Pseudochalaraspidum hanseni Birstein and Chindonova, 1962

Yolanda, Rofiza, Lheknim, Vachira, Price, W. Wayne & Hendrickx, Michel E., 2023, The lophogastrids (Crustacea: Peracarida: Lophogastrida) of Indonesia and its adjacent waters. An updated checklist, Zootaxa 5330 (3), pp. 413-429 : 417-418

Pseudochalaraspidum hanseni Birstein and Chindonova, 1962

Record from Indonesia. Eastern part of Indonesia, Papua. Depth range: 2825–4000 m ( Fage 1941) .

Remarks. Pseudochalaraspidum hanseni Birstein and Chindonova, 1962 and Chalaraspidum alatum (Willemoes-Suhm 1876) belong to two monotypic genera that have a confused history as detailed by W.M. Tattersall (1951) and Richter (2003). Willemoes-Suhm (1874) briefly described the latter species in 1874 from a specimen collected by the Challenger Expedition in the southern Indian Ocean. The specimen had been lost by the time G.O. Sars, in 1885, described the species in more detail based on notes and illustrations found in the papers of R. Willemoes-Suhm after his death. Both Hansen (1912) and Fage (1939, 1941) examined small numbers (all males) of specimens from the “Albatross” and “Dana” expeditions, respectively, and identified them as Chalaraspidum alatum . W.M. Tattersall (1951) examined three specimens (all immatures) from the “Albatross” expedition and concluded that the two specimens from Japan were the ‘true’ Chalaraspidum alatum , but the third, from off the coast of California, agreed closely with the descriptions of Hansen (1912) and Fage (1939, 1941) and represented a different species. However, he declined to describe a new species. Banner (1954) made the same decision after examining four immature specimens collected from the Hancock Foundation surveys in Baja California, Mexico although the specimens agreed closely with the descriptions of Hansen and Fage.

In 1958, Birstein and Tchindonova concluded that the species described by H.J. Hansen and L. Fage was the same as the original Challenger specimen and different from Tattersall’s two Japanese specimens and the four specimens they collected from the Northwest Pacific. They proposed that these latter six specimens belonged to a new species, Parachalaraspis vitjazi . Later, Birstein and Tchindonova (1962) reconsidered their opinion and proposed that P. vitjazi and the species described by Willemoes-Suhm were the same species, namely Chalaraspidum alatum . In the same paper, they proposed the name Pseudochalaraspidum hanseni for the “Albatross” and “Dana” specimens described by H.J. Hansen and L. Fage.

Pseudochalaraspidum hanseni can be distinguished from Chalaraspidum alatum as follows: in P. hanseni , the outer margin of the antennal scale has 9–12 teeth, the frontal margin of the carapace is convex and may be without or with minute serrations, the epimera of the last abdominal somite has two distinct and pointed projections, the mandible has a reduced molar process and the palp of the second maxilla has one article with three setae. For C. alatum , the outer margin of the antennal scale is armed with 2–4 teeth, the frontal margin of the carapace is serrated and concave, the epimera of the last abdominal somite at the middle part is armed with one small projection, the mandible has a well-developed molar process and the palp of the second maxilla is divided into two articles and bears several setae on the distal segment ( Richter 2003).