bythograeidae

Mclay, Colin, 2007, New crabs from hydrothermal vents of the Kermadec Ridge submarine volcanoes, New Zealand: Gandalfus gen. nov. (Bythograeidae) and Xenograpsus (Varunidae) (Decapoda: Brachyura), Zootaxa 1524, pp. 1-22 : 14-15

Key to the bythograeidae

(Modified after Guinot & Segonzac 1997; Hessler & Martin 1989; Tsuchida & Hashimoto 2002)

1. Eyes, antennules and antennae not deeply recessed. Orbits well circumscribed (complete). Frontal border of carapace in dorsal view nearly straight ................................................................................................... 2

- Eyes, antennules and antennae deeply recessed under front. Orbits open and not well circumscribed (incomplete). Frontal border of carapace rounded in dorsal view............................................................... 3

2. Cornea present but unpigmented and without facets. Orbits ovate. Body covered by uniformly short tomentum, carapace flat and smooth. Widest point of carapace at about one third of carapace length ........ ......................................................................... Allograea tomentosa Guinot, Hurtado & Vrijenhoek, 2002.

- Cornea well-developed, pigmented but without facets. Orbits rounded. Carapace vaulted and with colourtipped tubercles on fronto-lateral region; tomentum confined to patches. Widest point of carapace just posterior to frontal border .................................................... Cyanagraea praedator de Saint Laurent, 1984

3. Eyes mobile, peduncle well developed. Coxa of third maxilliped not obscured in ventral view, lateral extension visible, not hidden by ventral pterygostomial margin of carapace, sternum and cheliped coxa. 4

- Eyes immobile, peduncle vestigial and embedded in orbit wall. Coxa of third maxilliped partially obscured in ventral view, lateral extension hidden by juxtaposition of ventral margin of carapace in pterygostomial region with anterolateral sternal border and cheliped coxa ........................................................ 9

4. Shallow concavity ventrolateral to orbit, filled with soft setae Segonzacia mesatlantica ( Williams, 1988) .

- Area ventrolateral to orbit finely punctate, without cavity or dense patch of setae .................................... 5

5. Ocular peduncles dilated at their extremity; corneal region clearly visible. P2–5 thin, lengthened, with propodi clearly longer than wide especially P4........................................................................................... 6

- Ocular peduncles slender and almost cylindrical for their entire length except for marked dilation of the cornea, which is deeply seated. P2–5 short and thick, with propodi only slightly longer than wide .......... 7

6. Tuft of plumose setae on internal face of cheliped propodus in female and occasionally in male. Thicker

eyestalks and broad cornea in both sexes. Corneal region hoof-shaped. G1 Stout, strongly curved, markedly twisted, apex covered in short setae, tip rounded, glabrous. P5 merus length 3 times width in male ... ........................................................................................................ Bythograea thermydron Williams, 1980 - No tufts of setae on cheliped. Thinner eyestalks, with fusiform cornea. G1 stout, strongly curved, twisted, many minute spinules on distal part (except the tip), dense row of long setae sub-distally, tip acute. P5 merus length 2.5 times width ........................................ Bythograea galapagensis Guinot & Hurtado, 2003

7. Setae on internal face of cheliped propodus not arranged in a tuft. Chelipeds of female not dimorphic, propodus narrow, granulose and setose on both faces with the exception of a swollen smooth non-setose area near the inferior border. Chelipeds of male dimorphic in size and ornamentation: propodus of crusher cheliped stout, smooth and non-setose; cutter cheliped the same as in female. G1 strongly curved, weakly twisted. ..................................................................................... Bythograea microps de Saint Laurent, 1984

- Setae on internal face of cheliped propodus arranged in a tuft. Chelipeds dimorphic in both sexes, weakly granulose. G1 slightly curved, not twisted. ................................................................................................. 8

8. Pale brown areas on chelae. Carapace granules white tipped. G1 without setae; without lateral apical flap. Suborbital plate smooth. Walking legs longer thinner; P5 merus length 2.9 times width in male; P5 propodus length 2.3 times width in male ................................. Bythograea vrijenhoeki Guinot & Hurtado, 2003.

- Pale violet areas on chelae. Carapace granules red or brown tipped. G1 distal third with field of short setae, lateral apical flap present. Suborbital plate granular. Walking legs shorter and thicker; P5 merus 2.2 times width in male. P5 propodus length 1.3 times width in male................................................................ ............................................................................................ Bythograea laubieri Guinot & Segonzac, 1997

9. Epistome strongly sinuous in frontal view. Male G2 distinctly shorter than G1....................................... 10

- Epistome gently sinuous in frontal view. Male G2 approximately as long as G1..................................... 12

10. Dense patch of setae covering subhepatic region of carapace. Chelae with inner occluding margins of dactylus and mid-central section of propodus with dense patch of setae. Eyestalks deeply buried in orbital wall, scarcely visible. G1 with few spines................................................................................................. 11

- No patch of setae covering subhepatic region of carapace or chelae. Eyestalks fused to orbital wall, just visible, with unpigmented cornea. G1 with dense long spines scattered continuously along its length ....... ............................................................................................................. Austinograea alayseae Guinot, 1990

11. G1 with approximately four small spines arranged in a row on dorsal surface. Cutter cheliped fingers deeply dished, with occluding margins almost straight; teeth on fingers of similar size .............................. ......................................................................... Austinograea rodriguezensis Tsuchida & Hashimoto, 2002

- G1 with many spines arranged in double or triple rows. Cutter cheliped deeply dished, with occluding margins slightly curved; several larger teeth especially on fixed finger ....................................................... ........................................................................................... Austinograea williamsi Hessler & Martin, 1989

12. Carapace finely granular. Cornea of eye visible in frontal view. Peduncle of G2 about one third of overall length .................................................................... Gandalfus yunohana ( Takeda, Hashimoto & Ohta, 2000

- Carapace coarsely granular. Cornea of eye almost totally obscured in frontal view by orbital wall. Peduncle of G2 about one half of overall length ............................................................... Gandalfus puia sp. nov.