Laticallichirus, Komai & Yokooka & Henmi & Itani, 2019

Laticallichirus n. gen.

[New Japanese name: Oo-suna-moguri-zoku]

Type species. “ Neocallichirus ” grandis Karasawa & Goda, 1996 . Gender: masculine.

Diagnosis. Carapace with clearly defined dorsal oval ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 ). Rostral spine well developed ( Fig. 2B View FIGURE 2 ). Pleomere 2 as long as pleomere 6 ( Fig. 1C, E View FIGURE 1 ); pleomeres 3–5 without patterns of dorsal grooves and transverse setal rows ( Fig. 1D View FIGURE 1 ). Telson wider than long ( Fig. 1F View FIGURE 1 ). Cornea dorsal, subterminal, disk-shaped ( Fig. 2B View FIGURE 2 ). Antennular peduncle longer and stouter than antennal peduncle, furnished with 2 rows of dense long setae along lower margin ( Fig. 2B View FIGURE 2 ). Maxilliped 3 without exopod; ischium-merus broadly operculiform; ischium without crista dentata on mesial surface; distal margin of merus not projecting beyond articulation of carpus; propodus very broad, subovate; dactylus much longer than wide ( Fig. 4A, B View FIGURE 4 ). Chelipeds greatly unequal in both males and females ( Fig. 3 View FIGURE 3 ). Major cheliped without meral hook, blade-like denticulate margin instead ( Figs. 3B View FIGURE 3 , 5B View FIGURE 5 ); upper margin of merus to propodus and lower margin of carpus to propodus smooth, unarmed. Minor cheliped with dactylus unarmed on upper margin. Male pleopod 1 consisting of 2 articles, distal article simple, rounded distally ( Fig. 2C View FIGURE 2 ). Male pleopod 2 biramous, without appendix interna ( Fig. 2D, E View FIGURE 2 ). Female pleopod 1 uniramous ( Fig. 5C View FIGURE 5 ). Female pleopod 2 biramous, with subterminal digitiform appendix interna ( Fig. 5E, F View FIGURE 5 ). Pleopods 3–5 foliaceus; appendix interna triangular and embedded in margin of endopod ( Fig. 2G, H, I View FIGURE 2 ). Uropodal endopod elongate-ovate, longer than telson ( Fig. 1E View FIGURE 1 ).

Etymology. An arbitrary combination of the Latin word “ latus ” (= broad) and the generic name Callichirus . The name alludes the broadly operculiform ischium-merus of the maxilliped 3, one of the diagnostic features of the new genus.

Remarks. The species identification of our specimens was rather challenging, because fossil callianassid taxa are almost always diagnosed by characters derived only from a major cheliped or at best from both major and minor chelipeds ( Hyžný & Klompmaker 2015). Careful comparison between our specimens and fossil chelipeds identified with Neocallichirus (or Grynaminna or Podocallichirus ) grandis (cf. Karasawa & Goda 1996; Obata & Hayashi 2001; Karasawa et al. 2006; comparative material cited below) has shown that there are no significant differences. In particular, the following diagnostic points of the male major cheliped are well consistent between our specimens and the fossils: lower margin of merus strongly convex and denticulate, devoid of hook-like process or differentiated spine; carpus wider than long; palm approximately as long as wide; upper distal angle of palm slightly produced; distolateral margin of palm forming broad convexity; fixed finger bearing distinct tooth on occlusal margin ( Fig. 3A, B View FIGURE 3 versus Karasawa & Goda 1996: fig. 1; Hyžný & Karasawa 2012: fig. 1). The two locations where our specimens were collected, Suruga Bay and Tosa Bay, are within the known geographical range of the fossils (Kanto District to Kyushu Island, and Okinawa: Karasawa & Goda 1996; Kato & Karasawa 1998; Obata & Hayashi 2001; Karasawa et al. 2006, 2014; Ando et al. 2016; Ando & Kawano 2017). Considering further the known geologic range from the middle to late Pleistocene, we finally came to a conclusion that our specimens represent the fossil taxon described by Karasawa & Goda (1996). As discussed below, “ Neocallichirus ” grandis is now reassigned to a new genus, Laticallichirus .

The well-defined dorsal oval of the carapace ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 ) and the maxilliped 3 with a very broad, subovate propodus and slender dactylus ( Fig. 4A, B View FIGURE 4 ) place the new taxon in the subfamily Callichirinae , as diagnosed by Manning & Felder (1991). The complicated taxonomic history of the genus-level classification of Callichirinae was overviewed by Hyžný & Karasawa (2012), Komai et al. (2015) and Hyžný (2016). Callichirinae currently contains the following 15 genera (for extant species) presently recognized as valid ( Ngoc-Ho 2003; Hyžný 2016; WoRMS Editorial Board 2018; Komai et al. 2018): Balsscallichirus Sakai, 2011 [type species: Callianassa (Callichirus) balssi Monod, 1933 ], Calliapagurops de Saint Laurent, 1973 (type species: Calliapagurops charcoti de Saint Laurent, 1973 ), Callichiropsis Sakai, 2010 (type species: Callichiropis spiridonovi Sakai, 2010 ), Callichirus Stimpson, 1866 (type species: Callianassa major Say, 1818 ), Corallianassa Manning, 1987 (type species: Callianassa longiventris A. Milne-Edwards, 1870 ), Forestcallichirus Sakai, 2011 (type species: Callichirus foresti Le Loeuff & Intès, 1974 ), Glypturoides Sakai, 2011 (type species: Callianassa trilobata Biffar, 1970 ), Glypturus Stimpson, 1866 (type species: Glypturus acanthochirus Stimpson, 1866 ), Grynaminna Poore, 2000 (type species: Grynaminna tamakii Poore, 2000 ), Lepidophthalmus Holmes, 1904 (type species: Lepidophthalmus eiseni Holmes, 1904 ), Michaelcallianassa Sakai, 2002 (type species: Michaelcallianassa indica Sakai, 2002 ), Neocallichirus Sakai, 1988 (type species: Neocallichirus horneri Sakai, 1988 ), Podocallichirus Sakai, 1999 (type species: Callianassa madagassa Lenz & Richters, 1881 ), Sergio Manning & Lemaitre, 1994 (type species: Callianassa guassutinga Rodrigues, 1971 ) and Thailandcallichirus Sakai, 2011 (type species: Callianassa ranongensis Sakai, 1983 ). Laticallichirus n. gen. is characterized by a combination of the following characters: (1) the rostrum is spiniform ( Figs. 1A View FIGURE 1 , 2B View FIGURE 2 ); (2) the antennular peduncle is distinctly longer and stouter than the antennal peduncle ( Fig. 2B View FIGURE 2 ); (3) the maxilliped 3 is devoid of an exopod ( Fig. 4A View FIGURE 4 ); (4) the ischium-merus of the maxilliped 3 is broadly operculiform ( Fig. 4A, B View FIGURE 4 ); (5) the maxilliped 3 ischium is devoid of a crista dentata ( Fig. 4B View FIGURE 4 ); (6) the major cheliped merus is devoid of a hooklike process or conspicuous spine on the lower margin ( Figs. 3A, B View FIGURE 3 ; 5A, B View FIGURE 5 ); (7) the tergites of the pleomeres 3–5 are smooth, without conspicuous ornamentation ( Fig. 1D View FIGURE 1 ); (8) the male pleopod 2 is biramous, its endopod is devoid of appendices interna and masculina ( Fig. 2D, E View FIGURE 2 ); (9) the uropodal endopod is suboval in shape ( Fig. 1E View FIGURE 1 ); (10) the telson is distinctly wider than long, with a shallowly concave posterior margin ( Fig. 1E, F View FIGURE 1 ).

Of the above diagnostic characters, the second character (the antennular peduncle is distinctly longer and stout- er than the antennal peduncle) is shared by Balsscallichirus , Callichirus , Callichiropsis , Grynaminna , Michaelcallianassa , Lepidophthalmus and Podocallichirus ( Le Loeuff & Intès 1974; de Saint Laurent & Le Loeuff 1979; Manning & Felder 1991; Sakai 1999, 2002, 2005, 2010, 2011; Poore 2000; Felder & Robles 2015). Callichirus , represented by seven extant species ( Manning & Felder 1991; Felder & Dworschak 2015; Hernáes et al. 2015), C. adamas ( Kensley, 1974) , C. garthi Retamal, 1975 , C. islagrande ( Schmitt 1935) , C. kraussi ( Stebbing, 1900) , C. major ( Say, 1818) , C. santarosaensis Sakai & T̹rkay, 2012, and C. seilacheri ( Bott, 1955) , is quite characteristic in having a strong pattern of grooves and integumental glands on the pleomeres 3–5 and the strap-like uropodal endopod ( Manning & Felder 1986, 1991). In addition, in Callichirus , no rostral spine is developed; the major cheliped has a meral hook ( Manning & Felder 1991). None of the species of Callichirus occur in the West Pacific.

Balsscallichirus includes the following five extant species ( Hyžný 2016): B. balssi ( Monod, 1933) , B. gilchristi ( Barnard, 1946) , B. guineensis (de Man, 1928) , B. masoomi ( Tirmizi, 1970) , and B. tenuimanus (de Saint Laurent & Le Loeuff, 1979) . The genus differs from Laticallichirus n. gen. in the slender, pediform ischium-merus of the maxilliped 3 bearing a crista dentata on the mesial face of the ischium (versus operculiform without a crista dentata on the ischium), and the presence of a meral hook on the major cheliped (versus no meral hook is present on the major cheliped) ( Tirmizi 1970; Sankolli 1971; Le Loeuff & Intès 1974; de Saint Laurent & Le Loeuff 1979; Hyžný 2016). None of the species of Balsscallichirus occur in the West Pacific, although only B. masoomi is known from the Arabian Sea ( Tirmizi 1970; Sankolli 1971).

The monotypic Callichiropsis , represented only by its type species C. spiridonovi Sakai, 2010 described from Tonkin Bay (South China Sea), differs from Laticallichirus n. gen. in the subrectangular ischium-merus of the maxilliped 3 and the telson being as wide as long ( Sakai 2010). It should be noted that the two type specimens of C. spiridonovi might be juveniles because of the very small size (holotype cl 3.9 mm, paratype cl 4.0 mm) and the simple, non-articulated pleopod 1. Thus, further comparison with Callichiropsis is difficult.

Grynaminna becomes again monotypic with the reassignment of Grynaminna grandis to the present new genus. Grynaminna is differentiated from Laticallichirus n. gen. by the obtuse rostrum (versus spiniform), the subrectangular, non-operculiform ischium-merus of the maxilliped 3 (versus operculiform), the presence of a crista dentata on the maxilliped 3 ischium (versus absent) and the possession of an appendix interna on the male pleopod 2 endopod (versus absent) ( Poore 2000). Furthermore, the type species Grynaminna tamakii appears characteristic in having an elongate article 4 of the antennal peduncle, being approximately twice as long as article 5.

Lepidophthalmus is represented by 16 species, distributed in the Atlantic, Indo-West Pacific and East Pacific (cf. Robles & Felder 2015; Komai et al. 2018). It differs from Laticallichirus n. gen. in the presence of a minute exopod on maxilliped 3 (versus exopod absent), the subrectangular, non-operculiform ischium-merus of maxilliped 3 (versus operculiform), the presence of a hook-like projection or spine, associated with a blade-like lobe, on the lower margin of the major cheliped merus (cf. Hyžný & Dulai 2014) (versus no meral hook or blade-like lobe) and the presence of an appendix interna on the endopod of the male pleopod 2 (appendix interna absent on male pleopod 2) ( Manning & Felder 1991; Lemaitre & Rodrigues 1991; Felder & Rodrigues 1993; Felder & Manning 1997, 1998; Felder & Staton 2000; Felder 2015; Felder & Robles 2015; Komai et al. 2018).

Michaelcallianassa , represented by M. indica Sakai, 2002 known from the Andaman Sea and M. sinica Liu & Liu, 2009 from the South China Sea, is easily distinguished from Laticallichirus n. gen. by having a conspicuous ornamentation on the pleomeres 3–5, which consists of anteriorly converging longitudinal grooves and obliquely transverse or transverse rows of long setae on each somite and the narrowly subrectangular ischium-merus of the maxilliped 3, of which the ischium bears a crista dentata on the mesial face, and the uniramous male pleopod 2 (versus biramous) (Sakai 2002; Liu & Liu 2009).

Podocallichirus , presently represented only by P. madagassus ( Lenz & Richters, 1881) from the western Indian Ocean, differs from Laticallichirus n. gen. in the presence of a minute exopod on maxilliped 3, the subrectangular, non-operculiform ischium-merus of maxilliped 3, the presence of a prominent meral hook on the major cheliped, the spinose dactylus of the minor cheliped and the presence of a stout appendix interna on the endopod of the male pleopod 2 ( Sakai 1999, 2005, 2011; Sakai & Apel 2002, as Lepidophthalmus socotrensis ). In particular, the presence of a row of spines on the upper margin of the dactylus of the minor cheliped is unique for Podocallichirus .

The phylogenetic relationship between Laticallichirus grandis n. comb. and other 34 callichirine species from eight genera (cf. Table 1 View TABLE 1 ) inferred from Maximum Likelihood (ML) analysis of partial 16S sequences is shown in Fig. 7 View FIGURE 7 . The ML analysis suggests that Laticallichirus grandis n. comb. is the sister group to a clade of three species of Callichirus , although bootstrap support for major branches are generally low. K2P genetic divergence between Laticallichirus grandis n. comb. and the other callichirine species ranges from 18.8–27.2 %. The establishment of the new genus is consistent with the estimated relationships.