As the newly discovered one has a medium sized horn, it has been imaginatively dated in between the two.
Three points:-
Note how the dating is achieved by the unproven 'mid link' connection being placed between the two others - a typical slick trick of the evolutionary paleontologist. Force the evidence to fit the argument then call it 'scientific'.
Secondly; Texan Longhorn cattle have, well, long horns. Illawara short horned have short horns and Friesians have medium sized ones.
So. Which cow evolved into which other?
Finally, note how the previously predicted medium horned beastie is then adduced as evidence of evolution.
May I suggest that the BBC's nutty Primeval series makes slightly more sense and is certainly more fun.
http://ibtimes.com/apnews/20070304/new-dinosaur.htm