Coleusia

Giraldes, Bruno Welter, Al-Maslamani, Ibrahim & Smyth, David, 2017, A new species of leucosiid crab (Decapoda: Brachyura: Leucosiidae) from the Arabian Gulf, Zootaxa 4250 (4), pp. 389-395 : 394

Key to species of Coleusia

1. Cheliped merus bearing conic granules; pterygostomial region with a beaded crest; fourth thoracic sternite with a granular band anteriorly; telson lunulate; greatly elongated apical process on male first pleopod, not spatulate........... C. rangita

- Cheliped merus bearing perliform granules; pterygostomian region smooth; fourth thoracic sternite smooth; telson triangular; apical process on male first pleopod not greatly elongated, and when long with spatulate shape....................... 2

2. Large-size, cl> 30 mm; palm lenticular, 1.1 times as long as wide; prominently granular pereiopodal meri and expanded, leaflike pereiopodal propodi; broad pale stripe medially on the carapace, with two large rust-coloured blotches posteriorly, and two smaller ones postero-laterally............................................................................3

- Carapace length <30 mm; palm elongate, 1.3–1.4 times as long as wide; pereiopodal propodi carinate; no broad pale stripe medially on the carapace and no rust-coloured blotches on the posterolateral margins............................... 4

3. Perliform granules of posterior margins of cheliped merus diminishing in size distally; dense granulation on ambulatory meri, and on lower external surface of the palm; male first pleopod with beak-like apical process and interiorly curved.. C. urania

- Perliform granules of posterior margins of cheliped merus disappearing distally; smaller and sparser granulation on ambulatory meri, absent from lower external surface of the palm; male first pleopod with apical process cornute, digitate, and curved externally....................................................................................... C. huilianae

4. Frontal margin tridentate; thoracic sinus with row of 8–9 elongate granules above cheliped basis, anterior margin straight; carapace with a pair of dark markings on gastric region; carapace with thin orange stripes and with Y-shaped orange mark posteriorly; spatulate apical process on the male first pleopod................................................. C. magna

- Frontal margin unidentate; thoracic sinus with no more than 5 granules above cheliped basis, anterior margin rounded; colour marking of carapace otherwise; no orange stripes and straight lines..............................................5

5. Upper margin of palm rounded (not cristate); thoracic sinus with row of 4–5 perliform granules; gastric region with a pair of large ocelli on each side of the carapace (8-shaped) lined by thin red outer rings, with small white centres.............. 6

- Dorsal surface of carapace punctate anteriorly; upper margin of palm cristate; thoracic sinus with row of 4–5 elongate, flattopped granules; carapace with dark indistinct patches; looped apical process of the male first pleopod......... C. signata

6. Palm more elongate, 1.4 times as long as wide; dorsal surface of carapace closely punctate; male first pleopod with apical process distally spatulate, twisted, curved outwards at right angle to shaft................................. C. biannulata

- Palm less elongate, 1.3 times as long as wide; carapace closely punctate only at proximal regions, slightly punctate posteriorly; male first pleopod with apical process distally straight and upward (not curved)............................. C. janani