The jaguar (Panthera onca) is a New World mammal of the Felidae family and one of four "big cats" in the Panthera genus, along with the tiger, the lion and the leopard of the Old World. The jaguar is the third-largest feline after the tiger and the lion, and on average the largest and most powerful feline in the Western Hemisphere. The jaguar's present range extends from Mexico (with occasional sightings in the southwestern United States) across much of Central America and south to Paraguay and northern Argentina.
The jaguar, Panthera onca, is the only New World member of the Panthera genus. DNA evidence shows that the lion, the tiger, the leopard, the jaguar, the snow leopard and the clouded leopard share a common ancestor and that this group is between six and ten million years old; the fossil record points to the emergence of Panthera just two to 3.8 million years ago. The jaguar closely resembles the leopard, but is sturdier and heavier, and the two animals can be distinguished by their rosettes: the rosettes on a jaguar's coat are larger, fewer in number, usually darker, and have thicker lines and small spots in the middle that the leopard lacks. Jaguars also have rounder heads and shorter, stockier limbs compared to leopards.