Calliax de Saint Laurent, 1973

Hyžný, Matúš & Gašparič, Rok, 2014, Ghost shrimp Calliax de Saint Laurent, 1973 (Decapoda: Axiidea: Callianassidae) in the fossil record: systematics, palaeoecology and palaeobiogeography, Zootaxa 3821 (1), pp. 37-57 : 42-45

Genus Calliax de Saint Laurent, 1973

Type species. — Callianassa (Callichirus) lobata de Gaillande & Lagardère, 1966 .

Extant species included. — Three species (including one referred species but not formally named): Calliax doerjesti Sakai, 1999 ( Figs 3A–B ); Calliax lobata ( de Gaillande & Lagardère, 1966) ( Figs 3C–D ); Calliax sp. sensu Taviani et al. (2013).

Fossil species included.– Calliax michelottii (A. Milne Edwards, 1860) comb. nov. More fossil occurrences in open nomenclature are recognized (see Table 1 ).

Diagnosis. Carapace lacking dorsal oval; rostrum short, with blunt tip, rostral spine absent. Pleonal segment 2 longest, no lateral tufts of setae on segments 3–5. Telson slightly wider than long, lateral margin curved, posterior margin straight or slightly convex. Eyestalk about twice as long as wide, slightly flattened dorso-ventrally; cornea small, weakly pigmented. A1 peduncle shorter than that of A2. Mxp1 epipod tapering anteriorly. Mxp2 with small, leaf-like epipod. Mxp3 subpediform (sensu Ngoc-Ho 2003), propodus and dactylus rounded, exopod absent. P1 unequal, dissimilar. Major P1 propodus rectangular, usually longer than high, fixed finger shorter than manus, with a double ridge accompanied by a furrow extending onto manus and parallel to the lower margin of propodus. Fixed finger as long as dactylus in major P1, shorter than dactylus in minor P1, with wide proximal gap and large triangular proximal tooth on cutting edge. Major P1 carpus shorter than high, distinctly shorter than propodus. Major P1 merus longer than high, keeled, lower margin armed with small spines. P3 with small proximal heel on propodus, P5 subchelate. Paired arthrobranch on Mxp3 and P1–4. Male and female Plp1 uniramous male and female Plp2 biramous, all lacking appendix interna, male Plp2 with appendix masculina overreaching endopod. Plp3–5 biramous, foliaceous, appendix interna finger-like in both sexes. Uropodal endopod and exopod slightly longer than telson, with rounded posterior margin; exopod with dorsal plate terminating in short distal setal row [emended from Ngoc-Ho (2003: 489) with characters on major P1].

Remarks on the taxonomy. Calliax has a complex taxonomic history. The genus was erected by de Saint Laurent (1973) with Callianassa lobata de Gaillande & Lagardère, 1966 , as the type species. Since then the concept of the genus has been changed several times (cf. Manning & Felder 1991; Sakai 1999, 2005, 2011; Ngoc- Ho 2003; Hyžný 2012; see also Dworschak 2007). Here the view of Ngoc-Ho (2003) and Sakai (2011) is adopted, and thus, only two formally described extant species are recognized. Discussion on distinguishing Calliax from related taxa based on soft-part morphology was provided by Ngoc-Ho (2003) and will not be repeated here.

When dealing with chelipeds the two known extant species of Calliax can be characterized by unequal and dissimilar chelae, from which the minor one has „fixed finger shorter than and separated from the dactylus by a wide gap, bearing a large triangular proximal tooth ( Ngoc-Ho 2003: 490)“. This morphology approaches a subchelate cheliped state. Comparison of the illustrated major P1 propodus of C. lobata ( de Gaillande & Lagardère 1966: fig. 2a; de Saint Laurent & Božić 1976: fig. 23; Ngoc-Ho 2003: fig. 17D), C. doerjesti ( Sakai 1999: figs. 28, 29b) and Calliax sp. ( Taviani et al. 2013: fig. 8) clearly shows consistency in its general shape, i.e. propodus is rectangular and usually longer than high and on its lateral surface the fixed finger possesses two ridges accompanied by furrow (or furrows) parallel to the lower margin of propodus and extending onto manus. The ridges are visible especially when viewing under low angle light ( Fig. 2C ). There are several distinct setal pores (accompanied by tubercles) arranged obliquely across the lateral surface of propodus. In Calliax the major P1 carpus is always much shorter than manus, with rounded proximo-lower margin ( Fig. 3 ). The merus is longer than high with a distinct meral keel and its lower margin is usually armed with small spines. The above mentioned combination of the characters of minor chela and major propodus, carpus and merus is unique for Calliax ; thus, the genus can be identified on the basis of chelipeds alone.

The number of spines on the lower margin of P1 merus may vary between respective members of Calliax and may help in distinguishing taxa at the species level, although possible variation has not been studied in detail yet. Regarding the number of meral spines, there are discrepancies in the literature. Sakai (1999: 114) in the description of C. doerjesti mentioned that the lower margin of the merus was “armed with three interspaced denticles”. One of the figures ( Sakai 1999: fig. 29b) indeed shows three small spines, however, in the other one ( Sakai 1999: fig. 28) depicting the same specimen (holotype) the merus is armed with seven spines ( Fig. 3a ). Ngoc-Ho (2003: fig. 17D; note that the published figure depicts the right major chela, whereas the caption refers to it as the left one) figured the holotype (male) of C. lobata with seven spines on the merus and de Saint Laurent & Božić (1976: fig. 23a) figured a female specimen of C. lobata also with seven spines. Calliax cf. C. lobata , examined and figured herein ( Figs 2 , 3E–F ), possesses only four blunt spines, presumably mirroring its small size ( Fig. 4 ).

Remarks on the fossil record. Articulated chelipeds are relatively sparse in the fossil state and often only isolated propodi are at hand. In this respect, the major P1 propodus of Calliax is distinct enough to be differentiated from all other ghost shrimp genera. It must be stressed, however, that the more cheliped elements are found, the more secure assignment at the genus level can be provided.

The best preserved and most numerous remains of Calliax in the fossil record belong to species originally described as Callianassa michelottii ( Figs 5–10 ). It is discussed in detail below.

Feldmann et al. (2005) reported several isolated cheliped elements from the Miocene of the Navidad Formation of Chile as Callianassoidea sp. 1. Although the authors stated that it does not resemble any callianassoid genus ( Feldmann et al. 2005: 431), the figured material ( Feldmann et al. 2005: fig. 2A) exhibits striking similarities with Calliax as discussed herein. Interestingly, Callianassa szobensis Müller, 1984 , which is herein considered a junior subjective synonym of C. michelottii (see below) and hence a member of Calliax , is mentioned by Feldmann et al. (2005) as similar to their Callianassoidea sp. 1. The same locality also yielded another specimen which has been identified as Callichirus sp. The figured propodus ( Feldmann et al. 2005: fig. 2A) shows a relatively short manus; however, the fixed finger with ridges and a furrow indicates its affinities to Callianassoidea sp. 1 ( Feldmann et al. 2005: fig. 2D). Both specimens are treated here as Calliax sp. 1 .

Feldmann et al. (2011) reported fragmented material from the Miocene of Tierra del Fuego ( Argentina) as “Cheliped Form B” of indeterminate callianassoid. As already noted by Hyžný & Hudáčková (2012: 13), the minor chela exhibits remarkable similarities to Calliax , ( Feldmann et al. 2011: fig. 5E) showing a fixed finger shorter than the dactylus and separated from it by a wide gap with a proximal tooth (cf. Ngoc-Ho 2003: 490). The major P1 propodus ( Feldmann et al. 2011: fig. 5B), however, does not possess the ridges on the fixed finger. It is fairly likely that the two specimens do not belong to the same taxon, as they were not found associated with each other. For the purposes of this contribution only the minor chela is referred to here as Calliax sp. 2 .

Charbonnier et al. (2013) reported a single near-complete propodus from the Paleocene of Pakistan identified as a minor chela of Calliax . Indeed, the specimen shows all features typical for minor chelae of the genus ( Charbonnier et al. 2013: fig. 2) as discussed above. This occurrence is considered the oldest confirmed fossil record of the genus, treated here as Calliax sp. 3 .

Callianassa whiteavesi Woodward, 1896 from the Campanian of Canada ( Woodward 1896; Feldmann & McPherson 1980; Schweitzer et al. 2003) was assigned to Calliax by Schweitzer et al. (2003). The material is rich and sufficiently preserved to reconstruct both chelipeds ( Feldmann & McPherson 1980). The species differs markedly from any Calliax species. It does not possess the typically shaped minor cheliped as discussed above, nor has it parallel ridges on the base of the fixed finger. Moreover, some specimens exhibit a rather deep dactylus, a character not observed in Calliax . As a result, the species is excluded from Calliax herein. Until the type material is restudied we suggest to keep the species under Callianassa sensu lato.

Swen et al. (2001) reported a single fragmentary right propodus from the Maastrichtian of the Netherlands as “ Calliax ? sp.”. The material is too fragmentary for resolving its generic status. The oblique development of the ridge at the base of fixed finger ( Swen et al. 2001: fig. 5.3), however, points to closer affinities to Eucalliax or Calliaxina rather than Calliax .

Van Bakel et al. (2006) listed in a table of Cenozoic decapods from Belgium the presence of Calliax in the Miocene strata. The material was recently described as a new member of the family Axiidae ( Fraaije et al. 2011) .

Occurrence and distribution. Paleocene–Holocene. Two formally described extant species are known from West Atlantic (Florida) and Mediterranean ( Sakai 2011). Based on the reports discussed above ( Feldmann et al. 2005, 2011), the geographical distribution of the genus was much wider during the Miocene than today, and the genus was apparently also present in the East Pacific (see below). All occurrences are reviewed in Table 1 .

Figures

FIGURE 2. Calliax cf. C. lobata, NHMW 25511, female, Anastasya mud volcano, 457 m, Gulf of Cádiz, Spain: A, inner view of major P1; B, outer view of major P1; C, ridges (arrows) on the fixed finger under low-angled light; D; outer view of minor P1; E, entire animal (major P1 is detached).

FIGURE 3. Extant Calliax species: A–B, Calliax doerjesti Sakai, 1999, note the discrepancy in figuring lower margin of major P1 merus in „A“ and „a“ (redrawn after Sakai 1999: figs 28–29); C–D, Calliax lobata (de Gaillande & Lagardère, 1966) (redrawn after Ngoc-Ho 2003: figs 17D–E); E–F, Calliax cf. C. lobata, line drawings of NHMW 25511 (Fig. 2). Left column=major chelae (outer surface), right column=minor chelae (outer surface). Setae are omitted. From two ridges at the base of the fixed finger only the more developed one is depicted in the sketches (see text for details). Scale bar equals 1 mm.

FIGURE 4. Comparison of figured major chela of Calliax: A, Calliax cf. C. lobata (NHMW 25511); B, Calliax lobata (redrawn after de Saint Laurent & Božić 1976: fig. 23a); C, Calliax lobata (redrawn after Ngoc-Ho 2003: fig. 17D); D, Calliax doerjesti (redrawn after Sakai 1999: fig. 29b). All figures are to scale.

FIGURE 5. Callianassa michelottii A. Milne Edwards, 1860: holotype (MNHN-F-B32690): A–B, refigured from A. Milne Edwards (1860: pl. 14, fig. 3); C–D, photo of the holotype. A, C=inner surface; B, D=outer surface. Arrows indicate ridges. Photo by Lilian Cazes (MNHN).

FIGURE 6. Calliax michelottii (A. Milne Edwards, 1860) comb. nov., occurrences published previously. A–G: Oligocene of the Mainz Basin, Flörsheim and Offenbach at Frankfurt (Germany). A–C, right major P1 propodus articulated with dactylus from inner, outer and upper view, respectively; D, cross section of major P1 propodus; E, right major P1 merus articulated with carpus; F, right major P1 propodus articulated with carpus in inner view; G, left major P1 propodus associated with right minor P1 chela (propodus articulated with dactylus). H: Miocene of Sardinia (Italy), the assignment to C. michelottii comb. nov. is questionable. I–L: Oligocene of „Sternberger Gestein“, Kobrow (Germany), left major P1 propodus in inner (I), outer (J), lower (K) and upper view (L). A–G are refigured from Fritsch (1871), H is refigured from Lőrenthey (1907), I–L are refigured from Noetling (1886). A–H are to scale, scale bar equals 5 mm.

FIGURE 7. Calliax michelottii (A. Milne Edwards, 1860) comb. nov. from the Oligocene of the European plate: isolated propodi (A–K) and carpus (L–M). A–B, NHMW 1874/0029/1154 a; C, D, G, NHMW 1874/0029/1154 a, G shows the specimen under a low-angle light to show the ridges on the fixed finger; E–F, NHMW 1874/0029/1154 c; H, NHMW 1874/ 0029/1154 d; I, NHMW 1874/0029/1155; J–K, NHMW 1874/0029/1154 e; L–M, NHMW 1874/0029/1154 f. Specimens in A–H, J–M are from Sternberg (Germany), specimen in I is from Pinnow bei Schwerin (Germany). All specimens are to scale and were covered with ammonium chloride prior to photography. Scale bar equals 5 mm.

FIGURE 8. Calliax michelottii (A. Milne Edwards, 1860) comb. nov. from the Alpine-Carpathian orogenic system. A–B, UMJGP 77873–77874, isolated propodi from Jarenina (Slovenia); C, NHMW 2003/0026/0913, right propodus articulated with dactylus from Pucking (Austria); D–H, KGP-MH RO-001, fragmentary right propodus from Rohožník (Slovakia), note large setal pores on the outer lateral surface (E), arrows (in F) indicate ridges; I, NHMW 2010/0089/0001, counterpart of the major left cheliped from Neuhofen bei Tettenweis (Germany), arrows indicate ridges; J–K, M.2004.158.1, holotype of Callianassa szobensis Müller, 1984 from Szob (Hungary), refigured from Müller (1984: pl. 7, figs 3–4); L, left major propodus from Želiezovce (Slovakia), refigured from Špinar et al. (1965: fig. X-184). Scale bar equals 5 mm.

FIGURE 9. Calliax michelottii (A. Milne Edwards, 1860) comb. nov. from the Middle Miocene of Kamnik, Slovenia. A, RGA/SMNH 0754, right propodus; B, RGA/SMNH 0779, left propodus; C, RGA/SMNH 0864, right propodus; D, RGA/ SMNH 0773, left propodus; E, RGA/SMNH 1191, left major chela consisting of propodus, carpus and merus; F, RGA/SMNH 1075, left propodus articulated with dactylus; G, RGA/SMNH 1187, left propodus articulated with dactylus; H, RGA/SMNH 1069, left major chela consisting of dactylus, propodus and carpus; I, GBA 2009/014/0027, right propodus. All specimens are to scale and were covered with ammonium chloride prior to photography. Scale bar equals 5 mm.

FIGURE 10. Calliax michelottii (A. Milne Edwards, 1860) comb. nov., reconstruction: A, major chela; B, minor chela (based on Fritsch 1871: pl. 17, fig. 14). Both chelae are depicted in outer lateral aspect.