Hephthopelta Alcock, 1899

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 48-52

publication ID

https://doi.org/ 10.11646/zootaxa.4209.1.1

publication LSID

lsid:zoobank.org:pub:849BAB5C-464A-4B4A-A586-5742411EDC01

DOI

https://doi.org/10.5281/zenodo.5617117

persistent identifier

https://treatment.plazi.org/id/F16BFB33-FF8C-FFC8-FF6A-FBFFFBDFFE76

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scientific name

Hephthopelta Alcock, 1899
status

 

Genus Hephthopelta Alcock, 1899 View in CoL

Hephthopelta Alcock, 1899: 76 View in CoL ; 1900: 327.— Tesch 1918: 202 [in key], 233.— Serène 1964a: 239.—Ng et al. 2008: 76 [in list].— De Grave et al. 2009: 32 [in list].

Type species. Hephthopelta lugubris Alcock, 1899 (gender feminine) Other species included:

Hephthopelta occidentalis n. sp.

Diagnosis. Carapace subtrapezoidal, strongly globose, only slightly wider than long; front bilobed, with shallow to well-defined median cleft; anterolateral margins arcuate, minutely granular, entire or with small tubercle. Epistome slightly depressed; median lobe of posterior margin distinctly broad, with deep median fissure, semicircular lateral margins. Eye peduncle filling orbit, distinctly short, gently tapering to cornea, immobile; cornea reduced, pigmented. Third maxillipeds fill buccal cavern; merus subquadrate to elongated, outer margin nearly straight, anteriorly flattened, anteroexternal angle rounded; ischium ovate to elongated, slightly longer than merus. Chelipeds subequal in length, slightly dissimilar in female, heterochelous in males; fingers of minor chela distinctly flattened laterally, broad throughout most of length, shear-like, cutting margins with low, broad teeth. Ventral surface of cheliped merus with 3 large teeth (sometimes additional small tooth or large tubercle) on outer margin in both sexes, inner margin unarmed. Inner margin of carpus with long distal tooth, short proximal part rounded to dentiform. Inner margin of basis-ischium of adult major cheliped gently granuliform. Inner margin of basis-ischium of adult major cheliped gently granuliform ( Fig. 42 View FIGURE 42 G). Meri of P2, P3 with short teeth, meri of other ambulatory legs with microscopic granules, unarmed. P5 dactylus straight to gently curved. Fused thoracic sternites 1, 2 transversely narrow, high, triangular; fused thoracic sternites 3, 4 transversely narrow. Male pleon with lateral margins of somite 6, fused somites 3‒5 nearly straight; postero-lateral regions prominently swollen; telson proportionally short. Sterno-pleonal cavity of male deep, press-button for pleonal holding as small, short tubercle posterior to thoracic sternal suture 4/5 near edge of sterno-pleonal cavity. Male thoracic sternite 8 distinctly short, quadrate; “supplementary plate” short, rectangular; structures tightly appressed with most of penis concealed. G1 with stout basal part, distal part tapering, with short spinules. G2 longer than G1; distal segment long, evenly broad throughout length to tip. Somites of female pleon with convex lateral margins; telson proportionally short, narrow (unknown in H occidentalis ). Sterno-pleonal cavity of female deep, vulvae widely separated, on outer margins of cavity close to suture 5/6.

Remarks. Hephthopelta was established by Alcock (1899) for one species, H. lugubris , from the Indian Ocean. At least ten more species have since been added over the years to the genus (Ng et al. 2008). Of these, all are from the Indo-West Pacific region except for Hephthopelta superba Boone, 1927 , described from the western Atlantic and now placed in Deltopelta n. gen. (see above).

Examination of the good series of “ Hephthopelta ” specimens on hand shows that the 10 Indo-West Pacific species can be separated into six distinct groups on the basis of the carapace form, eyestalks, structures of the third maxillipeds, chelipeds, ambulatory legs, male thoracic sternum, gonopods, and vulvae. We here recognise six genera: Hephthopelta s. str. (for H. lugubris Alcock, 1899 , and H. occidentalis n. sp.), Angustopelta n. gen. (for H. aurita Rathbun, 1932 , H. cribrorum Rathbun, 1932 , A. modesta n. sp. and A. robusta n. sp.), Chinommatia n. gen. (for H. cavimanus Rathbun, 1914 , C. bicuspida n. sp., H. littoralis Tesch, 1918 , H. bruuni Serène, 1964 , and C. turpis n. sp.), Notopelta n. gen. (for H. mortenseni Serène, 1964 ), Statommatia n. gen. (for H. apta Rathbun, 1914 , S. granulosa n. sp., H. knudseni Serène, 1964 , and H. pubescens Chen, 1987 ) and Tenagopelta n. gen. (for T. pacifica n. sp., T. potens (Davie & Richer de Forges, 2013) , and T. brachyphallus n. sp.).

The six genera are all very distinct, easily distinguished by a suite of characters associated with the morphology of the carapace, chelipeds, ambulatory legs, thoracic sternum, male pleon, gonopods, and vulvae ( Table 2 View TABLE 2 ). Hephthopelta s. str. is closest to Tenagopelta n. gen. because of the rounded form of its carapace and prominently inflated globose appearance when viewed frontally (e.g., Fig. 24 View FIGURE 24 A). The G2 of members of both genera also have well-developed distal segments and are longer than the G1. Members of both genera are also found in deep waters with the former occurring in much greater depths (exceeding 500 m). Compared to Hephthopelta s. str., Tenagopelta n. gen. has mobile eyestalks (immobile in Hephthopelta s. str.); a relatively wider thoracic male sternum (notably sternites 1‒4) but also evident in females ( Figs. 54 View FIGURE 54 F; 88C) (distinctly narrower in Hephthopelta s. str., e.g., Figs. 52 View FIGURE 52 A; 91A); the epistome is relatively narrow with a triangular median lobe and sinuous lateral margins with marked fissures) (e.g., Fig. 26 View FIGURE 26 F) (relatively broad, truncated and nearly rectangular with the lateral margins semicircular without fissures in Hephthopelta s. str., e.g., Fig. 24 View FIGURE 24 A); the merus of the third maxilliped is more quadrate (e. g., Fig. 33 View FIGURE 33 G) (subovate in Hephthopelta s. str., e.g., Fig. 31 View FIGURE 31 A); the base of the basal segment of the G2 is distinctly elongated (e.g., Fig. 79 View FIGURE 79 O) (short and rounded in Hephthopelta s. str., e.g., Fig. 71 View FIGURE 71 M); and the distal segment of the G2 is distinctly narrowed medially with the proximal part wider than the distal part (e.g., Fig. 79 View FIGURE 79 E) (G2 distal segment is of uniform width in Hephthopelta s. str., e.g., Fig. 71 View FIGURE 71 E). There are also several other characters that separate the two genera but they may prove to be more species-specific when more species are discovered in the future: the teeth on the inner margin of the cheliped merus are typically shorter in Tenagopelta n. gen. ( Fig. 42 View FIGURE 42 I) than in Hephthopelta ( Fig. 42 View FIGURE 42 G) and male pleonite 6 relatively narrower (e.g., Fig. 54 View FIGURE 54 F) than in Hephthopelta (e.g., 52A) with the swollen area of postero-lateral regions of somite 3‒5 less marked in Tenagopelta n. gen. (e.g., Fig. 61 View FIGURE 61 E) than in Hephthopelta (e.g., Fig. 59 View FIGURE 59 A).

The remaining species previously placed in Hephthopelta may be placed in two major groups, both with G2s distinctly shorter than the G1 and the distal segment of the G2 poorly developed. One group has immobile eyestalks that are completely immobile in their orbits, the ischium and merus of the third maxilliped are short and quadrate and the G2 is short, half or less than half the length of the G1 ( Angustopelta n. gen. and Statommatia n. gen.). The other group has mobile eyestalks, the ischium and merus of the third maxilliped are more elongated, and the G2 is about three-quarters the length of the G1 ( Chinommatia n. gen. and Notopelta n. gen.).

The two genera with immobile eyestalks are easily distinguished by the form of their thoracic sterna and gonopods. One genus ( Angustopelta n. gen.) has a relatively narrow anterior male thoracic sternum (sternites 1‒4) that is also evident in adult females (e.g., Fig. 52 View FIGURE 52 D); the female sterno-pleonal cavity is relatively deep, with the vulvae on the steep outer margin of the sterno-pleonal cavity (e.g., Fig. 91 View FIGURE 91 B); and the G1 is stout and medially bent (e.g., Fig. 73 View FIGURE 73 A). The second genus ( Statommatia n. gen.) has a relatively narrower anterior male thoracic sternum (sternites 1‒4) also evident in adult females (e.g., Fig. 54 View FIGURE 54 B); the female sterno-pleonal cavity is relatively shallow, with the vulvae mesial in the flat portion of thoracic sternite 6 (e.g., Fig. 91 View FIGURE 91 E); and the G1 is more slender, with the distal half almost lanceiform and straight (e.g., Fig. 77 View FIGURE 77 A).

Inner margin of major Gently granuliform Gently granuliform (e.g., Gently granuliform (e.g., With long prolongation Gently granuliform (e.g., Gently granuliform (e.g., cheliped basis-ischium in (e.g., Fig. 42 View FIGURE 42 G) Fig. 42 View FIGURE 42 H) Fig. 42 View FIGURE 42 J, K) visible from dorsal view Fig. 42 View FIGURE 42 M, N) Fig. 42 View FIGURE 42 I) adults ( Figs. 15 View FIGURE 15 G; 42L)

……continued on the next page Character Hephthopelta s. str. Angustopelta n. gen. Chinommatia n. gen. Notopelta n. gen. Statommatia n. gen. Tenagopelta n. gen. Fingers of minor chela Distinctly laterally Subcircular in Subcircular in Subcircular in cross-section, Subcircular in Subcircular in

flatteneđ, broađ cross-section, not cross-section, not not đistinctly laterally cross-section, not cross-section, not throughout most of đistinctly laterally đistinctly laterally flatteneđ, gently tapering to đistinctly laterally đistinctly laterally length; shear-like, cutting flatteneđ, gently tapering flatteneđ, gently tapering tip; scissor-like, cutting flatteneđ, gently flatteneđ, gently tapering margins with low, broađ to tip; scissor-like, cutting to tip; scissor-like, cutting margins with đistinct sharp tapering to tip; to tip; scissor-like, cutting teeth (e.g., Fig. 40 View FIGURE 40 E) margins with đistinct margins with đistinct teeth ( Fig. 45 View FIGURE 45 B) scissor-like, cutting margins with đistinct

sharp teeth (e.g., Fig. sharp teeth (e.g., Fig. margins with đistinct sharp teeth (e.g., Fig. View FIGURE 41

41D) 43B) sharp teeth (e.g., Fig. 47 View FIGURE 47 B)

45D)

The group with mobile eyestalks also contains two genera ( Chinommatia n. gen. and Notopelta n. gen.), separated by the form of their eyestalks, thoracic sterna, and chelipeds. Chinommatia n. gen. has an eye peduncle that is evenly subcylindrical in cross-section (e.g., Fig. 25 View FIGURE 25 B); a proportionately wider anterior male thoracic sternum (sternites 1‒4) that is also evident in adult females (e.g., Fig. 53 View FIGURE 53 A); and the basis-ischium of the male major cheliped does not have an elongated process (e.g., Fig. 14 View FIGURE 14 B). In contrast, Notopelta n. gen. has the median part of the eye peduncle distinctly constricted and dorso-ventrally flattened, appearing reniform ( Fig. 25 View FIGURE 25 G); a proportionately broader anterior male thoracic sternum (sternites 1‒4) ( Figs. 53 View FIGURE 53 F); and the male major cheliped basis-ischium has a markedly long hook-like process (e.g., Fig. 42 View FIGURE 42 L).

Distribution. Indo-West Pacific region: Indian and western Pacific oceans.

TABLE 2. Comparison of characters of Hephthopelta s. str. and five new genera described for species previously included in Hephthopelta s. lato.

Character Carapace shape Hephthopelta s. str. Subtrapezoidal; slightly wider than long; strongly globose (e.g., Figs. 10A; 24A) Angustopelta n. gen. Subtrapezoidal; wider than long; dorsal surface gently convex (e.g., Figs. 12A; 24E) Chinommatia n. gen. Subtrapezoidal to subovate; wider than long; dorsal surfaces gently convex (e.g., Figs. 14B; 25B) Notopelta n. gen. Subtrapezoidal; distinctly wider than long; dorsal surfaces gently convex (Figs. 15G; 25G) Statommatia n. gen. Subtrapezoidal to subovate; distinctly wider than long; dorsal surfaces gently convex (e.g., Figs. 16A; 26A) Tenagopelta n. gen. Subtrapezoidal; slightly wider than long; globose (e.g., Figs. 17A; 26H)
Anterolateral margins With small tubercle or entire (e.g., Fig. 10A, C) With sharp tubercle or tooth, or entire (e.g., Fig. 11A, E) Usually entire, occasionally with low tooth or granule (e.g., Figs. 14E, F; 15F) With straight, granular, submarginal crest (Fig. 15G, H) Entire, never armed, sometimes granular (e.g., Fig. 16A) With low tubercle or entire (e.g., Fig.17A, D)
Eye peduncles Distinctly short, gently tapering to cornea; immobile (e.g., Fig. 24A) Short, gently tapering to cornea; immobile (e.g., Fig. 24E) Short to long, gently tapering to cornea; mobile (e.g., Fig. 25B, F) Short, median part of peduncle distinctly constricted, dorso-ventrally flattened, appearing reniform; mobile (Fig. 25G) Short, gently tapering to cornea; immobile (e.g., Fig. 26B) Distinctly short, gently tapering to cornea; mobile (e.g., Fig. 26H)
Posterior margin of epistome Median lobe distinctly broad (e.g., Fig. 24B) Median lobe broad (e.g., Fig. 24D) Median lobe broad to narrow (e.g., Fig. 25A, D) Median lobe narrow (Fig. 25G) Median lobe broad to narrow (e.g., Fig. 26B, D) Median lobe broad (e.g., Fig. 26G)
Third maxillipeds Ischium ovate, elongated; merus subquadrate to elongated (e.g., Fig. 31A–C) Ischium quadrate to rectangular; merus rounded to quadrate (e.g., Fig. 31D–I) Ischium rectangular; merus ovate (e.g., Fig. 32A–E) Ischium rectangular; merus ovate (Fig. 32F) Ischium rectangular to quadrate; merus ovate to quadrate (e.g., Fig. 33A–F) Ischium rectangular; merus quadrate (e.g., Fig. 33G–I)
Ventral surface of cheliped merus Outer margin with 3 or 4 long sharp teeth; inner margin unarmed (Fig. 42G) Outer margin with 3 or 4 sharp teeth; inner margin with strong distal tooth (Fig. 42H) Outer margin with 4 or more sharp tubercles or dentiform granules, sometimes low; inner margin unarmed (Fig. 42J, K) Outer margin with row of sharp tubercles; inner margin unarmed (Fig. 42L) Outer margin granuliform to dentiform with more than 4 sharp tubercles; inner margin unarmed (Fig. 42M, N) Outer margin with 3 or 4 sharp teeth; inner margin unarmed (Fig. 42I)
Inner margin of cheliped carpus Distal angle with long distal tooth (e.g., Fig. 10D, I); proximal part rounded (e.g., Fig. 10F) to dentiform (e.g., Fig. 10I) Distal angle with long tooth (e.g., Fig. 11E); proximal part rounded (e.g., Fig.11E) to slightly angular (e.g., Fig. 11C) Distal angle with short tooth (e.g., Fig. 14A, B, E); proximal part rounded (e.g., Fig. 14A, E) Distal angle with short tooth (Fig. 15G); proximal part rounded (Fig. 15G) Distal angle with short tooth (e.g., Fig. 16A, B); proximal part rounded (e.g., Fig. 16A, E) Distal angle with long tooth (e.g., Fig. 17A, B); short proximal part angular (e.g., Fig. 17B) or prominently dentiform (e.g., Fig. 17A, C)

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Chasmocarcinidae

Loc

Hephthopelta Alcock, 1899

Ng, Peter K. L. & Castro, Peter 2016
2016
Loc

Hephthopelta

De 2009: 32
Serene 1964: 239
Tesch 1918: 202
1918
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