Parvonotus samoensis, Davie & Ng, 2024

Davie, Peter J. F. & Ng, Ngan Kee, 2024, A new genus for the small shore crab previously known as Brachynotus spinosus (H. Milne Edwards, 1853) (Crustacea: Brachyura: Varunidae), with two new species from southern Australia and Samoa, Zootaxa 5476 (1), pp. 66-81 : 74-78

publication ID	https://doi.org/ 10.11646/zootaxa.5476.1.9
publication LSID	lsid:zoobank.org:pub:4E13F9E5-77F5-4DAE-88EC-2320FD3860BE
DOI	https://doi.org/10.5281/zenodo.12681541
persistent identifier	https://treatment.plazi.org/id/266887C1-FFD7-B80F-5CBA-96E2FF6554FA
treatment provided by	Plazi
scientific name	Parvonotus samoensis
status	sp. nov.

Treatment

Parvonotus samoensis sp. nov.

( Figs 5 View FIGURE 5 , 6A, C, F, H, J View FIGURE 6 , 7C, D View FIGURE 7 , 8 View FIGURE 8 )

Heterograpsus spinosus View in CoL . — Kingsley 1880: 210 [in list, specimens from Upolu].—de Man 1891: 56–58, pl. 4, fig. 15.

Type material. Holotype: RMNH. CRUS.D.1219, male (11.5 × 10.3 mm), Upolu, Samoa, western Polynesia , SW Pacific Ocean . Paratype: RMNH exCRUS.D.1219, female (14.0 × 11.7 mm), same data as holotype .

Diagnosis. Small species (<15 mm cb). Carapace subquadrate, slightly broader than long (1.12–1.19 ×), moderately convex transversely and longitudinally, especially in the female, surface smooth but uneven, regions moderately well-defined, cervical groove clearly marked. Anterolateral margins moderately divergent posteriorly (greatest cb c. 1.12–1.15 × exorbital width); 4 anterolateral teeth, exorbital tooth large, outer margin convex, second tooth smaller but prominent, anteriorly projecting, third tooth smallest, similar shape to second; last tooth slightly larger similar shape, anteriorly pointed; greatest carapace breadth at last tooth. Crest marking posterolateral carapace facet runs from tip of last tooth to just above base of last leg. Front broad, deflexed, straight, without obvious lobes. Postorbital lobes prominent, broad, straight to slightly convex in dorsal view ( Figs. 5A–F View FIGURE 5 , 7D View FIGURE 7 ); almost confluent with lateral inner orbital lobes, being separated by only shallow depression. Infra-orbital ridge finely granulate ( Fig. 5B View FIGURE 5 ).

Chelipeds subequal, homochelous. Male chelae moderately enlarged; smooth; fingers with only slight gape when closed; smooth on outer face, with patch of short, matted setae at base of fingers on inner and outer surfaces ( Fig. 5G, H View FIGURE 5 ). Chelae of female more slender, lacking setal patch at base of gape ( Fig. 5E View FIGURE 5 ). P2–P5 flattened, ventral margin of merus, carpus and propodus narrowly emarginate ( Fig. 6F View FIGURE 6 ); meri with strong anterior sub-distal spine. Males with tuft of short setae on distal half of posterior edge of propodus of P2 and P3 ( Fig. 5B View FIGURE 5 ), absent in female. P4 propodus c.2.8 × longer than wide. P5 propodus c.1.8 × longer than wide.

Pleon with six somites plus telson; male pleon ( Figs. 1B View FIGURE 1 , 6I, K View FIGURE 6 ) widest towards distal edge of laterally convex third somite; following somites evenly tapering; somite 6, c. 2.8 times wider than long ( Fig. 6H, J View FIGURE 6 ); distal edge of sixth narrowing to meet telson, telson narrower than sixth, c. 1.4 times wider than long, apically rounded; fifth somite moderately concave laterally. Female pleon ( Fig. 5E View FIGURE 5 ) very broad, rounded. Female gonopore and male G1 unavailable for examination.

Remarks. De Man (1891) reported on a young male (11.5 × 10.3 mm) and an ovigerous female (14.0 × 11.7 mm) from Samoa in the collections of the Nationaal Natuurhistorisch Museum, Leiden (apparently originally acquired from the Museum Godeffroy according to the label in the jar) (see Fig. 5I View FIGURE 5 ). He also examined an Australian male specimen (15.8 × 13.3 mm) as part of his examination. His published figures ( Figs 5G View FIGURE 5 , 7C View FIGURE 7 ), however, are both of the Samoan specimens—the main figure of the crab in dorsal view is of the ovigerous female ( Fig. 7C, D View FIGURE 7 ), and the detail of the claw ( Fig. 5G View FIGURE 5 ) is from the young male.

De Man (1891: 58) wrongfully stated that he had measured ‘… a male type-specimen from Australia of the Paris Museum.’ In fact, A. Milne-Edwards (1873b) had already said that the sole type specimen described by H. Milne Edwards (1852) from Vanikoro was a female, but that he had also examined numerous specimens from Australia in the Museum Godeffroy that he had referred to Heterograpsus spinosus . In the MNHN there ae two Australian specimens from Port Phillip, Victoria (IU-2013-14772) and it may have been one of these that de Man had referred to and mistaken for a ‘type-specimen’. In all likelihood, those two specimens were donated to the Paris Museum from the Museum Godeffroy at the time of A. Milne-Edwards’ study, especially given the fact that there were “numerous specimens” available. The bulk of the Godeffroy material is still likely to be present in the Zoological Museum of Hamburg, which purchased the collection in 1886, after the privately owned Museum Godeffroy museum had gone into liquidation ( Fransen et al. 1997: 267).

Distribution. So far only known from the type specimens from Upolu, Samoa, western Polynesia (de Man, 1891), about 2300 km to the south-east of type locality of Parvonotus spinosus (H. Milne Edwards, 1853) , comb. nov.