Pseudambasia Stephensen 1927
Creators: name: Kilgallen, N. M.
name: Lowry, J. K.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Lysianassidae
Pseudambasia

description: Pseudambasia Stephensen, 1927
Pseudambasia Stephensen, 1927: 305. Barnard & Karaman, 1991: 522. Lowry & Stoddart, 1995: 113.
Type species. Pseudambasia bipartita Stephensen, 1927, monotypy (= junior subjective synonym of Parambasia rossii Stephensen, 1927).
Diagnosis. Antenna 2 peduncular article 3 elongate (length 3 – 3.6 × breadth), geniculate between articles 3 and 4. Maxilla 1 inner plate without apical setae. Mandible left lacinia mobilis absent, palp attached slightly to extremely proximally. Labium without inner plates. Gnathopod 1 sexually dimorphic, simple or weakly to strongly subchelate. Urosomites 2–3 coalesced. Telson entire.
Included species. Pseudambasia includes 11 species: P. acuticaudata (Ledoyer, 1984); P. dartnalli sp. nov.; P. indentata (Ledoyer, 1986); P. kalaupapa Longenecker & Bolick, 2007; P. l o ch i sp. nov.; P. nui (Myers, 1985); P. ponderi sp. nov.; P. poorei sp. nov.; P. rossii (Stephensen, 1927); P. sheardi sp. nov.; P. springthorpei sp. nov.
Remarks. The type taxon of the genus Parambasia, P. forbesii Walker & Scott, 1903, from Abd-el-Kuri, may be part of this species complex, but important diagnostic characters for the taxon are not known and the type material is lost (see Lowry & Stoddart 1995, Barnard & Karaman 1991). Until such time as new material of this species is discovered and a neotype can be designated, the name Parambasia must be treated as dubious. See Lowry and Stoddart (1995) for further remarks.
Pseudambasia differs from other lysianassids by a combination of geniculate antenna 2, no well-developed apical setae on the inner plate of maxilla 1, sexually dimorphic subchelate gnathopod 1 and coalesced urosomites 2–3. It may be related to the highly derived genus Azotostoma (which has peculiar mouthparts and non-coalesced urosomites). Pseudambasia is also similar to Kakanui Lowry and Stoddart (1983), but Kakanui has well-developed apical robust setae on the maxilla 1 palp and free urosomites.
Some species of Pseudambasia have peculiar distolateral tubular stylets on the outer lobes of the labium. These stylets protrude from a duct which opens externally via an apical pore. The role of these structures is unknown but, given their position on the labium, they may play a role in digestion.
Pseudambasia species variously display a strong dark pigment on the head and body (Longenecker & Bolick 2007), which may be sexually dimorphic in some species (see Lowry & Stoddart 1983 for P. rossii). In general, species described from Australia do not show any strong colouration pattern, with the exception of some specimens of P. s h e a rd i sp. nov. from Tasmania.
Key to species of Pseudambasia
Longenecker and Bolick (2007) published a key to the species of Pseudambasia, which was based mainly on body pigment. Here we present an updated morphology-based key to include the species described herein.
1. Uropod 2 inner ramus strongly to slightly constricted........................................................ 5
- Uropod 2 inner ramus not constricted..................................................................... 2
2. Pereopod 7 basis with posteroventral corner rounded........................................................ 3
- Pereopod 7 basis with posteroventral corner excavate................................................. P. ponderi
3. Gnathopod 1 simple (in female). Uropod 3 rami short and stout........................................... P. poorei
- Gnathopod 1 subchelate (in male and female). Uropod 3 rami slender............................................ 4
4. Eyes round. Uropod 3 inner ramus shorter than outer............................................... P. kalaupapa
- Eyes oval. Uropod 3 rami subequal in length................................................... P. springthorpei
5. Epimeron 3 posteroventral corner without notch............................................................ 6
- Epimeron 3 posteroventral corner minutely notched......................................................... 9
6. Gnathopod 2 carpus length greater than 6 × breadth. Telson strongly tapering distally, apically subacute............. P. nu i
- Gnathopod 2 carpus length less than 4 × breadth. Telson distolateral margins subparallel, apically rounded or truncated..... 7
7. Pereopod 7 basis with posteroventral margin excavate................................................... P. rossii
- Pereopod 7 basis with posteroventral margin oblique.......................................................... 8
8. Lateral cephalic lobes broadly rounded. Epimeron 3 posterior margin straight, posterodistal corner subquadrate...... P. lochi
- Lateral cephalic lobes distally truncated. Epimeron 3 posterior margin with small cusp above broadly rounded posterodistal corner......................................................................................... dartnalli
9. Antenna 1 peduncular article 1 without anterodorsal lobe.................................................... 10
- Antenna 1 peduncular article 1 with anterodorsal lobe................................................. P. sheardi
10. Lateral cephalic lobe broadly rounded. Uropod 3 peduncle with dorsolateral flange..................... P. acuticaudata
- Lateral cephalic lobe subquadrate. Uropod 3 peduncle without dorsolateral flange......................... P. indentata
description: Published as part of Kilgallen, N. M. & Lowry, J. K., 2013, The lysianassid genus Pseudambasia in Australian waters (Crustacea, Amphipoda, Lysianassidae, Lysianassinae), pp. 301-321 in Zootaxa 3710 (4) on pages 301-302, DOI: 10.11646/zootaxa.3710.4.1, http://zenodo.org/record/216146