Zehntneriana serrata Ng & Lin, 2015, n. sp.
Creators: name: Ng, Peter K. L.
name: Lin, Chia-Wei
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pilumnidae
Zehntneriana
Zehntneriana serrata

description: Zehntneriana serrata n. sp.
(Figs. 1–3)
Material examined. Holotype male (7.5 × 5.2 mm) (NMMBCD 4045), under rock with sandy sediment, coral reef, 12 m, Kentin, southern Taiwan, coll. C.-W. Lin, 4 October 2011.
Comparative material. Zehtneriana villosa (Zehntner, 1894): Holotype male (3.3 × 2.8 mm) (MNHG), Ambon, Indonesia. Zehtneriana aff. villosa: 1 male (5.1 × 3.5 mm), 4 females (3.6 × 2.6 mm – 5.2 × 3.6 mm) (ZRC 2011.0673), Ohyama, Ginowan City, Okinawa, Japan, coll. T. Maenosono, 12 March 2008; 1 female (7.6 × 5.8 mm) (NSMT Cr 5781), Shiono-Misaki, Kii Peninsula, Japan, coll. M. Takeda, 20 July 1978; 1 male (7.6 × 6.1 mm) (NSMT Cr 5882), Shiono-Misaki, Kii Peninsula, Japan, coll. M. Takeda, 20 July 1978; 1 female (8.0 × 5.8 mm) (NSMT Cr 5809), Kushimoto, Kii Peninsula, Japan, coll. M. Takeda, 21 July 1978. Zehntneriana amakusae (Takeda & Miyake, 1969): 1 male (8.5 × 6.0 mm) (NSMT Cr 4133), Tsujishima, Amasuka, Japan, no other data; 1 male (5.9 × 4.1 mm) (NSMT), station K 5-26-2, 7 m, Doren, Kakeroma I., Amami Is., Japan, coll. 4 March 2005; 1 female (5.5 × 3.7 mm) (ZRC), Chagwido, Jeju I., Korea, coll. S. H. Kim, 8 June 2001. Zehntneriana miyakei (Takeda, 1972): Holotype male (4.8 × 3.5 mm) (NSMT Cr 976), southwest Madlâi, Goréor I., Palau, 7°20’30”N 134°28’28”E, coll. S. Murakami, 20 May 1938; 1 paratype male (5.2 × 3.7 mm), 1 paratype female (5.7 × 3.9 mm) (NSMT Cr 977–978), same data as holotype; 1 male (5.4 × 3.9 mm) (NSMT Cr 9747), station 20, 45 m, west side of Nominoura, Oshima Passage, Amami Is., Japan, coll. M. Takeda, 6 August 1988; 1 juvenile female (3.9 × 2.7 mm) (NSMT Cr 9746), station 18, 30 m, near Tawara, Oshima Passage, Amami Is., Japan, coll. M. Takeda, 6 August 1988. Zehntneriana novaeinsulicola (Takeda & Kurata, 1977): holotype male (4.1 × 2.8 mm) (NSMT Cr 5469), under coral block, Nishino-shima-shinto I., Ogasawara Is., Japan, coll. Y. Kurata, 25 July 1975.
Diagnosis. Carapace transversely oval, width 1.44 times length; dorsal surface smooth, glabrous, without setae or pubescence; anterolateral margin separated into 2 parts (including external orbital angle) by broadly U-shaped cleft, margin distinctly serrated; anterolateral margin not clearly demarcated from posterolateral margin (Fig. 1 B, 2A, B); posterior margin of epistome with prominent median triangular projection, separated medially by long fissure; lateral margins concave (Fig. 2 C); merus of third maxilliped with auriculate antero-external angle, exopod relatively stout (Figs. 2 C, 3D); thoracic sternum relatively wide; sternoabdominal cavity reaching posterior third of fused sternites 3, 4, to imaginary joining of posterior part of coxae of chelipeds (Fig. 3 D); meri and carpi of both chelipeds mostly glabrous except for short setae on margins (Fig. 1); fingers shorter than palm (Figs. 1 B, 2A, 3F, G); ambulatory legs slender, merus with anterior margin gently serrated (Fig. 3 F–I), propodus much longer than broad, lateral margins gently crenulated (Figs. 1, 2 A, 3F–I); G1 sinuous, apical part gently curved, tip elongated (Fig. 3 A, B).
Description. Carapace transversely oval, width 1.44 times length; dorsal surface smooth, glabrous, without setae or pubescence; regions poorly indicated, gastric, cardiac, branchial regions gently convex; anterolateral margin convex, with very short setae which do not obscure margin, separated into 2 low lobes by broadly U-shaped cleft, external orbital angle not demarcated from rest of anterolateral margin, entire margin distinctly serrated; posterolateral margin not clearly demarcated from anterolateral margin, confluent medially, anterior half distinctly serrated, converging towards gently sinuous posterior carapace margin (Fig. 1 B, 2A, B). Front broad, 0.32 times carapace width, separated medially by wide cleft, margin of each lobe gently convex, separated from supraorbital margin by small, low lobe (Figs. 1 B, 2A, B). Orbit wide; supraorbital margin gently concave, entire, with fine, low granules; gradually confluent with external orbital angle; suborbital margin short, entire, without inner tooth; ocular peduncle short, stout, with large black pigmented cornea, completely filling orbit (Fig. 2 B, C). Suborbital, pterygostomial regions almost smooth; subhepatic region with low granules (Fig. 2 C). Antennal basal article quadrate, mobile; flagellum short, extending to anteroexternal angle of front (Fig. 2 C). Antennules folding transversely (Fig. 2 C). Epistome narrow; posterior margin with prominent triangular median projection, separated medially by long fissure; lateral margin concave with submedian notches (Fig. 2 C). Endostome with distinct oblique ridge on each side.
Third maxilliped covered with short setae, especially along margins. Merus quadrate with auriculate anteroexternal angle; margins, adjacent areas covered with small granules. Ischium longer than broad, with shallow submedian oblique sulcus. Exopod relatively stout, with triangular tooth along inner subdistal margin, flagellum long (Figs. 2 C, 3D).
Thoracic sternum relatively wide, surface smooth, glabrous. Sternites 1, 2 completely fused, separated from sternite 3 by distinct sinuous suture. Sternites 3, 4 almost completely fused except for lateral notches. Sternoabdominal cavity reaching to posterior third of fused sternites 3, 4, to imaginary line joining posterior parts of cheliped coxae. Sternites 4/5, 5/6 medially interrupted; sutures for sternites 6/7, 7/8 complete. Sternite 8 visible when abdomen closed (Fig. 3 E). Male abdominal locking tubercle rounded, on anterior third of sternite 5. Gonopores coxo-sternal; penis extending from condyle of coxa of fourth ambulatory leg, partially exposed on groove formed between sternites 7, 8 when abdomen closed.
Chelipeds subequal (Figs. 1 B, 2A). Merus, carpus mostly glabrous except for short setae on margins (Fig. 1). Basis-ischium short, anterior margin lined with small granules; merus short, unarmed except for granulated anterior margin. Carpus subtriangular, with distinct, slightly curved subtruncate inner distal tooth, margin lined with low granules on both sides (Fig. 2 A). Palm stout, outer surfaces smooth, glabrous except for scattered short setae on dorsal margin; fingers shorter than palm, pigmented light brown for ca. 2/3 of length, tips curved, cutting margins with large, small teeth (Figs. 1 B, 2A, 3F, G)
Ambulatory legs slender, second leg longest, first leg shortest (Figs. 2 A, 3F–I). Merus almost glabrous; anterior margin gently serrated to different degrees, without anterior subdistal tooth or spine; posterior margin almost smooth (Fig. 3 F–I). Propodus much longer than broad, lateral margins gently crenulated, lined with numerous short setae; dactylus falciform, long, subequal to or slightly longer than propodus; margins lined with numerous short setae, tip sharp, corneous (Figs. 1, 2 A, 3F–I).
Abdomen triangular, all somites, telson freely articulating, outer surface smooth, glabrous (Figs. 2 D, E, 3E). Somite 1 narrow, wide, reaching to bases of coxa of last ambulatory legs; somite 2 longer, less wide than somite 1; somite 3 widest, lateral parts gently curved posteriorly, as wide as somite 1, touching episternite 7; somites 4, 5 trapezoidal with sinuous lateral margins; somite 6 rectangular, much wider than long, lateral margins sinuous. Telson broadly triangular with rounded tip, lateral margins gently sinuous (Figs. 2 D, E, 3E).
G1 sinuous, relatively slender, with row of spines on outer margin of subdistal part; distal part gently curved, tip slender, elongated, terminating in sharp point (Fig. 3 A, B). G2 short, sigmoid, with short distal segment (Fig. 3 C).
Colour. In life, carapace yellowish white in life; ventral surfaces of cephalothorax, chelipeds, and ambulatory legs white; setae yellowish brown to brown (Fig. 1).
Etymology. The species is named after its serrated anterolateral margins.
Remarks. Zehntneriana serrata n. sp. is unusual among all congeners in having the anterolateral margin of the carapace distinctly serrated and divided approximately into two broad lobes, including the undifferentiated external orbital angle (Figs. 1, 2 A, B). All the other known species have trilobed (Z. miyakei), quadrilobed (Z. amakusae), tridentate (Z. aff. villosa), or quadridentate (Z. villosa s. str. and Z. novaeinsulicola) anterolateral margins (cf. Figs. 4A, F, 5A, E; Takeda 1972: fig. 2A; Zehntner 1894: pl. 7 fig. 8; Lee et al. in press). The carapace and chelae of Z. serrata n. sp. are also quite glabrous (Figs. 1, 2 A, B) and resemble those of Z. novaeinsulicola (Fig. 4 F). This character is in contrast to the carapace and chelae of Z. villosa s. str. and Z. aff. villosa, which are densely setose (Zehntner 1894: pl. 7 fig. 8; Takeda 1972: fig. 1). In Z. miyakei and Z. amakusae (Figs. 2 A, B, 4A, 5A, E; Takeda 1972: fig. 2), the anterolateral margins and regions are covered with a short pubescence. The posterior margin of the epistome of Z. serrata n. sp. is characteristic in that the lateral margins are distinctly concave (Fig. 2 C) rather than sinuous in congeners (Figs. 4C, G, 5C, F; Lee et al. in press). The auriculiform anteroexternal angle of the third maxilliped of Z. serrata n. sp. (Figs. 2 C, 3D) is a character shared only with Z. aff. villosa (Lee et al. in press). All other Zehtneriana species have the anteroexternal angle of the third maxilliped rounded and not produced (Figs. 4B, F, 5F; Zehntner 1894: pl. 7 fig. 8a; Takeda & Miyake 1969: fig. 1b; Takeda & Kurata 1977: fig. 4d). The exopod of the third maxilliped of Z. serrata n. sp. is also proportionately the widest and stoutest (Fig. 3 D); all other congeners have more slender exopods (Fig. 4B, F; Zehntner, 1894: pl. 7 fig. 8a; Takeda & Miyake 1969: fig. 1b; Takeda & Kurata 1977: fig. 4d; Lee et al. in press).
The relative width of the anterior male thoracic sternum of Z. serrata n. sp. resembles that of Z. villosa s. str. (Lee et al. in press); all other Zehntneriana species have proportionately narrower structures (Figs. 4B, H, 5B; Lee et al. in press). Zehtneriana miyakei and Z. novaeinsulicola are easily separated from all congeners (including Z. serrata n. sp.) in possessing cheliped fingers that are shorter than the palm (Fig. 4 I, 5F; Takeda 1972: fig. 2C, D) (versus fingers distinctly longer than the palm; Figs. 2 F, G, 4D, EI; Zehntner 1894: pl. 7 fig. 8b; Takeda & Miyake 1969: fig. 1c; Takeda 1972: fig. 1). Zehtneriana miyakei has proportionately the longest ambulatory legs of any species in the genus, notably in the lengths of the merus and propodus (Fig. 4A; Takeda, 1972: fig. 3B, C) (relatively shorter; Figs. 1 B, 2A, 3F–I, 4A; Zehntner 1894: pl. 7 fig. 8; Takeda 1972: fig. 1; Takeda & Miyake 1969: fig. 1d; Takeda & Kurata 1977: fig. 4e–g). The prominently serrated anterior margin of the ambulatory merus of Z. serrata n. sp. is distinctive (Figs. 2 A, 4F–I), and is a character it shares with Z. novaeinsulicola (cf. Takeda & Kurata 1977: fig. 4e–g). In the other Zehntneriana species, the anterior meral margins of the ambulatory legs are gently uneven to smooth, and if there are low serrations, they are only present on one section (cf. Figs. 4A, 5A; Takeda & Miyake 1969: fig. 1d; Takeda 1972: fig. 3B, C; Lee et al. in press).
The G1 of Z. serrata n. sp. is generally similar to those of congeners, except for the structure of the distal part. In Z. serrata n. sp., the distal part is gently curved and somewhat elongate, tapering distally into an acute tip (Fig. 4A, B). The distal part of the G1 of Z. villosa, Z. aff. villosa and Z. miyakei is strongly bent and hook-like (cf. Takeda & Miyake 1969: fig. 1f, g; Takeda 1972: fig. 3D; Lee et al. in press). The G1 of Z. serrata n. sp. appears closest to Z. novaeinsulicola in the curvature of the distal part, but in the latter species, the G1 is relatively shorter overall with the tip being rather truncate (cf. Takeda & Kurata 1977: fig. 4i, j).
description: Published as part of Ng, Peter K. L. & Lin, Chia-Wei, 2015, Zehntneriana serrata n. sp., a new species of pilumnid crab from southern Taiwan (Crustacea, Decapoda, Brachyura), pp. 263-271 in Zootaxa 3915 (2) on pages 264-271, DOI: 10.11646/zootaxa.3915.2.5, http://zenodo.org/record/243386