Richerius, Isyeb, 2020

D., Guinot & de, Mazancourt V., 2020, A new freshwater crab of the family Hymenosomatidae MacLeay, 1838 from New Caledonia (Crustacea, Decapoda, Brachyura) and an updated review of the hymenosomatid fauna of New Caledonia, European Journal of Taxonomy 671 (671), pp. 1-29 : 3-4

Genus Richerius gen. nov.

urn:lsid:zoobank.org:act:5B6DC66F-A878-4511-8CF5-06DD245F1896

Type species

Richerius marqueti sp. nov. by present designation.

Diagnosis

Carapace circular to oval, width only slightly exceeding length; dorsal carapace surface not strongly outlined by grooves; only gastrocardiac and thoracic grooves well defined, not reaching antero- and posterolateral margins; carapace rim continuous across behind rostrum. Rostrum broadly rounded, spade-shaped, slightly deflexed but not ending in narrow triangular tip extending between antennules. Proepistome represented by ventral expansion of rostrum (and not rostrum itself). Antennules obliquely folded along hollowed ventral parts of rostrum, entirely hidden dorsally. Antennae well separated from antennules, at least at their bases; urinary article at level of moderately developed epistome. Proepistome represented by ventral expansion of rostrum (and not rostrum itself). Lower orbital margin with one conspicuous knob, not visible dorsally. Mxp3 gaping at level of ischion/merus junction; merus and ischium broad, short, about subequal.

Sternum/pterygostome junction substantially developed due to extension of sternite 4. Milne-Edwards openings separated from chelipeds. Sternites 1 and 2 not separated by suture, with demarcation only visible on lateral margins; sternite 2 separated from sternite 3 by complete suture (suture 2/3); suture 3/4 tiny, only lateral, at level of extension of sternite 4. No longitudinal line. Sternopleonal cavity short, triangular. Pleons in both sexes without fused somites, except 6 fused to telson (pleotelson).

Male pleon widely triangular, regularly widening; pleotelson widely triangular, somewhat trilobed; intercalated plates salient, partially delineated, distinctly visible laterally. Male gonopore sternal. Pressbutton for pleonal-locking mechanism on lateral side of sternopleonal cavity. Female pleon oval, with five free somites plus pleotelson, discoid in ovigerous females with few, large eggs, not carried by pleopods. Vulvae located at level of sternite 6, as normally, thus not deplaced anteriorly. Gonopods stout, filling most of sternopleonal cavity. G1 curved at base, otherwise with little curvature; terminal portion bearing fine setae, terminating in one lobe, without corneous process. Paired branchiosternal canal apertures posterolaterally on sternite 8, concealed.

Male chelipeds much stouter than walking legs; propodus inflated, covered with long soft setae partially extending on fingers; merus and carpus with stiff, regularly spaced setae; fingers not gaping. Female chelipeds narrow, propodus only slighly inflated, devoid of long setae; fingers very elongate and with finely denticulate cutting edges completely joined. Pereiopods in both sexes rather long, with margins bearing stiff, regularly spaced setae.

Etymology

The genus name is in honour of Bertrand Richer de Forges for his lifetime commitment to carcinology, especially of New Caledonia, for having always been an excellent and untiring researcher, and for his friendship.