Raoulia Ng, 1987

Ng, Peter K. L. & Rahayu, Dwi Listyo, 2014, Revision of the family Acidopsidae Števčić, 2005, and the systematic position of Typhlocarcinodes Alcock, 1900, Caecopilumnus Borradaile, 1902, and Raoulia Ng, 1987, with descriptions of two new genera and five new species (Crustacea: Brachyura: Goneplacoidea), Zootaxa 3773 (1), pp. 1-63 : 21-23

publication ID	https://doi.org/ 10.11646/zootaxa.3773.1.1
publication LSID	lsid:zoobank.org:pub:19F28753-B2D0-4D1F-9D47-88886F7333FD
DOI	https://doi.org/10.5281/zenodo.5047762
persistent identifier	https://treatment.plazi.org/id/03E287AE-5451-E22D-8A9D-42ACFEF80DB9
treatment provided by	Felipe
scientific name	Raoulia Ng, 1987
status

Treatment

Raoulia Ng, 1987

Raoulia Ng, 1987: 93 .— Ng et al. 2008: 76 (part).

Diagnosis. Carapace subovate ( Figs. 13A View FIGURE 13 ); dorsal surfaces mostly smooth; regions poorly defined, grooves very shallow; front entire, slightly produced, bent downwards; margin granular, lined with numerous long setae obscuring margin; anterolateral margins prominently arcuate, subcristate (to anterior part of posterolateral margin), granular, without lobes or teeth, lined with numerous long setae; anterolateral margins not distinctly separated from subparallel posterolateral margins. Epistome narrow, prominently sunken. Basal antennal 3 quadrate; article 4 dorsoventrally flattened, twice as long as broad, lateral margins with numerous long plumose setae ( Fig. 6C View FIGURE 6 ). Basal antennular article subrectangular ( Fig. 6C View FIGURE 6 ); antennules folding almost vertically. Eyes immobile, pear-shaped, tapering towards small cornea, cornea partially or completely pigmented. Third maxillipeds relatively short, covering buccal cavern when closed; merus semicircular, anterolateral angle rounded; exopod narrow with long flagellum ( Figs. 5C View FIGURE 5 , 14B View FIGURE 14 ). Outer surface of palm with small granules, rugose or smooth. Propodus, dactylus of last ambulatory leg long. Male thoracic sternum wide ( Figs. 14B View FIGURE 14 , 15B View FIGURE 15 ), st1, st2 completely fused to form triangular plate, st3, 4 fused with only lateral sutures discernible; sterno-abdominal cavity reaching to imaginary line joining posterior third of coxae of chelipeds; penis sits partially exposed between narrow gap between most length of st7, 8, outer part of st7, st8 appressed, covering penis; large part of st8 exposed when abdomen closed, broadly rectangular in shape ( Fig. 14D View FIGURE 14 ); press-button mechanism for holding male abdomen present as small rounded tubercle on anterior third of st5. Male abdomen with a1 reaching cx5 ( Fig. 1G View FIGURE 1 ), lateral parts tapering to sharp edge, somite appearing subtriangular; lateral margin of a3 produced, forming triangular structure; a3–5 fused, with only edges of sutures visible. Gl relatively stout basally, tapering to slender distal half, distal surfaces with scattered spinules; G2 as long as or longer than G1, distal segment ca. half length of proximal segment.

Remarks. In establishing the genus, Ng (1987) did not make it explicit that the type species was a new species, R. limosa Ng, 1987 . His discussion is somewhat confusing as he was arguing that the material identified as “ Typhlocarcinodes piroculatus ” by Serène (1964) was actually not the species described as Typhlocarcinops piroculata Rathbun, 1911 . As such, he referred Serène’s (1964) “ Typhlocarcinodes piroculatus ” to new species, Raoulia limosa . He nevertheless identified the type species of Raoulia as “ Typhlocarcinodes piroculatus Serène, 1964 (not Typhlocarcinops piroculatus Rathbun, 1911 )” ( Ng 1987: 93). To make things clear, Ng et al. (2008: 76) fixed the type species of Raoulia Ng, 1987 , as Raoulia limosa Ng, 1987 .

Superficially, at least in dorsal view, Raoulia is similar to Caecopilumnus Borradaile, 1902 , and Typhlocarcinodes Alcock, 1900 ; sharing a general carapace shape, the presence of long setae on the carapace and pereopods, and a reduced eye that is fused to the carapace (see Manning & Holthuis 1981: 165; Ng 1987: 91–93). The confusion was not made clear by the figure of Typhlocarcinodes integrifrons by Miers (1881), which is somewhat schematic (see discussion below for the species). Tesch (1918: 227) argued that Caecopilumnus was synonymous with Typhlocarcinodes , noting there were no major differences:

“With the preceding genus [ Scalopidia ] the present one [ Typhlocarcinodes ] is distinguished by the epistome being sunken, not at all prominent, so that the external maxillipeds nearly encroach upon the antennules, which latter are very minute, and directed almost longitudinally. The merus of the external maxillipeds is almost circular, distinctly smaller than the ischium, the palp is weak and short, inserted at the antero-internal angle of the merus and the exognath is very narrow, between one-third and one-fourth the breadth of the ischium. Eyes are not or scarcely visible and their peduncles are firmly fixed. The type species is the Atlantic T. integrifrons (Miers 1), which in two essential features differs from the three species of the "Siboga": firstly the flagellum of the antennules of Miers' species is multi-articulate, hairy and 1onger than the peduncle, whereas in the Indian specimens this flagellum is shorter than the peduncle, almost completely hairless, and made up of very few (5—6) joints; secondly in T. integrifrons the abdomen does not entirely cover the last sternal segment, but in my specimens it touches the bases of the last pair of legs 2)” ( Tesch 1918: 227).

Miers (1881) description of Typhlocarcinus integrifrons is relatively simple and does not mention the sunken epistome, rounded third maxilliped merus or fused eyes. Tesch (1918) almost certainly deduced this from Alcock’s (1900) comments when he decided to establish a new genus, Typhlocarcinodes for Miers’ species, which he had identified as T. integrifrons , on the basis of a damaged specimen he had from the Indian Museum collected from “Indian Seas.” Alcock (1900: 326) wrote: “Carapace moderately deep, shaped much as in Typhlocarcinus , but slightly more elongate, the free edges hairy. Fronto-orbital border about three-fifths, front about a third, the greatest breadth of the carapace: front prominent, its free edge convex and entire. Orbits in the normal position, narrow, button-hole shaped; eye-stalks tapering, immovable; eyes obsolete or nearly so. Antennules cramped, folding very obliquely—nearly longitudinally —in proper pits. Antennal penduncle small and cramped, the flagellum standing in the orbital hiatus. Epistome sunken, linear: buccal cavern square, its anterior angles, like the antero-external angles of the merus of the external maxillipeds, rounded off: the external maxillipeds completely close the buccal cavern and have the flagellum articulated to the antero-internal angle of the merus. The abdomen does not nearly occupy all the space between the last pair of legs.”

Alcock’s (1900) account is noteworthy because his description of “ Typhlocarcinodes ” actually agrees very well with what is here defined as Caecopilumnus , including the arrangement of the abdomen, even though he did not give the sex of his specimen. In Raoulia , the thoracic sternum is wide and the abdomen (even the female one) is relatively narrow. In Caecopilumnus , because the thoracic sternum is relatively narrower than Raoulia , the abdomen fills more of the sternal space between the last pair of ambulatory legs. Almost certainly, Alcock’s (1900) specimen belongs to what is here recognised as Caecopilumnus . Takeda (1973) and Takeda & Shimazaki (1974) questioned Tesch’s recognition of the West African Typhlocarcinus integrifrons Miers, 1881 , as the type species of Typhlocarcinodes Alcock, 1900 , suggesting that the Indo-West Pacific taxa (including Alcock’s specimen of “ Typhlocarcinodes integrifrons ”) are not congeneric with the African one. In any case, as summarised by Manning & Holthuis (1981: 165), the type species of Typhlocarcinodes Alcock, 1900 , is Typhlocarcinus integrifrons Miers, 1881 , as fixed by Tesch (1918: 227). Ng (1987: 92), acting on the type species designation by Tesch (1918), and the views of Takeda (1973) and Takeda & Shimazaki (1974), decided to refer all the Indo-West Pacific species of Typhlocarcinodes to Caecopilumnus (see Ng et al. 2008).

The present material clarifies the systematic position of Raoulia , Caecopilumnus and Typhlocarcinodes . They can easily be distinguished by the structures of their carapaces, eyes, thoracic sterna, male abdomens and gonopods (see key to genera).