Genus

Diagnosis.

Head with rostrum. Eyes lacking. Antenna 1 longer than antenna 2, slender, accessory flagellum longer than peduncle. Mandible robust, incisor with large tooth laterally; left lacinia mobilis almost smooth distally, right lacinia mobilis absent; molar absent; palp article length 2> 3> 1, article 1 without distal tooth, article 3 not falciform. Maxilla 1 inner plate with one apical seta; palp two-articulate. Maxilla 2 inner plate with long setae on medial margin; outer plate with setae apically. Maxilliped inner and out plates reduced; palp with 4 articles, slender. Coxae shallow; coxa 4 not excavate posteriorly; gills on coxae 2–7; oostegites on pereonites 2–5. Both gnathopods similar, subchelate, palmar margin smooth. Pereopods with simple dactyli: pereopods 5–7 gradually increasing in length. Urosomites 1–2 with dorsomedian teeth. Uropods 1–2 rami with apical robust setae. Uropod 3 biramous and uniarticulate, rami subequal, with apical robust setae, outer ramus with long plumose setae. Telson deeply cleft.

Etymology.

The genus is named in honor of the retired Professor Xianqiu Ren of the Institute of Oceanology, Chinese Academy of Sciences, for his great contributions to Chinese carcinology, combined with the family name Maeridae. The name is masculine in gender.

Remarks.

The family Maeridae Krapp-Schickel, 2008, was distinguished from Melitidae Bousfield, 1973, by the morphology of uropod 3 and originally comprised three clades: the Ceradocus clade, the Elasmopus clade, and the Maera clade (Krapp-Schickel 2008). Subsequently, twenty-two additional genera have been included in Maeridae (e. g., Lowry and Hughes 2009; Lowry and Myers 2013; Corbari and Sorbe 2015; Hughes 2015, 2016; Ariyama 2018; SOSA et al. 2024). Renomaera gen. nov. clearly belongs to Maeridae because its uropod 3 bears subequal rami (Krapp-Schickel 2008).

Within Maeridae, three groups are recognized. The Ceradocus group is characterized by the inner plates of both maxillae being fully setose medially, the inner plate of maxilla 2 being widened and often triangular, the third article of the mandibular palp showing varying degrees of reduction, and the first article typically being distally elongate and pointed, forming a “ knee ” at this articulation (Krapp-Schickel 2009). The Elasmopus group is characterized by well-developed eyes, a notch or slit on the head cheek and a rounded to subacute anteroventral corner, a short to minute accessory flagellum, the third article of the maxillipedal palp with a distomedial flap, coxa 1 produced anteroventrally, pleonites and urosomites without dorsally serrate posterodistal margins, and the rami of uropod 3 never more than twice the length of the peduncle (Lowry and Hughes 2009). The Maera group is characterized by a three-articulate mandibular palp with article 3 straight, the inner plates of both maxillae apically setose, the medial margin of the inner plate of maxilla 2 sometimes bearing distal setae together with apical setae, and the medial margins of the inner plates of maxillae 1–2 often with feeble setae (Ariyama 2018). Renomaera gen. nov. cannot be placed in any of these three groups due to the following characters: eyes absent; head lacking a notch or slit; the inner plate of maxilla 1 bearing only one apical plumose seta, whereas the inner plate of maxilla 2 is strongly setose medially; the first article of the mandibular palp not pointed distally and the third article not falcate; the accessory flagellum elongate; coxa 1 not produced anteroventrally; a gill present on coxa 7; and the telson without apical setae (Krapp-Schickel 2009; Lowry and Hughes 2009; Corbari and Sorbe 2015; Ariyama 2018).

Another fifteen maerid genera were not assigned to the three groups above: Anelasmopus Oliveira, 1953 (monotypic, shallow water), Animoceradocus G. Karaman, 1984 (monotypic, shallow water), Bathyceradocus Pirlot, 1934 (five species, 330–7340 m depth, associated with sunken wood), Ceradocoides Nicholls, 1938 (monotypic, intertidal), Ceradocopsis Schellenberg, 1926 (seven species, shallow water, algal habitats), Coxomaerella G. Karaman, 1981 (monotypic, shallow water), Cuniculomaera Tandberg & Jażdżewska, 2024 (monotypic, 3416 m depth), Elasmopoides Stebbing, 1908 (monotypic, shallow water), Jerbarnia Croker, 1971 (four species, shallow water), Maerella Chevreux, 1911 (four species, shallow water), Metaceradocoides Birstein & N. Vinogradova, 1960 (monotypic, 7210–7230 m depth), Papuadocus Corbari & Sorbe, 2015 (monotypic, 500–580 m depth, associated with sunken wood), Paraceradocus Stebbing, 1899 (six species, shallow water), Pseudelasmopus Ledoyer, 1978 (two species, shallow water), and Wimvadocus Krapp-Schickel & Jarrett, 2000 (monotypic, with the holotype found in cod stomachs) (Stebbing 1908; Oliveira 1953; Birstein and Vinogradova 1960; Croker 1971; G. Karaman 1981, 1984; Andres 1984; Krapp-Schickel and Jarrett 2000; Krapp-Schickel 2008, 2009; Lowry and Hughes 2009; Corbari and Sorbe 2015; Hughes 2015; Ariyama 2018; Ariyama and Moritaki 2020; SOSA et al. 2024). Renomaera gen. nov. differs from all genera occurring in intertidal or shallow-water habitats by the absence of eyes, only the inner plates of maxilla 2 bearing long plumose setae, and the reduced inner and outer plates of the maxilliped (Nicholls 1938; Oliveira 1953; Croker 1971; G. Karaman 1981, 1984; Krapp-Schickel 2008; Hughes 2015).

Similar to the present new genus, species of five other genera – Bathyceradocus, Cuniculomaera, Metaceradocoides, Papuadocus, and Wimvadocus – have been recorded from deep-sea or abyssal environments. Renomaera gen. nov. differs from these genera by the absence of a mandibular molar, the inner plate of maxilla 1 bearing only one apical plumose seta, reduced inner and outer plates of the maxilliped, the presence of a peduncular spur on uropod 1, and long plumose setae present on the inner ramus of uropod 3 (Pirlot 1934; Birstein and Vinogradova 1960; Krapp-Schickel and Jarrett 2000; Corbari and Sorbe 2015; SOSA et al. 2024).

The diagnosis of Maeridae should be amended as follows: mandible molar triturative or absent; uropod 3 inner ramus with or without long plumose setae (after Lowry and Myers 2013; Corbari and Sorbe 2015).