Sue is a huge Longneck (Supersaurus) who goes with Littlefoot and his grandparents in The Land Before Time X: The Great Longneck Migration. Not much is known about her except that she is a kind Longneck.
She first appears after stepping on a large Belly Dragger who had tried to eat Littlefoot after he jumped off a log, almost landing in it's mouth. At first, him and his grandparents are scared of her huge size. She then lowers her neck and they calm down. She is then thanked by his grandparents for saving him. She asks if she could tag along and they accept. That night, she talks to Littlefoot about how she was having strange sleep stories like him too, and talking about her being the tallest one, and that she wants to have someone to look up to. Littlefoot falls asleep while she talks.
At the crater later in the film, she walks into a large Ultrasauros that is even taller than her. She quickly falls in love with him.
At the end of the film, she is asked by Grandpa and Grandma Longneck if she wants to walk back with them, but she declines, as she wants to walk back with her new Ultrasauros boyfriend.
- She is the first and only Supersaurus in the franchise.