- "I say they're vegetarian. You say Grr. I say can we talk about this. You say Grr. I don't call that communication.
See? That's your answer to everything."
- ―Sid talking to Momma Dino[src]
A protective mother, Momma cared deeply for her young, despite her fearsome appearance and brutish demeanor, and resided with her family in a vast underground world in which dinosaurs were still extant.
Leaving the subterranean Dinosaur World for a spell, Momma laid three eggs and went up to the surface to set them down in an underground ice cave. The eggs were found by a ground sloth named Sid, who took them as his own and raised them, if only for one day. The next day, Momma returned to the cave to find her eggs missing. Knowing they must have hatched by that point, Momma searched for them on the surface, much to the shock and fear of the animals on the surface at seeing a living dinosaur, for the animals on the surface had long since believed that dinosaurs were extinct.
Momma found her three young hatchlings, who, never having seen their brood mother, were terrified of her, along with Sid. Regardless, Momma picked the three hatchlings, along with Sid, up with her jaws and returned to the warmth and security of the world below.
Momma returned to the world below with her young as they yelped in fear to Sid, who was also frightened. After reaching a wooded area, Momma let her three children down on the ground and proceeded to attempt eating Sid. The sloth, however, proved troublesome to eat, as he grabbed onto a nearby branch as Momma tugged at him and would not let go, launching himself straight into her nostril. Momma snorted Sid out onto a tree branch and continued her attempt to eat him, to which Sid tried to reason with her as he hopped through the tree, working out a plan to share care of the children. Momma was uninterested and still attempted to snap down on the sloth, who dodged her bites until he landed in a mass of vines, entertaining the hatchlings. Momma, seeing that Sid was bound and unable to escape, tried to eat him but her children would not allow it, growling at her as she tried to eat Sid. In annoyance with Sid, Momma swatted him aside, binding him in the vines onto a tree.
Later when Sid tried to feed the dino babies with vegetables, (which they don't like) but Momma dinosaur tries to show Sid that it is in their nature to eat meat, but Sid wouldn't listen (again) and after a few attempts to win the argument, Momma dinosaur wins the argument after her babies eat the dead leg, giving Sid an eyebrow. She then hesitates as she hears Rudy roaring, but Sid doesn't know what it is, since he doesn't know about Rudy. He and the other dino babies are taken to safety. That night as Momma dinosaur takes her babies up to her nest, for sleep, but leaves Sid to sleep on the ground below. Sid tries to sound optimistic about this, but admits to himself quietly and softly that he misses his friends, and thinks that they aren't missing him, because of his clumsy nature and the damage he caused to Manny and Ellie's kid's playground, thinking that because of this, everybody hates him. Momma dinosaur senses Sid's hard time, takes pity on him and takes him up to her nest where her babies are sleeping. Sid gratefully says that she's a real softie, but she doesn't seem to hear him as she looks for any signs of Rudy, before she herself nestles in for the night. The next day, she, Sid and the kids are playing, when Rudy makes his roar, causing Momma and her babies to run in fear, leaving poor Sid behind. Except for when Sid passes her kids, Momma doesn't appear again, until later in the movie when she saves Sid from been eaten by Rudy and knocking him down towards an empty chasm. She then gives a roar of triumph, knowing now that she and her family can now live without fear. She and her babies affectionately say good-bye to Sid as he goes back to his regular herd and she and her babies head off back home and possibly search for a new one.
Personality and Traits
An immense Tyrannosaurus, Momma appeared to many creatures as a predator first and a mother later, this grim image being proven wrong as she watched over her young with great dedication. Though initially reluctant to share any parental roles with the ground sloth Sid, Momma still looked closely after her three children alongside Sid.
Although Sid described Momma as being a "horrifying dinosaur" (which she seemed to take as a compliment), she had a softer side since she was a mother. Momma initially attempted to eat Sid but her children stood up to her and convinced her to let him live. Later, she lifted Sid into the cave that she and her children were using to hide from Rudy and Sid stated that she was actually a "softie" despite being a predator. Momma was shown to be a bit frightened of Rudy but also showed the courage to overcome this fear by attacking the larger dinosaur in order to protect Sid. She was extremely protective of her family and eventually considered Sid to be a member of it.