Ethusina Smith 1884
Creators: name: Castro, Peter
Publisher: name: Zenodo
Year: 2005
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Ethusidae
Ethusina

description: KEY TO INDO- WEST PACIFIC SPECIES OF ETHUSINA   
1. Outer orbital teeth short (less than 1/3 height of inner margin of orbital sinus), tubercle-like, or absent.......................................................................................... 2  
— Outer orbital teeth conspicuous, at least 1/2 height of inner margin of orbital sinus.............................................................................................................................. 7  
2. Frontal teeth in the form of two acute, triangular lateral frontal teeth and two sinuous, lobe-like or slightly pointed median teeth................................................ 3  
 — Frontal teeth in the form of four clearly defined acute or obtuse teeth.................. 4 3. Outer orbital teeth in the form of a rounded tubercle. G1 each with rounded tip, band of numerous setae near tip (Fig. 16B). Eyes large, oval (Fig. 16A)...... E. challengeri   
 — Outer orbital teeth acute. G1 arrow shaped, with smooth sides. Eyes small............................................................................................................................ E. dofleini   
 4. Orbital sinus very elongated, merging with anterolateral borders of carapace. Outer orbital teeth may be absent in large females (Chen 2000: figs 1a, 2a, 5)........ E. microspina   
— Orbital sinus V-shaped, clearly demarcated from anterolateral borders of carapace. Outer orbital teeth small but always well defined................................................ 5  
 5. Outer orbital teeth about 1/3 height of outer margin of orbital sinus. G1 each with bilobbed tip (Chen 1997: fig. 6g, h).................................................... E. bicornuta   
— Outer orbital teeth very short, less than 1/4 height outer margin of orbital sinus. G1 each with single tip.............................................................................................. 6  
 6. Lateral frontal teeth almost as high as median frontal teeth. Eye peduncles not short so eyes visible dorsally (Chen 1993: fig. 16a, b). Dorsal surface of carapace granular.......................................................................................................... E. brevidentata   
 — Lateral frontal teeth much shorter than median frontal teeth. Eye peduncles very short so eyes not visible dorsally (Fig. 23A). Dorsal surface of carapace smooth.............................................................................................................. E. ocellata n. sp.   
7. Complete cornea of eye and distal portion of eye peduncle visible, projecting vertically or slightly obliquely above lower margin of each orbital sinus...................... 8  
— Cornea of eye not visible or only partially visible (together with part of eye peduncle) above lower margin of each orbital sinus (if completely or partially visible, eye oriented laterally, not vertically or obliquely above margin)................ 9  
 8. Eye peduncles not greatly elongated (Miers 1886: pl 29, fig. 1). Orbital sinuses V-shaped. Meri of P2, P3 very slender (P2 meri 10 times longer than broad)...................................................................................................................... E. gracilipes   
 — Eye peduncles greatly elongated (Fig. 21A). Orbital sinuses very broad, U-shaped. Meri of P2, P3 long but stout in appearance (P2 meri 6.1-7.6 times longer than broad).................................................................................. E. exophthalma n. sp.   
9. Dorsal surface of lower margin of each orbital sinus with short vertical fissure (Fig. 28A).......................................................................................................... 10  
— Dorsal surface of lower margin of each orbital sinus entire, without a vertical fissure.............................................................................................................................. 11  
 10. Very short, thick P2, P3 (P2 meri 5-6 times longer than broad).... E. crenulata n. sp.   
 — More slender P2, P3 (P2 meri 8-9 times longer than broad).......... E. isolata n. sp.   
 11. Anterior and anterolateral borders of carapace bordered by conspicuous long hairs (Fig. 18A)................................................................................ E. ciliacirrata n. sp.   
— Anterior and anterolateral borders of carapace not bordered by conspicuous long hairs.................................................................................................................. 12  
12. Outer orbital teeth almost as high, nearly as high, or higher than frontal teeth (reaching only around 1/2 height of inner margin of orbital sinuses in very small males)................................................................................................................ 13  
— Outer orbital teeth do not reach as high as frontal teeth, only reaching 1/2 to 3/4 height of inner margin of orbital sinuses............................................................ 18  
 13. P2, P3 very slender (P2 meri 11 times longer than broad), exceptionally long, reaching much higher than frontal teeth when folded (Doflein 1904: pl. 13, figs 5, 6)................................................................................................ E. somalica n. comb.   
— P2, P3 stout or moderately slender (P2 meri less than 10 times longer than broad) not exceptionally long (just reaching or reaching slightly over frontal teeth when folded).... 14  
14. Outer orbital teeth triangular, much broader proximally.................................... 15  
— Outer orbital teeth needle-like, only slightly broader proximally........................ 17  
 15. Outer orbital teeth conspicuous, high, reaching or nearly reaching frontal teeth (Fig. 19A).................................................................................... E. coronata n. sp.   
— Outer orbital teeth small, not reaching frontal teeth.......................................... 16  
 16. Orbital sinuses narrow (Ng & Ho 2003: fig. 1). Median frontal teeth often not acute, sinuous, lobe-like (Ng & Ho 2003: figs 12, 13A, as E. insolita Ng & Ho, 2003). Male abdomen with transverse ridge on somite 5...................... E. dilobotus   
 — Orbital sinuses broad, U-shaped (Ng & Ho 2003: figs 6, 7A). Median frontal teeth acute. Male abdomen unknown but most probably smooth, without transverse ridge on somite 5.................................................................................... E. chenae   
 17. P2, P3 slender, relatively long (Fig. 25A; Ng & Ho 2003: figs 4, 5C, as E. alcocki Ng & Ho, 2003). Eye peduncle slender, typically extending beyond sides of carapace in males.................................................................................... E. robusta   
 — P2, P3 stout, relatively short (Ng & Ho 2003: figs 8, 10B). Eye peduncle short, not extending beyond sides of carapace in males.................................... E. macrospina   
18. Outer orbital teeth triangular, much broader proximally.................................... 19  
— Outer orbital teeth needle-like, long and slender, only slightly broader proximally.............................................................................................................................. 21  
 19. P2, P3 slender, relatively long, reaching much higher than frontal teeth when folded.................................................................................................. E. pubescens   
— P2, P3 stout, relatively short, just reaching frontal teeth when folded................ 20  
 20. Anterolateral borders of carapace and outer margins of outer orbital teeth with delicate hairs; outer orbital, frontal teeth prominently acute (Ng & Ho 2003: figs 2, 3A).................................................................................................. E. taiwanensis   
 — Anterolateral borders of carapace and outer margins of outer orbital teeth without hairs; outer orbital, frontal teeth not prominently acute (Fig. 26A)........................................................................................................................ E. stenommata n. sp.   
 21. Outer orbital teeth not straight, proximal portions directed inwardly (Chen 2000: fig. 4a)............................................................................................ E. vanuatuensis   
— Outer orbital teeth straight................................................................................ 22  
 22. P2, P3 relatively short, just reaching frontal teeth when folded (Alcock & MacGilchrist 1905: pl. 72, fig. 2; Chen 1987: pl. 2, fig. F). Distal ends of G2 thick, stout (Chen 1987: fig. 7d).................................................................. E. desciscens   
— P2, P3 relatively long, reaching much higher than frontal teeth when folded. Distal ends of G2 long, slender.................................................................................... 23  
 23. Meri of P2, P3 noticeably thicker (Fig. 29), 7.0-8.5 times longer than broad. Eye peduncles short, eyes not visible beyond outer margins of outer orbital teeth (Fig. 30A).................................................................................. E. huilianae n. sp. — Meri of P2, P3 noticeably slender (Chen 1987: pl. 2, figs D, E), more than 10 times longer than short. Eye peduncles relatively long, making eyes visible beyond outer margins of outer orbital teeth in males (Chen 1993: fig. 18a)............................ 24   
 24. Meri of P2, P3 13.8 times longer than broad, 1.4 carapace length. G1 each with simple, rounded tip (Chen 1987: fig. 6d).............................................. E. longipes   
 — Meri of P2, P3 10.0-11.0 times longer than broad, 1.1-1.2 carapace length. G1 each with spur-like structure at tip (Chen 1993: fig. 18d).............. E. paralongipes
description: Published as part of Castro, Peter, 2005, Crabs of the subfamily Ethusinae Guinot, 1977 (Crustacea, Decapoda, Brachyura, Dorippidae) of the Indo-West Pacific region, pp. 499-600 in Zoosystema 27 (3) on pages 546-549, DOI: 10.5281/zenodo.5399909