Fauna
The Hammerhead Titanothere
This massive, grazing creature travels in small herds or packs. It is moderately social, but also extremely territorial and hierarchical. Constant threat displays, both visible and audible, are a large part of the titanothere's day. When angered (which happens easily and often), a titanothere will lower its head and charge at the perceived threat. The sheer momentum and ferocity of this display is usually enough to send any Pandoran creature running for cover.
Titanotheres also possess a series of brightly-colored skin flaps with rigid, chitinous backings that can be raised when confronted by an adversary. Both the hammerhead structure and the colored skin fan are also used to attract and compete for a mate.
The Mountain Banshee
Bonding with a banshee is a dangerous and required rite of passage for all would-be Na'vi warriors. Like the direhorse, a Na'vi can connect to a banshee through a neural interface that allows animal and rider to move with apparent effortlessness through the skies. Unlike the direhorse, however, the banshee will only bond with one Na'vi in its lifetime.
The mountain banshee rookery is high in the Hallelujah Mountains. The largest rookery, which features the biggest specimens (and therefore the best to tame for riding), is in grottoes and outcrops on a sheer cliff face of Mons Veritatis, one of the largest of the floating mountains. It is here that the Na'vi come to select (and be selected by) a banshee for domestication. The bonded mountain banshees nest in the highest branches of Hometree, where they can be close at hand for their Na'vi rider.
The Direhorse
Direhorses are nectarivores, vaguely horse-like in appearance, with very long necks and small heads. They are roughly the size of an elephant. They are native creatures of Pandora.
When wild, the animals move together in a loose herd through the forests, feeding on tree bark and shrubs. Herds numbering in the dozens have been spotted from aircraft, but evidence (including scatological and plant impact) suggests that herds of more than one hundred animals are not uncommon.
Direhorses can be tamed to aid their riders in the hunt and in battle. To bond with (or, in human terms, to "break") a direhorse, a Na'vi must mount the animal and connect their neural queue to one of the animal's antennae (or neural whips). Once queue and antenna touch, the feathery tendrils automatically intertwine as if possessed of free will. Although the exact motivating force remains unknown, it is believed that the antennae may secrete a pheromone that evokes the unique intertwining.
Flora
Helicoradium spirale
The helicoradian is a type of “sensitive zooplantae” that responds to touch by coiling up so that the single large leaf is no longer exposed to any herbivores that would eat it. Because it grows in clusters, the touch response, or thigmonasty, by one helicoradian often triggers the same response in others growing nearby so that the entire population recoils, one plant after another. This retraction is both defensive and an effective feeding mechanism to trap insects and small animals.
Cat Ear
The cat ear is a woody stem zooplantae, covered with modified leaves resembling cat ears. These are collected by the Na'vi as musical instruments due to the sound produced when wind moves across the leaves of the plant, and as children's playthings.
This species is both musical and beautiful with characteristics of both plants and animals. Cup-shaped leaves, which resemble cat ears, grow all over the stems of the plant. Inside the base of each cat ear, a small flower forms, which, when emerging, resembles small whiskers. The music is produced by wind passing over the leaves of the planimal, and is varied by the size of the specific planimal.The cat ear's music may resemble a small symphony when in a collective group. Besides the ability to produce music, this planimal has the uncanny ability to turn in the direction of movement and track it. This 'tracking' can become disconcerting to humans who feel as if they are being watched as the planimal turns in response to their presence.