They possess five to eight branchiostegal
rays, being gas-bladder and orbited-sphenoid bone absent.
Gill openings broad, gill membranes united to each other, but free from isthmus, with 10 branchiostegal
rays in each side.
rays were present at 4.4 mm; by 6.8 mm, 6 rays were formed, and, by 7.7 mm, the full complement of 7 rays was present (Table 2).
Line of melanophores on isthmus, pigment present on branchiostegal
membrane under operculum.
In opercular rotation, opercles are rotated outward and the branchial basket expands downward with separation of the branchiostegal
rays; the body is tilted slightly head-downward with median fins rigidly fanned out (Figs.
The LDF is based on three morphometric and meristic characters: total branchiostegal
ray count, principal anal ray count, and the ratio of upper jaw length to standard length.
Although present, the number of branchiostegal
rays cannot be assessed with confidence due to the poor preservation of the specimens.
Hepatic spine absent; branchiostegal
spine present (Genus Palaemonetes) (Fig.
Peculiar long and thin cartilages of branchiostegal
rays for articulation with hyoid arch.
 Number of branchiostegal
rays (Costa 2004e) (CI: 0.33; RI: 0): (0) 6; (1) 5.
Cervical spines corneous; branchiostegal
areas of carapace smooth to slightly granular, dorsal surface with scattered punctations.
Members of clade A showed the greatest mean divergence (0.0108); taken as a natural group, they might be characterized morphologically by the presence of an epipod on third maxilliped, pleurobranchiae on fifth pereiopod, ventral and dorsal rostral teeth, as well as by the absence of branchiostegal
, pterygostomian and parapenaeid spines, and transverse and longitudinal sutures on carapace.