Thelphusa rotunda Quoy & Gaimard, 1824

Ng, Ngan Kee, Rodríguez Moreno, Paula A., Naruse, Tohru, Guinot, Danièle & Mollaret, Noémy, 2019, Annotated type-catalogue of Brachyura (Crustacea, Decapoda) of the Muséum national d’Histoire naturelle, Paris. Part II. Gecarcinidae and Grapsidae (Thoracotremata, Grapsoidea), with an Appendix of pre- 1900 collectors, Zoosystema 41 (7), pp. 91-130 : 101

Thelphusa rotunda Quoy & Gaimard, 1824

( Fig. 3B )

Thelphusa rotunda Quoy & Gaimard, 1824: 527 , pl. 77, fig. 1.

Cardisoma frontalis H. Milne Edwards, 1853: 170 [204].

CURRENT TAXONOMIC STATUS. — Tuerkayana rotundum ( Quoy & Gaimard, 1824) , see Guinot et al. (2018: 564, 566, table 1).

LECTOTYPE (by present designation). — MNHN-IU-2000-3745 (= MNHN-B3745), ♂ 50.0 × 63.0 mm, Oceania, M. Guérin. — Original label: “ Cardisoma rotundum ( Quoy & Gaimard 1824) , Océanie, M. Guérin ”. Additional labels: “ Cardisoma rotundum ( Quoy & Gaimard 1824) , Type présumé de C. frontalis H. Milne-Edw. (1853) (Holotype), Rev. M. Türkay VI.1972 ”.

PRESERVATION. — Dry. Specimen stuck onto corkboard; carapace cracked on posterior region; two pereopods missing; pleon detached; G1 rehydrated, in alcohol.

REMARKS

The species, described by Quoy & Gaimard (1824: 527, pl. 77, fig. 1) and originating from the banks of rivers in Guam, Mariana Islands, was collected during the Expedition of L. de Freycinet on the Uranie (1817-1820) (see Appendix). Quoy & Gaimard (1824: 527) did not explicitly mention if the taxon was based on a single individual, but their description provides information on the behaviour of several crabs: “ces animaux extrêmement défiants” [“these extremely challenging animals ”], an indication that numerous specimens were probably collected in Guam. “Océanie” is a large area that can include Guam, thus the MNHN specimen such labelled may constitute a part of the type material.

Türkay (1974a: 971, 972; pers comm., Jan. 2013) did not considered any specimen as type of Thelphusa rotunda , assuming the species was a synonym of Cardisoma frontalis H. Milne Edwards, 1853 , and regarded the specimen of Quoy & Gaimard (1824) from Guam as the holotype of C. frontalis , instead of T. rotunda ; Türkay (1974b: 236) confirmed this choice (see Opinion 1205).

In the description of C. frontalis, H. Milne Edwards (1853: 170 [204]) stated that the locality of C. frontalis was not known. Although Davie (2002: 185) mentions under “Type data” of Cardisoma frontalis that “ syntypes ” are most probably deposited at the MNHN, the type material could not be traced in the MNHN collections and may be considered no longer extant. Since the description and illustration of Thelphusa rotunda Quoy & Gaimard, 1824 ( 1824: pl. 77, fig. 1) from Guam in the Mariana Islands (being considered good enough to identify the species) correctly corresponded with Cardisoma frontalis and the identity of the two species was not doubted, Türkay (1974a) judged the designation of a neotype for C. frontalis superfluous. He selected the specimen MNHN-IU-2000-3745 (= MNHN-B3745) labelled “ Cardisoma rotundum ( Quoy & Gaimard 1824) ” as the holotype of Cardisoma frontalis . By that action Türkay (1974b: 234-236, fig. 14) considered Guam the type locality of C. rotundum . But such an act by Türkay (1974a) is unwarranted (see Code, Art. 73.1.3), and the label in question actually concerns the type of Thelphusa rotunda Quoy & Gaimard, 1824 .

The statements that the type of Thelphusa rotunda was ‘in all likelihood’ lost and that Cardisoma frontalis was the junior synonym of C. rotunda are unjustified, with unsatisfactory arguments. Ng & Guinot (2001: 333), regarding Discoplax A. Milne-Edwards, 1867 as a distinct genus (see Guinot 1988, 1994), treated Cardisoma frontalis as the junior synonym of Discoplax rotunda . Even though the two species are synonymous, the specimen of Quoy & Gaimard (1824) from Guam is not the type of C. frontalis but, instead, that of Tuerkayana rotundum ( Quoy & Gaimard, 1824) . The MNHN specimen labelled “Océanie” and regarded as the holotype of C. frontalis by Türkay (1974a, b) is eligible to be designated as the lectotype of Tuerkayana rotundum ( Quoy & Gaimard, 1824) , see Guinot et al. (2018).

Figures

FIG. 3. — A, Pelocarcinus marchei A. Milne-Edwards, 1890, MNHN-IU-2000-3752 (= MNHN-B3752), lectotype, ♂; B, Thelphusa rotunda Quoy & Gaimard, 1824, MNHN-IU-2000-3745 (= MNHN-B3745), lectotype, ♂; C, Grapsus brevipes H. Milne Edwards, 1853, MNHN-IU-2000-10978 (= MNHN-B10978), lectotype, ♂; D, Grapsus cruentatus Latreille, 1803, MNHN-IU-2000-3407 (= MNHN-B3407), neotype, ♂; E, Grapsus fourmanoiri Crosnier, 1965, MNHN-IU-2008-10635 (= MNHN-B11803), lectotype, ♂; F, Grapsus gracilipes H. Milne Edwards, 1853, MNHN-IU-2000-3411 (= MNHN-B3411), lectotype, ♂; G, Grapsus granulosus H. Milne Edwards,1853,MNHN-IU-2000-3417 (= MNHN-B3417),lectotype,♂; H, Grapsus grayi H. Milne Edwards,1853,MNHN-IU-2000-3421 (= MNHN-B3421), lectotype, ♀. Scale bars: A-D, F, H, 2 cm; E, 10 mm; G, 5 cm.