Skulls, Skeletons, Canines & Claws

[peter]

(10-02-2017, 08:25 PM)johnny rex Wrote: Any thoughts on Kaziranga tiger skull measurements? It seems those guys could have some of the largest skulls of extant felid by looking at some size comparison between some males and rhino and water buffalo carcasses.

A - Panthera tigris tigris

Most unfortunately, there is no information about the size of tigers in that part of India today. However. In 1908, 'Thirty-seven years of big game shooting in Cooch Behar, the Duars, and Assam. A rough diary', written by the Maharajah of Cooch Behar, was published. Although the region in which the Maharajah and his guests hunted was a bit more to the (north)west, I propose to assume that Kazirangha is zoologically part of that region.

As his book has a lot of information. I decided for a number of tables based on his book. They were posted in the tiger-extinction thread in January 2016. If we want to compare tigers shot in region with tigers shot in other regions, we need information collected in the same period. Is there anything? Yes. Plenty. Most of it is in old books. 

To keep it short. The information in the book of the Maharajah was confirmed in other books in which Assam tigers featured. In that part of India, in those days (1870-1940 roughly), most tigers were measured 'over curves'. Compared to tigers shot in central parts of India (where they were measured 'between pegs'), they were about as long (referring to total length). The difference was in weight: Assam tigers were heavier.

And how about skulls? Things in that department are not as clear, but what we know confirms what is seen on photographs of Assam tigers in that they seem to have relatively large skulls.

Here's the 3 tables on male tigers I posted in January 2016. Notice the decline in size over time. You can find detailed information in the liner notes (at the bottom). Tigers with large skulls are significantly longer and heavier than average. Skull size could be related to age. Also watch the measurements for 'head' (head circumference):

*This image is copyright of its original author

*This image is copyright of its original author

*This image is copyright of its original author

     

The average greatest skull length of wild male Indian tigers in those days was 350,00 - 355,00 mm., say 14 inches roughly. I didn't see many skulls of wild male tigers, but there are skulls of captive male Indian tigers in museums and private collections. Today, with the exception of Pakistan perhaps, there are no captive Indian tigers outside India, but half a century ago the situation was different. The skulls I saw were a bit shorter, but wider than skulls of wild male Indian tigers. 

The longest skull measured by Pocock (1929, 1939) was 378,00 mm. in greatest total length, but that doesn't mean that reports about larger skulls provided by hunters can be dismissed as exaggerations. Hunters donated skulls of tigers to museums every now and then, but they often kept the largest skulls. 

B - Panthera tigris altaica

I never saw a skull of a wild male Amur tiger, but there are skulls of captive Amur tigers in museums and private collections. Most of them were longer than skulls of captive male Indian tigers, but not as wide and robust. There is reliable information about skulls of captive males well surpassing 335,00 mm. in condylobasal length, suggesting a greatest total length of ranging between 380,00 - 400,00 mm., but my guess is that skulls of Indian tigers could be more robust. In the canine department, however, Amur tigers are unsurpassed.

Every now and then, tiger skulls are found in northern China. Up until 1950-1960, Manchuria had Amur tigers. They are now extinct, but it is possible that some captive Amur tigers, as Grizzly suggested, still carry information of these giants. And giants they must have been. Some of these prehistoric skulls are much larger than the skulls I saw, again suggesting that tigers walking the edge, just like in Indonesia and Vietnam, quickly change in size when the heat is on. This is something that didn't quite happen in India and the result is that Indian tigers, also as a result of good conditions and severe competition in reserves, are now a bit more robust than wild Amur tigers. But the Russians are changing the situation and they have both time and room at their disposal. If the population exceeds a thousand adults or so and poaching of prey animals can be limited, things will change again.

C - Pleistocene big cats

Pleistocene and early Holocene tigers must have lived like kings. The bones and skulls found in the last century strongly suggest they, both in the north (Manchuria and the Russian Far East) and in the south (in what's now Indonesia), reached a size not seen today. Half a century ago or so, zoologists and biologists often quickly dismissed reports about tigers well exceeding the limits of their day, saying size wouldn't change a lot in a few hundred years only. But if tigers can dwarf in a century, and they did in a number of regions just before they were pushed off the cliff, the opposite also is possible.

So how big was big back then? I read a thesis about a prehistoric lion in Europe (Siegdorf, Germany). Compared to bones and skulls of lions found elsewhere in Europe, the Siegdorf male wasn't exceptional in any way. In spite of that, he most probably was 200-210 cm. in head and body length (measured in a straight line). In his prime, if he would have had a similar robustness ratio as male big cats today (1,0 - 1,5), he would have ranged somewhere between 200 - 315 kg. (441 - 695 lbs.). Exceptional males could have added 30-50%, meaning a very large individual could have exceeded 800 lbs.

Seems a bit inflated, but if you see the size of some captive big cats, it isn't. It's most often seen in captive Amur tigers, because lions, as social cats, would have been affected sooner by deteriorating conditions and smaller prey animals. It's more likely they lost information about size, that is. In northern China and Russia, however, pressure in general would have been less intense. Peoplenumberwise more so than anywhere else. In the end, that could prove to be the key to size. That, conditions and isolation (no influx of new genes).

And what kind of skull would 800 lbs. and over produce? Well, could be something like this:

*This image is copyright of its original author

D - The 15,75 inch tiger skull

Biologists, as stated before, never saw a tiger skull exceeding 15 inches (381,00 mm.) in greatest total length. But most didn't see much more than a hundred skulls and not one of them visit the natural history museums in Vladivostok and Chabarowsk. Per Christiansen, in one of his papers, mentioned a few skulls of captive male Amur tigers. One of these exceeded 350,00 mm. in condylobasal length, meaning that skull most probably was close to or just over 400,00 mm. in greatest total length. Baikov also mentioned skull of that size and my guess is there are more.

Skulls of Indian tigers also exceed 15 inches (381,00 mm.) in greatest total length (apparently up to 406,40 mm.) at times, but these two subspecies are the only ones to reach that size. This means that skulls of exceptional males of these subspecies are about 2-3 inches longer than an average male skull. The main difference with average skulls, however, isn't in length, but in robustness. A big skull can be twice as heavy as an average-sized skull.

Assuming that the average of Pleistocene big cats exceeded the average of big cats today by 5-15% and including the fact that tigers can reach 16 inches in greatest total length, one could assume that the largest Pleistocene tigers reached about 18 inches in greatest total length. The largest lions, assuming the difference in size would have been similar to the difference seen today, could have exceeded 19 inches or slightly over. I agree with Guate's estimate for maximum total length, but my guess is that his estimate for width (11,5 inches or 292,10 mm.), at least in tigers, is too low. Large skulls often are relatively wider than average-sized skulls. Width is age-related and age often results in more robustness (also seen in brown bears).

In many tiger skulls, the rostrum widens towards the canines. Both skulls featuring in the photograph below are atypical in that they lack a widening rostrum. The occiput of the skull right is narrow and compressed along the outer edge. This is often seen in Java tiger skulls, but the occiput in Java tiger skulls often is a bit longer. Sagittal crest in both skulls well developed, meaning both skulls belonged ot old animals.     

 

*This image is copyright of its original author

   
E - Skull of a young adult male Java tiger for comparison

Watch the shape of the occiput:     
 

*This image is copyright of its original author

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