DOTILLIDAE Stimpson, 1858

Ng, Peter K. L., 2012, The systematic status of two enigmatic ocypodoid crabs, " Paracleistostoma " dentatum Tesch, 1918, and " Paracleistostoma " fossulum Barnard, 1955 (Crustacea: Decapoda: Brachyura), Zootaxa 3206, pp. 58-68 : 59-60

Family DOTILLIDAE Stimpson, 1858

Lazarocleistostoma Štev ě i ć, 2011

Lazarocleistostoma Števčić, 2011: 136.

Type species. Paracleistostoma dentatum Tesch, 1918 , by original designation; gender neuter.

Diagnosis. Carapace transversely hexagonal, regions just discernible ( Figs. 1 A, D). Front narrow, entire, with shallow concave indentation medially; lateral margins angular, with low epigastric lobes; external orbital tooth prominent; anterolateral margin deeply concave with distinct lateral tooth; posterolateral margin short, convex ( Fig. 1 A, B, D). Eyes prominent, peduncle long, slender ( Fig. 1 A, D). Posterior margin of epistome with triangular median lobe, lateral margins deeply concave ( Fig. 1 E). Third maxillipeds operculiform, almost completely filling buccal cavity; exopod slender, partially hidden under ischium, reaching just beyond distal part of merus ( Fig. 1 C, F). Cheliped very slender, short, symmetrical; merus subcylindrical; chela slender, cutting edges of fingers unarmed setae ( Fig. 1 A, G). Ambulatory legs relatively long, third leg longest; merus unarmed; dactyli of first to third legs falciform; that of last leg spatuliform, lined with numerous setae ( Fig. 1 A, H).

Remarks. Manning & Holthuis (1981: 209) made it clear that Paracleistostoma dentatum Tesch, 1918 , was not a species of Paracleistosoma or of a camptandriid but did not know for certain where to place it. Ng et al. (2008: 236) agreed and commented that the only known type female of this species had been examined and the structure of its frontal carapace margin and third maxillipeds indicated it was likely to be a dotillid, probably close to the genus Ilyoplax Stimpson, 1858 , and certainly not a camptandriid.

Števčiċ (2011) established a new genus, Lazarocleistostoma, for Paracleistostoma dentatum Tesch, 1918 , without providing any explanation for why a new taxon was necessary. He also decided to recognise a new family, Lazarocleistostomidae Števčiċ, 2011 ( Števčiċ 2011: 127), again without comment or regard to earlier discussions by Manning & Holthuis (1981) or Ng et al. (2008: 236).

The type specimen is broken and in poor condition, but the narrow front, relatively long eyes and orbits, form of the female chelae as well as operculiform third maxillipeds ( Fig. 1 ) strongly suggest it is a member of the Dotillidae . Overall, this species is similar to Ilyoplax Stimpson, 1858 , or Dotilloplax Tweedie, 1950 . It is known that Ilyoplax is polyphyletic (Davie & Naruse 2011; Kitaura et al. 1998; Kitaura & Wada, 2006; P.J.F. Davie, unpublished data) and the carapace of P. dentatum is unusual for a dotillid or even an ocypodoid. The carapace is atypical for ocypodoids in that there is a wide space between the external orbital tooth and first lateral tooth, resulting in a relatively short posterolateral margin. The anterolateral margin is not as long even in species like Dotilloplax kempi Tweedie, 1950 (type locality Labuan, Borneo), which has well separated, sharp external orbital and lateral carapace teeth. A separate genus for Paracleistostoma dentatum Tesch, 1918 , is therefore probably warranted.

By referring Paracleistostoma dentatum Tesch, 1918 , to Lazarocleistostoma Števčiċ, 2011, and not to Ilyoplax also solves the homonymy problem with Ilyoplax dentata Ward, 1933 , at least for the time being.

Members of Ilyoplax (and clearly all dotillids), however, are intertidal, and the holotype of L. dentatum was collected from depths of 9 to 34 m. An allied family which lives in subtidal waters, Xenophthalmidae Stimpson, 1858 , was recognised by Ng et al. (2008: 245), and while it shared similar mouthparts and chelipeds with dotillids, differed from them markedly by the form of their epistome, orbits, eyes, ambulatory legs and carapace. In summary, with regard to the Lazarocleistostomidae Števčiċ, 2011, the structure of the mouthparts, ambulatory legs and chelae as discussed above leave little doubt that it is a dotillid. As such, Lazarocleistostomidae Števčiċ, 2011, is synonymised in the Dotillidae Stimpson, 1858 .

Lazarocleistostoma dentatum ( Tesch, 1918) ( Fig. 1 )

Paracleistostoma dentatum Tesch, 1918: 63 , pl. 3 fig. 2; Serène 1968: 101; Manning & Holthuis 1981: 209; Ng et al. 2008: 235, 236.

Lazarocleistostoma dentatum — Števčić 2011: 136.

Material examined. Holotype – ovigerous female (6.2 × 3.3 mm) ( ZMA De.102.997), Saleyer Island, south Celebes (Sulawesi), Indonesia, 9−34 m depth, coll. M. Webber, Siboga Expedition, 7−8 May 1899.

Redescription. Carapace transversely hexagonal, dorsal surface almost smooth, regions discernible but not prominent; cardiac region convex, prominent ( Figs. 1 A, D). Front narrow, entire, with shallow concave indentation medially; lateral margins angular, sharply separated from sinuous supraorbital margin; low epigastric lobes discernible ( Fig. 1 A, B, D). External orbital tooth prominent, directly obliquely anteriorly; anterolateral margin deeply concave with distinct tooth demarcating antero-, posterolateral junctions; posterolateral margin short, convex ( Fig. 1 A, D). Posterior carapace margin almost straight ( Fig. 1 A, D). Eyes prominent, entirely filling orbit; cornea distinctly pigmented; peduncle long, slender ( Fig. 1 A, D). Antennules folding obliquely ( Fig. 1 E). Antenna short, basal articles not fused to carapace; flagellum very short ( Fig. 1 E). Suborbital, subhepatic, sub-branchial surfaces relatively smooth; suborbital margin crenulated to dentate on outer two-thirds ( Fig. 1 E). Epistome longitudinally narrow; posterior margin with triangular median lobe, lateral margins deeply concave ( Fig. 1 E).

Third maxillipeds operculiform, almost completely filling buccal cavity ( Fig. 1 C, F). Palp short, carpus longest, partially hidden under merus ( Fig. 1 C, F). Merus subtriangular with margins rounded, without prominent sulcus ( Fig. 1 C, F). Ischium rectangular, symmetrical ( Fig. 1 C, F). Exopod slender, partially hidden under ischium, reaching just beyond distal part of merus, flagellum distinct ( Fig. 1 C, F).

Cheliped very slender, short, symmetrical ( Fig. 1 A, G). Merus subcylindrical, surface minutely granular, unarmed ( Fig. 1 A). Carpus elongated, surface minutely granular, unarmed ( Fig. 1 A). Chela slender, scattered short setae on inner subventral margin; fingers almost as long as palm, cutting edges unarmed with tufts of setae ( Fig. 1 A, G).

Ambulatory legs relatively long, third leg longest ( Fig. 1 ). Merus laterally flattened; unarmed ( Fig. 1 A, H). Propodus laterally flattened with long setae on both margins ( Fig. 1 A, H). Dactyli of first to third legs falciform; that of last leg spatuliform, lined with numerous setae ( Fig. 1 A, H).

Thoracic sternum badly damaged, detailed structures not discernible. Abdomen rounded, covering most of thoracic sternum; all somites freely articulating ( Fig. 1 ).

Colour. “Uniform ivory-white colour” ( Tesch 1918: 65).

Type locality. Saleyer Island, south Celebes (Sulawesi), Indonesia.

Remarks. The type specimen is in poor condition and most of its ventral structures are not discernible. The legs are also detached. Fortunately, Tesch’s (1918) description is detailed and the available structures confirm his observations.

Figures

FIGURE 1. Lazarocleistostoma dentatum (Tesch, 1918). Holotype female (6.2 × 3.3 mm) (ZMA De. 102.997), Saleyer Island. A, overall dorsal view; B, frontal view of frontal margin; C, buccal cavity showing third maxillipeds; D, dorsal view of carapace; E, frontal view of carapace; F, right third maxilliped; G, outer view of right chela; H, right last ambulatory leg. (A-C, after Tesch 1918: 63, pl. 3 fig. 2; other drawings by C. G. S. Tan). Scales = 1.0 mm.