Neobirsteiniamysis Hendrickx et Tchindonova, 2020

Daneliya, Mikhail E., 2023, Mysid Subfamily Boreomysinae (Crustacea: Mysida: Mysidae) in the Southeast Australian Deep-sea, Records of the Australian Museum (Rec. Aust. Mus.) 75 (2), pp. 87-124 : 110

Neobirsteiniamysis Hendrickx et Tchindonova, 2020

Neobirsteiniamysis Hendrickx et Tchindonova, 2019 in Hendrickx et al., 2020: 21 (unavailable, according to Hendrickx & Tchindonova, 2020)

Neobirsteiniamysis Hendrickx et Tchindonova, 2020: 1 , 2.—Hernández-Payán & Hendrickx, 2020: 2.

Birsteiniamysis Tchindonova, 1979: 102 ; 1981: 26, 28; 1993: 153.—Staff of the Zoological Society of London, 1985: 398, 399 (as Birsteiniamysis Tchindonova, 1981 ; noticed absence of the type species).— Beliaev, 1989: 189 (as Birsteiniamysis Tchindonova, 1981 ; first recognition as nomen nudum).— Petryashov, 1993a: 93, 103, 104 (as Birsteiniamysis Tchindonova ; without publication year); 1993b: 71 (as Birsteiniamysis Tchindonova, 1979 ); 2004a: 126 (as Birsteiniamysis Tchindonova, 1979 ); 2005b: 963, 970 (as Birsteiniamysis Tchindonova, 1981 ); 2009b: 125; 2014a: 187 (as Birsteiniamysis Tchindonova, 1979 ); 2014b: 149; Lowry & Stoddart, 2003: 428 (as Birsteiniamysis Tchindonova, 1981 ); Wittmann et al., 2014: 332 (as Birsteiniamysis Tchindonova, 1981 ). Nomen nudum.

Birsteiniamysis .—Hendrickx et al., 2020: 19, 20.— Hendrickx & Tchindonova, 2020: 1.—Hernández-Payán & Hendrickx, 2020: 2. Referred to as unavailable name.

Type species. Petalophthalmus inermis Willemoes-Suhm, 1874 ; by subsequent designation (Hendrickx & Tchindonova, 2020).

Diagnosis. Telson rather broad in the central part, as wide as or wider than anterior part. Eyes without cornea, calyciform, with lateral concavity.

Distribution. Bipolar-amphitropical genus found in all oceans of the world. In the Antarctic, the genus is generally distributed circumpolarly. In the Pacific, it is mostly found along the South and North American continental slope, with a break in equatorial waters, and further alongAleutian Ridge towards the Okhotsk Sea and Kuril-Kamchatka trench. With the new findings the range of the genus is now extended to the Australian region.

Habitat. Bathyal-abyssal. Depth 700–7200 m. Visual apparatus adapted to low-light intensities (Elofsson & Hallberg, 1977).

Remarks. Specimens of this genus were first collected in the course of HMS Challenger Expedition in 1873 by Rudolf von Willemoes-Suhm, who included them into the genus Petalophthalmus Willemoes-Suhm, 1874 ( Willemoes-Suhm, 1874, 1875, 1876a,b). Later, some new specimens were made a part of Boreomysis by G. O. Sars (1879b), and this was also the fate of Willemoes-Suhm’s material (G. O. Sars, 1883). G. O. Sars (1885a) described the nervous system of N. inermis , and found that its mouthpart ganglion masses were rather primitively separated from each other by connectives (more condensed in other Mysida ) ( Wittmann et al., 2014). The taxonomic significance of this variation has yet to be evaluated by the studies of the nervous systems across the order. Tchindonova (1993) described the concavity of the maxilliped 2 carpus only for Neobirsteiniamysis caeca (Birstein et Tchindonova, 1958) . Although not so strongly developed, the concavity, with a number of modified setae, is also found in N. inermis , which was first discovered by G. O. Sars (1885a) and confirmed here. Since Elofsson & Hallberg (1977) discovered the pigmented cell layer in the eyes of N. inermis , the absence of the pigmentation can no longer serve as a diagnostic feature of the genus, and I exclude it from the update. With the exclusion of non-diagnostic characters, I updated here the diagnosis of Neobirsteiniamysis in comparison with Boreomysis .

Tchindonova (1993) proposed three informal groups within Birsteiniamysis: Inermis group, Scyphops group and Caeca group, probably indicating some additional differentiation within the species. She, however, did not clarify the meaning of her proposal.

Composition. The genus contains two species, N. caeca and N. inermis . Among them, only the latter is recorded in the Australian waters. Tchindonova (1981; also Beliaev, 1989, referring to Tchindonova, 1981) mentioned some undescribed species and subspecies of this genus from the Southern Ocean, and the case still waits for a resolution.