The banth is a ten-legged Barsoomian "lion." Of course, the banth is not a true lion, or member of the feline family. They naturally prey upon the thoat, but any animal or being is a potential meal for the giant banth. Banths have protruding green eyes, hairless bodies, and stiff-bristling manes. They are sleek in the manner of earthly felines. Their long jaws house a double row of hooked teeth, like the smaller calot, suggesting a common ancestry somewhere in the dim Barsoomian past. Obviously, it is a separate (non-feline) family of mammalian carnivores unique to Barsoom. All life-forms on the planet apparently began with ten legs; those with less evidently dispensed with those limbs during the long course of Barsoomian evolution. It may, in fact be mere comi coincidence that Earth's vertebrate life forms sport four limbs. Other six or more legged plans may exist throughout the universe.

Thoats are eight-legged Barsoomian "horses." Again, they are not true equines, or related to anything else on earth. They are often vicious and foul-tempered, but the sentient Martian races can train them as steeds, and use them in gladiatorial jousting. Their powerful legs sport great padded toes, the hoof never having evolved upon Mars.

The monstrous white apes of Barsoom are an anomaly. They have the multiple limbs as the majority of other life forms indicating a common ancestry with all other life on the planet; however unlike the thoat, banth, and others, they apparently share the same family as the true primates of earth. John Carter even describes the face of the white ape as being strikingly similar to the African gorilla. 

So...why are primates represented both on Earth and on Mars? It seems very unlikely that identical families should evolve -- but apparently, it happened. The copper-skinned humans of Mars are also primates, and though they lack an extra set of limbs, they share the same basic reproductive system with other Barsoomian life forms. The primate family it seems, is found throughout the ERB universe on trillions of worlds. 

Tarzan was able to communicate with the first white ape he stumbled upon being attacked by a swarm of ulsios (in the comic) Tarzan/John Carter: Warlords of Mars: "I speak the language of all mangani!" Mangani must be a universal tongue among Burroughs' primates, even on distant worlds. White apes roam in bands throughout Barsoom, but especially are encountered among the ruins of abandoned cities.

They perhaps are an example of a protist (kingdom of life forms that exhibit both plant and animal characteristics) that has developed into a large multi-cellular species. They sport a crop of angleworm-like tendrils for "hair," a single, whitish eye that takes up their entire "face," a single nostril-like orifice for breathing, arm-like appendages which terminate in mouthlike orifices (through which the creatures graze), and massive, powerful tail. Their entire bodies are a weird, ghoulish blue color. Though they are "normal" four-limbed creatures, the plant-men have undoubtedly evolved along as separate trajectory than the other of Barsoomian species.

The calot is something of an equivalent of a Martian canine, as the banth has evolved parallel with the great cats. Calots chase down their prey on ten powerful stout legs, and latch onto it with their multiple rows of hooked teeth. Calots are often trained by the red and green Martians and are fiercely loyal, bonding with their owners after the same manner as earthly canines. The most famous calot is Woola, who remained loyal to Carter after saving him from a Martian ape.

The apt is a monstrous, white-furred denizen of polar Mars. It sports six limbs, four o which carry it over the glaciers, the other two it can grasp prey with. Its head is described as something like the earthly hippopotamus (although the Whelan illustration above depicts it as a bit more rhinocerine), with mighty fanged jaws. Two horns of bone depend on either side of the great lower jaw. Its huge, insectasoid eyes encompass the majority of the apt's face. Each eye is composed of thousands of ocelli, all of which it can open or close independently and at will.

The orluk is another arctic monster, described as "a great elephantine beast of prey." it has yellow and black striped pelt. It conjures up the image of a giant, furred, multi-legged carnivorous mammoth striped in gold and black. I could find no image (so far), but in the Thomas Yeates illustration above, some men appear to be clothed in orluk hides.

The sith is monstrous wasp-like insect-creature common to the Forest of Kabool, the size of a hereford bull. It has thrumming wings and a deadly tail-stinger. The huge compound eyes are its one vulnerability. In the Thomas Yeates illustration above, Woola attacks this weakness, driving his rows of fangs deep into the eye. The insect in the Whelan painting may, in fact, be a related species native to the Tantolian marshes.

A giant, "prehistoric" Martian bird with a 40-ft wingspread. They are used as beasts of burden in the country surrounding the Tantolian Marshes. A relic from Barsoom's primeval past, the malagor combines features both avian and reptilian, much like the dinosaur ancestors of birds on earth.

The ulsio is a repulsive scavenger found underneath barsoomian cities, rather like a large, multi-legged rodent. The term "ulsio" is not one of endearment.

The zitidars are gigantic draft animals used by the red and green races of Barsoom. They are proboscidian in form, resembling a Terran elephant or mastodon, though unrelated.

Other animals have been added to the Barsoomian fauna in comics and pastiches, most notably in the DC comics Tarzan family series. There was a one-shot story called "Amazon of Barsoom," which told the story of Martian princess. A predatory lizard-beast is pillaging the eggs when the princess hatches. Before she is eaten herself she slays the creature with his own sword. The "cannibal lizard" seems more than a mere beast however, as he wears both a tunic and a sword with scabbard! Later the Amazon of the title saves her Jeddak father from the "demon apes of the misty caves." She slaughters the red-furred simians en masse, proving herself as worthy to her father as any son would have been. Now about those apes -- now we have TWO primate species (other than the red, yellow, black-skinned humans) native to Mars!

Another, separate, storyline involves a series of "lost journals" or John Carter. They are discovered in a trunk by a member of the aquatic Myopsian race (which are, in fact, native to Amtor (Venus), NOT Barsoom!

The first journal sees John Carter rescuing a beautiful princess who is trapped within a giant green gemstone. While searching for an implement to cut the crystal, he encounters a multi-legged styracosaurus-like beast that is unnamed in any of the canonical tales. The beast charges the gemstone, shattering it and freeing the princess. Carter then slays the beast with his sword. Later, the two are menaced by "the scavengers of Barsoom," flying reptiles which resemble three-headed pteranodons!

The "Amazon" story also shows flying reptiles which it refers to as "sky-kites."