Purussaurus brasiliensis

[DinoFan83]

Apologies for deleting and reposting this for the third time. I really don't want to make it seem like spam but I've gotten so much new information since I made the last post that it had to be redone.

I actually got the chance to ask Jorge W. Moreno-Bernal about the 2007 abstract, in the comments of here. As he wrote:

Quote:As you point out, the Dorsal Skull length I provided for Purussaurus brasiliensis UFAC 1403 (134) cm was incorrect, as it was an estimate I made from published total and basal skull lengths. Now I have a direct measurement of the dorsal length, kindly provided by a Brazilian colleague. This measured (and not yet published) value of dorsal skull length is several centimeters shorter than my 2007 estimate of 134 cm.

You are also right in that specimen UFAC 1118 does represent the mandible of UFAC 1403. Measurements of this mandible have been published by Bocquentin et al (1989) as well as by Aguilera et al (2006), together with others made on mandibles and skulls of P. brasiliensis and P. mirandai. You can use those in conjunction with measurements of the DGM mandible, published by Price (1967), in order to make your own Dorsal Skull Length estimates for the DGM specimen. If you don't have access to those papers, I can send them to you.

The problem this causes for estimating the size of Purussaurus is some major uncertainty in terms of mandible measurements (UFAC 1118 in particular). Aguilera et al. (2006) report the UFAC 1118 mandible as 159.5 cm, but I am very skeptical of this measurement, for 2 reasons:

-They worked with casts, as they wrote under Figure 5. But casts can be rather fickle, shrinking to a degree from the real bone especially as they get larger. In this case, we don't know if they were cast separately or not, nor whether the temperature change and therefore shrinkage was consistent between them.

-The mandible/dorsal skull length ratio in those casts is not consistent with the figures in Aureliano et al. (2015), and nothing I could find seemed to indicate those figures being drawn from casts instead of the real bones. So what I think is by far the most likely is that the Aguilera et al. (2006) measurements are from mismatched casts while the Aureliano et al. (2015) figures are the most accurate representation of the specimens.

-This gives another contradiction. Moreno-Bernal states that the dorsal skull length of UFAC 1403 is smaller than 134 cm, yet even assuming that dorsal skull length, UFAC 1118 comes out well below 159.5 cm (143.8 to be precise) - more reason still to suspect the casts Aguilera et al. used are mismatched in terms of shrinkage, as a lower dorsal skull length than 134 cm only brings the mandible's measurement further down.

But we're not out of the woods yet. Given the aforementioned problems with the published measurements as well as some now known to be explicitly incorrect, the skull length of UFAC 1403 and mandible length of UFAC 1118 aren't exactly deductible at this time, so unlike in the last post, I will not be attempting to measure or estimate their size and will have no opinion on it unless or until more consistent measurements are published. I also do not have any opinion on what the biteforce of Purussaurus could have been, because all the above makes it anything except easy to estimate.

What I will be using for size estimates is the mandible DGM 527-R, which Aguilera et al., Aureliano et al., and Moreno-Bernal all appear to agree with on the 175 cm estimated length. In order to avoid any problems with published measurements, it will be estimated directly from the mandible length of the American alligator.

Mandible length and body size of the base alligator:

Bailleul et al. (2016) provides the skull length of a 3.3 meter alligator (ROM R4411) as 44.5 cm. I could not find in the paper how this measurement was taken, so I will tentatively assume it represents dorsal cranial length, which is almost always used for crocodilian skulls. Campione & Evans (2012) give the body size of this alligator as 168 kg.
No mandible length was given for this specimen, but that can be inferred from other alligator skulls. For example, based on the alligator skull in Erickson et al. (2012), the dorsal skull length is around 91% of the mandible length, so the mandible of ROM R4411 was probably around 48.9 cm.

Size estimate for Purussaurus:

Assuming the figures for ROM R4411 as written above are accurate, DGM 527-R would be 11.8 meters and 7700 kg assuming isometry with mandible length. This is about the same as my previous weight estimate but somewhat shorter in length.

Conclusions:

-UFAC 1403 and UFAC 1118 probably cannot be estimated at this time, we don't have consistent measurements.
-DGM 527-R, by contrast, can be estimated. It comes out very similar in size to my older estimates and quite large to boot.
-Bite force would certainly be very high, but how high is uncertain.

Note that this post is prone to updates and/or complete deletion and revision as I learn more. Reply