Taken primarily from Kozloff, 1987, 1996 p. 406 (Copyright 1987, 1996, University of Washington Press. Used in this web page by permission of University of Washington Press)
An alternate, up to date key can be found in Wicksten,
2009 page 242.
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| Lower taxonomic level | Main Page | Alphabetic Index | Systematic Index | Glossary |
| 1a | Abdomen mostly soft (but the telson may be calcified, and there may be a few other calcified plates), and not tightly applied to the underside of the thorax | 2 |
| 1b | Abdomen largely or completely covered by calcified plates and tightly pressed against the underside of the thorax (picture) | 6 |
| 2a | Abdomen rather thin and flat (picture); chelipeds nearly equal (the right cheliped only slightly larger than the left) (picture); carapace and legs with protuberances that resemble scales | Placetron wosnessenskii |
| 2b | Abdomen thick; chelipeds decidedly unequal; dactyl of chelipeds generally shorter than the palm (propodus) of the chela; carapace and legs without protuberances that resemble scales (they may, however, have spines, setae, and tubercles | 3 |
| 3a | Rostrum, from its base to its tip, studded with stout spines | Acantholithodes hispidus |
| 3b | Rostrum without spines (but it may be setose and its tip is sharp | 4 |
| 4a | Cephalothorax and legs much flattened dorsoventrally and very setose; upper surface of chelipeds with spines; anterior margins of most articles of legs 2-4 with large, flattened spines (the spines are so broad that they give the margins of the articles from which they originate a serrated appearance) | 5 |
| 4b | Cephalothorax and legs not much flattened dorsoventrally and not especially setose; upper surface of chelipeds with prominent, granular tubercles but without obvious spines; anterior margins of articles of legs 2-4 without large spines (there are, however, some setae, as well as tubercles and small spines) | Oedignathus inermis |
| 5a | Length of rostrum about twice its width at the base (photo); upper surface of palm (dactyl) of right chela usually with 4 rows of spines running lengthwise | Hapalogaster mertensii |
| 5b | Length of rostrum less than twice its width at the base; upper surface of right chela with 3 rows of spines running lengthwise | Hapalogaster grebnitzkii |
| 6a | Carapace with lateral expansions that completely conceal the legs when the animal is viewed from above (picture) | 7 |
| 6b | Carapace without lateral expansions that completely conceal the legs when the animal is viewed from above | 8 |
| 7a | Propodus of chelipeds smooth; rostrum broader distally than proximally (picture); abdominal plates without raised margins (picture) | Cryptolithodes sitchensis |
| 7b | Propodus of chelipeds with coarse tubercles; rostrum generally broader proximally than distally (picture); abdominal plates with raised margins | Cryptolithodes typicus |
| 8a | Outline of carapace, in dorsal view, similar to that of an equilateral triangle (there are blunt or sharp-tipped spines along the lateral margins, however); posterior half of dorsal surface of carapace with a pronounced concavity or semicircular depression (picture) | 9 |
| 8b | Outline of carapace, in dorsal view, rounded posterolaterally, not at all similar to that of an equilateral triangle; posterior half of dorsal surface of carapace with neither a pronounced concavity nor a semicircular depression | 10 |
| 9a | Rostrum divided into 2 blunt lobes; most spines on legs blunt, papillate; legs with few if any conspicuous setae; posterior half of carapace with an extensive concavity, this consisting essentially of 2 depressions, 1 on each side of the midline, the concavity as a whole bordered by large tubercles; lateral margins of carapace with stout, blunt spines | Phyllolithodes papillosus
Brandt, 1849 |
| 9b | Rostrum not divided into 2 blunt lobes; spines on legs sharp-tipped; legs with many long, curved setae (most of these are longer than the spines); posterior half of carapace with a semicircular depression, this not bordered by prominent tubercles; lateral margins of carapace with sharp-tipped spines | Rhinolithodes wosnessenskii
Brandt, 1849 |
| 10a | Carapace bumpy, due to the presence of large, granular tubercles; legs 2-4 stout, not appreciably longer than the width of the carapace | 11 |
| 10b | Carapace spiny, but without large tubercles; legs 2-4 decidedly longer than the width of the carapace | 12 |
| 11a | Tubercles on chelipeds and other legs spinelike; posterior edge of carpus of chelipeds excavated into a deep sinus (when this is in apposition to a shallow sinus on the anterior edge of the carpus of leg 2, a circular hole is formed) | Lopholithodes foraminatus
Stimpson, 1862 |
| 11b | Tubercles on chelipeds and other legs mostly rounded and blunt; posterior edge of carpus of chelipeds not excavated into a sinus | Lopholithodes mandtii
Brandt, 1849 |
| 12a | ||
| 12b | ||
| 13a | ||
| 13b | ||
| 14a | ||
| 14b | ||
| 15a | ||
| 15b |
