Caudipteryx was a small herbivorous theropod dinosaur.
Caudipteryx is a feathered dinosaur part of an Oviraptor family. They were flightless like most dinosaurs. They walked on their long hind legs and had long arms with wings (that were useless for flight, possibly only used to attract mates). They had beaks like birds. They had a bony tail.
One Caudipteryx was captured by Momma T-Rex and was stunned to be eaten her children, keeping it out of reach of scavengers. Later, a Ground Sloth named Sid, in an attempt to raise three young Tyrannosaurus hatchlings and foster in them a vegetarian diet, provided his them with broccoli, turnips and radishes, but the babies would not eat them. As Sid asked them how they expected to grow up big, Momma dropped the unconscious animal in front of her children so that they might eat it, but Sid tried to convince her otherwise, pulling off a worm from its foot, which caused it to come to and screech in shock at Sid, the hatchlings and screech loudest at the sight of Momma. The bird then rushed to Sid, clinging onto the sloth, but Sid, trying to set it free despite its protests, dropped it off a cliff, where it fell and was snatched by a Quetzacoatlus.
It was shown to have a long bony tail and teeth, even though real Caudipteryx never had such a tail (it was actually very short) and it didn't had teeth neither. The differences are probably due to the movie's dinosaurs having millions of years to evolve under the ice, making them look different from their real-life versions.
Ice Age: Dawn Of The Dinosaurs (Film) (referred as Flightless Bird)