Rochinia A. Milne-Edwards 1875
Creators: name: Ng, Peter K. L.
name: Forges, Bertrand Richer De
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Epialtidae
Rochinia

description: Genus Rochinia A. Milne-Edwards, 1875
Type species. Rochinia gracilipes A. Milne-Edwards, 1875, by monotypy. Gender of genus feminine.
Remarks. Rochinia is a large genus, with 38 recognised species from the Atlantic and Indo-West Pacific (modified from Ng et al. 2008; Richer de Forges & Ng 2013). Many authors (e.g., Ng & Richer de Forges 2007; Richer de Forges & Ng 2009a, b, 2013; Richer de Forges & Poore 2008) have argued that the genus is heterogeneous, but splitting it into discrete groups has proved difficult. A precise definition for the genus has also proven to be difficult, with the diagnosis given in Griffin & Tranter (1986: 174) no longer accurate. In the years since, authors have removed Sphenocarcinus A. Milne-Edwards, 1875, and Oxypleurodon Miers, 1885, from its synonymy (see Richer de Forges 2009a for discussion); and Sakai (1986) established a new genus, Goniopugettia, for one Japanese species. Richer de Forges & Ng (2009b) also separated two very unusual species, R. nodosa (Rathbun, 1916) and R. carinata Griffin & Tranter, 1986, into a new genus, Laubierinia.
Of the remaining species, several groups of Rochinia that can be recognised, and they can be briefly diagnosed as follows. Adults of Rochinia s. str. (type species R. gracilipes A. Milne-Edwards, 1875, and R. carpenteri (Thompson, 1873)) have raised and distinct carapace regions, and may be covered by large tubercles or spines with the rest of the surface smooth, the anterior male thoracic sternum is transversely broad and the male abdomen acutely triangular to T-shaped (Fig. 5 A, B). A second group has relatively distinct carapace regions, with the surfaces smooth but the lateral branchial spine is low or even absent (e.g., R. brevirostris (Doflein, 1904)), and these species have a transversely broad male anterior thoracic sternum with a triangular or T-shaped male abdomen (Fig. 5 C). A third group contains species that have numerous sharp spines on the prominent carapace regions (e.g., R. pulchra (Miers, 1885)), and the constituent species have relatively more transversely narrow anterior male thoracic sternum, with sternite 4 anteriorly constricted and their male abdomens are acutely triangular or T-shaped (Fig. 5 D). A fourth group of species has prominent lateral branchial spines with some tubercles on the carapace regions but otherwise smooth (e.g., R. kotakae Takeda, 2001), and while their male anterior thoracic sternums are transversely narrow with sternite 4 constricted, their male abdomens are acutely triangular (Fig. 5 E). A fifth group (e.g., R. fultoni (Grant, 1905)) has more elongated carapaces with distinct carapace regions and several sharp tubercles, and the male anterior thoracic sternum is transversely narrow and sternite 4 constricted, the male abdomen being acutely triangular (Fig. 5 F). Until all or most of the species are redescribed or re-examined, establishing new genera for each of these groups seems premature, especially because some characters may vary between species.
Samadinia longispina n. gen., n. sp. is characterised by having a poorly defined regions of the dorsal surface of the carapace and by being covered with numerous small, rounded granules (Figs. 1 A, 3A) (covered with large spines and/or sharp tubercles in Rochinia sensu lato); the hepatic and lateral branchial spines are long, sharp and directed laterally (Figs. 1 A, 3A) (carapace regions also with long spines in Rochinia sensu lato when this spines are long); the male anterior thoracic sternum is transversely conspicuously narrow, with sternite 4 strongly constricted anteriorly, with the anterolateral margins almost parallel and the median lateral margins strongly convex, forming a distinct structure (Fig. 2 A) (relatively more constricted, with the lateral margins of the constricted portion almost parallel in Samadinia n. gen. [Fig. 2 A] but diverging in other Rochinia species [Fig. 5 D?F]); and the male abdomen is broadly triangular, with somites 3 and 4 broadly trapezoidal and somites 5 and 6 subrectangular (Fig. 2 A) (abdomen acutely triangular to T-shaped in Rochinia, with somites 3?6 trapezoidal, with the condition most similar to R. brevirostris [Fig. 5 C] but still relatively broader). This combination of characters is unique. No other species of Rochinia sensu lato has the kind of dorsal carapace surface and very broad male abdomen present in S. longispina n. gen., n. sp. As such, rather than placing it in Rochinia and stretching the generic definition even further, it was felt that it was better to establish a separate genus for S. longispina n. sp.
The new species of Rochinia described here, R. granulosa n. sp., also possesses a carapace that has relatively large granules covering the dorsal regions. The structure of these granules, however, is quite different, being relatively large and sub-fungiform rather than small and rounded. It also has a relatively broader male anterior thoracic sternum with a triangular male abdomen (Fig. 3D), more similar to that of Rochinia species such as R. brevirostris (Fig. 5 C).
description: Published as part of Ng, Peter K. L. & Forges, Bertrand Richer De, 2013, Samadinia longispina, a new genus and species of deep-sea spider crab from the western Pacific, and a new species of Rochinia A. Milne-Edwards, 1875, from Papua New Guinea (Crustacea: Brachyura: Majoidea: Epialtidae), pp. 357-366 in Zootaxa 3718 (4) on pages 362-363, DOI: 10.11646/zootaxa.3718.4.5, http://zenodo.org/record/221762