Key:  Suborder Gammaridea, Group I (Uropod 3 with 1 ramus which never greatly exceeds length of peduncle; if second ramus is present it is scarcely noticeable)

Phylum Arthropoda
  Subphylum Crustacea
    Class Malacostraca
      Subclass Eumalacostraca
        Superorder Peracarida
          Order Amphipoda
           Suborder Gammaridea

Taken primarily from  Kozloff, 1987, 1996 p. 348 (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)
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1a  Article 4 of antenna 2 extraordinarily thickened and bearing large ventral spines or teeth; urosome dorsoventrally flattened; ramus of uropod 3 flattened and paddlelike (Corophium) 2
1b Article 4 of antenna 2 not especially thickened and without spines or teeth; urosome laterally compressed; ramus of uropod 3 somewhat conical or bladelike 8
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a Coxa 1 much reduced and coxa 4 greatly enlarged (often more than 3 times the width of coxa 2); ramus of uropod 3 with distinct articles Stenotheidae
8b Coxae 1-4 nearly equal in size (although becoming slightly wider posteriorly); obvious ramus of uropod 3 with a minute second article or uniarticulate 9
9a Eyes borne on prominent anteriorly-directed lateral lobes of head; proximal posterior margin of coxa 4 without a deep concavity; peduncle of uropod 3 slender and distinctly longer than the telson; telson thick and fleshy, not cleft 10
9b Eyes not borne on lateral lobes; proximal posterior margin of coxa 4 with a deep concavity in its posteroproximal portion; peduncle of uropod 3 stout, never greatly exceeding the length of the telson; telson sometimes thickened, but usually thin and cleft 18
10a
10b
11a
11b
12a
12b
13a
13b
14a
14b
15a
15b
16a
16b
17a
17b
18a Ramus of uropod 3 vestigial; scarcely one-fourth as long as the peduncle 19
18b Ramus of uropod 3 distinct; at least one-half as long as the peduncle 20
19a
19b
20a Antenna 1 longer than the peduncle of antenna 2; telson bearing no more than 2 stiff spines 21
20b Antenna 1 shorter than the peduncle of antenna 2; telson with more than 2 spines (Talitridae, "beach hoppers") 27
21a Antenna 1 slightly longer than antenna 2; uropod 3 bearing a minute inner ramus (hidden in lateral view); telson bearing 2 stiff spines Parallorchestes spp.
21b Antenna 1 shorter than, or about as long as antenna 2; uropod 3 truly uniramous; telson naked or bearing setae or small, flexible spines 22
22a Antenna 1 of female only slightly shorter than antenna 2 (in males, it is distinctly shorter than antenna 2); apex of uropod 3 bearing only setae or flexible spinules; telson not cleft to its base (Allorchestes) 23
22b Antenna 1 of both sexes distinctly shorter than antenna 2; apex of uropod 3 bearing stiff spines; telson cleft to its base 24
23a
23b
24a Flagellum of antenna 2 long (with 20 or more articles in adult specimens); uropod 1 with an enlarged peduncular spine at the base of the rami (this spine lateral to the rami); telson naked (Keyed as Hyale frequens in Kozloff key) Protohyale sp.
24b Flagellum of antenna 2 short (with less than 20 articles in adult specimens); uropod 1 with or without an enlarged peduncular spine at the base of the rami (when present, this spine is between the rami); telson bearing slender spinules 25
25a
25b
26a
26b
27a Gnathopod 1 subchelate (especially in males), its dactyl not longer than the width of article 6; pereopod 6 not exceeding the length of pereopod 7; ramus of uropod 3 shorter than the peduncle and tapering to a point 28
27b Gnathopod 1 simple, its dactyl longer than the width of article 6; pereopod 6 slightly longer than pereopod 7; ramus of uropod 3 at least as long as the peduncle, not tapering distally (Megalorchestia) 31
28a
28b
29a
29b
30a
30b
31a Flagellum of antenna 2 shorter than peduncle; bases of peduncles of pleopods only slightly expanded; inner margin of outer ramus of uropod 2 without spines Megalorchestia pugettensis
31b Flagellum of antenna 2 not shorter than the peduncle (in males it is much longer than the peduncle); bases of peduncles of pleopods nearly twice as wide as their distal ends; inner margin of outer ramus of uropod 2 with spines 32
32a Article 5 of gnathopod 1 of female with a posterodistal tubercle; ventral margins of epimera 2-3 each bearing several small spines; rami of pleopods less than half the length of the peduncles (the antennae are pinkish orange in life) Megalorchestia californiana
32b Article 5 of gnathopod 1 of female without a tubercle; ventral margins of epimera without spines; rami of pleopods at least one-half the length of the peduncles Megalorchestia columbiana



Taxonomic Levels Represented in This Key:

  Megalorchestia californiana
  Protohyale sp.
 



Page created by Dave Cowles, 2008
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