Size comparison scale

[Verdugo]

Aug 15, 2019 17:20:33 GMT 5 Infinity Blade said:

I recently tried revising my silly little T. rex vs. jaguar skull at total body mass parity comparison to fit the data in Sakamoto et al. (2019)'s supplementary material. According to their data, Stan has a skull 142.6 cm long, while a 97 kg jaguar has a skull ~22.7 cm (rounding) in length. I tried to upsize the jaguar's skull as if the whole animal weighed 7,722 kg (this is Franoys' estimate for Stan, which is probably the most liberal estimate I don't consider to be pushing it), giving us a skull of ~97.65 cm long.

It definitely can't be perfect, so I'd appreciate if someone can check my comparison, maybe do a better job than I can. The T. rex skull is by Greg Paul->, while the jaguar skull is Figure 1 of Naish et al. (2014)->; the skull is labeled "Peruvian tiger" but it was resolved as part of P. onca.

What is the Skull length measurement for the Jaguar though? 22.7 cm seems rather small for a Pantherine up to 97 kg. I suppose it's not the Greatest skull length measurement?

[dinosauria101]

Verdugo

I would not be surprised if jaguar skulls were proportionately shorter for more power in bite force

[Infinity Blade]

Aug 15, 2019 18:10:23 GMT 5 Verdugo said:

Aug 15, 2019 17:20:33 GMT 5 Infinity Blade said:

I recently tried revising my silly little T. rex vs. jaguar skull at total body mass parity comparison to fit the data in Sakamoto et al. (2019)'s supplementary material. According to their data, Stan has a skull 142.6 cm long, while a 97 kg jaguar has a skull ~22.7 cm (rounding) in length. I tried to upsize the jaguar's skull as if the whole animal weighed 7,722 kg (this is Franoys' estimate for Stan, which is probably the most liberal estimate I don't consider to be pushing it), giving us a skull of ~97.65 cm long.

It definitely can't be perfect, so I'd appreciate if someone can check my comparison, maybe do a better job than I can. The T. rex skull is by Greg Paul->, while the jaguar skull is Figure 1 of Naish et al. (2014)->; the skull is labeled "Peruvian tiger" but it was resolved as part of P. onca.

What is the Skull length measurement for the Jaguar though? 22.7 cm seems rather small for a Pantherine up to 97 kg. I suppose it's not the Greatest skull length measurement?

They don't seem to explain it in their supplementary material or what I think is their original source. However, even if it was greatest skull length I don't see a whole lot off about it, and I say this based off of other cat species for comparison. For example, this is the skull of a snow leopard, and as you can see it's ~19 cm long in greatest skull length.


Sure enough, Sakamoto et al.'s supplementary info lists a 50 kg snow leopard as having a skull 17.98 cm long, an insignificant difference.

Likewise, this is the skull of a leopard. As you can see, it's ~18.5 cm in greatest length.


Sure enough, Sakamoto et al.'s supplementary info lists a 59 kg leopard as having a skull 19.74 cm long, which again, is an insignificant difference.

Maybe I'll go ask how massive the owners of the skulls above were.

[dinosauria101]

Lower Deinosuchus estimate vs Spinosaurus by brolyeuphyfusion

[dinosauria101]

Skulls of various carnosaurs

[dinosauria101]

By brolyeuphyfusion:

[Infinity Blade]

I added dorsal views so people can compare the width of each skull and snout. Again, this is assuming Franoys' mass estimate for Stan (~7.7t), which may very well be too high. If it's too high, then the jaguar's skull would be smaller by comparison than that suggested here.

But again, not the best size comp. creator.

[Verdugo]

Infinity Blade
Here are some of the skull length measurements and body mass that i have seen in literatures:
Wroe (2005)
Table 1. Basal Skull Length = 22.25 cm, BM = 83.2 kg. Very similar to that of Sakamoto (2019) in dimensions but the skull length is BSL. The Greatest SL should be much greater.

Per Christiansen (2007)
Tabble 1. Condylo-basal Skull Length = 23.04 cm, BM = 73.3 kg. This specimen is estimated to be lighter than the one from Sakamoto, however, its CBL is already greater than the skull length from Sakamoto. Since this is only CBL, its Greatest should be even longer.

Kupczik & Stynder (2012)
No Jaguar but there is a Lioness. Maximum Skull Length (= Greatest Skull Length?) = 32.88 cm (Table 4), BM = 120 kg. Assuming the Jaguar weighs up to 97 kg, i would not expect its Greatest Skull length to be much smaller than this.

It seems like the measurement from Sakamoto 2019 is a Basal Skull length to me. Could you check carefully to see if they say anything about the skull length measurement in the texts? (probably in the Methods section)

Btw, why do you think Franoys overestimated Stan? His estimate is fairly consistent with other recent (some volumetric) estimates of Stan i have seen (i'm sure you already seen them too).

[theropod]

The body mass figures in Wroe et al. 2005 are only estimates, usually based on skull length themselves, so I wouldn’t rely on their figures as datapoints. They cite this for how they predicted those body masses: books.google.at/books?hl=en&lr=&id=7kxI0Zzr_R8C&oi=fnd&pg=PA181&dq=Skeletal+and+dental+predictors+of+body+mass+in+carnivores&ots=XjwTUoP6Sh&sig=vUvHtSBfblHwUEHlq6cGki0hSPw&redir_esc=y#v=onepage&q&f=false
At first I thought you could use this to make a better estimate of the skull length of a hypothetical T. rex-sized jaguar using their equations or at least their datapoints.
The problem is that Van Valkenburgh et al., while they made their own cranial measurements, also didn’t actually record body masses of the same specimens, instead using the average weight of the respective species and sex based on averaging values from the literature.
It’s easy to see how this introduces and proliferates error, especially when using only small samples. It’s unlikely the specimens were all exactly average-sized individuals, and they could have been larger or smaller. So some of the data points were probably smaller than assumed, and their relative skull size would be underestimated, while others were larger and their skull size was overestimated, and we have no way of knowing which ones, or which differences in proportions are related to this statistical error, and which reflect the genuine difference between taxa or specimens.
Over a very large sample and in very rough terms, this might not matter so much, but I don’t think this meets the standard of precision we are generally striving for.

[Infinity Blade]

Edit: I got ninja'd by theropod.

If wanted, I'll have to get to the jaguar skull later. That will require some reading to do of the paper; for some reason the search bar function isn't working for the PDF unfortunately.

www.biorxiv.org/content/biorxiv/early/2018/05/30/333351.full.pdf

Unless it works for anyone else by any chance?

Edit: it works now for some reason. I guess it needed some time to load results. Anyway, I got no results.

Btw, why do you think Franoys overestimated Stan? His estimate is fairly consistent with other recent (some volumetric) estimates of Stan i have seen (i'm sure you already seen them too).

Well, I didn't say it was definitively wrong, but if anything broly and theropod have said to me that a ~7.2t estimate for Stan (cited by Sellers et al., 2017) was either an overestimate or at least may or may not be realistic (and if a ~7.2t estimate may be too high, a ~7.7t one would be even more so). This was by virtue of both Asier Larramendi and blaze both getting lower estimates of the specimen.

[dinosauria101]

Infinity Blade

I thought Larramendi only did mammals and not dinosaurs? Have they started doing dinosaur skeletons recently?

[dinosauria101]

Elasmotherium vs Mamenchisaurus hochuanensis

[dinosauria101]

Titanoceratops vs Dacentrurus

[dinosauria101]

Therizinosaurus vs Mapusaurus

[dinosauria101]

Tyrannosaurus vs Columbian mammoth - average vs average