A new genus for the western Caucasian Lyurella (Amphipoda, Crangonyctidae), with descriptions of three new hypogean species from the western foothills of the Russian Caucasus

A new genus, Caucasirella gen. nov . (Crustacea, Amphipoda, Crangonyctidae), is proposed for the Caucasian representatives of the genus Lyurella Derzhavin, 1939, namely Caucasirella fontinalis (Marin & Palatov, 2021), comb. nov . (the type species), Caucasirella shepsiensis (Sidorov, 2015), comb. nov ., Caucasirella asheensis (Palatov & Marin, 2021), comb. nov ., Caucasirella fanagorica (Palatov & Marin, 2021), comb. nov ., and Caucasirella mikhailovi (Marin & Palatov, 2021), comb. nov . Three new species, Caucasirella shapsuhica sp. nov ., Caucasirella mzymtiensis sp. nov ., Caucasirella lazareviensis sp. nov ., are also described from the hypogean (riverine hyporhea, springs) habitats of western foothills of the Russian Caucasus. An integrative approach using uni-locus (COI) phylogeny, morphological and geographical data clearly support the creation of a new genus for Caucasian species. Caucasirella gen. nov . could be separated from Hyrcanian Lyurella hyrcana Derzhavin, 1939 mainly by the presence of two or three coupling hooks in the retinacules of pleopods (vs. four hooks), a deep distal notch on the telson and, most notably, the absence of a peduncular distoventral distal serrate process of the uropod I in ♂♂. They probably diverged ca 10–7.5 Mya (Miocene), during the uplift of the area of the Caucasian Ridge. The morphology of juveniles of Caucasirella lazareviensis sp. nov ., described for the first time, revealed their significant difference from adults and important morphological features for the entire “ Synurella ” clade.