Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Superorder Peracarida
Order
Amphipoda
Suborder Gammaridea
Taken primarily from Kozloff,
1987, 1996 p. 355 (Copyright 1987, 1996, University of
Washington Press. Used in this web page by permission of University
of Washington Press)
Original Key created by Craig P. Staude (see reference
above)
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| Lower taxonomic level | Main Page | Alphabetic Index | Systematic Index | Glossary |
| 1a | Outer ramus of uropod 3 with 1 or 2 curved apical spines or teeth (photo) | 2 |
| 1b | Neither ramus of uropod 3 with curved apical spines or teeth (apical spines, if present, are small and straight) | 15 |
| 2a | Outer ramus of uropod 3 with 2 curved apical spines; inner ramus of uropod 3 flattened, with setae as well as spines; outer lobe of lower lip with a deep cleft (Family Ampithoidae) | 3 |
| 2b | Outer ramus of uropod 3 with a single hooked apical spine and some smaller proximal teeth; inner ramus of uropod 3 conical, with one or more spines but no setae; outer lobe of lower lip broadly rounded, not cleft | 14 |
| 3a | Accessory flagellum present and consisting of about 3-5 articles | Cymadusa uncinata |
| 3b | Accessory flagellum absent or consisting of a single minute article | 4 |
| 4a | Palm of gnathopod 1 nearly transverse (slightly oblique to nearly chelate); article 2 of pereopods 3 and 4 ovate; uropod 1 with a distal peduncular tooth extending between the rami (Genus Peramphithoe) (photo) | 5 |
| 4b | Palm of gnathopod 1 distinctly oblique; article 2 of pereopods 3 and 4 rectangular; uropod 1 without a distal peduncular tooth (Genus Amphithoe) | 9 |
| 5a | Adults 2-3 cm in length; proximal flagellar articles of antenna 2 typical, not fused; gnathopod 2 of male only slightly enlarged, if at all | 6 |
| 5b | Adults rarely over 1 cm; proximal flagellar articles of antenna 2 usually fused into a single article which is distinctly longer than the subsequent articles; gnathopod 2 of male distinctly enlarged | 7 |
| 6a | Article 5 of gnathopod 1 distinctly longer than article 6; gnathopod 2 of male not obviously different from gnathopod 1; pereopod 7 longer than pereopod 6 | Peramphithoe humeralis |
| 6b | Articles 5 and 6 of gnathopod 1 nearly equal in length; article 6 of gnathopod 2 of male about twice as broad as in gnathopod 1; pereopods 6 and 7 nearly equal in length | Peramphithoe mea |
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