Determining the phylogeny of Panthera palaeosinensis.

The feline subfamily Pantherinae is comprised of the so-called "big cats" and includes the four extant species of the Panthera genus (tigers, lions, jaguars, and leopards), which are set apart by their unique ability to roar, and also the two species of clouded leopards and the snow leopard. There is some debate as to whether or not snow leopards should belong in Panthera, but that is neither here nor there.

Artist's reconstruction of P. palaeosinensis.

One of the oldest known species of Pantherinae from the fossil record is Panthera palaeosinensis from Plio-Pleistocene China. It has been primarily assumed to be an ancestor of tigers, but others have suggested that it may be the ancestor to leopards, or possibly two or more lineages in Panthera. These estimates are primarily based on the fact that the size of the only known intact skull is somewhere between the size of a large leopard or a tiger, but skull size alone isn't enough to determine phylogenetic relationships. Genetic and life history factors can contribute to the growth of an animal, and many ecological factors can affect skull size, meaning that taxonomists need to look at specific morphologies as well as size when determining phylogeny.

A cast of P. palaeosinensis. Source.

It is with this in mind that Mazák set out to determine P. palaeosinensis's affinity by comparing a cast of the holotype skull to over 600 skulls of extant and extinct Pantherinae specimens. He found that when shape was considered in the absence of size considerations, P. palaeosinensis is closer to lions and leopards rather than tigers. His methods were somewhat validated by the fact that three distinct clusters emerged: clouded leopards, snow leopards, and all of Panthera, which is in agreement with classical descriptions of the clade.

P. palaeosinensis comfortably nestled between lions and leopards.

These results suggest that P. palaeosinensis is most likely the ancestor of at least two extant lineages of Panthera and not a primitive tiger as previously believed. It is also possible that P. palaeosinensis is basal to the entire genus. This has implications for current theories as to the evolution and radiation of the Pantherinae. The current theory based on molecular phylogenies is that Pantherinae radiated out of Asia over 5 million years ago, however the oldest fossil specimens are found in Africa from about 3 million years ago. The morphologies of P. palaeosinensis appear to be more primitive than those of the African fossils, which lends further evidence towards the Asian origin hypothesis for Panthera.

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MAZÁK, J. (2010). What is Panthera palaeosinensis?
Mammal Review, 40 (1), 90-102 DOI: 10.1111/j.1365-2907.2009.00151.x