Two new nematode species of the genus Cosmocephalus Molin, 1858 (Spirurida: Acuariidae), with an amended generic diagnosis and an identification key to Cosmocephalus spp. Author Mutafchiev, Yasen Author Halajian, Ali Author Georgiev, Boyko B. text Zootaxa 2010 2349 1 20 journal article 10.5281/zenodo.193420 dd7f086e-6df6-4c73-a338-837cee1ab9e2 1175-5326 193420 Key to the species of Cosmocephalus 1a. Anterior loops of cordons reach between one quarter and one third of the length of cordons ......................... C. faridi 1b. Anterior loops of cordons markedly shorter, do not exceed one quarter of the length of cordons.............................. 2 2a. Lateral alae absent ........................................................................................................................................ C. pelecani 2b. Lateral alae present ....................................................................................................................................................... 3 3a. Deirids bicuspid ........................................................................................................................................................... 4 3b. Deirids tricuspid........................................................................................................................................................... 6 4a. Cordons with both descending and ascending arms scalloped ..................................................................................... 5 4b. Cordons with descending arm scalloped, ascending arm not scalloped ...................................................... C. podicipis 5a. Cordons shorter than 450 µm in males and than 550 µm in females, rarely longer; distal end of left spicule with sub- terminal projection ...................................................................................................................................... C. obvelatus 5b. Cordons 450–470 µm long in males and 540–650 µm long in females; tip of left spicule pointed, without projection ................................................................................................................................................................... C. imperialis 6a. Cordons with well-expressed scalloped structure; inner row of plates 38 µm wide in males; left spicule more than 600 µm long .................................................................................................................................................. C. jaenschi 6b. Cordons not scalloped, width 25 in female and 20 in males; left spicule less than 400 µm long .............. C. capellae