big cats

Big cat distinguishes the large wild cats from much smaller species. One definition of big cat includes only the four species of cat in the genus Panthera: the lion, tiger, leopard, and jaguar. Members of this genus are the only cats able to roar, and this is sometimes considered a distinguishing characteristic of big cats. A more expansive definition also includes the cheetah, snow leopard, clouded leopard, and cougar. The roaring cats may also be distinguished from the other big cats by referring to them as "great cats". Another distinction is the offspring of the great cats are called cubs while the offspring of the lesser big cats are referred to as kittens.
Three of the four largest cats are members of the genus Panthera; the cougar is the fourth largest cat, exceeding the leopard in size.
Despite enormous differences in size, the various species of cat are amazingly similar in both structure and behavior. All cats are carnivores and efficient predators. Their range includes the Americas, Africa, Asia, and Europe; Australia and Antarctica have no indigenous species of cats.
The ability to roar comes from an elongated and specially adapted larynx and hyoid apparatus. When air passes through the larynx on the way to the lungs, the cartilage walls of the larynx vibrate, producing sound. The lion's larynx is longest, giving it the most robust roar. Though jaguars are considered great cats, they are not often known to roar and have a less developed larynx. The snow leopard is also said to have a larynx nearly adapted for roaring, but it is far less developed than the jaguar. Cats that cannot roar have vocal chords more suited for purring, while roaring cats cannot purr.
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Species
Big cats
Family Felidae
Genus Panthera (roaring or great cats)
－　Tiger, Panthera tigris (Asia)
－　Lion, Panthera leo (Africa, Gir Forest in India; extinct in former range of in southeast Europe and the Middle East)
－　Jaguar, Panthera onca (the Americas; from Mexico to northern Argentina)
－　Leopard, Panthera pardus (Asia and Africa)
Genus Acionynx
－　Cheetah, Acinonyx jubatus (Africa and Iran)
Genus Puma
－　Cougar, Puma concolor (North and South America)
Genus Uncia
－　Snow Leopard, Uncia uncia (mountains of central and south Asia)
Genus Neofelis
－　Clouded Leopard, Neofelis nebulosa (southeast and south Asia)
－　Bornean Clouded Leopard, Neofelis diardi (Borneo and Sumatra)
I hope this can help with your understanding. =)