Notahypsibius arcticus (Murray, 1907) Tumanov, 2020

Tumanov, Denis V., 2020, Integrative redescription of Hypsibius pallidoides Pilato et al., 2011 (Eutardigrada: Hypsibioidea) with the erection of a new genus and discussion on the phylogeny of Hypsibiidae, European Journal of Taxonomy 681, pp. 1-37 : 25

Notahypsibius arcticus (Murray, 1907) gen. et comb. nov.

Macrobiotus arcticus Murray, 1907b: 677 , pl. 1, fig. 5a–f (description).

Macrobiotus heinisi Richters, 1911: 15 , fig. 15.

Hypsibius arcticus – Thulin 1911: 27. — Marcus 1930: 380. — Dastych 1991: 141–159 (taxonomical notes).

Ramazzottius arcticus Gąsiorek et al. 2018: 52 .

Type locality

Franz Joseph Land ( Murray 1907b).

Notes

The species Hypsibius arcticus (Murray, 1907) was recently transferred by Gąsiorek et al. (2018) to the genus Ramazzottius on the basis of having Ramazzottius -like claws and freely laid eggs. In my opinion, the type of the chorion ornamentation in this species, consisting of the internal pillars, is definitely different from the external processes that are typical of the genus Ramazzottius (see Discussion). The combination of the Ramazzottius -like claws and eggs with developed internal pillars in the egg chorion makes this species more similar to N. pallidoides gen. et comb. nov. It should, therefore, be transferred to the new genus as Notahypsibius arcticus gen. et comb. nov. This species differs from N. pallidoides gen. et comb. nov. by having better developed pillars in the egg chorion and by laying free eggs. However, the latter trait requires confirmation as it is assumed upon the basis of a single observation ( Murray 1907b), especially taking into consideration that Macrobiotus heinisi ( Richters, 1911) – a similar species described from the same locality (Franz Joseph Land) and later synonymized with H. arcticus ( Marcus 1930) – has eggs with a similar chorion structure laid within the exuvium ( Richters 1911). Also, Acutuncus antarcticus , which shares an eggshell structure of a similar appearance, is known to lay eggs both within the exuvium and freely ( Dastych 1991; pers. obs.). Other key characteristics, such as the presence of the minute septulum and cuticular sculpture, may have been overlooked by Murray (1907b) in his original description, as visualisation of these structures requires the use of high quality optics unavailable at that time. The specimen and the egg from Scotland, which were described and figured by Murray (1907a: 658, pl. IV, fig. 27a–d) as “ Macrobiotus oberhäuseri Doy. ?”, could not be attributed to N. arcticus gen. et comb. nov. because of the evident differencies in the claw structure (claws similar to the Cryoconicus type), the egg chorion appearance (much shorter pillars), and the significant difference in the value of the pt index for the stylet support insertion point (57% in Scottish specimen vs 70% in N. arcticus gen. et comb. nov., measurements taken from the original Murray’s drawings). This material possibly represents an undescribed species of the genus Cryoconicus .