The Tinysauruses are a small herd of kitten-sized, multicolored Mussaurus 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. 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.
- Big Daddy, voiced by the late Michael Clarke Duncan, is the leader of the Tinysauruses. He is the voice of authority in the Tinysaurus herd. He has been met with much derision from the younger Tinysauruses, of whom he is over-protective. His name is doubly ironic, considering he is short even for a Tinysaurus, being dwarfed by his own daughter, Lizzie. Interestingly, although all of the children refer to him as "Big Daddy", only Lizzie appears to be his daughter. She is the only one who calls him "Dad", and when he is speaking to Topps at the end of the film, he mentions that he is grateful that "You also saved my daughter's life." Big Daddy is one of the Tinysauruses that appears in The Land Before Time XII: The Great Day of the Flyers in the song "Flip, Flap and Fly".
- Lizzie, voiced by Cree Summer, is the daughter of Big Daddy, she was fed up with her father's over-protectiveness and distrust of Littlefoot and his friends, similarly to Cera's situation with her father, Topps. Lizzie and Cera quickly became friends due to their understandings of each other's situations, and sang a song together about girls and dads. Both eventually made amends with their fathers.
- Skitter, voiced by Leigh Kelly, is the first of the Tinysauruses to befriend Littlefoot. When the Tinysauruses were eating the fallen treesweets, Skitter stood on top of Littlefoot and ate one off of his nose, which he proudly remarks on down in the herd's underground dwelling. When Littlefoot first fell down the hole by accident, Skitter happened to be right underneath, and was temporarily squashed when Littlefoot landed on him. This happened again when Cera, Ducky, Petrie, and Spike all fell down the hole several nights later. Skitter seems to pal with Lizzie the most of all the Tinysaurus children.
Rocky and Dusty
- Rocky and Dusty, voiced by Nika Futterman (Rocky) and Ashley Rose Orr (Dusty), are twin Tinysauruses. Rocky is a male and Dusty is a female. They usually speak in fragments, with one starting a sentence, and the other finishing it. Rocky is most often the beginner of the sentence, while Dusty usually finishes what her brother says. When Skitter is introducing Littlefoot to Rocky and Dusty, he confuses them with each other at first.
- Chatter: One of the background Tinysauruses.