Simpsonichthys filamentosus,

Wilson J. E. M. Costa, 2007, Taxonomic revision of the seasonal South American killifish genus Simpsonichthys (Teleostei: Cyprinodontiformes: Aplocheiloidei: Rivulidae)., Zootaxa 1669, pp. 1-134: 50-51

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Simpsonichthys filamentosus


Simpsonichthys filamentosus  ZBK  Costa, Barrera & Sarmiento, 1997

(Fig. 31)

Simpsonichthys filamentosus  ZBK  Costa, Barrera & Sarmiento, 1997: 83 ( type locality: swamp close to rio San Pablo, rio Mamore basin, about 60 km N from Ascencion de Guarayos, road Santa Cruz-Trinidad , Departamento de Santa Cruz, Bolivia, about 15°37’S 63°35’W; holotype: CBF 3002GoogleMaps  ).

Material examined

Bolivia: Departamento de Santa Cruz, rio Mamoré drainage, rio Amazonas basin: CBF 3002, holotype, male, 30.3 mm SL; CBF 3003, 7 paratypes; UFRJ 3989, 4 paratypes; UFRJ 3990, 4 paratypes; MZUSP 51328, 2 paratypes; swamp close to the rio San Pablo, road Santa Cruz-Trinidad, about 60 km N from Ascencion de Guarayos , about 15° 37’ S, 63° 35’ W; W. J. E. M. Costa, S. Barrera and C. P. Bove, 22 Feb. 1997.GoogleMaps 


Distinguished from remaining species in having pelvic-fin bases separated by an interspace (vs. in contact), long filamentous rays on tip of dorsal and anal fins in males (vs. filaments absent, or present only on dorsal fin in S. semiocellatus  , or present only on anal fin in S. chacoensis  ), and presence (vs. absence) of contact organs on scales of flank in males.


Morphometric data appear in Table 3. Largest specimen examined 31.4 mm SL. Dorsal profile slightly concave on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile slightly convex on head, with distinct short ventral expansion on vertical through anterior margin of orbit, gently convex on trunk, slightly concave on caudal peduncle. Body moderately deep, compressed, greatest body depth on vertical just anterior to dorsal-fin origin. Eye positioned on dorsal portion of side of head. Snout blunt. Urogenital papilla cylindrical and long in males, pocket-shaped in females.

Tip of both dorsal and anal fins pointed in males, rounded in females; anal fin long in females, spatulashaped. Long filamentous rays on tip of dorsal and anal fins in males, tip reaching vertical posterior to distal margin of caudal fin. Dorsal-fin rays unbranched. Caudal fin rounded. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical between base of 10th and 12th anal-fin ray in males, and between base of 5th and 7th anal-fin ray in females. Tip of each pelvic fin reaching base of 5th or 6th anal-fin ray in males, and base of 2nd or 3rd anal-fin ray in females. Pelvic-fin bases separated by interspace about equal to width of pelvic-fin base. Dorsal-fin origin on vertical through base of 6th or 7th anal-fin rays, between neural spines of vertebrae9 and 10 in males, and neural spines of vertebrae 10 and 12 in females. Anal-fin origin between pleural ribs of vertebrae 5 and 6 in males, and pleural ribs of vertebrae 7 and 8 in females. Dorsal-fin rays 16-19 in males, 13-16 in females; anal-fin rays 22-25 in males, 20-23 in females; caudal-fin rays 21-24; pectoral-fin rays 12-13; pelvic-fin rays 6.

Frontal squamation E-patterned; E-scales overlapping medially; no scale anterior to G-scale; supraorbital scales absent. Longitudinal series of scales 28-29; transverse series of scales 11-12; scale rows around caudal peduncle 14. Contact organ on each scale of anteroventral portion of flank in males. Contact organs of pectoral fin absent.

Cephalic neuromasts: supraorbital 11-14, parietal 2-3, anterior rostral 1, posterior rostral 1, infraorbital 2 + 19-20, preorbital 3, otic 2, post-otic 2, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 15-17, mandibular 9-11, lateral mandibular 2-3, paramandibular 1. One neuromast on center of each scale of lateral line. Vertical row of 3-4 neuromasts on caudal-fin base.

Basihyal subtriangular, width about 70% of length; basihyal cartilage about 20% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 2-3. Gill-rakers on first branchial arch 3 + 13. Vomerine teeth absent. Dermosphenotic minute. Ventral process of posttemporal long. Total vertebrae 28-29.


Males. Side of body dark orange, with 15 vertical rows of white dots. Dorsum pale brown. Venter orangish golden. Head side dark orange, opercular region greenish golden. Iris yellow, with dark reddish brown bar through center of eye. Unpaired fins pale reddish brown, with light blue dots. Pectoral fins hyaline. Pelvic fins reddish brown.

Females. Side of body light brown, with 15 dark gray bars; one or two black spots on anterocentral portion of flank. Sides of head light brown, opercular region pale greenish golden. Iris yellow, with dark brown bar through center of eye. Fins hyaline, with faint small gray spots on dorsal and anal fins.


Río Mamoré and río Beni drainages, rio Madeira basin, Bolivia (Fig. 4).


Temporary pools in the Mata Ciliar, Llanuras Benianas.