Hypsimetopidae Nicholls, 1943

Wilson, George D. F. & Reddy, Yenumula Ranga, 2011, Andhracoides shabuddin gen. nov., sp. nov., a new phreatoicidean isopod (Crustacea, Hypsimetopidae) from hypogean aquatic habitats in Andhra Pradesh, India, Zootaxa 2869, pp. 37-53 : 40

Hypsimetopidae Nicholls, 1943

Phreatoicidae .— Sayce, 1902: 218; Sheppard, 1927: 93.

Nichollsidae Tiwari, 1955a: 293 .— Gupta, 1989:14 (part); Knott 1986:486 (part). Hypsimetopinae.— Nicholls, 1943: 130 [subfamily of Amphisopidae ].

Hypsimetopodinae.— Wilson & Keable, 2001: 184.

Hypsimetopodidae .— Wilson & Keable, 2002: 43; Poore et al., 2002: 62; Harvey, 2002: 559; ABRS, 2009. Hypsimetopidae .— Knott 1986: 486 (part); Wilson & Keable, 2004: 741; Wilson, 2008: 303.

Type. Hypsimetopus Sayce, 1902

Genera included. Andhracoides gen. nov.; Hyperoedesipus Nicholls & Milner, 1923 ; Hypsimetopus Sayce, 1902 ; Nichollsia Chopra & Tiwari, 1950 ; Phreatoicoides Sayce, 1900 ; Pilbarophreatoicus Knott & Halse, 1999 .

Diagnosis. Head without tubercles or eyes. Pereon without dorsal ridges or lateral tergal plates. Pleonites with small pleurae, depth in lateral view similar to pereonites depth, basal region of pleopods visible; pleonite 1 pleura near depth pleonites 2–5 pleurae; pleonite 5 dorsally smooth, without ridges or tubercles. Pleotelson dorsal surface smooth, without median or lateral ridges; lateral uropodal ridge absent; lateral length greater than depth, ventral surface anterior to uropods flattened, only slightly concave; postanal ventral surface absent; posterior apex free, not reflexed, without pairs of robust setae. Antennula with more than 6 articles in male (most Phreatoicidea), article 3 secondary flagellum absent, article 4 shorter than article 3. Antennal flagellum proximal articles without dense cover of cuticular hairs. Mandible palp article 3 relatively linear, with more than 5 setae on medial-distal margins, lacking coarsely spinulate setae; incisor processes broad, width greater than thickness; left lacinia mobilis with 3 cusps; right lacinia mobilis well separated and distinct from remainder of spine row; spine rows on projecting ridge between incisor and molar; left and right spine row with first spine not separated from remaining spines. Pereopodal coxae ring-like, without projections. Pereopod I propodus without robust palm; dactylus shorter than propodus. Pereopod IV in male propodus not sexually dimorphic (except in Hyperoedesipus ), without distinct palm, distal width less than midpoint width; basis dorsal ridge not distinctly separated from basis shaft. Pereopod VII basis dorsal ridge distal margin indented. Penes cuticle smooth, lacking setae. Pleopod exopods II–V biarticulate, pleopod I uniarticulate; medial proximal lobes absent; endopods I–V without setae on margins; protopods I–V lateral epipods absent. Uropod protopod dorsomedial ridge medially directed, opposing denticulate posterior margin on pleotelson; protopod ventral ridge without rows of long laterally projecting setae.

Remarks. The above diagnosis is more extensive than previous versions (currently ABRS, 2009) because the implicit characters found in many phreatoicideans (e.g., antennula with more than 6 articles) have been incorporated. The DELTA database from which this diagnosis is derived ( Wilson & Keable, 2004) also is more complete so more detail could be included. The suffixes for the family name have been somewhat unstable, owing to a strict correction to the family name ( Wilson & Keable, 2001, 2002): the Latin genitive of “..isopus” was construed to be “..isopodis” so the family name was changed to Hypsimetopodidae . ICZN (1999) allowed more freedom for the spelling of family names, so the original spelling of Nicholls (1943), which is preferable, has been used subsequently.

Because hypsimetopids dwell in hypogean zones, either deep in caves and aquifers or in surficial habitats like burrows or submerged roots, all species of the family are blind and typically have elongate antennae and thin bodies. Synapomorphies of this family are most evident in features associated with the pleon. Reduced pleonite pleurae expose the pleopods and make them appear substantially large, although the pleopods are not especially larger than in other genera, where they are hidden behind much larger pleurae. The pleotelson varies considerably among the hypsimetopid taxa, but has several consistent features in all: the ventral surface anterior to the uropods is not strongly concave as it is in the other phreatoicideans, the uropodal ridge (extending from the posteroventral margin behind the uropods) is absent, and the terminal margin lacks a reflected tip with the postanal ventral surface being substantially absent. The anus is directly adjacent to posterior margin, which typically consists of the dorsal edge of the anal ring. Many species have denticles or teeth on the posterior pleotelson margin. The uropodal dorsomedial ridge projects medially so that when the uropods are retracted, the protopod opposes the pleotelson margin like a movable finger. This adaptation is most evident in the new genus Andhracoides , where both the uropodal protopod and the pleotelson margin have teeth that interdigitate. In Phreatoicoides , the medial side of the uropodal protopod is furnished with a dense group of digitate setae, and the dorsomedial ridge is reduced to a blunt medially projecting spine. The male pereopod I of all hypsimetopids has a weakly developed propodal palm, unlike other phreatoicideans where it is strongly sexually dimorphic, being inflated, robust, and generally furnished with one or several rows of robust spine-like setae. Andhracoides gen. nov. extends this hypsimetopid trend to having nearly complete absence of sexual dimorphism in the first pereopod, as well as pereopod IV. In other hypsimetopids, however, pereopod I becomes substantially enlarged, with the most modified propodus appearing in Hyperoedesipus .