Аннотация:Study of the four poorly known species of genus Camptocercus – C. oklahomensis Machin, 1930, C. fennicus Stenroos, 1898, C. uncinatus Smirnov, 1971 and C. lilljeborgi Schoedler, 1862 revealed high level of differences in both outer morphology and morphology of appendages. The first three species have typical for the genus morphology of valves, while C. lilljeborgi have straight ventral margin of valves with very dense setae, being similar to the species of Graptoleberis. C. lilleborgi also have most modified appendages, exopodites of limbs III-V uniformly have seta 4 reduced to the small stub and seta 3 with extremely wide basal part. C. oklahomensis lacks head keel, typical for the most species of the genus, and have numerous characters, confirming its basal position within the genus – less elongated postabdomen with groups of elementary marginal denticles and less specialized morphology of thoracic limbs. The level of differences observed in thoracic limb morphology in Camptocercus is unusual for Aloninae, in most genera of the subfamily limb morphology is uniform. In this feature, Camptocercus is similar to Leydigia, the other very specialized genus of the group. Uniform thoracic limb morphology within the most Aloninae genera can be attributed to high level of competition between genera, where most “optimal” combinations are already attained. Camptocercus and Leydigia have extremely specialized outer morphology and free from competition from other genera, so diversification of thoracic limbs morphology between species became possible.
This study has been funded by the Russian Science Foundation (grant 14-14-00778).