Jordan Mallon wrote:
I think T. calicornis was synonymized with T. horridus long before Cathy Forster's work. Ostrom and Wellnhofer synonymized all Triceratops species with T. horridus in:
Ostrom, J. H., and P. Wellnhofer. 1986. The Munich specimen of Triceratops with a revision of the genus. Zitteliana 14: 111 - 158.
Cheers
Tim