Lion

The American lion is one of the largest types of cat ever to have existed, slightly larger than the Early Middle Pleistocene primitive cave lion,  and about 25% larger than the modern African lion.  It originated in North America  and the head-body length of the American lion is estimated to have been 1.6–2.5 m (5 ft 3 in–8 ft 2 in) and it would have stood 1.2 metres (4 ft) at the shoulder. Thus it was smaller than its contemporary competitor for prey, the giant short-faced bear, which was the largest carnivoran of North America at the time.  Sorkin (2008) estimated the American lion to weigh roughly 420 kilograms (930 lb) but a more recent study showed an average weight for males of 256 kg (560 lb) and 351 kg (770 lb) for the largest specimen analyzed.  Approximately one hundred specimens of American lions have been recovered from the La Brea Tar Pits, so their body structure is well known. The features and teeth of the extinct American lion strongly resemble modern lions, but they were considerably larger. The American lion is believed to be the largest subspecies of lion.

DNA sequence data from remains of the American lion from Wyoming and Alberta show that it is a sister lineage to the cave lion, and likely arose when an early cave lion population became isolated south of the North American continental ice sheet. The most recent common ancestor of the two populations apparently lived about 340,000 (194,000–489,000) years ago. The most recent common ancestor of the atrox lineage is estimated to have lived about 200,000 (118,000–246,000) years ago.

The earliest lions known in the Americas south of Alaska are from the Sangamonian Stage (the last interglacial).  In North America, it has been found in more locations in the west than in the east; and as far south as Chiapas, Mexico. It was generally not present in the same areas as the jaguar, as the latter favored forests, while American lions preferred open habitats. Like many other large mammals, it went extinct at the end of the Pleistocene. The most recent fossil, from Edmonton, dates to 11,355 ± 55 years ago.  By then, the American lion was one of the abundant Pleistocene megafauna, a wide variety of very large mammals that lived during the Pleistocene. The most abundant remains have come from the La Brea Tar Pits.

In some areas of its range, the American lion lived under cold climatic conditions. They probably used caves or fissures for shelter from the cold weather.  They may have lined their dens with grass or leaves, as the Siberian tiger does, another great cat that currently lives in the north.

There are fewer American lions in the La Brea tar pits than other predators such as saber-toothed cats (Smilodon fatalis) or dire wolves (Canis dirus), which suggests they may have been smart enough to avoid the hazard.  American lions likely preyed on deer, North American horses (now extinct), North American camels, North American tapirs, American bison, mammoths, and other large, herbivorous animals.  This species disappeared about the same time as other megafaunal species during the Quaternary extinction event, which wiped out many of the species that the American lion would have preyed on. Lion bones have been found in the trash heaps of Paleolithic American Indians, suggesting human predation may have contributed to its extinction.

A replica of the jaw of the first specimen of American lion discovered can be seen in the hand of a statue of paleontologist Joseph Leidy, which is currently standing outside the Academy of Natural Sciences in Philadelphia.