens there are of D. riograndensis, the type specimen is the largest known member of its genus, but compared to Deinosuchus as a whole Purussaurus brasiliensis is still clearly bigger, as all four individuals are huge, with skull lenghts considerably greater than that of the typical Deinosuchus.

[Grey]

As I said, it's a very cautious statement I'm lookin at. I know all the problematics. Now basically, without more detailled data about their respective postcranial anatomy, since Purussaurus appears to have the most massive skull, theoretically I'd consider it as the bigger. Furthermore, one can keep in mind the not (yet ?) published data hinted by Hartman to blaze suggesting a somewhat slender body shape for Deinosuchus, then I think cautiously tenable to say that Purussaurus is the most spectacular crocodilian for now. Damn, look that skull...

[theropod]

If these hints turn out to hold true (the comparatively skinny hindquarters and tail in Hartman’s life reconstruction) generally, I agree.

Otherwise, that depends on their respective closest relatives, and in that case I wouldn’t propose significant differences in size between the D. riograndensis holotype and large P. brasiliensis..

As Black Ice posted earlier, large caimans may be bulkier than other crocodilians of equal lenght, but they also have proportionately longer skulls¹. However, that’s an isolated incident which I didn’t verify, and I wouldn’t make too much of it anyway.

EDIT: The data listed in Erickson et al. 2012² rather show the opposite, scaled to the same mean total lenght, Melanosuchus is actually considerably lighter than the Alligator or Crocodylus porosus. Absolute size probably plays a role here, the Melanosuchus specimens were comparatively small (the taxon as a whole is actually larger than an A. missisipiensis). Either way, there’s no verification that caimans are somehow bulkier than other crocodylians.

¹ www.oocities.org/vermont_herpetology/article3.htm
² www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031781

[Grey]

I've followed the discussion and seen that claim of caimans being heavier than crocs, not verified. That's why, beside Hartman's suggestion and awaiting for more verifiable data, I tend to see then Purussaurs and Deinosuchus with a similar body proportion, with Purussaurus having this more massive, robust skull, hence owning the edge toward the title of biggest/most spectacular IMO. That's subject to potentiel change of course.

[blaze]

We also have to take into account how tall the skulls are from the side view, that of P. mirandai is pretty flat but I don't know if its because of crushing, the occipital region when looked from the posterior view doesn't look distorted, I've also seen one of P. neivensis but it comes from an very small individual, DCL of 52cm and since P. neivensis is the oldest of the species it might not look as derived.

[Grey]

Well, the reconstruction at the Lima Museum does not seem to exhibit a particularly flat skull structure.

[theropod]

The effect the slight difference in skull robusticity will have on overall weight, all else being equal, will be rather neglegible.

[Grey]

To me there's no slight difference in their skull robusticity, there's a clear difference.

[blaze]

I missed that Aguilera et al. (2006) say that the skull in P. mirandai is much flatter than in the other two species.

btw I think this are the actual fossils of the P. brasiliensis skull that was used to make the line drawing in my size chart.



Regarding the size of Purussaurus as a whole compared to Deinosuchus, known P. neivensis skulls range from 52cm to 103cm in DCL, those of P. mirandai range from 103cm to 110cm and excluding the estimated length of the largest skull, those of P. brasiliensis range from 119cm to 134cm. According to Schwimmer, the "average" skull length of adult D. rugosus is "slightly over 1m", the largest reasonably complete D. riograndensis skull has a dcl of 131cm, seems like the two genera are roughly matched.

[theropod]

blaze: I was just talking about P. brasiliensis, as I wrote I don’t know how many specimens there actually are of Deinosuchus riograndensis.

Grey: Yes, slightly in my opinion. There’s a difference of ~12% in the dorsal areas of these skulls when the fenestrae (considerably inflating the skull in Purussaurus. That’s likely one of the biggest nares in the animal kingdom!) are not included (owing to width, of course), if we assume Purussaurus’ skull is also deeper to a similar extend (which seems reasonable to assume), that makes it 1.12×1.12×1=1.25 times more voluminous. Keep in mind that’s merely the skull, all else being equal.
Clear or not, you think compared to their overall body mass the impact would be more than neglegible? More than maybe 200 or at most 300kg? What do you think the skulls of these guys massed?

If their skull to body-lenght ratios were the same (which I highly doubt, but I have nothing precise on that matter), there would probably not be any considerably mass discrepancy.

[Grey]

A skull 1/4 more voluminous is clearly bigger IMO. A really negligible difference would correpond about 10-15 % bigger from my viewpoint. That's not stating Purussaurus being as larger/bigger, but with a slight edge if the skull can really get 1.25 times more voluminous. 200-300 kg, if accurate, would be a small difference indeed given the immense size of the animals, but just not negligible at the point we are. Then one can keep in mind Hartman's reconstruction for Deinosuchus, even if a proper documentation is necessary. I place both animals even but nonethless with a pronounced edge toward the giant caiman, for now.

Nore sure how much their skulls would weigh, I've read on wiki that according to Guinness the fleshy skull of a very large male saltie can exceed 200 kg.

[theropod]

Unless the photographs (the latter is a cast, but still, it would have to be WAY off) are completely incorrect, it appears I was mistaken about the skull depth-part.

At the same skull lenght Deinosuchus’ skull is actually slightly deeper (11585 vs 11248px² of area covered). So Purussaurus’ skull mass would rather be something like 0.97×1.12×1=1.09 times that of Deinosuchus.
Really, if that’s all the difference there is to their overall weights, I consider it neglegible. Even the 25% difference in skull mass would have had a rather small impact on overall weight though, maybe 1/20th or so.

Also, it’s not as if increased bone mass was directly proportional to an increase in muscular mass. Specifically, the most broadened part in Purussaurus is the rostrum (especially that marked bulbous anterior end that you see so prominently in most pictures), which wasn’t bearing lots of soft tissue in life. Just as caimans don’t actually have stronger bite forces than other crocodylians despite having more robust snouts.

[blaze]

So, I got my hands on the recent death roll paper, some caveats, their "death roll indicator" utilizes bite force estimated from skull length, this is bound to overestimate the bite force of long-snouted species and therefore reduce their DRCI.

A value around 1 or higher suggest use of death roll behavior, extant species known to use the death roll got those values, as we suspected, Sarcosuchus got values similar to the gharial and the false gharial (0.18) but what surprised me is that both Deinosuchus and Purussuarus also got low values, Deinosuhus got 0.33 while Purussaurus brasiliensis and P. mirandai got 0.53 and 0.33 respectively, the one that definitely got a value well over 1 was the comparatively diminutive skull of P. neivensis.

Some things that I think are plain wrong is that they used the skull of Deinosuchus (based on the drawing in Schwimmer, 2002) scaled to 180cm in DCL, though bringing it back down to 147cm or even 1m doesn't increase its DRCI enough to get it over 1.

At the end they make mention of several allometric effects that indicate that for giant taxa like these, even low DRCI values as 0.33 shouldn't exclude them from being able to perform a death roll.

[Godzillasaurus]

Hmm, that does not sound right at all. Their skulls were quite perfectly designed for death rolling, as they were very robust and not that much unlike extant crocodilians. Purussaurus at least seemed to have had a skull and tooth morphology quite similar to the broad-snouted caiman, while deinosuchus is quite similar to most macrophagous crocodiles like the saltwater crocodile. I think they need to look into this greater because their skull shape suggests that they were highly adaptive for death rolling.

And as for sarcosuchus, that is believable. I don't know why I used to believe that it could death roll

[Infinity Blade]

I agree.