STILIPEDIDAE Holmes, 1908

Berge, Jørgen & Vader, Wim, 2005, The amphipod genus Alexandrella (Amphipoda, Stilipedidae): taxonomic status, allometric growth and description of two new species, Journal of Natural History 39 (17), pp. 1327-1346 : 1328-1329

Family STILIPEDIDAE Holmes, 1908 , sensu Coleman and Barnard 1991 Genus Alexandrella Chevreux, 1912

Alexandrella Chevreux 1912, p 213 ; Chevreux 1913, p 134.

Alexandrella: Holman and Watling 1983, p 32 .

Alexandrella: Barnard and Karaman 1991, p 703 .

Parandaniexis Nicholls 1938, p 42 [homonym of Parandaniexis Schellenberg, 1929 ].

Pseudandaniexis Nicholls 1938 , corrigendum [replacement name for Parandaniexis Nicholls, 1938 ].

[Note. The generic names Iphimediopsis Schellenberg, 1931 , Bathypanoploea Schellenberg, 1939 and Pseudiphimediopsis Ruffo, 1949 , all technically with type species Alexandrella australis ( Chilton, 1912) , were in reality based on a different species altogether, now known as Bathypanoploea schellenbergi Holman and Watling, 1983 . They are therefore not subjective junior synonyms of Alexandrella (cf. Holman and Watling 1983).]

Type species. Alexandrella dentata Chevreux, 1912 .

Species. Alexandrella australis ( Chilton, 1912) ; A. dentata Chevreux, 1912 (new syn: A. mixta ( Nicholls, 1938)) ; A. inermis Bellan-Santini and Ledoyer, 1987 ; A. mandibulata n. sp.; A. martae n. sp., A. subchelata Holman and Watling, 1983 .

Key to the species of Alexandrella 1. Pereonite 7 dorsally with a strong tooth, mandibular incisors smooth....

................... Alexandrella australis – Pereonite 7 dorsally smooth, mandibular incisors fully or partly toothed... 2 2. Pleonites 1–3 strongly toothed, pereopod 1 with oostegite....... 3 – Pleonites 1–3 weakly toothed, pereopod 1 without oostegite....... 4

3. Right mandible with lacinia mobilis reduced to a simple tooth......

................ Alexandrella mandibulata n. sp. – Right mandible with lacinia mobilis smaller than left, but broad and toothed............... Alexandrella martae n. sp.

4. Pereopods 1 and 2 subchelate, body dorsally strongly carinate......

................... Alexandrella subchelata – Pereopods 1 and 2 simple, body dorsally weakly or not carinate..... 5

5. Mandibular incisors not toothed along the entire margin, antennae subequal......... Alexandrella dentata (syn. A. mixta , see below)

– Mandibular incisors toothed along the entire margin, antenna 1 shorter than antenna 2................ Alexandrella inermis

Remarks

The genus Alexandrella was revised by Holman and Watling (1983), and was at that time considered as encompassing four different species, two of which were considered as a possible set of synonyms. Until their revision, Alexandrella was considered a monotypic genus for the type species A. dentata . Alexandrella australis had been described as a Acanthonotozoma species , whereas A. mixta originally was described as a stegocephalid (first as Parandaniexis mixtus n. gen. n. sp., later renamed Pseudandaniexis ). Holman and Watling (1983, p 44) described one further species, A. subchelata , and another species was added by Bellan-Santini and Ledoyer (1987), A. inermis . Finally, A. pulchra was described by Ren and Huang (1991), but this species was recently put into synonymy with Bathypanoploea schellenbergi by Berge and Vader (in press). As a consequence, after synonymizing A. mixta with A. dentata , the genus, as treated here, now comprises six species, two of which are new to science.

As this paper is part of a series that will eventually lead to a revision and phylogenetic analysis of the two families Astyridae and Stilipedidae (both sensu Coleman and Barnard 1991), the relationships within the Stilipedidae generally fall outside the scope of this paper. However, the generic differences between the three genera Bathypanoploea Schellenberg, 1939 , Astyroides Birstein and Vinogradova, 1960 and Alexandrella Chevreux, 1912 need to be examined more closely. As pointed out by Holman and Watling (1983, p 46), the only characters that can be used to separate Astyroides from Alexandrella are the absence of an articulation on the palp of the first maxilla in the former and the morphology of the labium. The latter of these two characters is probably not suitable as a diagnostic character at all, as it appears to be highly variable within the two genera Alexandrella (see figures herein) and Bathypanoploea (see Berge and Vader in press). Thus, except for the absence of an articulation of the palp of the first maxilla in Astyroides , an autapomorphic character within the family, no clear distinctions can be made between Astyroides and Alexandrella . Furthermore, the only character that seemed to separate Bathypanoploea from Astyroides and Alexandrella (see Berge and Vader in press), was the presence of a rudimentary molar in the former. However, as also the type species of Alexandrella ( A. dentata , see below) possesses a rudimentary molar, no real distinction between the two genera Alexandrella and Bathypanoploea remains. Otherwise, all species within the three genera possess characters such as a cuspidate dactylus of the maxilliped palp and pereopods 1 and 2, asymmetrical labrum with right lobe larger than left, elongate antenna 2, and morphologically a very similar telson and maxilliped, all characters that suggest a close relationship between the three genera. The close relationship between these three genera may also be illustrated by the fact that one Alexandrella species , A. pulchra Ren and Huang, 1991 , was recently put into synonymy with the type species of Bathypanoploea (see Berge and Vader in press).