Metapseudinae Lang, 1970

Heard, Richard W., Stępień, Anna, Drumm, David T., Błażewicz, Magdalena & Anderson, Gary, 2018, Systematic and taxonomic observations on the subfamily Synapseudinae Guţu, 1972 and related metapseudid taxa (Crustacea: Tanaidacea: Apseudomorpha), with the erection of a new genus and descriptions of three new species, Zootaxa 4370 (4), pp. 301-344 : 308-311

Subfamily Metapseudinae Lang, 1970

Diagnosis (modified from Guţu 1996). Body usually dorsoventrally flattened; pleon with five free, partially fused, or fused pleonites. Antennule peduncle usually with apophyses or spinose processes; inner flagellum with two or more articles, outer flagella with three or more articles. Antenna with squama usually present; peduncle having four or five articles with apophyses; flagellum with three or more articles. Cheliped with short carpus and large propodus; exopod present or absent; pereopod-1 with or without exopod; dactylus of pereopods 4–6 with ventral apophysis. Pleopods in two to five pairs in male, usually reduced; in female present or absent. Sexual dimorphism expressed in chelipeds, pleopods, and antennules.

Type species. Metapseudes aucklandiae Stephensen, 1927 .

Other genera included: Apseudomorpha ; Cryptapseudes ; Cyclopoapseudes ; Labraxeudes Błażewicz- Paszkowycz & Bamber, 2007; Metapseudes ; Plectrocopus Guţu, 2006 ; Pseudoapseudomorpha Guţu, 1991 ; Ronabus n. gen. (see below).

Remarks. Metapseudes and Ronabus n. gen. are the only members of the Metapseudinae that lack an antennal squama. The other genera have retained the squama and some have exopods on the cheliped and pereopod-1. When present, pleopods occurring on members of the subfamily are weakly developed with few setae.

Ronabus Stępień, Drumm and Heard, n. gen.

Synonymy. Synapseudes Gardiner, 1973 (in part).

Etymology. Abbreviation for Roger Norman Bamber = ronab + us. Named in honor of the late Roger N. Bamber in recognition of his expertise and many contributions to our knowledge of the arthropod classes Pycnogonida and Malacostraca, especially the Tanaidacea .

Gender: male.

Type species. Synapseudes idios Gardiner, 1973 .

Species included

Diagnosis. Body about 3 mm long, about 5.7 times as long as wide; strongly calcified. Cephalothorax length twice that of antennular peduncle article-1. Pleon functionally fused, but with dorsal surface showing vestiges of five pleonites, pleonite-1 and usually pleonite-2, distinctly indicated both dorsally and ventrally, pleonites 3–5 reduced and only indicated dorsally. Antennular peduncle article-1 having inner row tubercles, article-2 with apophyses on outer and inner distal margins; inner flagellum with two articles and outer flagellum with three. Antenna with seven articles, apparently four peduncular and three flagella. Mandibular palp triarticulate, with articles 1–2 each having single seta, article-3 with five or six terminal setae, largest distally serrate. Cheliped without exopod. Pereopod-1 without exopod. Pleopods, one reduced pair, either uniramous or biramous, usually present on pleonite-1. Uropodal exopod with three articles, endopod with four.

Remarks. Ronabus n. gen. appears to be transitional between the subfamilies Synapseudinae and Metapseudinae . Because it lacks an antennal squama and exopods on the cheliped and pereopod-1, the new genus cannot be included among the more plesiomorphic members of the Chondropodinae . Ronabus can no longer be accommodated within the Synapseudinae as defined here, since its members exhibit more highly derived characters (e.g., complete fusion of at least the last four pleonites with telson, reduced setation of the mandibular palp, one or two articles in the antennal flagellum, and complete absence of pleopods). The genus does, however, appear to have affinities to Metapseudes , which also lacks an antennal squama and has pleopods.

In addition to the partial fusion of the pleon and presence of single pair of uniramous or biramous pleopods on pleonite-1 ( Fig. 3I –K ), Ronabus differs further from Metapseudes (see Fig. 3A, C , E-H) by having (1) an antenna composed of seven articles ( Fig. 3B ), (2), mandibular palp with distal article having several terminal setae, including at least two being distally serrate ( Fig. 3D ), and (3) the uropodal endopod composed of three articles ( Fig. 3L ). In Metapseudes , article-3 of the mandibular palp lacks terminal serrate setae ( Fig. 3C ), and the antenna ( Fig. 3A ) and uropodal endopod ( Fig. 3H ) resemble those of Synapseudes (see Fig. 4G, N ).

Characters such as the absence of an antennal squama and chelipedal and pereopod-1 exopods, as well as other characters shared by Ronabus and Metapseudes , may eventually warrant a systematic re-evaluation of the Metapseudinae . Pending future study, we place Ronabus within the Metapseudinae .

Figures

FIGURE 3. Metapseudes wilsoni. A, antenna; C, right mandible with palp; H, uropod, endopod biarticulate. Metapseudes aucklandiae. E, abdomen, pleonites completely delineated (five pairs of biramous pleopods not illustrated); F, biramous pleopod with terminal setulate setae; G, pleonites 4–5 and pleotelson, dorsal aspect. Ronabus idios. B, antenna; D, left mandible with palp.I, male pleon and pleotelson, lateral aspect,showing partially fused pleonites1–5 and biramous pleopod-1; J, female, uniramous pleopod-1; K, partially fused pleonites and pleotelson, dorsal aspect; L, uropod, endopod triarticulate. A, C, H from Błażewicz-Paszkowycz & Bamber (2007); B, D–G, I–L from, or modified from, Gardiner (1973).

FIGURE 4. Some atypical species of Synapseudes. Synapseudes aflagellatus: A, antennule; B, antenna; C, maxilla; D, pereopod-1. Synapseudes mediterraneus: E, antennule; F, antenna; G, pleon and pleotelson, dorsal aspect; H, pleon andpleotelson, lateral aspect. Synapseudes shiinoi: I, antennule; J, right mandible with palp terminating in multiple setae. Synapseudes acroporae. K, carapace with lateral setulate setae and minute setae covering surface; L, pereonite-6, pleon and pleotelson, lateral aspect, showing same types of setation; M, chela of female with spiniform setae on mid-proximal region of propodus. Synapseudes violaceus: N, uropod with endopod bearing long setulate terminal seta. A–D modified from Sieg (1986); E–H; modified after Băcescu (1977); I–Jmodified from Riggio (1977); K–N modified from Băcescu (1976).