Cyclorma, Naruse, Tohru & Ng, Ngan Kee, 2012

Naruse, Tohru & Ng, Ngan Kee, 2012, Establishment of a new genus for Cyclograpsus lophopus Nobili, 1905, within Sesarmidae Dana, 1851 (Crustacea: Decapoda: Brachyura), Zootaxa 3572, pp. 63-68 : 63-67

publication ID	https://doi.org/ 10.5281/zenodo.213204
publication LSID	lsid:zoobank.org:pub:B31F6A0F-47B9-41A4-90DE-A59EAB76B373
DOI	https://doi.org/10.5281/zenodo.6170989
persistent identifier	https://treatment.plazi.org/id/2D1AED25-9C32-4EC1-B606-AE39FD924451
taxon LSID	lsid:zoobank.org:act:2D1AED25-9C32-4EC1-B606-AE39FD924451
treatment provided by	Plazi
scientific name	Cyclorma
status	gen. nov.

Treatment

Cyclorma View in CoL gen. nov.

Type species. Cyclograpsus lophopus Nobili, 1905 , by monotypy.

Diagnosis. Carapace ( Fig. 1 View FIGURE 1 ) sub-quadrate, slightly wider than long, frontal width less than half-width of carapace; frontal margin, anterior margin of eyestalk (when folded) and carapace proper forming smooth arc ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ). Supraorbital margin laterally directed, J-shaped, entire; inner orbital tooth ( Fig. 2 View FIGURE 2 c) triangular, reaching midway to lateral angle of front, leaving wide gape for antenna. Anterolateral, posterolateral margins continuous, entire. Suborbital, pterygostomial, subhepatic regions ( Fig. 2 View FIGURE 2 c) covered with reticulated setal pattern, longitudinal groove on pterygostomial region along buccal cavern absent. Antennule set transversely. Antenna not excluded from orbit. Eye ( Fig. 2 View FIGURE 2 a, c) short, with trigonal peduncle, dorsal, anterior surfaces compressed ( Fig. 2 View FIGURE 2 c). Third maxillipeds ( Figs. 2 View FIGURE 2 c, 3a) with rhomboidal gape when closed; ischium trapezoidal in shape, longer than merus, with median groove; merus subcircular, with oblique setose ridge; exopod with long flagellum. Female cheliped ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 a, b) short, subequal. Ambulatory legs ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 b–d) short, with remarkably flattened, widened meri to propodi; meri distally widened, disto-posterior part foliaceous.

Etymology. The genus name “ Cyclorma ” is derived from an arbitrary combination of the two words of the genera “ Cyclograpsus ” and “ Sesarma ”. Gender neuter.

Remarks. Davie (2002: 207) noted that varunid Cyclograpsus and allied genera differ morphologically from Sesarmidae sensu stricto in the “pattern of development of the grooves that direct respiratory water flow across the pterygostome, and in particular, a more or less clearly defined vertical groove running subparallel along the buccal cavity”, and “a strongly developed, typically stridulatory, sub-orbital crest that is relatively straight, and extends some distance across the lateral branchial region”. This suborbital crest of varunids is usually distinct even in female specimens.

Since the original description by Nobili (1905), and the additional observation by Nobili (1906), no one has reconsidered the systematic position of Cyclograpsus lophopus nor reported on its morphological characters. Recent molecular studies examined several Cyclograpsus species but C. lophopus . Our observation of the type specimens (MNHN-IU-2008-10673, ex- MNHN-B12566; MNHN-IU-2008-20697, ex- MNHN-B32611) have confirmed that C. lophopus lacks a suborbital crest and a vertical groove on the pterygostomial region along the buccal cavern but has an oblique setose ridge ( Fig. 2 View FIGURE 2 c). This indicates that C. lophopus should be placed in the family Sesarmidae . The other external morphological characters of C. lophopus are too distinct for the species to be accommodated in any of the existing sesarmid or gapsoid genera. This is especially true for the distinct entire contour of the carapace, including the eye peduncle ( Fig. 1 View FIGURE 1 ), and the short and wide ambulatory legs with foliaceous disto-posterior angles of the meri ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 b–d). We thus establish a new genus, Cyclorma n. gen., for this species. Cyclorma n. gen. is a monotypic genus at least for the present.

Lithoselatium Schubart, Liu & Ng, 2009 View in CoL , is morphologically similar to Cyclorma View in CoL n. gen. as they share a relatively smooth dorsal surface of the carapace ( Fig. 2 View FIGURE 2 a), a nearly entire carapace contour ( Fig. 1 View FIGURE 1 ), and proportionally wider ambulatory meri ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 b–d). Cyclorma View in CoL n. gen., however, differs from Lithoselatium View in CoL by having a convex anterolateral and concave posterolateral margins of the carapace ( Fig. 1 View FIGURE 1 ) (lateral margins of the carapace divergent posteriorly in Lithoselatium View in CoL ; Schubart et al. 2009: figs 9B, 14B); distinctly shorter ambulatory legs ( Figs 1 View FIGURE 1 , 3 View FIGURE 3 b–d) (proportionally longer in Lithoselatium View in CoL ; Schubart et al. 2009: figs 9B, 13A); and anteriorly and dorsally compressed, trigonal and small eyes ( Fig. 2 View FIGURE 2 a, c) (well-developed, bulb-shaped and proportionally larger in Lithoselatium View in CoL ; Schubart et al. 2009: figs 9B, 10C, 13A, 14C).