In the first attempt to understand the many species, Lull found two groups, although he did not say how he distinguished them: one composed of "T. horridus", "T. prorsus", and "T. brevicornus"; the other of "T. elatus" and "T. calicornis".
Ta primerek so poslali Othnielu Charlesu Marshu, ki je sprva verjel, da gre za najdbo iz pliocena in da so kosti pripadale vrsti velikega bizona, ki ga je poimenoval "Bison alticornis".