Panthera youngi is known from Choukoutien, northeastern China and Japan, and lived about 350,000 years ago in the Pleistocene epoch, Harington, 1969 suggested that the American lion, the Eurasian cave lion and the large Chinese "Panthera youngi" are conspecific, The American lion ("Panthera leo atrox" or "P. atrox" ) – also known as the North American lion, Naegele’s giant jaguar or American cave lion – is an extinct lion of the family Felidae, endemic to which location during the Pleistocene epoch?
American lion The American lion ("Panthera leo atrox" or "P. atrox" ) – also known as the North American lion, Naegele’s giant jaguar or American cave lion – is an extinct lion of the family Felidae, endemic to North America during the Pleistocene epoch (340,000 to 11,000 years ago), existing for about 0.33 million years. It has been shown by genetic analysis to be a sister lineage to the Eurasian cave lion ("Panthera leo spelaea" or "P. spelaea"). It was part of the abundant Pleistocene megafauna, a wide variety of very large mammals that lived at the time. The most abundant remains have come from the La Brea Tar Pits.
Panthera hybrid It is known that four of the five species of the "Panthera" genus, the exception being the snow leopard, "P. uncia", can hybridize with each other to produce numerous hybrids. Most hybrids would not survive in the wild due to the males being infertile, but a few (such as the Leopon) are fertile and have a chance of survival in the wild. However, recent mitochondrial genome research by Texas A&M University geneticist William Murphy et al. reveals that wild hybrids did also occur in ancient times. In snow leopards and lions, the mitochondrial genomes of both species was more similar to each other than to other Panthera species, indicating that at some point in their history, the female progeny of the male ancestors of modern snow leopards and female ancestors of modern lions interbred with male ancestors of modern snow leopards.