Munididae, Ahyong & Baba & Macpherson & Poore, 2010

Ahyong, Shane T., Baba, Keiji, Macpherson, Enrique & Poore, Gary C. B., 2010, A new classification of the Galatheoidea (Crustacea: Decapoda: Anomura), Zootaxa 2676 (1), pp. 57-68 : 59-63

Munididae fam. nov.

( Figs 1G, H , 2H–E )

Diagnosis. Rostrum slender, dorsally ridged, usually spiniform; supraocular spines present. Carapace (excluding rostrum) as long as or longer than wide; dorsally with transverse striae. Tailfan well developed, not folded against preceding somite; telson distinctly or indistinctly subdivided into multiple plates. Eyes with well-developed cornea. Antennal peduncle directed anteriorly or anterolaterally. Maxilliped 1 exopod flagellum well developed. Maxilliped 3 pediform; ischium and merus elongate, not expanded mesially; epipod present. Chelipeds subcylindical to ovate in cross-section.

Type genus. Munida Leach, 1820 .

Composition. Extant genera: Agononida Baba & de Saint Laurent, 1996 , Anomoeomunida Baba, 1993 ; Anoplonida Baba & de Saint Laurent, 1996 ; Babamunida Cabezas, Macpherson & Machordom, 2008 ; Bathymunida Balss, 1914 ; Cervimunida Benedict, 1902 ; Crosnierita Macpherson, 1998 ; Enriquea Baba, 2005 ; Heteronida Baba & de Saint Laurent, 1996 ; Sadayoshia Baba, 1969 ; Munida Leach, 1820 ; Neonida Baba & de Saint Laurent, 1996 ; Onconida Baba & de Saint Laurent, 1996 ; Paramunida Baba, 1988 ; Pleuroncodes Stimpson, 1860 ; Plesionida Baba & de Saint Laurent, 1996 ; Raymunida Macpherson & Machordom, 2000 ; Setanida Macpherson, 2006 ; Tasmanida Ahyong, 2007 ; Torbenella Baba, 2008 .

Fossil genera: Protomunida Beurlen, 1930 [Paleocene to Eocene]; Cretagalathea Garassino, De Angeli & Pasini, 2008 [Upper Cretaceous].

Remarks. The family Munididae fam. nov. includes those genera formerly in the Galatheidae having a trifid frontal margin of the carapace, usually in the form of a spiniform rostrum flanked on either side by supraorbital spines. In some genera, however, particularly those allied to Bathymunida (see Baba & de Saint Laurent 1996), the rostrum and supraorbital spines may be variously reduced, sometimes present as small points or tubercles along the protruding front (compare Fig. 2G, H ). As such, these taxa may appear to have a truncated, subquadrate or subtrapezoid rostrum, although careful examination will reveal the three anterior points, homologous with the rostral and supraorbital spines of other munidids.

Although the family Munididae is formally erected here, it should be noted that Dana (1852: 478) used the Latin construction, Munidae (as well as Munida ) in comparisons with Galathea and the invalid Grimothea (= Munida ). Munidae was clearly used by Dana only as a plural noun referring to species of Munida , rather than as a new suprageneric taxon, and as such is not an available family-group name (ICZN Article 11.7.1.2).

Munididae fam. nov. is the most diverse family of the galatheoids with 20 extant and two fossil genera, and more than 350 species. The Cretaceous Cretagalathea is regarded as a munidid. The rostrum of the only known specimen is not preserved, but its long, slender pereopods closely resemble those of many munidids, especially species of Munida . Schweitzer et al. (2010) listed the Middle Eocene Austromunida Schweitzer & Feldmann, 2000 , as a valid genus, although we follow Garassino & De Angeli (2003) and Casadío et al. (2004) in treating it as a junior synonym of Munida .

Machordom & Macpherson (2004) studied the phylogenetic relationships of a large suite of primarily munidids and recovered three main clades, one containing Agononida , Bathymunida , Paramunida and allies (sharing the loss of pleopod 1 in males and absence of pereopodal epipods), one containing Munida , Cervimunida , Pleuroncodes and allies (sharing the presence of pleopod 1 in males and the absence of pereopodal epipods), and a third containing Raymunida and Alainius (sharing the presence of pleopod 1 in males and the presence of pereopodal epipods). The Raymunida + Alainius clade was sister to other munidids, but the position of Alainius is anomalous under the present concept of the family. Alainius corresponds more closely to the Galatheidae than Munididae fam. nov. by its broad triangular rostrum, and apart from the presence of epipods, is dissimilar to Raymunida . The presence of pereopodal epipods is not unique to Alainius and Raymunida , being present, or even variable in several other galatheid genera ( Baba 2005). Schnabel et al. (in press) also found a similar position for Alainius as sister to the clade of munidids. The nodal support for the position of Alainius recovered by both Machordom & Macpherson (2004) and Schnabel et al. (in press) is not universally high, so its position may represent an analytical artefact. Conversely, the position may be correct; although Alainius has a galatheid-like rostrum, it also has well-developed supraocular spines ( Fig. 2C ) that are also present in munidids; similarly for Phylladiorhynchus . Also, the morphology of the walkingleg dactyli of Alainius and Phylladiorhynchus might support a close relationship to munidids. In most Galatheidae , the flexor margin of the dactylus of each walking leg is either biunguiculate or evenly toothed, with each tooth usually bearing a small movable spine at its base ( Fig. 1B–D ). These flexor marginal teeth range from obtusely to acutely triangular. In Munididae fam. nov., the walking leg dactylus also usually has small movable spines, but the flexor margin itself is not toothed, instead being smooth, crenulated or stepped ( Fig. 1G, H ). Of the genera presently assigned to the Galatheidae , the walking leg dactyli of Alainius and Phylladiorhynchus correspond to the munidid form ( Fig. 1E, F ), and in the case of Alainius , corroborates its position in current phylogenetic analyses. Unfortunately, the polarity of evolution of the walking leg dactylus armature is not clear because all of the states found in galatheids and munidids are also present in munidopsids. Thus, whether or not these features of dactylar morphology reflect fundamental phylogenetic differences remains to be determined and more detailed analyses of the relationships within the Munididae fam. nov. are currently underway in collaboration with N. Andreakis. It is conceivable that even further subdivision of the galatheoid families may eventually be warranted, but at present, Alainius and Phylladiorhynchus are retained in the Galatheidae .

Members of the Munididae fam. nov. usually occur at outer shelf or slope depths, although some species may enter shallow water ( Baba et al. 2008).

Figures

FIGURE 1. A, Phylogenetic relationships of the families of the Galatheoidea based on Ahyong et al. (2009) and Schnabel et al. (in press). B–H, walking leg dactyli of selected Galatheoidea. Galatheidae: B, Allomunida magnicheles Baba, 1988; C, Galathea tropis Baba, 2005; D, Lauriea gardineri (Laurie, 1926); E, Phylladiorhynchus cf. pusillus (Henderson, 1885); F, Alainius crosnieri Baba, 1991. Munididae fam. nov.: G, Munida exilis Ahyong, 2007; H, Agononida eminens (Baba, 1988). Figure sources: B (Baba 1988); C (Baba 2005); D (Baba 1994); E, G (Ahyong 2007); F (Baba 1991); H (Baba et al. 2008).

FIGURE 2. Carapace and abdomen (A–N) and anterior carapace (O) of selected Galatheoidea. Galatheidae: A, Galathea tropis Baba, 2005; B, Lauriea siagiani Baba, 1994; C, Alainius crosneri Baba, 1991; D, Allomunida magnicheles Baba, 1988. Munididae fam. nov.: E, Munida exilis Ahyong, 2007; F, Agononida eminens (Baba, 1988); G, Bathymunida ocularis Baba & de Saint Laurent, 1996; H, B. frontis Baba & de Saint Laurent, 1996; Munidopsidae: I, Munidopsis pycnopoda Baba, 2005; J, M. norfanz Ahyong, 2007; K, M. bractea Ahyong 2007; L, M. laciniosa Baba, 2005; M, Leiogalathea laevirostris (Balss, 1913); N, Galacantha rostrata A. Milne-Edwards, 1880; O, Shinkaia crosnieri Baba & Williams, 1998. Figure sources: A, I, L (Baba 2005); B (Baba 1994); C (Baba 1991); D (Baba 1988); E, J, K, M (Ahyong 2007); F, O (Baba et al. 2009); G, H (Baba & de Saint Laurent 1996); N (Baba & Poore 2002).