The baby triceratops seen in The Lost World isn’t an animatronic, it’s a person in a suit
It is well known that the animatronic triceratops that was made for Jurassic Park (1993) wasn’t used, but it did make appearance in The Lost World, although not as an animatronic. The Stan Winston Studio crew retained the original radio-controlled head but the animatronic body was refurbished as a foam latex Triceratops suit, worn by SWS employee Lindsay MacGowan in the scene.
Here’s a quote from the book Jurassic Park: The Ultimate Visual History by James Mottram:
To create a caged baby Triceratops, Winston's team dug out the abandoned infant Trike animatronic from Jurassic Park. The mechanics were removed so Winston employee Lindsay MacGowan could climb into the creature's skin via its belly and perform the creature on set. "I was on all fours basically, inside the cage," says MacGowan, who admits it was physically tough to be in that position for any length of time. "The takes were kind of long. So by the time you finished the take, your arms were a little bit like jelly!"