Review of the Oxynoemacheilus tigris group with the description of two new species from the Euphrates drainage (Teleostei: Nemacheilidae) Author Freyhof, Jörg Author Kaya, Cüneyt Author Turan, Davut Author Geiger, Matthias text Zootaxa 2019 2019-05-28 4612 1 29 57 journal article 26666 10.11646/zootaxa.4612.1.2 b0a3a5c6-0885-4f87-a931-3d629233ad37 1175-5326 3233571 FE1913E9-E308-4807-A706-1D0F7A7C674B Oxynoemacheilus hazarensis Freyhof & Özuluğ, 2017 ( Fig. 5–6 ) Oxynoemacheilus hazarensis Freyhof & Özuluğ, 2017:379 , figs. 1–6 ( type locality: Turkey : North-eastern shore of Lake Hazar, Elazığ province , 38°28.398‘N 39°18.093‘E ). Material examined. FFR 1487, 3, 51–63 mm SL; FFR 15526, 9, 39–67 mm SL; Turkey , Elazığ prov. : lower stream Behremas, 38.501 39.509 .— FSJF 2512, paratypes , 11, 44– 62 mm SL; Turkey : Elazığ prov. : north-eastern shore of Lake Hazar , 38.4733 39.3016 . Material used in molecular genetic analysis. FSJF DNA 905 ; Turkey : Elazığ prov. : north-eastern shore of Lake Hazar , 38.4733 39.3016 . (GenBank accession number: MK 546459 ). — FSJF-DNA-1419; Turkey : Elazığ prov. : north-eastern shore of Lake Hazar , 38.4733 39.3016 (GenBank accession number: MK 546460 ) . Diagnosis. Oxynoemacheilus hazarensis is distinguished from O . ercisianus by having a suborbital groove in the male (vs. absent), the caudal peduncle behind the anus with scales (vs. scales absent), a more slender body (body depth at dorsal-fin origin 15–17% SL vs. 16–21), a more slender caudal peduncle (caudal peduncle length 1.3–1.5 times its depth vs. 1.0–1.3) and a shorter prepelvic distance (47–52% SL vs. 52–57). Oxynoemacheilus hazarensis is found together with O. kurdistanicus in the stream Behremas, a tributary to Lake Hazer. It is distinguished from this species by having an incomplete lateral line in most individuals (vs. complete), a slightly emarginate caudal fin (vs. deeply emarginate or slightly forked), a deeper caudal peduncle (11–13% SL vs. 9–11 in O. kurdistanicus ), and the back and the flank in front of the anus without scales (vs. scales present on entire back and flank). Distribution. Oxynoemacheilus hazarensis is endemic to Lake Hazer basin in the uppermost Tigris drainage. Remarks. Our molecular data ( Fig. 1 ) place O. hazarensis in the O. tigris species group. Based on DNA barcoding it is well separated from all other species in the O. tigris group, with O . kaynaki being the closest relative based on the DNA barcode data with a minimum K2P distance of 4.7% separating the two taxa. It is also supported by the PTP approach and by the mPTP delimitation as a distinct entity. Oxynoemacheilus hazarensis is the only species of the O. tigris species group found in the Tigris River drainage. While we were unable to find published evidence for a past hydrological connection of Lake Hazer with the Euphrates drainage, the Lake Hazar basin is situated immediately adjacent to the Euphrates catchment and it seems very likely that the ancestor of O. hazarensis found its way through a past connection from the Euphrates into Lake Hazar. On the other hand, many Oxynoemacheilus species from the Tigris have quite restricted ranges and are locally endemic to one or few tributaries of the Tigris. As O. hazarensis is the phylogenetic sister of the other species of the O. tigris group, which are all found in the Euphrates (and Lake Van basin), we could also speculate that the common ancestor of the O . tigris group invaded the Euphrates from the Tigris, maybe from Lake Hazer or its forerunners. Oxynoemacheilus hazarensis was described lacking a suborbital groove in the male but in additional material examined for this study, we found males having a suborbital groove. While the suborbital groove is a very stable and sound character in Oxynoemacheilus loaches, it can only be seen in fully adult males. In the type series studied by Freyhof & Özuluğ (2017) there were only few fully grown individuals.