The Tinysauruses are a small herd of miniature, multicolored sauropods that made their debut in The Land Before Time XI: Invasion of the Tinysauruses. Their name is a combination of "tiny" and "-saurus". Unlike their slower relatives, they are quite fast and are very lightweight, and their small size is useful for crawling into small spaces. In the film, Littlefoot accuses the Tinysauruses for knocking down and stealing tree-sweets from the tree-sweet tree. Because of this, the other dinosaurs are eventually fearful of these rather alien creatures, and have a desire to kill them if they could. When Littlefoot befriends these creatures, however, they turn out to be more sentient than he imagined.
The Tinysauruses are never actually called "Tinysauruses" on screen in the film, which make sense since the dinosaurs would probably not use such prefixes as "-saurus" to refer to each other - instead, they are called "Tiny Longnecks". However, in "Stranger From the Mysterious Above", an episode of the TV series, Ducky does refer to them as Tinysauruses.
The Tinysauruses can be spotted in The Land Before Time XII: The Great Day of the Flyers during the song Flip, Flap and Fly.