Chaceon

S, M A R C O S Tava R E & Pinheiro, Allysson P., 2011, A new species of Chaceon Manning & Holthuis, 1989, from the southwestern Atlantic, with a key to the western Atlantic species (Crustacea, Decapoda, Geryonidae), Zootaxa 3086, pp. 57-68 : 66

Key to western Atlantic species of Chaceon

1. P2–P5 dactyli dorsoventrally depressed.................................................................... 2

- P2–P5 dactyli laterally compressed....................................................................... 5

2. Distal end of P5 merus extending far beyond tip of last anterolateral tooth of carapace............................... 3

- Distal end of P5 merus reaching at most tip of the last anterolateral tooth of carapace........................ C. notialis

3. Distance between median frontal teeth half that between one median frontal tooth and its adjacent lateral frontal tooth. P2–P5 meri with distodorsal distinct spine; P1 merus with one distodorsal and one subdistodorsal distinct spines; P1 propodus with one, distinct distodorsal spine; P1 carpus with one strong distal outer spine............................ C. quinquedens

- Distance between median frontal teeth much more than half that between one median frontal tooth and its adjacent lateral frontal tooth. P2–P5 meri with obsolete distodorsal tubercle at most; P1 merus with one subdistodorsal distinct spine only; P1 propodus lacking a distodorsal spine; P1 carpus with distal low lobe at most...................................... 4

4. P5 merus maximum length distinctly more than twice as long as the P5 dactylus. G2 distinctly short, not reaching to the thoracic sternal suture 6/7. Chelae, branchial, and intestinal regions finely granulated......................... C. eldorado

- P5 merus maximum length twice as long as the P5 dactylus. G2 longer, overreaching sternal suture 6/7. Chelae, branchial, and intestinal regions coarsely granulated............................................................ C. ramosae

5. Distal end of merus of P5 extending far beyond the tip of the last carapace anterolateral tooth or extending only a little beyond the tip of the last carapace anterolateral tooth............................................................... 6

- Distal end of merus of P5 not reaching to the tip of the last carapace anterolateral tooth...................... C. fenneri

6. All five anterolateral teeth of carapace strong and sharp; P2–P5 meri with distodorsal distinct spine; P1 merus with one distodorsal and one subdistodorsal distinct spines; P1 propodus with one, distinct distodorsal spine; P1 carpus with one strong distal outer spine; P5 carpus with dorsolongitudinal line of distinct spinules.......................................... 7

- Anterolateral teeth of carapace small or obsolete; P2–P5 meri with no spine distodorsally; P1 merus with one subdistodorsal distinct spine only; P1 propodus with no distodorsal spine; P1 carpus with no outer spine; P5 carpus smooth dorsally or with dorsolongitudinal line of low granules at most............................................................. 8

7. Outer margin of inner orbital tooth with slight, convex projection, indicating position of inner orbital angle. Distance from second to third anterolateral teeth about the same as distance between inner and outer orbital teeth................. C. atopus

- No slight, convex projection on outer margin of inner orbital tooth. Distance from second to third anterolateral teeth distinctly less than distance between inner and outer orbital teeth............................................... C. inghami

8. Distal end of merus of P5 extending far beyond the tip of the last anterolateral tooth. Frontal teeth prominent, triangular. Maximum length of dorsolongitudinal, corneous ridges of P5 dactylus about 1/4 of maximum length of P5 dactylus ( Fig. 4 A, D, F)..................................................................................... Chaceon linsi n. sp.

- Distal end of merus of P5 extending only a little beyond the tip of the last anterolateral tooth. Frontal teeth low, lobe-like. Corneous ridges of P5 dactylus slightly longer than 1/6 of the maximum length of P5 dactylus ( Fig. 4 B, E, G)...................................................................................................... C. sanctaehelenae

Figures

FIGURE 4. P 5 dactylus terminal corneous ridges. A, D, F, Chaceon linsi n. sp., male holotype cl 136 mm, cw 149 mm (MZUSP 22287). B, E, G, Chaceon sanctaehelenae Manning & Holthuis, 1989, male holotype cl 112 mm, cw 134 mm (USNM 125510). C, H, Chaceon fenneri (Manning & Holthuis, 1984), female paratype cl 90 mm, cw 113 mm (USNM 71003). Scale bars: A, D, 6 mm; B, 3.8 mm; C, 4.3 mm; E, 3.2 mm; F, 12 mm; G, 10 mm; H, 11. 5 mm.