摘要：Elements of species of Drepanoistodus Lindstrom,Panderodus Ethington,and Protopanderodus Lindstrom systematically vary from symmetrical to pronouncedly asymmetrical (symmetry-transition series) within each species,and a group of elements with systematic increase in curvature of the cusp can be recognized for each element type;each such group is named a curvature-transition series. Panderodus and Protopanderodus,both of the Panderodontacea,have essentially identical apparatuses with regard to symmetry and curvature-transition series whereas Drepanoistodus,of the Distacodontacea,differs in type of symme try-transition series a nd number of curvature-transit ion series . The curvature-transition series is considered to represent a taxonomically distinct character at the suprageneric level.
其他摘要：W zespola ch e lernen tow kazd ego z ga tunkow ko no don t6w z r od zaj6w Drepano i stodus Lindstrom,Panderodus Ethington i Protopa nderodus Lindstrom objawia sie zrniennosc stopnia as ymetrii ele me nt6w i stopnia za giecia ic h zebow. W obreb ie sze reg
