In reality, Triceratops fossils have only been found dating back to between 68 and 65 millions years ago, almost 20 million years after the time that Terra Nova is set.
Also, Triceratops fossils are only known from North America, while Carnotaurus is only known from South America. See the Science & Speculation section of the Ankylosaurus article for a discussion of how it might be possible to rationalize a mix of North American and South American species in Terra Nova in terms of a land bridge which is thought to have existed between the continents in the Late Cretaceous.
The baby Triceratops skeleton seen in Malcolm's lab in unrealistic, since a real baby would not have had such developed horns and shield--a reconstructed version of a real baby Triceratops skull can be found on this page.
It could also be a model, just for decoration or demonstration purposes.
Triceratops is from the Latest Cretaceous 68-65 MYA, but if the portals are a natural occurance they must show up on a regular basis than the Triceroptops could have come through a portal from 65 MYA to 85 MYA.