Brachyura, LATREILLE, 1802

Wicksten, Mary K., 2012, Decapod Crustacea of the Californian and Oregonian Zoogeographic Provinces 3371, Zootaxa 3371, pp. 1-307 : 201-202

Key to families of Brachyura

1. Fifth pereopods conspicuously smaller than anterior legs, subdorsal, dactyls with hooks or spines, capable of gripping objects. Male, female genital openings coxal....................................................................... 2

– Fifth pereopods usually nearly as long as anterior legs, but if smaller, usually lateral; dactyls usually without hooks or spines, not capable of gripping objects. Female genital opening sternal, male opening coxal or sternal......................... 4

2. Carapace with pair longitudinal suture lines. Eye not retractile into orbits. Third maxilliped slender, not rectangular or triangular, not forming cover over oral field.............................................................. Homolidae

– Carapace without pair longitudinal suture lines. Eye at least partially retractile into orbits. Third maxilliped rectangular or triangular, forming cover over oral fields..................................................................... 3

3. Oral field square. Carapace inflated. In life, carrying piece of shell, sponge or ascidian over dorsal surface of body, usually concealing entire animal when seen in dorsal view................................................... Dromiidae

– Oral field triangular. Carapace flat. In life, carrying piece of shell or sponge over dorsal surface of body but often partially visible when seen in dorsal view............................................................... Cyclodorippidae

4. Oral field triangular. Outgoing branchial channels opening at middle of endostome. Often into living on or buried in sandy substrates.............................................................................................. 5

– Oral field square to oval. Outgoing branchial channels opening laterally. Living on various substrates.................. 6

5. Chelipeds folding flat against body, dactyl or chelipeds at right angle to palm.............................. Calappidae

– Chelipeds not folding flat against body, dactyl of chelipeds extending horizontally from palm................ Leucosiidae

6. Front of carapace narrow, often with rostrum carapace triangular to rounded, branchial region inflated.................. 7

– Front of carapace broad, usually without rostrum, carapace oval to square, branchial region not inflated................ 12

7. Chelipeds projecting laterally, fingers deflexed. Carapace, posterior pereopods without hooked setae. Carapace triangular............................................................................................ Parthenopidae

– Chelipeds not projecting laterally, fingers not deflexed. Carapace, posterior pereopods with hooked setae, at least in juveniles. Carapace pear-shaped, squarish to rounded but not triangular.................................................. 8

8. Eye without orbits; ocular peduncles long, either non-retractile or retractile against sides of carapace or against acute postorbital spine. Basal antennal article extremely long, slender..................................................... 9

– Eye with incomplete or commencing orbits. Basal antennal article not extremely long............................. 10

9. Lateral edges of carapace set in groove of gill chamber walls, with external part visible as pleural plates. First pleonite joined to carapace. Carapace pubescent, especially in small individuals...................................... Inachoididae

– Lateral edges of carapace not set in groove of gill chamber walls, without external part visible as pleural plates. First pleonite not joined to carapace. Carapace not pubescent....................................................... Inachidae

10. Male abdomen terminally broadened, seventh segment subquadrate, inserted deeply into sixth segment. Inhabiting continental shelf, slope or subtidal north of Monterey Bay , California ............................................ Oregoniidae

– Male abdomen not terminally broadened, seventh segment subtriangular, not inserted deeply into sixth segment. Intertidal or deeper, with ranges extending south of Monterey Bay , California .............................................. 11

11. Eyestalk either concealed by supraocular spine or sunk in sides of rostrum. Usually found among algae......... Epialtidae

– Eyestalk with commencing orbits having, in addition to supraocular spine, large cupped postocular process into which eye retracts. Usually found among rocks, sponges or mixed habitats............................................ Pisidae

12. Front of carapace with 3 teeth, one of these medial; antennules folding longitudinally. Carapace broadly oval, with 9–11 lateral teeth........................................................................................ Cancridae

– Front of carapace with or without teeth, but if present, never with median tooth; antennules folding obliquely or transversely. Carapace oval-square, with or without lateral teeth.......................................................... 13

13. Fifth pereopods ending in flattened dactyls, usually forming swimming paddles; carapace with 5 or more sharp lateral teeth.............................................................................................. Portunidae

– Fifth pereopods not ending in flattened dactyls, not forming swimming paddles; carapace with or without lateral teeth..... 14

14. Ocular peduncles elongate, folding horizontally against front of cephalothorax. Carapace rectangular, front narrow.................................................................................................... Ocypodidae

– Ocular peduncles short, folding into sockets. Carapace rectangular or not, front usually wide......................... 15

15. Last pair of walking legs short, at most slightly longer than merus of preceding leg; often subdorsal................... 16

– Last pair of walking legs only slightly shorter than entire length of anterior leg, always lateral....................... 17

16. Eyes very large. Carapace broadly transverse, anterolateral margins dentate. Not symbiotic, well calcified......... Palicidae

– Eyes small. Carapace round to subcylindrical, anterolateral margins without teeth. Usually symbiotic with larger invertebrates, sometimes poorly calcified.................................................................... Pinnotheridae

17. Carpus of third maxilliped not articulating at or near anterointernal angle of merus, lateral margins of mouth frame parallel to extremely convergent. Carapace square to trapezoidal, intertidal zone or living on floating debris or sea turtles........... 18

– Carpus of third maxilliped not articulating at or near antero-internal angle of merus, lateral margins of oral frame parallel to divergent. Carapace square to oval, intertidal to subtidal zones................................................ 19

18. Lower margin of orbit oriented downward toward buccal cavity, not distantly supplemented by suborbital crest. Intertidal or pelagic on sea turtles or floating debris............................................................. Grapsidae

– Lower margin of orbit not oriented downward toward buccal cavity, distantly supplemented by suborbital crest. Intertidal to shallow subtidal, not pelagic...................................................................... Varunidae

19. Carapace, appendages set with coarse setae......................................................... Pilumnidae

– Carapace, appendages not set with coarse setae............................................................. 20

20. Male first gonopod apex having numerous complex folds. Carapace more or less squarish to pentagonal, usually with no more than 3 lateral teeth; if 5 teeth, posterior ones smaller than anterior 3 teeth................................ Panopeidae

– Male first gonopod with simple apex. Carapace usually more or less oval, usually with 4–9 lateral teeth.......... Xanthidae