Alexandrella, Chevreux, 1911, 1911

Souza-Filho, Jesser F., Guedes-Silva, Elkênita & Andrade, Luiz F., 2024, Four new species and two new records of deep-sea Amphipoda (Crustacea: Peracarida) from Potiguar Basin, north-eastern Brazil, Journal of Natural History 58 (41 - 44), pp. 1615-1655 : 1649-1650

Key to world species of Alexandrella (adapted from d’Udekem d’Acoz and Verheye 2017)

1a. Pereonite 7 with a strong dorsal pointed carina.................................................................. 2

1b. Pereonite 7 dorsally smooth ....................................................................................................... 7

2a. Article 1 of peduncle of antenna 1 with short dorsomedial tooth; dactylus of pereopods 3–4 long; posteroventral border of coxa 4 straight or nearly so .......... 3

2b. Article 1 of peduncle of antenna 1 with long dorsomedial tooth; dactylus of pereopods 3–4 short; posteroventral border of coxa 4 strongly concave .............. 5

3a. First posterodorsal carina on pereonite 7 .............................................................................. 4 3b. First posterodorsal carina on pereonite 6 ..................... ..................... Alexandrella sp. 1 * 3c. First posterodorsal carina on pereonite 5 or more anterior pereonite(s) ........................ ................................................................................................................................ Alexandrella sp. 2 *

4a. Telson 0.37 cleft ........................................ Al. schellenbergi ( Holman and Watling, 1983) 4b. Telson 0.2 cleft or less ...................................... Al. pulchra Ren in Ren and Huang, 1991

5a. Anteroventral lobe of head moderately developed, triangular or bluntly triangular; dorsal carina of pleonite 3 with straight profile; posterodistal corner of basis of pereopod 6 broadly rounded ....................................................................................................... 6

5b. Anteroventral lobe of head very strong, hemi-elliptic; dorsal carina of pleonite 3 with distinctly sigmoid profile; posterodistal corner of basis of pereopod 6 forming a blunt squared angle ........... ........... Al. chione d’Udekem d’Acoz and Verheye, 2017

6a. Pereonite 6 with small posterodorsal carina; crest of urosomite 1 with long posterior tooth and deep posterior notch .............................................. Al. australis ( Chilton, 1912) 6b. Pereonite 6 without posterodorsal carina; crest of urosomite 1 with small posterior carina and no posterior notch .................................................................. Alexandrella sp. 3 *

7a. Telson truncate, notched or cleft but not convex .............................................................. 8 7b. Telson convex and entire (carina of urosomite 1 compact, not elongate) .................... ....................................................................................... Al. polarsterni ( Berge and Vader, 2005)

8a. Gnathopods 1–2 subchelate ......................................................................................................... 9 8b. Gnathopods 1–2 simple .............................................................................................................. 10

9a. Gnathopods 1–2 lacking facial setae; pleonites 1–2 with a weak dorsal ridge; pleonite 3 with a low rounded carina .... Al. subchelata Holman and Watling, 1983 9b. Gnathopods 1–2 densely setose; pleonites 1–3 with a dorsal well-developed pointed carina ........................................................................................ Al. setosa Serejo, 2014

10a. Pleonites 1–3 strongly toothed; female pereopod 1 with oostegite ....................... 11 10b. Pleonites 1–3 weakly toothed or absent; female pereopod 1 without oostegite 12

11a. Right mandible with lacinia mobilis reduced to a simple tooth ......................................... ...................................................................................... Al. mandibulata Berge and Vader, 2005 11b. Right mandible with lacinia mobilis broad and toothed, but smaller than left one .. ................................................................................................. Al. martae Berge and Vader, 2005

12a. Mandibular incisors not toothed along the entire margin; antennae 1–2 subequal in length .................................................................................................................................................. 13 12b. Mandibular incisors toothed along the entire margin; antenna 1 shorter than antenna 2 ........................................................................................................................................ 14

13a. Pereonites 1–7 with a pair of lateral triangular teeth.. .. Al. dentata Chevreux, 1912 13b. Pereonites 1–7 smooth ................................................................ Al. mixta Nichols, 1938 s. l.

14a. Mandible right lacinia mobilis absent; epimeron 3 posteroventral corner rounded; telson entire......................... ......................... Al. inermis Bellan-Santini and Ledoyer, 1987 14b. Mandible right lacinia mobilis present and well developed; epimeron 3 posteroventral corner pointed; telson cleft .......................................................... Al. cedrici sp. n. (*) in d’Udekem d’Acoz and Verheye (2017).