Evidence states that Torosaurus and Triceratops are distinct dinosaur genera, not synonyms.
Here is the paper: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0032623#abstract0
Then here is the abstract:
Background
In horned dinosaurs, taxonomy is complicated by the fact that the cranial ornament that distinguishes species changes with age. Based on this observation, it has been proposed that the genera Triceratops and Torosaurus are in fact synonymous, with specimens identified as Torosaurus representing the adult form of Triceratops.
The hypothesis of synonymy makes three testable predictions:
1) the species in ques