Elasmopus cf. magnispinatus Kunkel, 1910

Vader, Wim & Krapp-Schickel, Traudl, 2012, On some maerid and melitid material (Crustacea: Amphipoda) collected by the Hourglass Cruises (Florida). Part 2: Genera Dulichiella and Elasmopus, with a key to world Elasmopus, Journal of Natural History 46 (19 - 20), pp. 1179-1218 : 1185-1216

Elasmopus cf. magnispinatus Kunkel, 1910

( Figures 4–6 )

Kunkel, 1910: 54–56, fig. 20.

Material examined

44626 (EJ 67329) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m Dredge. 11 September 1967. One female .

4654 (EJ 67217) Hillsborough County; 65 miles (104 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 58 ′ W 55-m Dredge. 3 June 1967. One female .

(EJ 67337) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet. 5 October 1967. One female .

44663 (EJ 67363) Hillsborough County; 65 miles (104 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 58 ′ W 55-m, 20-ft (6-m) balloon trynet. 5 October 1967. One male .

44671 (EJ 67340) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 37-m. Dredge. 5 October 1967. One female .

44675 (EJ 67379) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m Dredge. 14 November 1967. One female .

44685 (EJ 66376) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 37-m, 20-ft (6-m) flat trynet. 8 September 1966. One male 4 mm .

4687 (EJ 66042) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 83 ◦ 07 ′ W; 18-m. 7 February 1966. One specimen 3 mm .

44693 (EJ 65268) Hillsborough County; 4 miles (6 km) west of Egmont Key. 27 ◦ 35 ′ N, 82 ◦ 50 ′ W 6-m, 20-ft (6-m) flat trynet .

44698 (EJ 66192) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m Dredge. 11 May 1966. One juvenile .

44702 (EJ 67131) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m Dredge .

44703 (EJ 67390) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m Dredge. 20 November 1967. One female .

44704 (EJ 67300) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m Dredge .

44708 (EJ 67165) Hillsborough County; 65 miles (104 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 58 ′ W 55-m. Dredge. 12 May 1967. One juvenile .

44710 (EJ 65354) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m Dredge .

44714 (EJ 66469) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m Dredge .

44823 (EJ 66305) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 37-m, Dredge. 1 August 1966. One male 4 mm .

44847 (EJ 66041) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m 20-ft (6-m) flat trynet .

45109 (EJ 67248) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 37-m Dredge. 1/7/1967. One female 5 mm dissected: slide FSBC I 79920 .

45111 (EJ 66182) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 37-m 20-ft (6-m) flat trynet. 2 March 1966 .

45126 (EJ 67216) Hillsborough County; 65 miles (104 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 58 ′ W 55-m 20-ft (6-m) balloon trynet 3 June 1967. One juvenile .

45132 (EJ 66325) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 37-m, 20-ft (6-m) flat trynet. 11 August 1966. One female 4 mm .

45135 (EJ 67268) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W. 37-m Dredge. 11 July 1967. One immature .

45145 (EJ 67245) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet .

45210 (EJ 67120) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m. Dredge. 7 April 1967. One female .

45219 (EJ 66083) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m, Dredge. 21 March 1966. One immature .

45319 (EJ 66368) Lee County; 51 miles (82 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 58 ′ W 37-m, 20-ft (6-m) flat trynet. 4 September 1966. One male, one female; 6 mm with seven eggs dissected: slide FSBC I 79921 .

45330 (EJ 67058) Lee County; 51 miles (82 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 58 ′ W 37-m, 20-ft (6-m) balloon trynet. 15 February 1967. Two specimens .

45334 (EJ 67292) Lee County; 51 miles (82 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 58 ′ W 37-m, 20-ft (6-m) balloon trynet. 7 August 1967. One specimen .

45386 (EJ 65373) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W; 6-m, flat trynet. 6 December 1965. One male 4 mm .

45389 (EJ 66225) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m, Dredge. 12 June1966. One immature .

45395 (EJ 65372) Lee County; 4 miles (6 km) west of Sanibel Island Light. ◦ 24 ′ N, 82 ◦ 06 ′ W; 6-m, flat trynet. 6 December 1965. Two males 4 mm, one dissected: slide FSBC I 79922 .

45402 (EJ 66045) Hillsborough County; 65 miles (104 km) west of Egmont Key. 27 ◦ 37 ′ N, 27 ◦ 37 ′ N, 83 ◦ 58 ′ W 83 ◦ 58 ′ W; 55-m, flat trynet. 8 February 1966. One male 4 mm, one female 4 mm .

45410 (EJ 66072) Hillsborough County; 19 miles (30 km) west of Egmont Key. ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) flat trynet. 3 March1966. One female 4 mm, one female 5 mm .

45420 (EJ 67073) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet. 2 March1967. Two females 5 mm (one with eggs) .

45421 (EJ 66312) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m, Dredge. 5 August 1966. One female 4 mm .

45429 (EJ 67266) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m. Dredge. Two female .

45430 (EJ 67113) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 28 ′ W 83 28 ′ W. 37 m. Dredge. 3 April 1967. Two males, 4.5 mm, one female ovigerous 4 mm .

45435 (EJ 66080) Lee County; 4 miles (6 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 06 ′ W 6-m, 20-ft (6-m) flat trynet. 9 March 1966. One male subadult, two females ovigerous 4 mm .

45436 (EJ 67160) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet. 11 May 1967. Two immatures .

45451 (EJ 67336) Hillsborough County; 4 miles (6 km) west of Egmont Key. 27 ◦ 35 ′ N, 82 ◦ 50 ′ W 6-m Dredge .

45455 (EJ 67159) Hillsborough County; 4 miles (6 km) west of Egmont Key. 27 ◦ 35 ′ N, 82 ◦ 50 ′ W 6-m Dredge .

45456 (EJ 66214) Hillsborough County; 4 miles (6 km) west of Egmont Key. 27 ◦ 35 ′ N, 82 ◦ 50 ′ W 6-m, 20-ft (6-m) flat trynet .

45465 (EJ 67006) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet. 6 January 1967. Four specimens .

45467 (EJ 67323) Lee County; 51 miles (82 km) west of Sanibel Island 26 ◦ 24 ′ N, 82 ◦ 58 ′ W 37-m Dredge. 4 September 1967. One female .

45470 (EJ 67123) Lee County; 51 miles (82 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 82 ◦ 58 ′ W 37-m, 20-ft (6-m) balloon trynet. 7 April 1967. Four specimens .

45472 (EJ 67130) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet. 11 April 1967 .

45481 (EJ 67215) Hillsborough County; 38 miles (61 km) west of Egmont Key. 27 ◦ 37 ′ 83 ◦ 28 ′ W 37-m. Dredge. 2 June 1967. Four males 4 mm, one female ovigerous 4 mm, one juvenile.

45489 (EJ 67280) Hillsborough County; 19 miles (30 km) west of Egmont Key. 27 ◦ 37 ′ N, 83 ◦ 07 ′ W 18-m, 20-ft (6-m) balloon trynet .

45640 (EJ 67261) Lee County; 73 miles (117 km) west of Sanibel Island Light. 26 ◦ 24 ′ N, 83 ◦ 22 ′ W 55-m Dredge .

Description of the Hourglass-material

Length. 4–5 mm (Kunkel: 4 mm).

Head. A1 reaching somewhat more than half body length; peduncle robust, art 3 more than half length of art 1; flagellum with 20–22 arts (Kunkel: 10 arts!), setose; acc. flagellum with three arts (Kunkel: one art). A2 not much more than half length of A1, flagellum with six arts (Kunkel: four arts), about as long as peduncle art 5.

Mouthparts. Md palp art 1 more than half art 2, art 1 distally rounded, art 2 ≤ art 3, art 3 l:b <3.

Pereon. Cx 1 anteroventral corner rounded. Gn1 propodus to merus posterior margin poorly spinose but densely setose; carpus triangular, wider than propodus; propodus facially near inner and outer margin setose, palm oblique to regularly rounded; dactylus shorter than half propodus, curved. Gn2 basis with many short spines along anterior margin (Kunkel: one single spine). Gn2 ratio propodus:carpus male 3–4. Gn2 dactylus <1/2 propodus. Gn2 palm male not excavate, smooth, with proximal bump, with robust, small spines on this bump; remaining posterior margin strongly setose. Gn2 dactylus strongly curved, “comes across”. P3,4 propodus distal spines normal. P5–7 basis hind margin with short setae. P5 basis broadened, with straight hind margin. P6–7 basis posterior margin minutely crenulate.

Pleon. Ep3 posterodistal corner vaguely acute, almost rectangular, with small acute tooth at posterodistal corner. Ep 3 male posterior margin serrate in distal third. Ep3 inferior margin with spination. Urosome smooth. U1 peduncle with one basofacial spine. U2 longer ramus longer than U3 longer ramus. U3 ratio peduncle: longer ramus>0.8. U3 rami ratio 1.25–1.5. Telson l subequal b (also Kunkel: about as long as broad), cleft, distally concave, with marginal acute lobes of about equal length or outer lobe longer (males) or inner one (females). Distally with two or three longer and one to three shorter strong spines (Kunkel: group of three or four stout spines), which are all shorter than telson length.

Distribution

Bermuda ( Kunkel, 1910),? Florida (present inv.).

Remarks

As Shoemaker (1938: 30) already suggested, Kunkel’s material is clearly not fully adult and therefore the assignment of the studied material is not totally certain. Kunkel’s illustration is not complete and neither is his verbal description, but we use here this species name, with a question mark, mainly based on the shape of Cx 1, Cx 2, Gn1, Gn2, U3 and T.

Some reports of the probable species-group around E. pectenicrus are similar, as well as the new species by Senna (2011), but our material does not have any castelloserration on the basis of the pereopods, in contrast to these mentioned species. Considering P5–7 basis not castelloserrate as well as without long setae, and Ep1–3 without long setae, there are still a quarter of all species with which to make comparisons.

From the Atlantic there are four similar species: E. affinis (Gn2, T different), E. balkomanus (Ep2, 3, T different), sp. B by LeCroy (Cx 1, Gn2, P6 different), E. thomasi (Gn2, T different).

From the Pacific 17 species: E. alalo (Gn2 excavate, T diff.), E. antennatus (A1,2 Gn1,2, P5–7 would match, but Ep2,3, U3 and T diff.), E. atolgidus (with “rapax-T”), E. dentiferus (Gn1,2, T diff.), E. excavatus (Gn2 and Ep3 similar, but T diff. and size much larger), E. hawaiensis (Gn2 similar, P6, T diff.), E. karlae (Gn2 different), E. marcelae (Cx 1, 4, Gn2, T different), E. minimus (Gn2, T diff.), E. molokai (Gn2, T diff.), E. mutatus (Gn2, T diff.), E. ocoroni (Gn2 similar, Ep3, T diff.), E. seticarpus (Gn2, T diff.), E. spinicarpus (Gn2, Ep3, T diff.), E. spinidactylus (P5–7, T diff.), E. spinimanus (Gn2, T diff.), E. zoanthidea (Cx 1, 4, Gn2, T).

From the Indian Ocean and Red Sea four species: E. dubius (Gn2 diff.), E. gracilis (Gn2, Ep3 diff.), E. palu (Gn2 similar but T diff.), E. waltersi (Gn2 diff.).

Key to the genus Elasmopus worldwide

The genus Elasmopus is a large and unwieldy one, with 100 valid species, many of which have been insufficiently described, while a number of other nominal species with a very wide distribution, such as E. hooheno , E. pectenicrus , E. pocillimanus and E. rapax , in reality probably consist of complexes of closely related species with more restricted distributions.

Elasmopus species are common in the warmer areas of the world, with a clear cline in body size, the larger species living in the colder areas. They live mostly in shallow waters, often even intertidally, among algae and epifauna. Most species seem to occupy a range of habitats, but a few are more specific: E. rishikondiensis and E. visakhapatnamensis were found among sponges ( Kanakadurga et al. 1981), while E. calliactis appears to be an obligate associate of a sea anemone–hermit crab symbiosis ( Edmondson 1951).

Constructing an identification key to world Elasmopus , based on the literature rather than on actual specimens, has proved to be a daunting task. As there are large sexual differences in most Elasmopus species , and in addition much allometry in especially gnathopod 2 during the lifetime of the animals, the key had to be restricted to adult males. It is not always certain, however, that the type material of some species indeed consisted of adult males. Where possible, the original descriptions of the different species have been used in constructing the key; where later descriptions deviated substantially, these have also been inserted in the key, noting whose material and description is relevant.

Elasmopus chilensis Walker, 1913, E. crassimanus (Miers, 1884), E. miersi (Wrzesniowsky, 1879), E. peruvianus (Dana, 1852), E. pubescens (Dana, 1852), and E. vagans K. H. Barnard, 1940 are treated as dubious, while E. latibrachium Walker, 1904 and E. sokotrae Walker and Scott, 1903 have already been transferred to Mallacoota. Elasmopus besnardi Oliveira, 1951 has already been synonymized with E. brasiliensis (Dana, 1853) by Barnard (1965); E. chevreuxi Cecchini, 1928 is treated here as a synonym of E. brasiliensis (Dana, 1853) , E. congoensis Shoemaker, 1920 as a synonym of E. affinis Della Valle, 1893 (see Ruffo 1959), E. yunde Barnard, 1974 as a synonym of E. spinibasus Sivaprakasam, 1970 (synonymized herewith), while E. molokai and E. minimus also could be the same species. Finally, the only cold-water nominal species in Elasmopus , E. smirnovi Bulycheva, 1952 is here removed from Elasmopu s to Maera s. l.; its somewhat summarial description does not allow us to place it more specifically in one of the new genera in the Maera group ( Krapp-Schickel 2008).

At this moment, therefore, we know 101 valid species within the genus Elasmopus , cited here alphabetically and there are a few species that are most probably valid and used in the key, but not yet named).

E. aduncus Myers, 1995 ; E. affinis Della Valle, 1893 ; E. alalo Myers, 1986 ; E. antennatus (Stout, 1913) ; E. arafura Hughes and Lowry, 2011 ; E. arrawarra Hughes and Lowry, 2006 ; E. atolgidus Barnard, 1965 ; E. balkomanus Thomas and Barnard, 1979 ; E. bampo Barnard, 1979 ; E. barbatus Schellenberg, 1925 ; E. bastidai Garcia Madrigal, 2010 ; E. bollonsi Chilton, 1915 ; E. brasiliensis (Dana, 1853) ; E. buchneri Spandl, 1924 ; E. calliactis Edmondson, 1951 ; E. canarius Krapp-Schickel and Ruffo, 1990 ; E. caprai Maccagno, 1936 ; E. carteri Hughes and Lowry, 2011 ; E. crenulatus Berents, 1983 ; E. delaplata Stebbing, 1888 ; E. dentiferus Schellenberg, 1938 ; E. dentipalmus Walker, 1916 ; E. diplonyx Schellenberg, 1938 ; E. dubius Walker, 1904 ; E. ecuadoriensis Schellenberg, 1936; E. elieri Ortiz, Lalana and Varela, 2006 ; E. erythraeus ( Kossmann, 1880) ; E. excavatus Schellenberg, 1938 ; E. fusimanus Oliveira, 1951 ; E. gracilis Schellenberg, 1938 ; E. hawaiensis Schellenberg, 1938 ; E. holgurus Barnard, 1962 ; E. hooheno Barnard, 1970 ; E. hyperopia Hughes and Lowry, 2011 ; E. integer Myers, 1989 ; E. japonicus Stephensen, 1932 ; E. karamani Souza-Filho, 2009 ; E. karlae Garcia Madrigal, 2010 ; E. koreanus Kim and Kim, 1991 ; E. lapu Myers, 1985 ; E. laufolii Myers, 1986 ; E. lecroyae Garcia Madrigal, 2010 ; E. lejeunei Souza- Filho et al., 2009; E. leveque Hughes and Lowry, 2011 ; E. lemaitrei Ortiz and Lalana, 1994 ; E. levis Smith, 1873 ; E. longipropodus Souza-Filho and Senna, 2011 ; E. magnispinatus Kunkel, 1910 ; E. marcelae Garcia Madrigal, 2010 ; E. marplatensis Alonso de Pina, 1997 ; E. mayo Barnard, 1979 ; E. mcluerensis Hughes and Lowry, 2011 ; E. menurte Barnard, 1974 ; E. minimus Chevreux, 1908 ; E. molokai Barnard, 1970 ; E. mutatus Barnard, 1962 ; E. nanshaensis Ren, 1998 ; E. neglectus Chilton, 1915 ; E. oaxaquensis Garcia Madrigal, 2010 ; E. ocoroni Barnard, 1979 ; E. otus Hughes and Lowry, 2011 ; E. palu Appadoo and Myers, 2003 ; E. pectenicrus (Bate, 1862) ; E. perditus Reid, 1951 ; E. piikoi Barnard, 1970 ; E. pilosus Ledoyer, 1978 ; E. pocillimanus (Bate, 1862) ; E. podotrichius Ruffo, 1969 ; E. polynesus Krapp-Schickel & Müller, 2011 ; E. pseudaffinis Schellenberg, 1938 ; E. pseudinteger Appadoo and Myers, 2003 ; E. puteus Appadoo and Myers, 2003 ; E. rapax Costa, 1853 ; E. rishikondiensis Kanakadurga et al, 1981 ; E. serricatus Barnard, 1969 ; E. seticarpus Myers, 1985 ; E. shepherdi Hughes and Lowry, 2011 ; E. slatyeri Lowry and Hughes, 2009 ; E. souillacensis Appadoo and Myers, 2003 ; E. souzafilhoi Senna, 2011 ; E. spinibasus Sivaprakasam, 1970 ; E. spinicarpus Berents, 1983 ; E. spinidactylus Chevreux, 1907 ; E. spinimanus Walker, 1904 ; E. spinipalpus Ledoyer, 1982 ; E. spinipes Mateus, Mateus and Afonso, 1986 ; E. steelei Appadoo and Myers, 2003 ; E. steinitzi Ruffo, 1959 ; E. takamotus Myers, 1986 ; E. temori Barnard, 1979 ; E. thomasi Ortiz and Lalana, 1994 ; E. tiburoni Barnard, 1979 ; E. tubar Barnard, 1979 ; E. vachoni Mateus and Mateus, 1966 ; E. varanocephalensis Lowry and Hughes, 2009 ; E. visakhapatnamensis Kanakadurga et al, 1981 ; E. wahine Barnard, 1972 ; E. waltersi Ledoyer, 1982 ; E. warra Kelaher and Lowry, 2002 ; E. woodjonesi Hughes and Lowry, 2011 ; E. zoanthidea Barnard, 1979 .

Not all nominal species of Elasmopus have been included in the key or the matrix. Because of insufficiently detailed descriptions, we felt unable to include the following nominal species: E. caprai Maccagno, 1936 (Red Sea), E. dentipalmus Walker, 1916 ( Brazil) , E. erythraeus ( Kossmann, 1880) (Red Sea) , E. fusimanus Oliveira, 1951 ( Brazil) , E. perditus Reid, 1951 ( Sao Tomé), E. rishikondiensis Kanakadurga, Rao and Shyamashundari, 1981 ( India) and E. spinipes Mateus and Mateus, 1986 (W. Africa) .

There are clear groupings within the large genus Elasmopus . One consists of most of the species with castelloserrate hind margins in one or more pairs of the posterior pereopods (the “ pectenicrus- group”), another of those species with long setae on these same hind margins (the “ rapax -group”). Unfortunately, further divisions based on telson shape, the epimeral plates, the shape and setosity of gnathopod 2, or the shape of uropod 3 gave equivocal results, not leading to further clear groupings.

In constructing the key, we were aware of, but were possibly not always able to avoid, several pitfalls. There is a considerable amount of allometry in the shape and the relative length of the rami of uropod 3, a character used frequently in the key, and this may lead to problems when males that are not fully adult are studied. Also, the long setae on the posterior pereopods and also the epimeral plates of the species in the rapax group may be rubbed off in the collection and fixation processes, making the key more difficult to use in those cases. Female Elasmopus have in many cases quite different telson shapes and even epimeral plates from the males, and this key can therefore not be used to identify female Elasmopus .

Identification key to the genus Elasmopus (adult males only)

Underlined text refers to illustrations within the key. Text in bold type refers back to earlier key entries by number

1. Gn2 asymmetrical (one much larger than the other)............................................. Elasmopus bollonsi Chilton, 1915 ; New Zealand; 8 mm Gn2 symmetrical........................................................ 2

2. P6 and/or P7 with hind margin of basis partly or entirely c a s t e l l o s e r r a t e................................................... 3

P6–7 with hind margin basis crenulate or smooth........................ 26

3. Both P6 and P7 with castelloserrate hind margin of basis.................. 4 Either P6 or P7 with castelloserrate hind margin of basis................. 17

4. Urosome segment 1 with strong dorsal hump............................................... Elasmopus neglectus Chilton, 1915 ; New Zealand; 14.5 mm Urosome segment 1 dorsally smooth..................................... 5

5. Gn2 propodus not densely setose (strong spines on dactylus P3–4).......................... Elasmopus diplonyx Schellenberg, 1938 ; Marshall Isl.; 5 mm Gn2 propodus densely setose............................................ 6

6. P6 hind margin basis clearly concave..................................... 7 P6 hind margin basis not clearly concave, but straight or convex........... 8

7. Antennae short, acc. flag. short, bi-articulate. U3 and telson short, telson halves with two spines.................................................................... Elasmopus hawaiensis Schellenberg, 1938 ; Hawaii; 3.5–7 mm Antenna long, acc. flag. long, 4–5-articulate. U3 and telson long, telson halves with four spines......................................................................... Elasmopus sp. (E. “ pseudaffinis ” s. Myers, 1985); Fiji; 6.0 mm

8. P6 basis hind margin castelloserrate only in lower third.................... 9 P6 basis castelloserrate over more than half its length.................... 10

9. Gn1 propodus nearly transverse................................. Elasmopus carteri Hughes and Lowry, 2011 ; Ningaloo Reef, Australia; 5.6 mm Gn1 propodus hind margin regularly rounded.................................. Elasmopus arrawarra Hughes and Lowry, 2006 ; NSW, Australia; 6.8 mm

10. Telson longer than broad, each half ending in two equal-sized acute lobes (Ep3 posterodistal corner acute, with small tooth. Gn2 propodus palm with proximal rounded hump).................................................... Elasmopus canarius Krapp-Schickel and Ruffo, 1990 ; Canary Isl.; 4.5 mm Telson broader than long, halves square-ending.......................... 11

11. A1–2 flagellum densely setose, with long setae........................... 12 A1–2 flagellum not very setose, setae short............................... 13

12. Telson halves with two spines. Ep3 posterodistal corner rectangular....................................... Elasmopus laufolii Myers, 1986 ; Niue; 6.0 mm Telson halves with more than five spines. Ep3 posterodistal corner acute........................ Elasmopus holgurus Barnard, 1962 ; S. California; 8.0 mm

13. Ep3 posterodistal corner more or less rectangular, without tooth.......... 14 Ep3 posterodistal corner acute, with small tooth......................... 15

14. Ep3 posterodistal corner rectangular, hind margin convex, slightly crenulated.... Elasmopus oaxaquensis Garcia Madrigal, 2010 ; Oaxaca, Mexico; 7.6 mm Ep3 posterodistal corner a bit less than 90 ◦, hind margin somewhat concave, smooth................................ Elasmopus otus Hughes and Lowry, 2011 ; Australia NSW; 7.3 mm (otherwise very similar to E. oaxaquensis )

15. Gn2 propodus palm with several proximal humps, divided by indentations........................ Elasmopus nanshaensis Ren, 1998 ; S. China Sea; 4 mm Gn2 propodus palm with single proximal hump.......................... 16

16. Gn1 propodus stout, l:b = 4:3, at palmar corner widest.......................... Elasmopus leveque Hughes and Lowry, 2011 ; Western Australia, 6.1 mm Gn1 propodus subrectangular, at palmar corner not wider................................... Elasmopus crenulatus Berents ; Great Barrier Reef; 4.4 mm

17. P6 hind margin of basis castelloserrate, P7 not............................................ Elasmopus pectenicrus (Sp. Bate, 1862) ; N. Guinea; 5–10 mm (NB. Probably a species complex!) P7 hind margin of basis castelloserrate, P6 not........................... 18

18. Urosomite 1 with clear hump, Telson with three long and two short spines......... Elasmopus shepherdi Hughes and Lowry, 2011 ; SouthAustralia; 10 mm Urosomite 1 dorsally smooth........................................... 19

19. P7 hind margin of basis “minutely castelloserrate” ( Lowry and Hughes 2009, 2011).................................................................. 20 P7 hind margin of basis clearly and coarsely castelloserrate. (Telson short with almost square-ending halves and long spines. Gn2 propodus densely setose)................................................................. 21

20. Telson long, with rounded tip and short spines. Gn2 propodus not very setose............................. Elasmopus alalo Myers, 1986 ; Tonga; 12.5 mm Telson short, truncate...... Elasmopus mcluerensis Hughes and Lowry, 2011 ; Australia Northern Territory; 4.6 mm.

21. P7 hind margin of basis castelloserrate only in distal third..................................... Elasmopus tubar Barnard, 1979 ; Baja California; 5.1 mm P7 hind margin of basis castelloserrate for at least two thirds............. 22

22. Telson halves with one or two long spines, telson broader than long....... 23 Telson halves with more long spines..................................... 24

23. P6 regularly expanded, hind margin convex.................................................................. Elasmopus lapu Myers, 1985 ; Fiji; 5.0 mm P6 narrowly expanded, hind margin straight to slightly concave......................... Elasmopus steelei Appadoo and Myers, 2003 ; Mauritius; 2.8 mm

24. Gn2 propodus palm proximally with high abrupt rounded hump. Telson with two or three long spines...................................................................... Elasmopus spinibasus Sivaprakasam, 1970 ; India; 10 mm .......................... (= E. yunde Barnard, 1974 ) W. Australia, 4.8 mm Gn2 propodus palm with triangular or rounded hump. Telson with three long and two short spines.................................................... 25 25. Ep3 posterior margin with a few coarse serrations distally. U3 with inner ramus clearly much longer than broad........................................................... Elasmopus souzafilhoi Senna 2011 ; NE Brazil; 5.9 mm Ep3 posterior margin lightly crenulate. U3 with inner ramus only slightly longer than broad... Elasmopus oaxaquensis Garcia Madrigal, 2010 ; Oaxaca, Mexico; 7.6 mm;...................... and E. serricatus Barnard, 1969 ; S. California; 8.0 mm...... (very close; for proposed differences, see Garcia Madrigal 2010, T. IV)

(from 2B: P6-7 hind margin basis c r e n u l a t e or s m o o t h):

26. P 7 b a s i s h i n d m a r g i n w i t h s e v e r a l t o m a n y l o n g s e t a e (NB. These may occasionally have been rubbed off after collection)....... 27

P7 basis hind margin without long setae................................. 47

27. Telson entire........................................................... 28 Telson cleft............................................................ 30

28. Gn2 propodus palm almost smooth. Ep3 with posterodistal corner acute................................................ Elasmopus visakhapatnamensis Kanakadurga, Rao and Shyamasundari, 1981 ; India; 6.6 mm Gn2 propodus palm with rounded protuberances. Ep3 with posterodistal corner rectangular...................................................... 29

29. Telson with posterior margin even. Gn2 propodus palm with large rounded indentation.................................................................... Elasmopus pseudinteger Appadoo and Myers, 2003 ; Mauritius; 3.9 mm Telson with posterior margin scalloped. Gn2 propodus palm without large rounded indentation......................... Elasmopus integer Myers, 1989 ; Bora Bora, 4.8 mm

30. Ep3 ventral margin with l o n g s e t a e [+ P6,7 basis hind margin with setae] (NB. These may occasionally have been rubbed off after collection)....... 31

Ep3 ventral margin s m o o t h or with s h o r t spines.................... 39

31. Gn2 propodus palm with large excavation, in which the dactylus rests..... 32 Gn2 propodus palm without large excavation, but with one or more protuberances.......................................................... 34

32. Telson halves with three spines......................................................... Elasmopus tiburoni Barnard, 1979 ; P. Penasco, Mexico, 8.7 mm Telson halves with one or two spines.................................... 33

33. Ep3 posterodistal corner with a number of serrations and a few long setae........................... Elasmopus molokai Barnard, 1970 ; Hawaii; 3.3 mm Ep3 posterodistal corner with small tooth, without long setae............... Elasmopus arafura Hughes and Lowry, 2011 ; Oxley Island, Australia; 6 mm

34. Ep3 posterodistal corner rounded, hind margin smooth.................................... Elasmopus hooheno Barnard, 1970 (material GBR); 6.0 mm Ep3 posterodistal corner rectangular, hind margin partly crenulate, with setules................................................................. 35

35. U3 rami very unequal................... Elasmopus hooheno Barnard, 1970 ; Hawaii; 4.3 mm (NB. This is probably a complex of species.) U3 rami subequal...................................................... 36

36. Coxa 4 with two ventral setae. Gn2 propodus palm with three protuberances. (Telson halves with only one large spine).................................................... Elasmopus mayo Barnard, 1974 ; Tiburon, Mexico; 8.7 mm Coxa 4 with more than five ventral setae. Gn2 propodus palm with four protuberances.......................................................... 37

37. Telson halves with two almost equal-sized spines........................................ Elasmopus rapax Costa, 1853 ; Napoli, Italy; neotype; 12.0 mm Telson halves with clearly unequal-sized spines.......................... 38

38. Telson halves regularly rounded distally, with two or three spines................... Elasmopus lecroyae Garcia Madrigal, 2010 ; Oaxaca, Mexico; 7.6 mm Telson halves irregularly rounded distally, with two spines........... Elasmopus bampo Barnard, 1979 ; Topolobambo, Mexico; 6-9 mm (NB rapax, lecroyae and bampo are very similar)

(From 30 B: Ep3 s m o o t h or with s h o r t s e t a e [+ P6,7 basis hind margin with setae])

39. Telson clearly much longer than broad.................................. 40 Telson at most slightly longer than broad, or even broader than long...... 42

40. Ep3 posterodistal corner rectangular, without tooth. (Telson halves with four spines)............. Elasmopus calliactis Edmondson, 1951 ; Hawaii; 10 mm Ep3 posterodistal corner with small tooth, rectangular or acute........... 41

41. Telson halves with three spines. Ep3 posterior margin convex, almost smooth Elasmopus piikoi Barnard, 1970 ; Hawaii; 5.0 mm Telson halves with one spine. Ep3 posterior margin crenulate....... Elasmopus karamani Souza-Filho and Senna, 2009 ; NE Brazil; 8.5 mm

42. Ep3 with posterior margin serrate or crenulate........................... 43 Ep3 with posterior margin smooth...................................... 45

43. Ep3 with part of posterior margin coarsely serrate. Telson halves distally acute.......... Elasmopus marplatensis Alonso de Pina, 1997 ; Buenos Aires, Argentina; 6.5 mm Ep3 with posterior margin slightly serrate or weakly crenulate............ 44

44. Ep3 posterior margin slighly serrate. Gn2 propodus about half as long as broad; basis with spines distally on anterior margin..... Elasmopus hooheno Barnard, 1970 (material Ledoyer– Madagascar); 8 mm Ep3 posterior margin weakly crenulate. Gn2 propodus very elongate, about 2.5 times as long as broad; basis without spines on anterior margin..... Elasmopus longipropodus Senna and Souza-Filho, 2010 ; Atol dos Rocas, Brazil; 5.8 mm

45. Telson halves with two very small spines Elasmopus spinimanus Walker sensu Ruffo, 1938 ; Red Sea, 6 mm Telson halves with one spine. Gn2 propodus palm with protuberances and/or indentations........................................................... 46

46. Gn2 propodus palm with large excavation, in which dactylus tip rests Elasmopus pocillimanus (Sp. Bate, 1862) ; Mediterranean, 6–8 mm Gn2 propodus palm with irregular surface and double row of spines............................ Elasmopus steinitzi Ruffo, 1959 ; Red Sea, 7 mm

(from 26 B: P7 basis hind margin without long setae)

47. Telson entire............. Elasmopus takamotus Myers, 1986 ; Niue; 4.2 mm Telson cleft............................................................ 48

48. Urosome segment 1 with dorsal hump................................... 49 Urosome segment 1 dorsally smooth.................................... 51

49. Urosome segment 1 with inconspicuous dorsal hump. Telson medium, halves ending in two rounded lobes........ Elasmopus menurte Barnard, 1974 ; SW Australia; 10.2 mm Urosome segment 1 with well-developed hump.......................... 50

50. Telson short, halves ending in two acute, equal-sized lobes................................... Elasmopus japonicus Stephensen, 1932 ; Seto, Japan; 9 mm Telson about as long as wide, with long spines... Elasmopus woodjonesi Hughes and Lowry, 2011 ; South Australia; 7.5 mm.

51. Ep3 posterodistal corner with strong tooth or clearly acute............... 52 Ep3 posterodistal corner with small tooth, serration, rectangular or rounded. (In case of doubt, try both alternatives).................................. 66

52. Ep3 posterodistal corner with corner upturned and upper side of tooth horizontal............................................................. 53 Ep3 posterodistal corner regularly acute, ending in a tooth............... 54

53. P5 basis with hind margin straight to slightly convex, not narrowing distally........................... Elasmopus sp. A ( LeCroy 2000) ; Florida; 3–5 mm P5 basis with hind margin strongly concave, narrowing distally... Elasmopus polynesus Krapp-Schickel and Müller, 2011 ; Polynesia; 4.5 mm

54. Telson longer than broad, or as long as broad........................... 55 Telson clearly broader than long........................................ 63

55. Telson halves with outer lobe shorter than inner lobe or even reduced to a notch.................................................................. 56 Telson halves with lobes of equal size, or outer lobe the longer............ 58

56. Gn1 propodus with palm subtransverse, forming an almost right angle with the posterior margin. Telson halves medium long, with stronger inner lobe subacute, outer lobe shorter, with three spines... Elasmopus levis S. I. Smith, 1873 ; N. England; 12 mm Gn1 propodus with oblique palm and posterior margin in a practically unbroken curve........................................................ 57 57. Telson halves long, outer lobe reduced to a notch, with 2 short spines; U3 long, rami distally pointed...................................................... Elasmopus delaplata Stebbing, 1888 ; Montevideo, Uruguay; 15 mm Telson halves medium long, outer lobe short, with 2 short spines; U3 rami distally narrower and tapering..................................................................... Elasmopus alalo Myers, 1988 (NB. material Barnard 1965; Ledoyer 1972, 1978 part., 1982 Madagascar; Berents 1983 Lizard Isl. all as E. pseudaffinis 9–11.5 mm; Myers 1995, Lowry and Hughes 2009 material; 11.5 mm)

58. Telson halves with outer lobe longer than inner lobe.Telson halves with apices acute. U3 with equal rami, longer than peduncle.............................. Elasmopus balkomanus Thomas and Barnard, 1988 ; Florida keys, 7.1 mm Telson halves ending in two equal-sized lobes............................ 59

59. Telson halves with three or four spines.................................. 60 Telson halves with one or two spines.................................... 61

60. Gn2 propodus palm smooth, densely setose.......................................... Elasmopus brasiliensis (Dana, 1853) ; Rio de Janeiro, Brazil; 7 mm Gn2 propodus palm with small irregular protuberances, moderately setose.. Elasmopus varanocephalensis Lowry and Hughes, 2009 ; Great Barrier Reef; 8.0 mm

61. Gn2 propodus moderately setose; palm smooth, with spines near dactylus. Telson halves with two spines... Elasmopus lejeunei Souza-Filho and Senna, 2009 ; Rio Grande de Norte, Brazil; 5.2 mm Gn2 propodus densely setose, with long setae. Telson halves with one spine.............................................................. 62

62. P5 basis similar to P6-7, with convex margins. Accessory flagellum biarticulate........................................................................ Elasmopus bastidai Garcia Madrigal, 2010 ; Oaxaca, Mexico; 7.6 mm P5 basis different from P6-7, with hind margin concave. Accessory flagellum 4-articulate.............. Elasmopus lemaitrei Ortiz and Lalana, 1994 ; N. Cuba, 3.5 mm

(from 46 B: Telson broader than long)

63. Gn2 propodus sparsely setose. U3 medium long, with narrow, subequal rami Elasmopus puteus Appadoo and Myers, 2003 ; Mauritius; 3 mm Gn2 propodus densely setose........................................... 64

64. U3 very short, with spiny unequal rami, peduncle longer than rami..................... Elasmopus vachoni Mateus and Mateus, 1966 ; Sao Tomé; 4 mm U3 normal, peduncle shorter than rami................................. 65

65. Gn1 carpus clearly much longer than propodus.................................................... Elasmopus buchneri Spandl, 1924 ; Red Sea; 7.5 mm Gn1 carpus shorter to subequal propodus.. Elasmopus hyperopia Hughes and Lowry, 2011 ; Western Australia; 6.3 mm.

(from 51 B: Ep3 posterodist. corner with s m a l l t o o t h, s e r r a t i o n, r e c t a n g u l a r or r o u n d e d)

66. Ep3 posterodistal corner with s m a l l t o o t h.......................... 67 Ep3 posterodistal corner rounded or rectangular, without corner tooth (When in doubt, try both alternatives!)......................................... 93

67. Ep3 with long ventral setae....... Elasmopus cf rapax sensu LeCroy (2000) ; Florida; 6–12 mm Ep3 without long ventral setae.......................................... 68

68. P3–7 dactyli coarsely toothed...... Elasmopus spinidactylus Chevreux, 1907 ; Gambier Archipelago; 6 mm P3–7 dactyli smooth.................................................... 69

69. Gn2 dactylus as long as propodus. Elasmopus karlae Garcia Madrigal, 2010 ; Oaxaca, Mexico; 4.9 mm Gn2 dactylus clearly shorter than propodus............................. 70

70. Gn2 dactylus long, clearly longer than half propodus.................... 71 Gn2 dactylus short, not longer than half propodus....................... 74

71. Telson of “ rapax - type ” (i.e. outer lobe much reduced, bearing short spines, inner lobe much the longer, may be rounded or subacute), with two small spines. Gn2 propodus not very setose

........... Elasmopus affinis Della Valle, 1893 ; Gulf of Napoli , Italy; 10 mm ........................ (= E. congoensis Shoemaker, 1920 ); Angola; 10 mm Telson not of “ rapax - type ”............................................. 72

72. U3 rami subequal. (Gn2 dactylus strong, blunt ending)........................... Elasmopus marcelae Garcia Madrigal, 2010 ; Oaxaca, Mexico; 5.7 mm U3 rami clearly unequal................................................ 73

73. Gn2 propodus smooth, with subpalmar ridge; dactylus narrow. Telson halves with outer lobe the stronger, with two spines

.......... Elasmopus gracilis Schellenberg, 1938 (material Myers– Fiji); 4 mm

Gn2 propodus without subpalmar ridge, palm with triangular proximal and small median hump; dactylus broad. Telson halves with lobes of equal size, with three spines

... Elasmopus zoanthidea Barnard, 1979 (material Garcia Madrigal, Oaxaca, Mexico); 5.2 mm

74. Gn2 propodus densely setose........................................... 75 Gn2 propodus not densely setose........................................ 80

75. Gn2 carpus with anterior margin smooth................................ 76 Gn2 carpus with anterior margin with long setae......................... 77

76. U3 with rami subequal. Ep3 posterodistal corner with several serrations Elasmopus cf. magnispinatus Kunkel, 1910 ; Hourglass-material, Florida; 4–5 mm U3 with rami clearly unequal. Ep3 posterodistal corner with one moderately large tooth...................... Elasmopus spinimanus Walker, 1904 ; Sri Lanka; 5 mm

77. U3 rami equal or subequal.............................................. 78 U3 rami clearly unequal................................................ 79

78. Telson medium long, telson halves with apex rounded.......................................... Elasmopus dentiferus Schellenberg, 1938 ; Kiribati; 7 mm Telson long, telson halves with apex ending in two acute points............... Elasmopus excavatus Schellenberg, 1938 ; Gilbert Isl.; 7.5 mm

79. A1 flagellum densely setose. Telson halves with three spines. Gn2 merus with acute posterior lobe. Elasmopus antennatus (Stout, 1913) ; California; 3.4 mm A1 flagellum sparsely setose. Telson halves with two spines. Gn2 merus with rounded posterior lobe....................... Elasmopus gracilis Schellenberg, 1938 ; Niue; 4.5 mm

80. Gn2 propodus palm very short; dactylus peculiar: short and strongly curved. Elasmopus dubius Walker, 1904 ; Sri Lanka; 5 mm Gn2 propodus and dactylus not like this................................. 81

81. Gn2 propodus palm with deep indentation.............................. 82 Gn2 propodus palm without deep indentation........................... 83

82. Gn2 propodus palm with narrow deep indentation...... Elasmopus minimus Chevreux, 1908 ; Gambier Archipelago, 3 mm Gn2 propodus with rounded deep indentation. Elasmopus alalo Myers, 1986 ; Tonga; 12.5 mm (material Lizard Isl. Berents, 1983, Lowry and Hughes, 2009)

83. Gn2 propodus with deep hollow medially. (Eyes large)................................. Elasmopus “ pocillimanus ” (material Ledoyer– Madagascar), 5 mm Gn2 propodus different................................................. 84

84. Telson of “ rapax- type ” (cf. 71 a)........................................ 85 Telson different........................................................ 86

85. Ep3 with small tooth, posterior margin otherwise smooth......................... Elasmopus atolgidus Barnard, 1965 ; Ifaluk Atoll; 3.5 mm (NB unique holotype female) Ep3 with small tooth and several serrations on posterior margin............... Elasmopus thomasi Ortiz and Lalana, 1994 ; N. Cuba; 3.3 mm

86. Gn2 with anterior margin of well-developed carpus densely setose........ 87 Gn2 with anterior margin of cup-shaped carpus not or poorly setose...... 88

87. Gn2 anterior margin of carpus densely beset with long setae. Ep3 with a few serrations above the tooth in the posterodistal corner.. Elasmopus seticarpus Myers, 1985 ; Fiji; 7.5 mm Gn2 anterior margin of carpus with moderate cover of not very long setae. Ep3 with no serrations above the tooth in the posterodistal corner............ Elasmopus spinicarpus Berents, 1983 ; Great Barrier Reef; 8.5 mm

88. Telson long, at least as long as broad.................................... 89 Telson short, clearly broader than long.................................. 91

89. Gn2 propodus palm with several humps and indentations. (P5–7 basis similar, with convex hind margins).. Elasmopus waltersi Ledoyer, 1982 ; Madagascar; 7.5 mm Gn2 propodus with only a single hump or seemingly smooth............. 90

90. Gn2 propodus with strong and high proximal hump. Telson halves with three or four spines...... Elasmopus magnispinatus Kunkel, 1910 ; Bermuda; 4 mm Gn2 propodus palm mostly smooth, with only one small medial tooth; carpus posterior margin densely setose. (P5 basis with concave hind margin)........................... Elasmopus sp B ( LeCroy 2000) ; Florida; 6–8 mm

91. Gn2 basis anterior margin smooth. (Coxae 1–2 without long ventral setae) Elasmopus palu Appadoo and Myers, 2003 ; Mauritius; 2.5 mm Gn2 basis anterior margin with long setae............................... 92

92. Gn2 basis anterior margin densely setose.. Elasmopus pilosus Ledoyer, 1978 ; Madagascar; 5 mm Gn2 basis anterior margin with scattered long setae........... Elasmopus molokai Barnard, 1970 (material Myers, Fiji); 5.0 mm

(From 66 B: Ep3 posterodistal c o r n e r r o u n d e d or r e c t a n g u l a r, wi t h o u t c o r n e r t o o t h)

93. Ep3 with posterodistal corner clearly rounded........................... 94 Ep3 with posterodistal corner rectangular (although perhaps with rounded corner)................................................................ 97

94. P7 hind margins of art. 2–5 densely setose.... Elasmopus podotrichius Ruffo, 1969 ; Red Sea; 3 mm P7 hind margins of art. 2–5 not densely setose........................... 95

95. Gn2 propodus densely setose............................................................... Elasmopus ocoroni Barnard, 1979 ; Galapagos Isl.; 5.0 mm Gn2 propodus not densely setose........................................ 96

96. A1 flagellum densely setose. Gn2 posterior margin of carpus and proximal half of propodus densely setose, with long setae Elasmopus mutatus Barnard, 1962 ; S. California; 7.5 mm A1 flagellum not very setose. Gn2 posterior margin of carpus and proximal half of propodus only moderately setose, with short setae................ Elasmopus koreanus Kim and Kim, 1991 ; S. Korea; 12.9 mm

97. T e l s o n of “ rapax - type ”.............................................. 98 Telson different........................................................ 99

98. Gn2 propodus palm with irregular humps; dactylus about half of propodus length; carpus anterior margin with long setae. U3 rami clearly unequal...................... Elasmopus wahine Barnard, 1972 ; New Zealand, 10.0 mm Gn2 propodus palm mostly smooth; dactylus about 2/3 of propodus length; carpus anterior margin smooth. U3 rami subequal........... Elasmopus affinis Della Valle, 1893 ; Gulf of Napoli, Italy; 10 mm

99. Telson long, at least as long as broad................................... 100 Telson short, clearly broader than long................................. 103

100. Telson halves with rounded apex....................................... 101 Telson halves with cleft apex........................................... 102

101. Gn2 propodus palm with ridge with triangular protuberance................... Elasmopus slatyeri Lowry and Hughes, 2009 ; Great Barrier Reef; 4.9 mm Gn2 propodus palm with deep “hollow”, in which dactylus rests................. Elasmopus pocillimanus (Sp. Bate, 1862) ; (sensu Ledoyer, Madagascar); 5.1 mm

(NB.This taxon has been synonymized with E. slatyeri by Lowry and Hughes (2009)

102. Gn2 propodus palm with low irregular protuberances, not very setose......................... Elasmopus temori Barnard, 1979 ; Galapagos Isl.; 4.2 mm Gn2 propodus with two strong square protuberances, densely setose

............... Elasmopus zoanthidea Barnard, 1979 ; Galapagos Isl.; 4.3 mm

103. Gn2 propodus palm very concave, leaving much room between palm and dactylus. (P6 basis with hind margin irregularly concave)... Elasmopus elieri Ortiz, Lalana and Varela, 2004 ; Cuba; 6 mm Gn2 propodus different............................................... 104

104. Telson halves ending square. (U3 rami very unequal).................... 105 Telson halves ending in two equal-sized lobes........................... 106

(NB See note at 108 b)

105. Mdb palp art. 1 with acute prolongation. Telson halves with one spine. Eyes large... Elasmopus (Dentelasmopus) spinipalpus Ledoyer, 1982 ; Madagascar; 5–6 mm Mdb palp art. 1 normal. Telson halves with four spines. Eyes normal......... Elasmopus ecuadorensis Schellenberg, 1936 ; Galapagos Isl.; 6.3 mm

106. Gn2 basis anterior margin with flange, bearing six spines in distal half. U3 rami very unequal...... Elasmopus aduncus Myers, 1965 ; Kosrae; 4.2 mm Gn2 basis anterior margin without flange or distal spines. U3 rami subequal....................................................................... 107

107. Gn2 propodus with several protuberances and a double row of spines. (P5–7 anterior margin of art. 3–5 sparsely spinose) Elasmopus souillacensis Appadoo and Myers, 2003 ; Mauritius; 3.5 mm Gn2 propodus with single large proximal protuberance................. 108

108. P5-7 anterior margins of art. 3-5 densely setose, with long setae..................... Elasmopus warra Kelaher and Lowry, 2002 ; NSW, Australia; 7.1 mm P5–7 anterior margins of art. 5–7 sparsely setose, with short setae............................... Elasmopus hawaiensis Schellenberg, 1938 ; Hawaii; 5 mm

(NB. Different authors have widely different telson shapes for this species)

Diagnostic characters for the genus:

Lateral cephalic lobe short, anteroventral cephalic notch present. A1> A2, flag. acc. with more than one art. Lower lip with inner lobes. Md palp 3-articulate, art 1 without distal acute prolongation (exception: E. spinipalpus Ledoyer, 1982 ), art 2 variable in length, art 3 strongly or weakly falciform (most important character for the genus), with D- and E-setae. Mx1 inner plate naked or beset with short setae, palp symmetrical, 2- articulate. Mx2 inner plate without facial setae, inner margin with simple setae. Gn1, 2 subchelate, symmetrical (exception E. bollonsi Chilton, 1915 ), different in size and shape, both sexually dimorphic (Gn 1 in males smaller, Gn 2 in females smaller). Cx4 with posterodistal lobe. Pereopods 5–7 strong, basis with posterodistal lobe present, posterior margin with or without long setae, with or without serration. Ep3 posterodistal corner rounded, rectangular or with upturned pointed tooth; posterior margin smooth or on inferior part serrate. U1 usually with basofacial spine, U3 rami short, subequal or somewhat unequal, uni-articulate or with vestigial second art, apically truncate. Telson usually deeply cleft, in a few species entire (fused).

The very species-rich genus Elasmopus Costa, 1853 constitutes, together with Maera Leach 1813 and a number of smaller genera, the family Maeridae ( Krapp-Schickel 2008) . Single Elasmopus species show relationships to probably closely related other genera by sharing synapomorphies, such as the asymmetrical gnathopods in E. bollonsi , shared with Linguimaera or Ceradocus, the distally lengthened and acute first article of the mandible palp of E. spinipalpus , shared with Maera , the humps on the urosome on a number of species, shared with Mallacoota, and also the very long Gn2 carpus in males of E. buchneri , again shared with Mallacoota. For the moment Elasmopus is a heterogeneous taxon, exclusively kept together by the falcate third article of the mandible palp, and only secondarily by the shape of male Gn2, and of Ep3 and T.

The characteristic mandible palp varies not only in the broadness and in the density of setation on art 3, but also in the different shape of art 1 distally: in some species it is illustrated as nearly straight or rounded, in others oblique to different degrees ( Figure 7 ). Hence, the step to an acute prolongation as in E. (Dentelasmopus) spinipalpus could be reasonable, although this species is also very aberrant in other respects.

We strongly hoped that we would be able to split the unwieldy genus Elasmopus by grouping the species according to telson shape ( Figure 8 ), but we found that there is considerable sexual variation within the same species, e.g. from rounded to acute tips, from short to long spines, from a shallow to a deep excavation, or from cleft to entire telsonic halves. It looks as if Elasmopus is extremely well able to adapt to ecological niches, and also uncommonly quick to speciate. It is not even wise to group those few species with an entire telson into a separate genus: three of them ( E. integer , E. pseudinteger , E. visakhapatnamensis ) have long setae on the basis of P6–7 and are probably closely related, but E. takamotus has these pereopod bases smooth. Moreover, Shoemaker (1933: 15–16) reports an Elasmopus “ rapax ” specimen from Florida which is “quite typical except that the telson is not cleft, which is of course an abnormality”. Barnard and Barnard (1983: 140) mention this paper and reason that the “telsonic fusion is not as remarkable as heretofore believed”. Garcia Madrigal (2010: Fig. 16) found fully, partly and not at all cleft telsons in E. oaxaquensis . The same tendency can also be observed in the genera Linguimaera and Zygomaera. In Elasmopus it is mainly found in the rapax -group, to which E. integer , E. pseudinteger and E. visakhapatnamensis (but not E. takamotus ) belong.

There are nevertheless a few clear groupings within the genus Elasmopus . There is the “ rapax - group ” of 20 species around the type species E. rapax . These are species with Md palp art 3 short (l:b <3), the T with rounded inner lobes and the outer lobe reduced almost to a notch, and with dense long setae on the hind margin of the basis of P7. Half of them also have long setae on the ventral margin of Ep3 (arafura, bampo, hooheno sensu Barnard 1972 , integer, lecroyae, mayo, molokai, rapax, tiburoni, vishakhapatnamensis), the other half (buchneri, calliactis, hooheno sensu Ledoyer, 1972 , karamani, longipropodus, marplatensis, piikoi, pocillimanus, pseudinteger, steinitzi) has only short spines here, and also fewer long setae on P7. In this group there are species of all different body sizes. The Md palp, where known, usually has art 2 <art 3, art 2 is mostly distally not oblique but symmetrical and art 1 longer than half of art 2. Hughes and Lowry (2011) list only 11 species within their “rapax-group”: their species arafura, bampo, calliactis, hooheno, integer, mayo, molokai, pseudinteger and rapax occur also in our enumeration, but they include E. mutatus and E. ocoroni , which have no setae on P7 basis nor on Ep3 (see also Barnard 1962: 98 who stresses expressis verbis the absence of such setae); these two species are therefore not included in our list.

The “ pectenicrus - group ” consists of species with a castelloserrate hind margin on the basis of P6 and/or P7. Elasmopus neglectus and E. shepherdi should be separated because of the hump on the urosome, and the special shape of P7 basis and T. They bridge the distance towards Mallacoota, where most species have a much more delicate mandible palp. (There are three other species with a urosome hump, but without castelloserrations on P6–7: E. japonicus , E. menurte and E. woodjonesi ).

The remaining species with castelloserrate pereopod bases seem to form a naturally related group with the following members:? alalo (acc. to some authors “with minute castelloserrations”), arrawarra, canarius, carteri, crenulatus, diplonyx, hawaiensis, holgurus, lapu, laufolii, leveque, nanshaensis, oaxaquensis, otus, pectenicrus, “ pseudaffinis ” s. Myers 1985, serricatus, spinibasus, steelei and tubar. Their telson halves have usually a straight or very shallowly excavated distal margin, with either outer or inner lobe a bit longer, although the inner corner can also be rounded as in the typical “ rapax- telson” (both shapes may in fact occur in the same species).

In Hughes and Lowry (2011) the “ pectenicrus - group” consists of 10 species: brasiliensis, canarius, carteri, crenulatus, leveque, nanshaensis, otus, pectenicrus, spinibasus and yunde. Elasmopus yunde is a junior synonym of E. spinibasus , whereas the other species also occur in our list, with the exception of E. brasiliensis . On p. 581, Hughes and Lowry (2011) define their group as having Md palp art 3 short (l:b <3), P5–7 basis with at least one margin castelloserrate, and T lobes apically truncate. But in E. brasiliensis Md palp art 3 is never shorter than l:b = 3, P5–7 have serrate but not castelloserrate margins and T lobes are apically excavate and not truncate. We therefore exclude E. brasiliensis from this group.

Hughes and Lowry present a third group of species within Elasmopus , i.e. the “ delaplata -group”. They define it by an elongate art 3 on Md palp (l:b ≥ 3), P5–7 posterior margin smooth, crenulate or setose, T lobes truncate, rounded or concave. After the cited authors, this group contains 15 species: aduncus, alalo, balkomanus, bollonsi, delaplata, hawaiensis, karamani, neglectus, piikoi, shepherdi, slatyeri, thomasi, varanocephalensis, wahine, woodjonesi. As this group seems to be exclusively defined by the lengthened Md palp (the other two characters occur in all possible character states), which may well have evolved independently several times, we do not accept this proposal.

Matrix

At the beginning we used as many characters as possible, e.g. also ratios of antennae (peduncle to flagellum, A1:A2, A1: body etc.), or ratios of gnathopods, but these characters vary too much, depending on age, and also vary among the sexes. Therefore, we put more weight on the posterior body half of male specimens, despite knowing that the ratios of telson length to width or the length of uropods can also differ with age.

This matrix ( Figure 9 ) did not produce any convincing results in various cladistic analyses for splitting the large amount of species into different genera. As already stated before, most species of the group with castelloserrate pereopodal hindmargins cluster closely within the analysis (but not all), and species with long setae on pereopodal hindmargins cluster around the type species E. rapax , and show relationships with those with entire telson. All the remaining species vary enormously in all possible character states.

Nevertheless we want to present the matrix of 36 characters and 93 coded species (in alphabetic order) as a basis for further efforts, as well as to help in classifying future new species.

Characters used:

1. body length 0: <4 mm 1: 4–6.9 mm 2: ≥ 7 mm

2. Md palp 0: art 2> art 3 1: art 2 = art 3 2: art 2 <art 3

3. Md palp art 3 l:b 0: = 3 1: <3 (thicker) 2:> 3 (slender)

4. Md art 1 0: distally obliquely ending 1: distally regularly rounded

5. Md art 1: art 2 0:> half 1: = half 2: <half

6. Cx 1 anterodistal corner 0: rounded 1: acutely lengthened

7. Gn1 palm 0: oblique to regularly rounded 1: almost transverse

8. Gn1 spination 0: propodus to merus poorly spinose 1: propodus to merus posterior margin densely spinose

9. Gn1 setation 0: propodus poorly setose 1: propodus facially near inner and outer margin setose

10. Gn2 dactylus 0: weakly curved 1: strongly curved

11. Gn2 dactylus: propodus male 0: <1/2 1: 1/2 2: 2/3-entire propodus

12. Gn 2 male dactylus 0: fits along the propodus 1: “comes across” 2: fits into an excavation or between two rows of spines or humps

13. Gn2 palm male

0: not excavate = smooth

1: almost smooth, irregular with bump or shallow hole

2: excavate with bump(s)

14. Gn2 palm 0: with robust, small spines 1: weakly to strongly setose

15. Gn2 ratio propodus:carpus male 0: <3 1: 3–4 2: 4–5 3:>5

16. P3, 4 propodus distal spines 0: normal 1: one pair larger, striate and broadened

17. basis P5–7 hind margin setation 0: no or short setae 1: long setae

18. P5 basis 0: broadened, convex 1: broadened, but straight or concave

19. P6 basis posterior margin 0: smooth–crenulate–serrate 1: castellate

20. P7 basis posterior margin 0: smooth–crenulate 1: serrate 2: castellate

21. Ep3 posterodistal corner 0: rectangular 1: rounded 2: vaguely acute, almost rectangular 3: acute tooth

22. Ep3 posterior margin 0: smooth 1: vaguely crenulate 2: serrate

23. Ep3 inferior margin 0: naked 1: with spination 2: with long setae

24. urosome with bump 0: absent 1: present

25. U1 peduncle 0: with one basofacial spine

1: with two basofacial spines

26. U2:U3 longer rami

0: <1

1: ≥ 1

27. U3 ratio peduncle: longer ramus

0: <0.6

1: 0.6–0.8

2:> 0.8

28. U3 rami ratio

0: subequal

1: 1–1.25

2: 1.25–1.5

3:> 1.5

29. Telson length

0: l ≥ b

1: l <b

30. Telson distally

0: straight

1: concave, with marginal lobes

2: convex, rounded with incision on outer margin

31. Telson cleft

0: cleft

1: entire, not cleft

32. Telson halves distally

0: straight, truncate

1: inner lobe longer or central tip rounded

2: outer lobe longer

33. Telson outer lobe

0: rounded

1: acute

2: absent

34. Telson inner lobe

0: rounded

1: acute

2: absent

35. Telson distal spines

0: small robust setae

1: strong spines

36. Telson distal spines

0: absent or shorter than telson length

1: equal to longer than telson length

Geographical overview

Finally, we add a geographical overview of the distribution of the genus Elasmopus , an amphipod genus of shallow waters in the warmer areas of the world. The type species, E. rapax Costa, is described from Napoli, Mediterranean, but the species has been reported from many areas; probably, as is the case for other very widely distributed Elasmopus species , this is in reality a species complex. Hughes and Lowry (2010) have described a neotype, and they recorded identical material from New South Wales, Australia, always near harbours, so the species is probably dispersed via ship traffic.

Five species have been reported from the Mediterranean: E. affinis , E. pectenicrus , E. pocillimanus , E. rapax , E. vachoni .

From the eastern Atlantic, from southern Norway to western Africa, we know of only a few species, in part the same ones: E. affinis , E. canarius , E. perditus , E. rapax , E. spinipes , E. vachoni .

The western Atlantic, from northern New England via the Caribbean and Brazil to Argentina and Uruguay, has a much greater Elasmopus diversity, with 20 reported species, many described recently: E. balkomanus , E. brasiliensis , E. delaplata , E. dentipalmus , E. dubius , E. elieri , E. fusimanus , E. karamani , E. lemaitrei , E. lejeunei , E. levis , E. longipropodus , E. magnispinatus , E. marplatensis , E. pectenicrus , E. souzafilhoi , E. spinidactylus , E. thomasi , and E. sp. A, E. sp. B, and E. “ rapax ”, all three in LeCroy (2000).

The American coasts of the Pacific Ocean also have a rich Elasmopus fauna, from California to Ecuador (and including the Galapagos Islands), with 19 reported species, many described very recently: E. antennatus , E. bampo , E. bastidai , E. ecuadoriensis, E. holgurus , E. karlae , E. lecroyae , E. marcelae , E. mayo , E. mutatus , E. oaxaquensis , E. ocoroni , E. serricatus , E. temori , E. tiburoni , E. tubar and E. zoanthidea .

Hawaii, in the northern Pacific, has 10 recorded Elasmopus species , most described by Barnard: E. bampo , E. calliactis , E. diplonyx , E. hawaiensis , E. hooheno , E. molokai , E. pectenicrus , E. piikoi , E. slatyeri and E. spinidactylus .

The central Pacific is well investigated, thanks to the studies of Schellenberg, Barnard and Myers, and at the moment 19 species are reported from there: E. aduncus , E. alalo , E. atolgidus , E. dentiferus , E. diplonyx , E. excavatus , E. gracilis , E. hooheno , E. integer , E. lapu , E. laufolii , E. minimus , E. molokai , E. polynesus , E. pseudaffinis , E. seticarpus , E. slatyeri , E. spinidactylus , E. spinimanus and E. takamotus .

Little is as yet known about the Elasmopus of the Indonesia –New Guinea area, and we have found only three reported Elasmopus species. No doubt this area will yield many more species eventually: E. hooheno , E. pectenicrus and E. spinimanus .

From Australia and New Zealand many Elasmopus species have been described, primarily by Barnard, Berents, Hughes and Lowry. The species from the entire Australian coast have been listed here, but of course those from the Northern Territory could have been incorporated with New Guinea, and those from Western Australia with the Indian Ocean group. Twenty-three species have been recorded hitherto: E. alalo , E. arafura , E. arrawarra , E. bollonsi , E. carteri , E. crenulatus , E. hooheno , E. hyperopia , E. leveque , E. mcluerensis , E. menurte , E. neglectus , E. otus , E. pectenicrus , E. rapax , E. shepherdi , E. slatyeri , E. spinibasus , E. varanocephalensis , E. wahine , E. warra and E. woodjonesi .

From the Asian coasts of the Pacific Ocean relatively few species of Elasmopus have been described hitherto, with six species recorded: E. alalo , E. hooheno , E. japonicus , E. koreanus , E. nanshaensis and E. slatyeri .

In the Indian Ocean especially Madagascar (Ledoyer), Mauritius (Ledoyer, Appadoo and Myers), India and Sri Lanka (various authors) have yielded many Elasmopus species [the species found on the Cocos Islands ( Hughes and Lowry 2011) have also been listed here]. Twenty-three species have been recorded: E. alalo , E. crenulatus , E. dubius , E. gracilis , E. hooheno , E. menurte , E. palu , E. pectenicrus , E. pilosus , E. pocillimanus , E. pseudinteger , E. puteus , E. rishikondiensis , E. slatyeri , E. souillacensis , E. spinibasus , E. spinicarpus , E. spinidactylus , E. spinimanus , E. spinipalpus , E. steelei , E. visakhapatnamensis , and E. waltersi .

Finally, from the Red Sea seven Elasmopus species have been described, several of which urgently need redescription: E. buchneri , E. caprai , E. erythraeus , E. gracilis , E. pectenicrus , E. podotrichius and E. steinitzi .

Most Elasmopus species seem to have a restricted area of distribution, but a number of species have been recorded from the Indian Ocean, Australia and the Pacific, while a few have a seemingly tropicopolitan distribution. As the descriptions of these species from different areas often show clear differences, it may well be that further research will show that species such as E. hawaiensis , E. hooheno , E. pectenicrus , E. pocillimanus , E. rapax and E. spinidactylus in reality consist of a complex of closely related species. In the case of E. rapax , a number of species have already been split off by different authors.

Figures

Figure 4. Elasmopus cf. magnispinatus A1,2, antennae; Mx2, second maxilla; Md, right and left mandible; slide FSBC I 79921.

Figure 5. Elasmopus cf. magnispinatus Gn1 (in male and female identical), Gn2 of both sexes, Gn1′ and Gn2′ of another specimen enlarged; slides FSBC I 79921, FSBC I 79922.

Figure 6. Elasmopus cf. magnispinatus P3, P5, P6, P7, pereopods; Ep2, Ep3 of both sexes, epimeral plates; U3, third uropods of both sexes; T, telson of both sexes; slides FSBC I 79921, FSBC I 79922.

Figure 7. Mandible shapes: (A) Elasmopus rapax; (B) Elasmopus pseudinteger; (C) Elasmopus diplonyx; (D) Elasmopus wahine (similar to Elasmopus alalo, Elasmopus elieri); (E) Elasmopus oaxaquensis; (F and G) Elasmopus spinipalpus.

Figure 8. Telson shapes: (A) Elasmopus rapax; (B) Elasmopus alalo male; (C) Elasmopus alalo female; (D) Elasmopus levis; (E) Elasmopus calliactis; (F) Elasmopus spinibasus; (G) Elasmopus ecuadoriensis two shapes; (H) Elasmopus holgurus; (I, J) Elasmopus bastidai male (I, above), female (J, below); (K) E gracilis; (L) Elasmopus steelei; and (M) Elasmopus pseudinteger.

Figure 9. Matrix of 93 Elasmopus species and 36 characters.