Papuadocus, Corbari, Laure & Sorbe, Jean Claude, 2015

Corbari, Laure & Sorbe, Jean Claude, 2015, Papuadocus blodiwai gen. nov., sp. nov. (Crustacea: Amphipoda: Maeridae), a new bathyal species associated with sunken wood in the Bismarck Sea (Papua New Guinea), Zootaxa 3914 (4), pp. 406-420 : 408-409

Genus Papuadocus gen. nov.

Diagnosis. Head lacking rostrum. Eyes lacking. Antennae unequal, slender; accessory flagellum long, shorter than peduncle. Mandible robust, incisor dentate; left lacinia mobilis distally dentate and bigger than the right one; molar very well developed; palp article 3 falciform. Maxilla 1 with inner plate medially setose; left and right palps not symmetrical. Maxilla 2 inner plate with oblique setal row near mesial margin. Maxilliped inner plate long, with three or four apical teeth; palp robust, article 4 stout and inserted subdistally on article 3. Gnathopod 1 small, subchelate, with transverse palm. Gnathopod 2 larger and longer, subchelate, palmar margin multidentate, not sexually dimorphic. Pereopods 5–7 gradually increasing in length. Coxa 4 slightly concave posteriorly, clearly higher than coxa 5, posterodistal corner slightly produced. Urosome 1–2 with dorsolateral teeth. Uropods 1–2 rami with stout apical setae. Uropod 3 biramous and uniarticulate, rami subequal, distally dentate and setose. Telson deeply cleft, with two lateral setae near outer margin. Gills on coxae 2–6. Oostegites on pereonites 2–5.

Etymology. Named after the geographical region where the specimens were collected, Papua New Guinea.

Remarks on genus assignation and Maeridae diagnosis. Following Barnard & Barnard (1983), Krapp- Schickel (2008) distinguished the Ceradocus-Maera-Elasmopus group (the 'ceradocid' complex containing the three oldest genera of this group), leading to the creation of the family Maeridae on the basis of uropod 3 structure (subequal rami versus unequal rami in Melitidae ). In Table 1, the BS specimens ( Papuadocus gen. nov.) are compared with these three first described genera, using genus diagnoses found in the literature (references in Table 1) as well as selected diagnostic characters given by Lowry & Myers (2013) for Maeridae . The new genus shares most of these maerid diagnostic characters with the other genera (leading to its assignment to Maeridae ), except for maxillas 1 with asymmetrical right and left palps and gnathopods 2 without sexual dimorphism. As shown in Table 1, the asymmetry of maxilla 1 palps is a distinguishing character shared with the genus Bathyceradocus , (see original genus diagnosis in Pirlot 1934 for B. stephenseni ; genus assigned to Maeridae by Krapp-Schickel 2008 and Lowry & Myers 2013), a morphological feature confirmed in subsequent descriptions of new species ( B. iberiensis in Andres 1977; B. wuzzae in Larsen & Krapp-Schickel 2007). However, the BS specimens cannot be assigned to genus Bathyceradocus due to the absence of gill on coxae 7 (present in Bathyceradocus ), a morphological feature shared with all other maerid genera (see Lowry & Myers 2013). Lowry & Myers (2013) overlooked this distinguishing feature (gill on coxae 7) in their diagnosis of Maeridae , although mentioned for all known Bathyceradocus species ( B. stephenseni in Pirlot 1934; B. iberiensis in Andres 1977; B. wuzzae in Larsen & Krapp- Schickel 2007). In accordance with the preceding genus comparisons, we conclude that the BS specimens belong to Maeridae and show a close morphological as well as genetic and ecological affinity to genus Bathyceradocus (see below). Accordingly, we propose to create the new genus Papuadocus for the BS specimens and to amend the Lowry & Myers’s diagnosis in order to maintain both genera Bathyceradocus and Papuadocus gen. nov. in Maeridae .

Amended diagnosis of Maeridae (after Lowry & Myers 2013). Body laterally compressed or subcylindrical. Eyes well developed or absent, if present then round, ovoid, reniform, lageniform or subrectangular. Antennae 1–2 calceoli absent. Antenna 1 subequal in length to, or longer than antenna 2; peduncular article 1 shorter than, subequal to, or longer than article 2; article 2 longer than article 3; article 3 shorter than article 1; peduncular articles 1–2 not geniculate; accessory flagellum long, short or minute. Antenna 2 peduncular article 1 not enlarged. Mandible molar triturative; palp symmetrical or absent. Maxilla 1 basal endite setose along medial margin or apically setose; palps symmetrical (most maerid genera) or asymmetrical (genera Bathyceradocus and Papuadocus gen. nov.). Maxilla 2 basal endite with or without oblique setal row. Labium inner lobes present, vestigial or absent. Coxal gills on pereopods 2–6 (most maerid genera, including Papuadocus gen. nov.) or on pereopods 2–7 (genus Bathyceradocus ), not stalked; sternal gills absent; sternal blisters absent; oostegites fringing setae simple. Gnathopod 1 subchelate, not sexually dimorphic; smaller (or weaker) than or similar in size to gnathopod 2; propodus palm without robust setae along palmar margin. Gnathopod 2 subchelate; sexually dimorphic (most maerid genera) or not ( Papuadocus gen. nov.); carpus not produced along posterior margin of propodus, projecting between merus and propodus. Pereopods 3–4 not sexually dimorphic. Pereopod 4 with welldeveloped posteroventral lobe or with small posteroventral lobe or without posteroventral lobe. Pereopod 5 shorter TABLE 1. Morphological comparison of maerid genera belonging to the Ceradocus - Maera - Elasmopus group (see Krapp-Schickel 2008), according to published diagnoses (1: Karaman 1982; 2: Vader & Krapp-Schickel 2012; 3: Barnard & Barnard 1983; 4: Krapp-Schickel 2008; 5: Krapp-Schickel & Vader 2009; 6: Pirlot 1934; 7: Larsen & Krapp-Schickel 2007; 8: Dahl 1959). The underlined characters are those which differ from the diagnosis given by Lowry and Myers (2013) for Maeridae .

……continued on the next page than or subequal in length to pereopod 6; coxa with posteroventral lobe or with large anteroventral lobe or with small anteroventral lobe or without lobes. Pereopod 7 subequal in length to, or longer than pereopod 5. Pleonites 1–3 without dorsal carina. Urosomites 1–3 free; with or without slender or robust dorsal setae. Urosomite 1 without large distoventral robust seta. Urosomite 2 with pair of dorsal concavities, each with 1–3 small setae or without dorsal setae. Uropod 1 with 1 or 2 basofacial robust setae or without basofacial robust setae. Uropod 3 sexually dimorphic or not; biramous, without plumose setae; endopod shorter than or subequal to exopod. Telson deeply cleft to entire; dorsal or lateral robust setae present or absent; apical robust setae present or absent.