Dimorphostylis Zimmer, 1921

Gerken, Sarah, 2014, Eleven New Species and a New Genus of Diastylidae (Crustacea: Cumacea) from Australia and One New Species from Canada, Records of the Australian Museum 66 (1), pp. 1-62 : 31-32

Dimorphostylis Zimmer, 1921

Type species. Dimorphostylis asiatica Zimmer, 1921 .

Diagnosis. Female and subadult male. Maxilliped 3 with exopod. Pereopods 3–4 without exopods. Adult male. With greatly expanded bases on pereopods 2–4 and exopods.

Remarks. The only consistent characteristics differentiating between Dimorphostylis and Paradiastylis are the presence of an exopod on maxilliped 3 and the lack of rudimentary exopods on pereopods 3–4 in Dimorphostylis females and the lack of the exopod on maxilliped 3 and the presence of rudimentary exopods on pereopods 3–4 in Paradiastylis females. The males of both genera have expanded bases on pereopods 2–4 and the exopods on those pereopods, thus it is impossible to determine the generic placement of the males without the conspecific female.

Australian species. Dimorphostylis australis Foxon, 1932 ; D. colefaxi Hale, 1945 ; D. cottoni Hale, 1936 ; D. inauspicata Hale, 1945 ; D. nordaustraliana n. sp.; D. roccatagliatai n. sp.; D. subaculeata Hale, 1945 ; D. tasmanica Hale, 1945 ; D. tribulis Hale, 1945 ; D. triplicata n. sp.; D. vieta ( Hale, 1936) .

Key to the Australian species of Dimorphostylis

1 Telson at least 1.5 × length of pleonite 6 .................................................................................. 2

—— Telson less than 1.5 × length of pleonite 6 ................................................................................ 3

2 Pereopod 1 propodus subequal to basis; adult male pereopod 2 basal expansion reaching only to mid-carpus ........................................................... D. australis

—— Pereopod 1 propodus distinctly shorter than basis; adult male pereopod 2 basal expansion reaching to at least mid-propodus ..................... D. triplicata n. sp.

3 Carapace covered in small spines, no ridges ....................................................... D. subaculeata

—— Carapace not covered in spines, spines if present only on anterior part of carapace ......................................................................................................................... 4

4 Lateral margin of telson with distinct tooth .............................................................................. 5

—— Lateral margin of telson entire .................................................................................................. 6

5 Carapace with distinct lateral ridges; uropod endopod article 2 shorter than article 3 ............................................................................................. D. inauspicata

—— Carapace without distinct lateral ridges; uropod endopod article 2 longer than article 3 ................................................................................................ D. tasmanica

6 Uropod endopod article 1 distinctly longer than articles 2 and 3 together ................................................................................................................................... 7

—— Uropod endopod article 1 not distinctly longer than articles 2 and 3 together ................................................................................................................................... 9

7 Carapace with folds but no distinct ridges; pereopod 1 short, propodus shorter than carpus ...................................................................................... D. colefaxi

—— Carapace with distinct ridges, may be serrate; pereopod 1 long, propodus longer than carpus ...................................................................................................... 8

8 Carapace with at least 4 lateral ridges on each side .................................................... D. cottoni

—— Carapace with no more than 3 lateral ridges on each side .......................................... D. tribulis

9 Uropod endopod article 1 not much longer than article 2 .............................................. D. vieta

—— Uropod endopod article 1 distinctly longer than article 2 ....................................................... 10 10 Carapace with 1 distinct lateral ridge, indistinct ridge or fold posterior of distinct ridge; pereopod 1 propodus subequal to basis ......... D. nordaustraliana n. sp.

—— Carapace with at least 2 distinct lateral ridges; pereopod 1 propodus distinctly shorter than basis .................................................... D. roccatagliatai n. sp.