Leptognathia birsteini Kudinova-Pasternak, 1965: 84 –88, figs 5–6. Kudinova-Pasternak, 1966: 532. Kudinova-Pasternak, 1970: 355. Larsen & Shimomura, 2007: 2, 15.
Remarks. A highly characteristic body shape marks out this taxon from most other ‘ Leptognathia ’ species, deriving from the small and sub-triangular cephalothorax and short and wide pereonites 1–2. A very similar species, L. microcephala Kudinova-Pasternak, 1977 differs slightly in body proportions, pleotelson shape and other details (see below). It is very highly probable that L. birsteini and L. microcephala belong in the genus Latitanais Kudinova-Pasternak, 1987, currently positioned in the Subfamily Cryptocopinae Sieg, 1973 of the Family Pseudotanaidae Sieg, 1976 after a phylogenetic analysis (Larsen & Wilson 2002). However, although this decision has not been made formally L. birsteini and L. microcephala have at least been correctly removed from Leptognathia sensu stricto and the Leptognathiidae by Larsen & Shimomura (2007).
It an abysso-hadal species which has been recorded from the Kurile-Kamchatka Trench at 4895 metres (Kudinova-Pasternak 1970), with earlier records from the widely separated Bougainville Trench, 6920–7657 metres (Kudinova-Pasternak 1965) and the North-west Pacific Basin, 6051 metres (Kudinova-Pasternak 1966). Three specimens of the birsteini-microcephala group from the present study seem referable to the latter species.