To their findings, Lehman added the old Lull-Sternberg lineages combined with maturity and sexual dimorphism, suggesting that the "T. horridus"-"T. prorsus"-"T. brevicornus" lineage was composed of females, the "T.calicornis"-"T.elatus" lineage was made up of males, and the "T. obtusus"-"T. hatcheri" lineage was of pathologic old males.
Eden od argumentov je bil, da sta v vsaki regiji samo ena ali dve vrsti vsake velike živali (od novejših primerov recimo žirafe in sloni v današnji Afriki).