Megapleonum Huang, Shih & Ahyong, 2018

Megapleonum Huang, Shih & Ahyong, 2018 View in CoL

Diagnosis.

Carapace broader than long, dorsal surface slightly convex; postorbital, epigastric cristae confluent or almost confluent; external orbital angle bluntly triangular, confluent or almost confluent with anterolateral margin. Epistome buccal margin with triangular median lobe. Maxilliped 3 ischium longitudinally subquadrate, length ~ 0.7 × width; exopod reaching slightly beyond distal edge of ischium, flagellum absent to well-developed. Male anterior thoracic sternum very broad, width 1.8–2.0 × length. Male pleon large, broadly triangular to sublinguiform, tip of telson rounded. Female pleon linguiform to subovate. G 1 large, sinuous, reaching beyond male pleonal locking tubercle, subterminal segment outer margin slightly to strongly concave, terminal segment highly variable. G 2 subterminal segment tapering, bent to slightly bent outwards distally, thin to thick flagelliform terminal segment. Vulvae ovate, large, reaching suture of sternites 5 / 6, relatively widely separated.

Composition.

Megapleonum ehuangzhang Huang, Shih & Ahyong, 2018 (type species), Megapleonum falx sp. nov., M. ferrumequinum sp. nov., Megapleonum shenzhen Huang & Mao, 2021 , M. yangdongense sp. nov., and M. wangjiani sp. nov.

Remarks.

With the description of four new species herein, the diagnosis of the genus has to be revised. The significant variation within the genus, particularly in the form of the G 1 poses challenges to establishing a uniform diagnosis. However, the key distinguishing features include the confluent or almost confluent postorbital and epigastric cristae, and external orbital angle and anterolateral margin, very broad male anterior thoracic sternum, large male pleon and the ovate, large vulvae, which extend to the suture of sternites 5 / 6 and are relatively widely spaced.