Sebadexius Ledoyer, 1984

Just, Jean, 2018, Review of Sebadexius Ledoyer, 1984 (Amphipoda, Dexaminidae, Dexamininae) based on new material from The Philippines, with Sebadexius cebuense sp. nov., Zootaxa 4500 (4), pp. 596-600 : 597

Sebadexius Ledoyer, 1984

Sebadexius Ledoyer, 1984 .— Barnard and Karaman, 1991: 272.

Sebadexius Ledoyer, 1984 .— Bousfield and Kendall, 1994: 37, (in key to Dexamininae).

Type species. Sebadexius neocaledoniensis Ledoyer, 1984 , original designation.

Additional species. Sebadexius cebuense sp. nov.

Diagnosis. Revised diagnosis (based on females only). Dexamininae with elongate, chelate gnathopods; mandibles without palp, molar triturative; maxilla 1 palp of single article; reduced maxilliped palp 4-articulate, as long as outer plate; antenna 1 short; antenna 2 shorter than 1, strongly reduced; pleonites with low middorsal carina, pleonites 2 and 3 tridentate; urosomites 2 and 3 fused; telson twice as long as proximal width, split nearly to base, each lobe with apical robust seta, lateral margins with row of robust setae and a few simple setae; gills and oostegites on pereonites 2–7.

Remarks. In his diagnosis of Sebadexius in French Ledoyer admitted of some uncertainties, especially regarding the mandible palp and the telson. He was correct in stating the mandible lacked a palp. For the telson, on the other hand, he wrote ‘telson fendu’ meaning ‘telson split’. In the description, he used the word ‘carrée’ about the telson, meaning ‘somewhat rectangular’, but he expressed doubt about this interpretation. Comparing Ledoyer’s fig. 26Tel with S. cebuense sp. nov. ( Fig.1 ) it seems clear that what Ledoyer thought might be the telson is in fact a dorsal view of urosomite 3; the ‘split’ being the line of the low but sharp dorsal carina. Some doubt also exists about the shape of the basis of pereopods 5 and 6, and apart from gnathopods 1 and 2, only pereopod 7 is drawn in full. The remaining parts of his diagnosis, mainly concerning mouthparts, gnathopods and uropods are correct.

Barnard and Karaman (1991: 272) provided the only subsequent diagnosis of Sebadexius . In addition to adding the pointed eye lobes and the feebly tridentate posterior body segments they mention only the mouthparts as given by Ledoyer. In the accompanying brief description Barnard and Karaman mention the chelate gnathopods and follow Ledoyer in describing the telson as ‘short, deeply cleft’. They further write ‘Antennae elongate, thin.’, an interpretation which is not substantiated by Ledoyer’s description or illustrations and is not borne out by the new specimen (see Fig. 1 ).

Barnard and Karaman (1991) placed Sebadexius within their broad concept of the Dexamininae together with 13 other genera. Bousfield and Kendall (1994) restricted Dexamininae to six genera including Sebadexius .

In providing a revised diagnosis for Sebadexius I follow Bousfield and Kendall’s (1994) concept of the Dexamininae.

Figures

FIGURE 1. Sebadexius cebuense sp. nov. Holotype, female. 1, 2, 3, antenna 2 peduncle articles 1–3; ll, lower lip; md, mandible; mp, maxilliped; mx1–2, maxilla 1 and 2; gp 1–2, gnathopods 1 and 2; ul, upper lip; us, urosome. Habitus scale: 0.5 mm.