Kosswigichthys Sözer, 1942

Freyhof, Jörg & Yoğurtçuoğlu, Baran, 2020, A proposal for a new generic structure of the killifish family Aphaniidae, with the description of Aphaniops teimorii (Teleostei: Cyprinodontiformes), Zootaxa 4810 (3), pp. 421-451 : 434-435

Kosswigichthys Sözer, 1942

Fig. 10

Type species. Kosswigichthys asquamatus Sözer 1942

Diagnosis. Kosswigichthys is distinguished from all other genera in the family Aphaniidae by possessing three (vs. one) rows of conical (vs. tricuspid) teeth. It is further distinguished from Anatolichthys , Aphanius , and Aphaniops by absence of black or dark-brown bars in the caudal fin of the male (vs. presence, except in Aphaniops furcatus ), possession of a hyaline caudal fin in the male (vs. yellow or orange in Aphanius ), absence of head canals (vs. presence in Aphanius and Aphaniops ), presence of a dermal sheath at the anal-fin base in the nuptial female (vs. absence in Aphaniops ), and possession of a naked body (vs. covered by scales in Aphanius ).

Included species. Kosswigichthys asquamatus

Distribution. Kosswigichthys is endemic to Lake Hazar in Eastern Turkey ( Fig. 4 ).

Remarks. The phylogenetic analysis by Hrbek et al. (2002) and our own unpublished COI data place K. asquamatus as the sister clade to Anatolichthys . The morphological differences between Kosswigichthys and Anatolichthys are very clear, and might be related to the specialised pelagic ecology of K. asquamatus . The slender body shape and lack of scales are comparable to the pelagic Anatolichthys species A. saldae and A. splendens , but in contrast K. asquamatus has conical teeth, no bars on the caudal fin in males, and a slightly upturned (vs. distinctly superior) lower jaw. As in the case of the sympatric loach Oxynoemacheilus hazerensis , K. asquamatus seems to be a relict species in the ancient rift lake Hazar ( Freyhof et al. 2019).

Figures

FIGURE 4. Records of Anatolichthys and Kosswigichthys species.

FIGURE 10. Kosswigichthys asquamatus, FSJF 2511, from the top: female, ~33 mm SL; male, ~30 mm SL; Turkey: Lake Hazer.