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Skulls, Skeletons, Canines & Claws
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- The old world big cats have straighter canine teeth, while the new world big cats have the greater curvature.
- Panthera atrox seemed to have been convergently evolved toward Jaguar since they both used to adapt in the similar living environment. - The leopard canine and lion canine seem to be proportionally very similar, the shape and curvature are also similar. - The Cave lion canine is very close to the African lion canine, except it is proportionally more robust, albeit not much longer in length. - Compared to the lion canine and tiger canine, the lion canine is more banana-like where the middle part is the broadest, while the tiger canine seems to be more refined in proportion. Please feel free to share your own knowledge here. 
1 - OLD WORLD BIG CATS
a - Zoologischer Garten Berlin The upper skull of a distant ancestor of modern big cats exhibited in the Zoologischer Garten in Berlin. This cat had extremely long and wide upper canines, but they were not thick and prone to breakage. The skull is shorter and narrower than that of a modern adult male lion or tiger:  *This image is copyright of its original author b - Panthera zdansky This Pleistocene tiger, one of the (quite distant) ancestors of modern tigers, already had shorter, but thicker (and conical) upper canines. The skull is short and not as wide as that of a modern big cat:  *This image is copyright of its original author c - China (private collection?) The skull of this big cat was found in China. It could have belonged to a Late Pleistocene or early Holocene tiger, when large herbivores were everywhere and humans avoided big cats for good reasons. The skull is elevated at the orbits, wide and very robust. The upper canines are extremely robust. An upgraded zdansky, one could say. The photograph was first posted by Grizzly:  *This image is copyright of its original author 2 - MODERN BIG CATS a - Panthera leo This skull, one of the largest I measured, belonged to a wild male lion. It had the longest upper canines I saw (66,00 mm.). They appear to be shortish, but that partly is a result of the length of the upper skull (384,60 mm.). The skull was elevated at the orbit, moderately wide and muscular. Notice the extended maxillary bone (snout). Also notice the position of the upper canines and the angle:  *This image is copyright of its original author b - Panthera tigris altaica This is the skull of a poached wild male Amur tiger. Skulls of wild male Amur tigers, for greatest total length (a trifle shorter) and zygomatic width (a tad wider), compare to those of wild male lions. Most wild male lions have a longer snout and a flatter profile (upper skull). The upper canines of Amur tigers are unsurpassed for length and width at the insertion of the upper jaw. Notice the angle is different as well:  *This image is copyright of its original author This is the skull of a captive adult male Amur tiger:  *This image is copyright of its original author c - Panthera tigris tigris (the Indian or Bengal tiger) This is the skull of a large wild male Nepal tiger (the Sauraha tiger). When darted, he entered a pool and accidentally drowned. Compare the skull to the one of the wild male Amur tiger poached (see above). Although they are shorter, nearly all skulls of Indian tigers I measured were heavier than those of Amur tigers (nearly all of them captive animals). The reason is not size, but bone density. Same in wild animals in that wild Amurs are a bit longer, but not as heavy:  *This image is copyright of its original author d - Panthera tigris sondaica (the Javan tiger) This skull is in the Wiesbaden Museum and belonged to an adult wild male Java tiger. Although undamaged, the skull was acquired before 1836 (...) in Java. Java skulls usually are vaulted (profile), whereas the mandibula often is concave. Although short compared to Indian tigers, the skulls are anything but feeble. Notice the short and low sagittal crest. This is a result of skull size (greatest total length). Uppercaninewise, Javan tigers often exceed those of wild male lions. Of all skulls I saw, I like those of Javan tigers best:  *This image is copyright of its original author
It is quite odd that the Amur tiger got the heaviest canine teeth, but the skull is overall lightly built.
Maybe it has put more weight on its muzzle part? (07-30-2015, 11:45 PM)'GrizzlyClaws' Wrote: It is quite odd that the Amur tiger got the heaviest canine teeth, but the skull is overall lightly built. Skulls of captive male Indian tigers, although shorter than those of captive male Amur tigers, often are heavier. If not, they are heavier for their size. Sample size no doubt had an effect, but I thought I saw a pattern. I don't know if captive Amurs have heavier canines. They are generally not as curved, longer and thicker at the insertion. Compared to the size of the total skull, they often seem (and are) very large. Skulls of Indian tigers are more robust, especially in the central area. The only explanation I have is density. A bit odd, as captive Amur tigers, and males in particular, are larger, taller and heavier than all other captive big cats (averages). Amur tiger skulls, more than those of all other big cats, are about the canines. They often appear to be big gun platforms, just like in the old battle cruisers (not the heavier battle ships). They remind me of the 'Hood'. The reason could be no heavy prey animals and long struggles. Density most probably is related to prolonged struggles with powerful animals. I know Amur tigers engage wild boars and bears of similar weight, but these fights seem to be about agility, movement and the ability to deliver a lethal strike or bite. Compare this to male tiger 'Raja', who restrained and throttled a gaur on his own. It took him a few minutes only, but the force he had to overcome had to be immense. I repeat I didn't see skulls of wild Amur tigers. They could be different. The ones I saw from a distance, however, didn't seem very different from the skulls of the captive Amur tigers I measured: long, not too wide and very long upper canines. They do seem to differ from Indian tiger skulls in that the maxillary bone, like in many lions, is a bit longer, more elevated and straighter. It seems to be strenghtened, but the extra strength, in my opinion, is a result of the extra long upper canines foremost. Wild Amur tigers seem to be a bit longer and taller than wild Indian tigers, but most are not as heavy. The extra length could be an adaption to the local conditions (deep snow, hills and long walks), but they seem more athletic than Indian tigers. In a fight with a dangerous opponent of similar weight, like a wild boar or a bear, both very compact and robust, this could be an advantage. Amur tigers, as far as I know, seldom succumb in a fight. There are, on the other hand, plenty of stories about Indian tigers struggling with large wild boars. Nepal and Terai tigers seem to compare to Amur tigers in that they are long, but they seem less compact than many tigers in central India. Even if they are heavier in absolutes, they seem to carry relatively less weight. The weight is concentrated in the parts that matter, whereas central Indian tigers often seem to be more massive overall. This was what the old hunters also stated: longer and larger in Bengal, but not as robust as those in central and south India. They could have been right. Captive Amurs, in contrast to captive Indian tigers, often are heavier than their wild relatives. We think captive Amurs get to their potential, but one could also say they are not as fit and combattive as their wild counterparts. Remember a heavy tiger will tire quickly in deep snow or hills and my guess is extra weight wouldn't help you in a fight with a wild boar or bear. When the opponent is strong, compact and robust, it is about something else. You need speed, athletic ability and strong fore-arms to position your opponent where you want him and you need to be able to administer severe damage fast. And that's what we see in wild Amur tigers. Fitness and the ability to move quickly are important when you are vulnarable. One trush is enough for a wild boar and bears also are able to eliminate a tiger quickly. Maybe a fight is a contest in strength, but my guess is it isn't. For robustness and the ability to take damage, a cat will never compare to a bear or boar, even if both are similar in weight. His best chance is in the ability to outmanouver his opponent and connect first. At his conditions. If he's able to do that, chances are he will be able to use his advantage, his teeth, first. And in the correct way. I saw fights between captive tigers more than once. Sumatrans are lightning fast, avoid strength contests and strike. Ten strikes is out. The fights are way more serious than in other subspecies or lions, because they do less damage when they strike. Amur tigers seldom fight. When they do, they rely on their size and power. When there is a fight, however, they are way more athletic than you expect. Amur tigers are masters in moving. In the fights I saw, they reminded me of very able boxers. They're heavyweights able to knock their opponent out. One blow or one bite will do it and they know. Indian tigers, as we saw in South Africa and India, don't do athletics and tactics. When they fight, they quickly connect, fasten their teeth and hold on. When lucky, they crush the windpipe or skull of their opponent. When not, they try again. Until one has had enough. In order to fight in that way, you need very strong neck muscles. And a very strong skull.
The jaguars are overall more prone to bite the skull of their preys.
Do you think the greater curvature of their canine teeth was designed to withstand from more impact of the skull biting? The American lions were also convergently evolved with this kind of canine teeth when they shared the similar living environment with the jaguars. 
@peter absolutely amazing post about the differences between the subespecies regarding behaviours and fighting. I really liked what you say about Amur tigers. They don't brag about it, but they know they're the boss and they know how to prove it. When the lion activity(this ones do like to brag about themselves [img]images/smilies/cool.gif[/img]) calms down a bit, I will try to catch up with the tigers, because it's simply amazing and there is so much info that I literally don't have enough time to read it all. Sorry for spoiling the thread, but I had to say it.
GRIZZLY
Your last two questions (one in this thread and one in the extinction thread) take some time to answer. Time I need to go over all the photographs I have and time I now want to invest in something else (the difference between tigers in northern China, Manchuria and Russia). Hope you understand. The jaguar skulls I saw, although often shorter than those of tigers and lions, were real big cat skulls. Even at 9-10 inches in greatest total length, female skulls were more robust than male leopard skulls of similar length. In length, there's overlap between both species, but not in robustness. Only very large male leopard skulls compare to a degree at times. Jaguar canines are not longer, thicker or more curved than those of other big cats. My guess is they learned a skull bite is the best way to overcome resistance. One reason they developed in this direction could have been the average size of most wild prey animals they hunt. But maybe jaguars use skull bites because they are aware of their power. I know captive jaguars are astute animals who don't fear their larger relatives. In confidence, they don't lack and they also like a good brawl. Not quite decided on that one. Jaguars could be big cats who lost size over the years. Must have been a recent development, as they kept their robustness (for no apparent reason). One indication is they know how to deal with large animals, but they struggle with agile and aggressive medium-sized animals like peccari's. Leopards, on the other hand, appear to be medium-sized cats who, in some regions, developed in the direction of big cats. In bone robustness, however, they definitely lack compared to jaguars. Even when they reach 200 pounds, and there's no doubt males in some regions do at times, they usually are not big-framed, but long and muscular. In this respect, they compare to tigers in a degree (skeletons of tigers are very similar to those of lions, but live animals often are a bit longer as a result of the muscular development of the limbs). Lions are social animals who often hunt large prey animals in groups. Individuals don't need to kill quickly, that is. They need the tools to contact, catch, hold on and restrain the animal. This way of hunting usually takes more time, meaning they need to have the frame (and the skull) to withstand immense pressure. Wild lions, although a bit smaller than their captive relatives and a bit shorter than most tigers, very often are compact and muscular animals, not in the limbs, but in the chest, neck and upper part of the torso. A bit like power lifters, I'd say. The long maxillary bone could have been a result of the need to strengthen the facial part of the skull. The reason is the canines are not used to kill directly, but to grab, hold on and restrain. The pressure exercised by struggling large prey animals resulted in an adaption in that the maxillary bone is a bit longer and, near the os frontalis (the bone on top of the skull), wider and a bit thicker than in tiger skulls of similar length. In most skulls, you can see it at a glance. The maxillary bone usually narrows towards the rostrum, because the canines are not as developed as other parts of the face. Upper canines of wild lions, compared to those of tigers, usually are shorter and a bit more curved near the insertion in the jaw. They compare to strong hooks, but there is a lot of individual variation. Tiger skulls of similar length usually as not as wide and robust in the centre, because they don't use the skull to lock on, hold and restrain, but to kill fast. Tiger skulls are platforms for the long canines. The upper canines often are straighter, longer and as strong or stronger as in lions, because they are used to kill large animals without help of others. For this reason, the upper skull is shorter, more vaulted, (relatively) wider and, near the rostrum, somewhat strengthened. Tiger skulls are jaw skulls, whereas lion skulls are face skulls. The difference in the sagittal crest is limited, because both need a solid anchor for the jaw and neck muscles. Lion crests could be a trifle higher, whereas tiger crests seem a bit wider, but that could be an impression only (I never measure the height and width of the sagittal crest). All in all, I'd say that the relatively large skull of lions (and males in particular) could be a result of a mix between hunting (resulting in a strengthened and extended maxillary bone) and, in particular, sexuality (the need to display age, status and health in a pride). In the more solitary tiger, it is mainly about function (hunting). Hunting animals don't need extra-large skulls and frames, because of the need to limit the total weight. The reason is you need to get to your prey first. When you have contact, you need the ability to topple the animal and quickly kill it in order to prevent damage and loss of energy. Terrestrial hunting specialists (cats), for this reason, tend to have long bodies and relatively small skulls. In most cases, the skulls are big guns platforms. Lions are a bit different in this respect and the main reason, especially in males, could be pride life. Jaguars, for relative bulk and proportions, compare to lions and tigers, but the reasons mentioned above do not seem to hold for them. There could be many reasons for their relative bulk, but my guess, as said before, is they are adapting downward. A medium-sized cat below 200 pounds is more than good enough to make a decent living in South America. They haven't quite finished, as some males easily exceed 300, but that occurs in regions with opportunities mostly. In leopards, it could be the other way round. The reason for adaption in jaguars could be lack of large prey animals, whereas room for improvement (for lack of the their larger relatives) could be the trigger to move upwards in leopards. When tigers had been exterminated in Sariska, leopards quit hunting at night and dragging kills into trees. They also started killing competitors (hyena's and smaller predators) more often to underline the new order. When a Ranthambore tigress and a young male tiger from the same reserve were transferred to Sariska, leopards were a bit slow to get the message. One of the females, treed by the tigress, was found dead and eaten next morning. Here's a large male jaguar:  *This image is copyright of its original author I assume it is clear that the remarks about jaguars (and the other big cats) in this post are based on a bit of experience with skulls and captive animals and, in particular, on a lot of ideas. I could be very wrong, that is. Interested in the opinions of others.
Nice, so you are now studying the regional variation of the Amur tiger, and what have you found so far?
I assume the diversification of the Amur tiger is just as much as that of the Bengal tiger, right?
The leopard canines resemble the mini lion canines, and they are also proportionally thinner than the canines of the lion and tiger.
The jaguar canines, on the other hand, are similar in length, but they are proportionally more robust. lion canines  *This image is copyright of its original author leopard canines  *This image is copyright of its original author  *This image is copyright of its original author jaguar canines  *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 old tiger and leopard remains in China, and I guess that the South China tiger also has the squared mandible. @tigerluver
Some remains could be subfossil. Check the robustness of the old school big cats. @peter  *This image is copyright of its original author
Wow, the jag canines certainly appear to be extremely robust and reinforced in the "rout" section. Or above the gum line, i guess you would call it.
Check the old tiger canines above, the leopard canine looks extremely gracile in comparison.
Your skull picture collection is awesome, @GrizzyClaws.
The mandible's symphysis looks pretty much the same as the fossil one. Maybe we could look at the current tiger phylogeny publications and insert the fossil species based on the skull characteristics.
Those old school tigers are super massive, since no modern big cats can dwarf the leopard like these.
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