Size comparisons

[tigerluver]

(04-29-2020, 03:32 AM)GuateGojira Wrote:

(04-29-2020, 02:26 AM)tigerluver Wrote: There are no published estimates but I can show a few methods.

One way is to compare the average modified mandible length published, link that to the average skull length of all tigers, and then extrapolate the fossil's skull length. Four subspecies were used in comparative data of Sherani (2019), P. t. altaica, P. t. tigris, P. t. corbetti, and P. t. sumatrae. The average skull length of each species combining males and females are 332 mm, 325 mm, 310 mm, and 294 mm respectively. Counting the data points in Sherani (2019) figure 4, there are 3 specimens in group of P. t. sumatrae, P. t. altaica, P. t. corbetti and 15 P. t. tigris. So the weighted average of the mandibles given the literature data described on skull would be 320 mm. The fossil is 1.5x than the average extant tiger in the data set. Multiply 1.5 by 320 we get an estimated skull length of 480 mm.

Another way to get a rough estimate is to compare to other giants. Compared to the 455 mm P. atrox skull, the canine of the Bornean fossil is ~16% longer. Even accounting for tigers having possibly wider canines, this would indicate the skull of the Bornean fossil was likely longer. Similarly, this comparative image (despite issues in inaccurate scale bars) indicates that Bornean mandible is a bit longer in the modified mandible length measurement:

*This image is copyright of its original author

Make sure to not confuse horizontal ramus height with ramus length. The P. fossilis-atrox group are superior to all tigers in proportional horizontal ramus height as such is a primitive trait of cats.

 @epaiva was able to kindly share the comparative measurements of the his cast of the 467 mm P. atrox as well. Here is one of his photos with scale:

*This image is copyright of its original author

The modified mandible length is a few percent shorter compared to the Bornean fossil while the horizontal ramus length is comparable, indicating the Bornean fossil is likely from a skull of similar to a bit longer in size.

In sum, the skull was probably no less than 450 mm, and likely in the 470-480 mm range.

In comparison to the Ngandong tiger, here is a rough femoral length extrapolation. The Bornean fossil length is 1.5x the average tiger. The average femur length of a tiger (mixing genders) is 353 mm (n=19) (Christiansen and Adolfssen 2007). Extrapolating, the estimated femur length of the Bornean mandible would be 530 mm. My gut tells me this may be a bit of an overestimate as the tigers in Sherani (2019) may be a bit smaller than those in Christiansen and Adolfssen (2007). Nonetheless, in femur length and thus body size the Bornean mandible would be a ways larger. Weight comparison is more complicated as we can't compare robustness between the specimens but just given how much longer and taller the Bornean specimen is, it is likely heavier than the largest Ngandong specimen.

Ok, that's it, I want to make a comparative image with this huge tiger! @tigerluver, can you provide me with the head-body, shoulder height, skull length and body mass estimated for this tiger? I want to make the comparison now that I have a little of time. By the way, do you think that we can use a Sunda tiger for comparative image, or a mainland tiger? I have two side-view images for that.

Head-body length based on the aforementioned calculation would be 260 cm. Using the data you compiled on tiger subspecies and having a weighted average of 175 cm body length for all 4 subspecies, the Bornean fossil's body length would be c. 260 cm (175 cm x 1.5). It seems shoulder height is half of body length generally, so that would be about c. 130 cm. Skull length from the above calculations would be c. 480 mm. We have an official peer-reviewed body weight of 480 kg (Sherani 2019). Looking forward to your work.

Either form of tiger as a representation should be fine. The PCA in Sherani (2019) did show that the tiger groups closer to P. t. corbetti and P. t. sumatrae and considering how young the specimen is, it likely had the color and large scruff of the island tigers. Reply