Modified from Kozloff, 1987, 1996 p. 392 (Copyright 1987, 1996, University of Washington Press. Used in this web page by permission of University of Washington Press)
An excellent alternate key can be found in Wicksten,
2009 on page 10.
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| Lower taxonomic level | Main Page | Alphabetic Index | Systematic Index | Glossary |
| 1a | Pereopod 3 chelate; epimera of abdominal segment 2 overlapped by those of segment 1; abdomen without a sharp bend; primarily oceanic and not likely found except in deep water | 2Suborder
Dendrobranchiata:
Prawns |
| 1b | Pereopod 3 not chelate; epimera of abdominal segment 1 overlapped by those of segment 2; abdomen with a sharp bend in some families but not in others; includes many littoral and shallow-water species as well as some that are mostly restricted to deep water | 5Suborder Pleocyemata, Infraorder
Caridea:
True shrimp |
| 2a | Pereopods 1-3 obviously chelate. Usually have a long rostrum which is much longer than the antennal scales | 3 Family Penaeidae |
| 2b | Pereopod 1 not chelate, and pereopods 2 and 3 with small, inconspicuous chelae. Usually have only a short, stubby rostrum | 4 Family Sergestidae |
| 3a | Curved transverse grooves on the carapace are interrupted by the median ridge; telson with 2 pairs of stout, movable spines | Bentheogennema borealis
(Rathbun, 1902) |
| 3b | Curved transverse grooves on the carapace not interrupted by the median ridge; telson with only 1 pair of stout, movable spines | Bentheogennema
burkenroadi
Krygier & Wasmer, 1975 |
| 4a | With a prominent spine on the dorsal part of the carapace just behind each eye, and with a similar spine on both sides of the carapace at a slightly more posterior level | Eusergestes
similis
(Hansen, 1903) |
| 4b | Without the spines described above | Sergia tenuiremis
(Kroyer, 1855) |
| 5a | Pereopods 1-5 with exopodites (mostly midwater and deep benthic species) (photo) | 6 |
| 5b | None of the pereopods with exopodites | 7 |
| 6a | Pereopods 1 and 2 longer and obviously more stout than the others | Family Pasiphaeidae |
| 6b | Pereopods 1 and 2 shorter than the others and not obviously more stout (mostly midwater and deep benthic species) | Family Oplophoridae |
| 7a | Pereopod 1 subchelate (picture); carpus of pereopod 2 not subdivided into several units (picture) | Family Crangonidae |
| 7b | Pereopod 1 not subchelate; carpus of pereopod 2 subdivided into several units | 8 |
| 8a | Carpus of pereopod 2 subdivided into more than 7 units; rostrum prominent and with movable dorsal spines | Family Pandalidae |
| 8b | Carpus of pereopod 2 divided into 3-7 units; rostrum, if present, without movable dorsal spines | 9 |
| 9a | Rostrum absent (picture); eyes at least partly covered dorsally by the carapace (picture) | Family Alpheidae |
| 9b | Rostrum present; eyes not covered dorsally by the carapace | Family
Hippolytidae
("broken-back shrimp") |