Melanorivulus amambaiensis

description

Description. Morphometric data are presented in Table 3. Females larger than males, largest female examined 28.7 mm SL, largest male 27.9 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, straight on caudal peduncle. Ventral profile weakly convex from lower jaw to operculum. Straight from operculum to origin of pelvic-fin and in the caudal peduncle. Body slender, cylindrical and compressed, greatest body depth at origin of pelvic-fin base. Snout blunt. Jaws short. Short dorsal and anal fins. Dorsal-fin rays 8 - 9. Dorsal fin slightly pointed in males, rounded in females. Dorsal-fin origin on a vertical through base of 8 th or 9 th anal-fin ray, and between neural spines of the 20 th and 21 th vertebrae. Anal-fin rays 12 - 14. Anal fin slightly pointed in males and females. Origin of anal fin at a vertical through pleural ribs of 15 th- 16 th vertebrae. Caudal fin oval shaped, longer than deep, 25 - 28 rays. Pectoral fin rays 11 - 13. Pectoral fins rounded, with posterior margin reaching vertical at about 70 - 90 % of length between pectoral-fin and pelvic-fin bases. Pelvic-fin rays 6 - 7. Posterior tip of pelvic fin reaching a vertical at slightly anterior

Unrecognized biodiversity in a world's hotspot: three new species of Melanorivulus (Cyprinodontiformes: Rivulidae) from tributaries of the right bank of the Rio Parana basin, Brazilian Cerrado

diagnosis

Diagnosis. The presence of an orange or orange-red anal fin with grey or dark grey distal margin (vs. no similar colour pattern) and chevron-like red bars in inverted Y-shape in the flank of males (vs. no similar pattern) distinguishes the M. amambaiensis from all other species of the M. pictus species group. Additionally, the new species is distinguished by the lower caudal fin ray count (25 - 28 vs. 29 - 34), except M. faucireticulatus; by the lower body depth in males (29.4 - 21.6 mm SL vs. 21.8 - 26.5), except from M. vittatus, M. polychromus, M. nigropunctatus, M. interruptus and M. ivinhemensis; by a lower caudal peduncle depth in males (12.4 - 13.5 mm SL vs. 13.5 - 16.8 mm SL), except in M. polychromus, M. nigropunctatus, M. interruptus and M. ivinhemensis. Females are distinguished from M. apiamici, M. faucireticulatus, M. giarettai, M. planaltinus, M. rutilicaudus, M. scalaris, M. nigropunctatus, M. proximus, M. linearis, M. nigromarginatus and M. formosensis by the lower body depth (19.1 - 21.5 mm SL vs. 21.6 - 26.0 mm SL); and from M. apiamici, M. egens, M. faucireticulatus, M. giarettai, M. planaltinus, M. nigropunctatus, M. linearis, M. nigromarginatus and M. ofaie by

Unrecognized biodiversity in a world's hotspot: three new species of Melanorivulus (Cyprinodontiformes: Rivulidae) from tributaries of the right bank of the Rio Parana basin, Brazilian Cerrado

distribution

Distribution. The species is only known from its type locality, a small first order drainage and direct tributary of Rio Amambai, state of Mato Grosso do Sul, Brazil (Fig. 3).

Unrecognized biodiversity in a world's hotspot: three new species of Melanorivulus (Cyprinodontiformes: Rivulidae) from tributaries of the right bank of the Rio Parana basin, Brazilian Cerrado

etymology

Etymology. The name amambaiensis is a reference to the occurrence of the new species in the Rio Amambai basin.

Unrecognized biodiversity in a world's hotspot: three new species of Melanorivulus (Cyprinodontiformes: Rivulidae) from tributaries of the right bank of the Rio Parana basin, Brazilian Cerrado