Haustoriidae, Stebbing, 1906

Hancock, Zachary B. & Wicksten, Mary K., 2018, Two new species of sand-burrowing amphipods of the genus Haustorius Müller, 1775 (Amphipoda: Haustoriidae) from the northwestern Gulf of Mexico, Zootaxa 4459 (1), pp. 101-127 : 123-125

Key to the Haustoriidae of the Gulf of Mexico

(modified from LeCroy 2002; Winfield et al. 2007; Sweet 1996)

1. Pleonite 3 overhanging urosome......................................................................... 2

- Pleonite 3 not overhanging urosome...................................................................... 16

2. Epimeron 3 rounded posteroventrally without tooth........................................................... 3

- Epimeron 3 rounded posteroventrally with tooth............................................................. 7

3. Rostrum exceeding ½ length of antenna 1 peduncular segment 1, acute; maxilla 2 outer plate narrow, lanceolate distally; pereopod 6, article 5 anterodistal margin rounded; uropod 1 peduncle with at least 3 proximal spines..................................................................................... Haustorius canadensis (Atlantic) Bousfield, 1962

- Rostrum less than ½ length of antenna 1 peduncular segment 1, subacute; maxilla 2 outer plate broad; uropod 1 peduncle with less than 2 proximal spines... Haustorius spp. (Gulf of Mexico)................................................. 4

4. Antenna 1 accessory flagellum 4–5 articulate; mandible with 8+ accessory blades; mandibular palp article 3 with 15+ spines in comb row; uropod 1 interramal area with 3 large spines..................... Haustorius jayneae Foster & LeCroy, 1991

- Antenna 1 accessory flagellum 2–3 articulate; mandible with less than 8 accessory blades; mandibular palp 3 with 12 or less spines in comb row; uropod 1 interramal area with 2 or less large spines.......................................... 5

5. Maxilla 2 outer plate very broad, minutely curved; pereopod 3, article 5 with posterior cup equal or slightly exceeding length of anterior margin; pereopod 6, article 5 distal margin with minute notch, not medially produced; telson cleft almost to base...................................................................................................... 6

- Maxilla 2 outer plate broad, lunate; pereopod 3, article 5 with posterior cup greater than 1.2x length of anterior margin; pereopod 6, article 5 anterodistal margin with distinct notch, medially produced; telson cleft 1/3 distance to base.............................................................................................. Haustorius galvezi sp. nov.

6. Antenna 1 accessory flagellum with 3 articles; mandible, incisor trifid; mandibular palp, article 3 with 5 spines in comb row; pereopod 5 coxa ovoid, not compressed medially; pereopod 6 article 4 proximal margin set-off from posterior margin, 2 spine groups............................................................... Haustorius mexicanus Ortiz et al., 2001

- Antenna 1 accessory flagellum with 2–3 articles; mandible, incisor bifid; mandibular palp, article 3 with 8 or more spines in comb row; pereopod 5 coxa dumbbell-shaped, compressed medially forming anterior and posterior lobes; pereopod 6 article 4 proximal margin continuous with posterior margin, only setae............................. Haustorius allardi sp. nov.

7. Accessory flagellum with 2 articles, inserted subterminally; maxilla 2 outer and inner plates roughly equal in length; maxilla 1 without bailer; uropod 1 inner ramus broad and longer than outer ramus; telson deeply notched, forming a V............................................................................. Pseudohaustorius carolinensis Bousfield, 1965

- Accessory flagellum with 2 articles, inserted terminally; maxilla 2 outer plate longer than inner; maxilla 1 with bailer; uropod 1 inner ramus slender and shorter than outer… Acanthohaustorius ............................................... 8

8. Uropod 1, peduncle very short with stubby spines........................... Acanthohaustorius bousfieldi Frame, 1980

- Uropod 1, peduncle with moderate to long slender spines...................................................... 9

9. Epimeron 3 posterior margin strongly recurved as a large shelf overhanging urosome................................................................................................ Acanthohaustorius intermedius Bousfield, 1965

- Epimeron 3 posterior margin decurved or recurved, slightly overhanging urosome................................. 10

10. Uropod 1 peduncle with stout, dorsally hooked interramal spine.................. Acanthohaustorius unicus, Foster, 1989

- Uropod 1 peduncle lacking stout hooked spine, with or without long curved spine................................. 11

11. Uropod 1 peduncle with long, stout distal spine greater in length than other interramal spines; outer ramus with stout apical spine subequal or shorter than subapical spines......................... Acanthohaustorius shoemakeri Bousfield, 1965

- Uropod 1 peduncle with distal spine not stouter or longer than other interramal spines; outer ramus with stout apical spine much shorter than subapical spines....................................................................... 12

12. Coxa 7, posterior lobe rounded or subacute; uropod 1 peduncle with very long, slender spines along dorsolateral margin, all roughly equal in length................................................................................ 13

- Coxa 7, posterior lobe acute posteriorly; uropod 1 peduncle with moderately long spines decreasing in length distally..... 14

13. Pereopod 6, article 5 bearing 4–7 long spines along distal margin; pereopod 7, article 5 posterior margin with 1–2 setae proximally to posterodistal angle; epimeron 3, posterodistal tooth slender and sharply curved; uropod 1 without ventral spines.......................................................................... Acanthohaustorius sp. A LeCroy, 2002

- Pereopod 6, article 5 with 1–3 short spines on distal margin; pereopod 7, article 5 without setae cluster; epimeron 3, posterodistal tooth short and stout; uropod 1 peduncle with 2–3 ventral spines..... Acanthohaustorius pansus Thomas & Barnard, 1984

14. Pereopod 6, article 5 with 9–10 spine groups on lateral surface; uropod 1 peduncle with 8–10 spines on dorsal margin............................................................................ Acanthohaustorius similis Frame, 1980

- Pereopod 6, article 5 with 3–7 spine groups on lateral surface; uropod 1 peduncle with 2–4 spines on dorsal margin....... 15

15. Pereopod 7, article 5 posterior margin evenly convex, lacking spines proximal to posterodistal angle; epimeron 3 posteroventral tooth very long, extending to pleonal notch; uropod 1 peduncle lacking ventral spines, inner ramus with 2 long apical setae................................................................... Acanthohaustorius millsi Bousfield, 1965

- Pereopod 7, article 5 posterior margin obtuse, 1–2 spines proximal to posterodistal angle; epimeron 3 posteroventral tooth moderately long but not reaching pleonal notch; uropod 1 peduncle with 1 ventral spine, inner ramus without long apical setae Acanthohaustorius sp. C LeCroy, 2002

16. Antenna 2, peduncular article 5 without expanded posterodistal lobe; mandible with incisor process; uropod 2 biramous; telson cleft into a V or entirely to base......................................................................... 17

- Antenna 2, peduncular article 5 with strong posterodistal lobe; mandible lacking incisor process; uropod 2 uniramous; telson entire or emarginate..................................................... Neohaustorius schmitzi Bousfield, 1965

17. Mandibular palp, article 3 with median row of comb setae; pereopod 6, article 5 distal margin subequal to the length of article 6; pereopod 7, article 4 roughly triangular; telson cleft nearly to base… Lepidactylus ............................... 18

- Mandibular palp, article 3 with proximal or distal row of comb setae; pereopod 6, article 5 distal margin less than the length of article 6; pereopod 6, article 4 subrectangular with posterior margin bearing 3–4 spines (occasionally subtriangular, if so coxa 7 is acute posteriorly)................................................................................. 19

18. Antenna 1, accessory flagellum with 2 articles; pereopod 7, article 2 posterior margin lined with setae; uropod 1 peduncle lined with spines continuously and with 1 long, hooked interramal spine; telson lobes narrowly separated................................................................................................ Lepidactylus dystiscus Say, 1818

- Antenna 1, accessory flagellum with 2-5 articles; pereopod 7, article 2 without setae along posterior margin; uropod 1 peduncle not continuously lined with spines and with 3–4 slender interramal spines; telson lobes deeply separated.......................................................................... Lepidactylus triarticulatus Robertson & Shelton, 1980

19. Antenna 1 geniculate; article 3 of mandibular palp with proximal setae; maxilla 2 outer plate subequal to inner; article 6 of pereopod 6 with or without distal spine on posterior margin; uropod 2 reduced, biramous....................................................................................... Protohaustorius bousfieldi Robertson & Shelton, 1978

- Antenna 1 not geniculate; article 3 of mandibular palp with distal setae; maxilla 2 outer plate much longer than inner; article 6 of pereopod 6 with 3–4 distal spines on posterior margin; uropod 2 well-developed, biramous… Parahaustorius ......... 20

20. Pereopod 6, article 4 roughly longer than article 5, with 4 rows of setae; article 6 without setae; pereopod 7, article 6 with long setae at apex......................................................... Parahaustorius holmesi Bousfield, 1965

- Pereopod 6, article 4 subequal in length to article 5, with 5 rows of setae; article 6 with setae; pereopod 7, article 6 with short setae at apex....................................................... Parahaustorius attenuatus Bousfield, 1965