Rhynchothorax, Costa, 1861

Matsushita, Hiroki & Kakui, Keiichi, 2024, Two new Rhynchothorax sea spiders from Japan, Spixiana 47 (1), pp. 15-28 : 26-27

Key to species in Rhynchothorax

The number of segments in the palp was not used in the key, as Staples (2019) suggested that this number was unclear for several species.

1 Auxiliary claws present, cephalic segment with anterodorsal extensions, eyes lacking............. 2

– Auxiliary claws present, cephalic segment lacking anterodorsal extensions, eyes present...... 8

– Auxiliary claws lacking, cephalic segment lacking anterodorsal extensions, eyes present..... 13

2 Terminal palp segment unilobed .................... 3

– Terminal palp segment bilobed....................... 7

3 Anterolateral border of cephalic segment with two horns.................................. R. philopsammum Hedgpeth, 1951

– Anterolateral border of cephalic segment lacking horns.............................................................. 4

4 Proboscis with several dorsal tubercles............ ........................................................... R. architectus Child, 1979

– Dorsal surface of proboscis nearly smooth.... 5

5 Second lateral process with single posterior tubercle, reaching beyond anterior margin of third lateral process.................. R. anophthalmus Arnaud, 1972

– Second lateral process with two posterior tubercles, not reaching anterior margin of third lateral process...................................................... 6

6 Auxiliary claws shorter than half claw length, first lateral process with two posterior tubercles, seventh to ninth segments of oviger respectively with two ventral (one middle and one distal), one mid-ventral, and one mid-ventral spines .................................................... R. vallatus Child, 1990

– Auxiliary claws longer than half claw length, first lateral process with one posterior tubercle, seventh to ninth segments of oviger respectively with four ventral (one middle and three distal), three ventro-subdistal, and three ventro-subdistal spines................. R. nopperabo sp. nov.

7 Several conical tubercles on lateral processes. ............................................................. R. alcicornis Krapp, 1973

– Conical tubercles lacking on lateral processes ............................................................ R. arenicolus Stock, 1989

8 Ocular tubercle length two or more times width ................................................................... 9

– Ocular tubercle less than or equal to 1.5 times width .................................................................. 11

9 Mouth triradiate, trunk four segmented.......... ........................................................... R. articulatus Stock, 1968

– Mouth vertical slit, trunk three segmented .. 10

10 Ocular tubercle with long, anteriorly directed apical extension overhanging approximately proximal half of proboscis................ R. percivali Clark, 1976

– Ocular tubercle with short apical extension not reaching to middle of proboscis............. R. swir Staples, 2019

11 All lateral processes with long tubercules, proboscis with dorsal tubercle one-third of way from proximal end........................... R. voxorinus Stock, 1966

– Lateral process with or without short tubercules, proboscis without dorsal tubercles ................ 12

12 Lateral processes all with dorsal tubercles, dorsodistal tubercle on fourth palp segment from distal end not greater than segment width.................................................. R. coralensis Staples, 2019

– Lateral process lacking dorsal tubercles, dorsodistal tubercle on fourth palp segment from distal end greater than segment width............. ............................................................... R. australis Hodgson, 1907

13 Trunk four segmented...................... R. oblongus (Pushkin, 1977)

– Trunk three segmented.................................... 14

14 Ocular tubercle with long, anteriorly directed apical extension overhanging approximately proximal half of proboscis............................... 15

– Ocular tubercle with short apical extension not reaching to middle of proboscis ..................... 17

15 First coxa of third leg with dorsal tubercle... 16

– First coxa of third leg lacking dorsal tubercle. .............................................................. R. orientalis Child, 1988

16 Third lateral process with dorsal tubercle, seventh segment of oviger with one mid-ventral and two ventrodistal spines.... R. mediterraneus Costa, 1861

– Third lateral process lacking dorsal tubercle, seventh segment of oviger with two ventrodistal spines............................ R. monoceros sp. nov.

17 Proboscis with dorsal tubercles...................... 18

– Proboscis lacking dorsal tubercle................... 20

18 More-proximal of two dorsal tubercles on palp longer than more-distal one........... R. unicornis Fage & Stock, 1966

– More-proximal of two dorsal tubercles on palp as long as more-distal one............................... 19

19 Ocular tubercle and dorsal tubercles on trunk as tall as dorsal tubercle on proboscis.............. .............................................................. R. monnioti Arnaud, 1974

– Ocular tubercle and dorsal tubercles on trunk taller than dorsal tubercle on proboscis........... ............................................................... R. crenatus Child, 1982

20 Two dorsal conical tubercles posterior to ocular tubercle ............................................................... 21

– No dorsal conical tubercles posterior to ocular tubercle............................................................... 22

21 Dorsal tubercles on trunk spiniform, longer than tubercle width, length of dorsal tubercle on third palp segment from distal end not greater than segment width..................................... R. sidereus Sabroux, Hassanin & Corbari, 2022

– Dorsal tubercles on trunk dome shaped, not longer than tubercle width, length of dorsal tubercle on third palp segment from distal end greater than segment width......... R. tiahurensis Müller, 1989

22 Dorsal tubercle on fourth palp segment from distal end longer than segment width, three dorsal tubercles on trunk.................. R. barnardi Child & Hedgpath, 1971

– Dorsal tubercle on fourth palp segment from distal end not longer than segment width, four dorsal tubercles on trunk............. R. malaccensis Stock, 1968