Periclimenes obscurus

Eilbracht, Joni & Fransen, Charles H. J. M., 2015, Periclimenes macrorhynchia sp. nov., a new hydrozoan-associated pontoniine shrimp (Crustacea, Decapoda, Palaemonidae) from North East Kalimantan, Indonesia, Zootaxa 3994 (3), pp. 377-395 : 394

Key to species of the Periclimenes obscurus and Periclimenes granulimanus species groups

1. Ambulatory pereiopods without or with minute accessory tooth................................................. 2

- Ambulatory pereiopods with distinct accessory tooth......................................................... 6

2. One pair of dorsal telson spines; carapace without epigastric spine; first pereiopod coxa with ventral setose process, fingers with cutting edges distinctly gaping.............................. P. tonga Bruce, 1988 [associated with scyphozoans]

- Two pairs of dorsal telson spines; carapace with epigastric spine; fingers with cutting edges not distinctly gaping.......... 3

3. First pereiopod coxa with ventral setose process; R. 9/2..... P. nomadophila Berggren, 1994 [associated with scyphozoans]

– First pereiopod coxa without setose process................................................................. 4

4. Major second pereiopod extremely long and slender, overreaching scaphocerite by proximal merus, carpus longer than both chela or merus; walking dactyli feebly biunguiculate with short distoventral tooth on corpus, propodi with long spines arranged to 4 distoventral pairs....................................... P. b r u c e i Ďuriš, 1990 [associated with antipatharians]

– Major second pereiopod longer than minor one, both pereiopods slender, overreaching scaphocerite by distal merus, carpus short – distinctly shorter than both chela or merus; walking dactyli simple or with rudimentary distoventral tooth on corpus, propodi with 1–3 single proximal spines in addition to 2–4 distoventral pairs of long spines......................... 5

5. Major second pereiopod smooth; minor second chela with cutting edges entire................................................................................................ P. laevimanus Ďuriš, 2010 [associated with hydroids]

– Major second pereiopod granulate; minor second chela with 1–2 teeth on cutting edges................................................................................... P. granulimanus Bruce, 1978 [associated with antipatharians]

6. Carapace with isolated epigastric spine.................................................................... 7

- Carapace without epigastric spine........................................................................ 13

7. Ambulatory dactyli robust, with accessory tooth stout, subequal to unguis; R. 1+5/ 1.................................................................................... P. incertus Borradaile, 1915 [usually associated with sponges]

- Ambulatory dactyli slender, without or with slender accessory tooth, shorter than unguis............................. 8

8. Second pereiopods subequal, similar, carpus about as long as palm.............................................. 9

- Second pereiopods clearly unequal and dissimilar, carpus shorter than palm...................................... 10

9. Unguis of dactylus of ambulatory pereiopods as long as corpus. R.1+6-9/1(rarely 2)................................................................................... P. obscurus Kemp, 1922 [associated with sponges and hydroids]

- Unguis of dactylus of ambulatory pereiopods 0.65 times as long as corpus; R.1+6-10/2(rarely 3).................................................................................. P. macrorhynchia sp. nov. [associated with hydroids]

10. Rostral lamina deep, 13–17 dorsal teeth, 3 or 4 ventral teeth.... P. hongkongensis Bruce, 1969 [associated with holothurians]

- Rostral lamina not deep, less than 11 dorsal teeth, 1 or 2 ventral teeth.......................................... 11

11. Dorsal telson spines minute: major chela 4.3 times longer than wide, finger length 0.4 times palm: dactylus with accessory spine 0.5 times unguis; R. 1+8/1..................... P. toloensis Bruce, 1969 [associated with Gorgonaria and hydroids]

- Dorsal telson spines normal............................................................................ 12

12. Fourth thoracic sternite with transverse ridge with keyhole shaped median notch; R. 1+8-9/2............................................................................................. P. terangeri Bruce, 1998 [host not known]

- Fourth thoracic sternite lacking transverse ridge with median notch...... P. delagoae Barnard, 1958 [associated with ‘coral’]

13. First pereiopod with carpus much shorter than chela; subequal to palm; R. 6/1.............................................................................................. P. batei ( Borradaile, 1917) [associated with Alcyonacea

- First pereiopod with carpus subequal to or longer than chela................................................... 14

14. Second pereiopods slender, subequal, with fingers of major chela subequal to palm, carpus more than half palm length; R. 9– 10/2...................................................... P. sinensis Bruce, 1969 [associated with Alcyonacea ]

- Second pereiopods robust, markedly unequal, with fingers of major chela distinctly shorter than palm, major carpus ca half palm length; R. 8–11/1–2...................................... P. burrup Bruce, 2007 [associated with Alcyonacea ]