Some Silurian conodont apparatuses and possible conodont dimorphism

Conodont apparatuses and many "single element taxa" can be divided into two groups based on morphology and sometimes, the composition of the apparatus. Between these two groups many similarities connect the apparatuses in pairs, in whidt eadt pair consists of one apparatus of eadt type. New taxa: Pelekysgnathus dubius n. sp., Ligonodina confluens n. sp., Ligonodina excavata novoexcavata n. ssp., and L. confluens n. ssp. New combinations: Distomodus dubius (Rhodes, 1953), Ligonodina excavata (Branson & Mehl, 1933), and Hindeodella steinhomensis (Ziegler, 1956).