Wild Arms is an unusual looking dinosaur, identified as (though only loosely resembling) a Nothronychus by official media. He has a beak, a yellow stomach that was somewhat similar to those of the Yellow Bellies in The Land Before Time XIII: The Wisdom of Friends, dark teal feathers behind his head, long feathers running down the length of his long, spindly arms, and a layer of protofeathers coating his back.
Though Wild Arms is intended to be seen as a protagonistic character, he has few redeeming traits. He is occasionally selfish, cowardly, and somewhat mean spirited. He is rather narcissistic, and is very reluctant to help those who need help the most. At the end of the movie, he arrogantly tries to take credit for helping with the rescue, saying he "volunteered" when boasting to Etta; who quickly laughs off his arrogance. He also has to be goaded into going into the Land of the Featherhead Sharpteeth, and, despite being told that Chomper is not a threat to him, passes out when Chomper attempts to greet him, forcing the others to have to carry him until they nearly encounter the Horned Sharptooth. However, he does sympathise with others occasionally. When Littlefoot asked what happened to Bron. Wild Arm’s voice went very quiet. And when he said that Bron “was a brave longneck,” he saw that Littlefoot was sad and quickly changed “was” to “still is”.
Wild Arms' first appearance in the film is during the opening act, in which he notifies Littlefoot and the rest of the valley that Bron has been imperiled in the Mysterious Beyond. In the evening, after the kids set off to find Littlefoot's father, he is enlisted by Grandpa Longneck and Daddy Topps to guide them to the Fire Mountain, the exact location where Bron was put in danger due to a volcanic eruption.
It is later revealed by Etta that Wild Arms' life was nearly cut short during the eruption of the Fire Mountain, the therizinosaur narrowly escaping death due to the involvement of Bron; though this rescue was ultimately what put Bron's life on the line. After Bron is rescued, he, alongside Etta, Grandpa, Topps, and the Gang of Seven, head back to the Great Valley as the sun sets.
- Wild Arms is similar in color scheme to Guido, a Microraptor character who appears in The Land Before Time XII: The Great Day of the Flyers and the television series.
- As "Wild Arms" appears to be a nickname given to the character by the other members of the herd due to his antics, alongside his tendancy to flail his arms, it is unknown if Wild Arms has an actual name, and if so, what that name is.