ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)

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The difference between lion and tiger skulls

These are some of my opinions from my communication with Peter, and I am sharing them here for everyone to discuss

There are some obvious differences between the skulls of tigers and lions, with major differences in Skull shape (tiger skull has a shorter and rounder face, lion skull has a longer and flatter face), nasal, ventricular margin of the mandibles, and Cranial volume,so on.

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In addition, there is a slight difference in the carnassial structure between lions and tigers, but this is not the main difference.

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These differences are obviously caused by multiple factors, but from my knowledge, I'm afraid I can only explain them in terms of biological evolution and skull morphology adapting to the environment

(1) Biological evolution

According to modern molecular biology research, the separation time between Neofelis and Panthera genera is approximately in the last period of the Miocene Li et al. (2016).

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In recent years, the fossil information related to the earliest members of the Panthera genus has been constantly revised, but it can be confirmed that the separation time in molecular biology is currently over million years earlier than the fossils of the earliest known members of the Panthera genus. Therefore, it is unknown when, how, and in what way the members of the Panthera genus in the Asian branch (Evolved into the later tigers and snow leopards) and the Panthera genus in the African branch (Evolved into the later jaguars, leopards, lions) were distinguished during this period.

The fossils of one of the earliest members of the Panthera genus(Panthera principialis), as well as the earliest fossils that can be defined as lions(Olduvai upper Bed II), may not provide us with good information to answer why the skulls of lions and tigers have such significant differences.

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So we can turn the question to why tigers have these different skull features from lions?

The fossil history of tigers is relative long. If the ancestral species Panthera palaeosinensis is included, the fossil history of tigers can exceed 2 million years, and the earliest tiger fossil can be traced back to 1.3 million years ago (a P4, similar in shape and size to modern male tigers, in Gongwangling, Lantian, Shaanxi Province).

Fortunately, the ancestor species of tigers, Panthera palaeosinensis, has preserved many relatively complete skulls, which can answer our question about the characteristics of tiger skulls.

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Ji H. mazák once proposed another species, Panthera zdanskyi, which is more likely to be the ancestor of tigers. However, his research only compared the holotype specimens of Panthera palaeosinensis and Panthera zdanskyi, and their differences may be due to age and gender. As more related fossil materials are studied, other paleontologists in China believe that they are actually the same, both Panthera palaeosinensis

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On multiple skull specimens of Panthera palaeosinensis, we can find skull features (Skull shape, nasal, ventricular margin of the mandibles, and cranial volume) that distinguish tigers from lions. Among them, the cranial volume is very significant. The holotype specimen of Panthera palaeosinensis is estimated to have a cranial volume of approximately 200-220 cubic centimeter based on Hemmer's morphology, which is larger than that of jaguars and comparable to modern African female lions and Asian lions. However, it should be noted that its maximum skull length is only 240mm, and its relative cranial volume is already comparable to that of modern continental tigers.

Therefore, we can say that as early as the earliest primitive species, some characteristics of tigers already existed

(2) morphology adapting to the environment

Here, I would like to give examples of snow leopards and jaguars. From the results of molecular biology research, they were almost simultaneously isolated from various branches of the Panthera genus (the latest Pliocene, about 2.7 million years ago).

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Their skull and tooth morphology are significantly different from other members of the Panthera genus, especially snow leopards.

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However, based on fossil evidence, their morphological features evolved in a very short period of time, and early fossil species of snow leopards and jaguars did not have very unique morphological features.

In the Panthera gombaszogensis jinpuensis of the Middle Pleistocene, the thick and robust premolars of the Jaguar appeared noticeably, and the true morphology of the Jaguar may not have officially appeared until the Late Pleistocene.

In a recent study on the fossil history of snow leopards(see <In a recent study on the fossil history of snow leopards, they newly described the Late Pleistocene snow leopard fossil species P u. lusitana ， This late Pleistocene snow leopard only showed obvious skull morphology adapted to the plateau> ), they newly described the Late Pleistocene snow leopard fossil species P.u. lusitana,This late Pleistocene snow leopard only showed obvious skull morphology adapted to the plateau.

From the above two examples, we can see that the environment can cause significant morphological evolution in Panthera species in a very short period of time.

Although tigers have a fossil history of millions of years, their distribution range has always been stable within Asia, or in other words, very stable habitats in southern Asia. The earliest tiger fossils were found in China and Java. Even after the end of the Pleistocene, tigers still thrived in Java and China, although unfortunately, the Javan tiger is now extinct. 

Although there have been changes in the animal populations, climate, and environment of China and Java over a long period of time, and tigers have indeed undergone changes in size and morphology, these effects are clearly not as significant as the extreme environment of the plateau and the different prey types in South America on snow leopards and jaguar

So my final conclusion is that many of the characteristics of tigers themselves are inherited from ancestral species, which have been different from lions for millions of years. And tigers have a relatively stable habitat area, which allows them to avoid making significant morphological adaptations to extreme environments like snow leopards do Reply