Littlefoot: I wonder what they are saying.
Cera: What, it's not like they can talk!
Sharptooth is the term for the language used by carnivorous dinosaurs. It consists of roars and grunts. It was first used, possibly, in The Land Before Time II: The Great Valley Adventure by Chomper and his parents when they talked, though no captions were used. The next time we see it, it is when Chomper and his parents are talking in The Land Before Time V: The Mysterious Island, though this time, captions are used. Cera doesn't think Sharpteeth can talk but Littlefoot thinks they do have thier own language, and he is correct.
Though Chomper talks in Sharptooth in The Cave of Many Voices (Episode), it doesn't use captions when he does. It doesn't show captions either in The Lonely Journey. However, it does show captions between Chomper and Thud in Escape From The Mysterious Beyond.
Ruby may also know Sharptooth, as indicated by her saying she had promised Chomper's parents to look after him, something that would seem hard to do if she didn't know it (barring Chomper translating for her anyway).
The term for the language was identified as "Sharptooth" by Littlefoot in "The Cave of Many Voices".