Subsequent discoveries and analyses, however, proved the correctness of Sternberg's view on the position of "Triceratops", with Thomas Lehman defining both subfamilies in 1990 and diagnosing "Triceratops" as "ceratopsine" on the basis of several morphological features. Apart from the one feature of a shortened frill, "Triceratops" shares no derived traits with centrosaurines. Further research by Peter Dodson, including a 1990 cladistic analysis and a 1993 study using RFTRA (resistant-fit theta-rho analysis), a morphometric technique which systematically measures similarities in skull shape, reinforces "Triceratops" placement in the chasmosaurines.