Melanorivulus ivinhemensis

description

Description. Morphometric data are presented in Table 2. Females usually larger than males, largest female 30.4 mm SL, largest male examined 30.1 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, straight on caudal peduncle. Ventral profile convex from lower jaw to origin of anal-fin, approximately straight to end of caudal peduncle. Body slender, approximately cylindrical and compressed, greatest body depth anterior of pelvic fin base, in the pelvic fin base or at the anus. Snout slightly pointed. Jaws short. Short dorsal and anal fins. Dorsal-fin rays 7 - 9. Dorsal fin rounded or 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 20 th and 22 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- 18 th vertebrae. Caudal fin oval shaped, deeper than long, 29 - 31 rays. Pectoral fin rays 11 - 13. Pectoral fins rounded, with posterior margin reaching vertical at about 60 - 90 % of the length between pectoral-fin and pelvic-fin bases. Pelvic-fin rays 6 - 7, one indivi

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. Melanorivulus ivinhemensis is distinguished from all other species of the M. pictus species group by having a yellow caudal fin with thin red bars arranged only in the median region of the fin in males (vs. red bars absent or red bars extending from the ventral or median region to the dorsal region of the caudal fin), except in M. rutilicaudus. Besides, it is distinguished from all M. pictus species by the origin of the anal fin at a vertical through pleural ribs of 15 th- 18 th vertebrae (vs. 13 - 15 vertebrae), except in M. amambaiensis, M. planaltinus, M. scalaris, M. polychromus, M. ofaie, M. interruptus and M. nigropunctatus; and by the greater snout length in males (16.1 - 21.3 vs. 11.4 - 16.3), except in M. amambaiensis, M. apiamici, M. interruptus, M. vittatus, M. polychromus and M. nigropunctatus. Distinguished from M. planaltinus, M. rutilicaudus, M. interruptus by a lower caudal fin ray count (29 - 31 vs. 32 - 34) and from M. amambaiensis by a higher caudal fin ray count (29 - 31 vs. 25 - 28). Distinguished from M. faucireticulatus, M. giarettai, M. interruptus, M. leali, M. vittatus and M. formosensis by a short basihyal cartilage 10 - 15 % of total basihyal

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. Melanorivulus ivinhemensis is so far only known from first order streams and small wetlands associated with both margins of the lower course of the Rio Ivinhema, Rio Parana basin (Figure 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 ivinhemensis is a reference to the occurrence of the new species in the Rio Ivinhema 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