The Fast Biter leader is a Velociraptor and is the true main antagonist in the third film The Land Before Time III: The Time of the Great Giving. Its gender is unknown, making it unknown as to whether it is male or female.
The relationship between it's pack members is uncertain, but from how it appears front and center it is implied that it is the leader.
The Fast Biter and it's pack first appeared when they approached Littlefoot and the leaf-eaters near the tar-pits. Whether if it was thirsty or hungry is unknown. At first it spotted the leaf-eaters with Mutt pointing at it on it's arrival, it soon roared at them from down below with the rest of pack closing in. It leaps down from a rock formation and prepares for battle, along with the rest of it's pack. It battles with Littlefoot's grandfather and the rest of the herd while Hyp's Father runs with the kids to safety and retrieve reinforcements. While the grown-ups stand their ground to fight the sharpteeth, they notice that the rest of the herd missing. In an effort to get past the grown-ups, it tries to intimidate them succeeding in scaring Mutt's father and then passed by him. They finally up catch to the children from atop of a cliff and continue to roar and snarl at them with the grown-ups right behind them, they soon engage in battle with it being intense for the cliff side to crumble. The sharptooth pack quickly regain consciouness and plan to kill the vunerable dinosaurs, but Hyp's father tells the kids to head towards a dam while he fends off the raptors. Hyp then goes to save his father when the raptors turn towards him only to be swept by the tail of Grandpa Longneck. With the uneven odds, the raptors aim for the youngsters, but Littlefoot comes up with a plan to cause a rockslide to crush the sharpteeth, although Hyp is skeptical about the idea. He eventually helps and brings his gang along; they succeed in pushing the giant rock, crushing the raptors. However, the sharpteeth still remain persistant and fight with the grown-ups again. Soon enough Littlefoot and friends realize that the giant rock they pushed was blocking the water and starts roaring down towards the battlefield. Grandpa Longneck and the others retreat to safety, but before the sharpteeth realize it, the dam bursts open, washing the them away, as the water flows back into the Great Valley. In the end the Fast Biters survived with the leader angrily roaring at the main characters from afar. This is the last time these villains were to appear in any Land Before Time film.
- It is hinted several times that it might be the de-facto leader of the group. This is hinted by the numerous times it is given close-ups and especially the first one to appear before the other pack members arrive. It is also shown to be the given the most screen time in intro of the battle.