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Abstract
Hopliancistrus is an Ancistrini genus diagnosed by having few and very strong cheek odontodes on interopercular area, and a patch of strong and stiff odontodes on the antero-lateral border of the snout. The type species is herein redescribed based on types and recently collected specimens. In addition, four new congeneric species are described based on specimens collected in other parts of the Rio Xingu and Rio Tapajo´s basins.

Hopliancistrus tricornis

is distributed in the lower Rio Tapajo´s and is diagnosed by the possession of four branched anal-fin rays and relatively large white to yellow spots on trunk and pectoral and pelvic fins, and dark brown spots on dorsal, caudal and anal fins.

Hopliancistrus munduruku

is described based on specimens from Rio Jamanxim (Rio Tapajo´s basin) and Rio Curua´ (Rio Xingu basin) and is diagnosed by the possession of five branched anal-fin rays and large yellow blotches on trunk and dark brown to black spots over the fins.

Hopliancistrus wolverine

is distributed in the rapids of the lower and middle Rio Xingu and is diagnosed by the possession of five branched anal-fin rays and conspicuous small yellow dots on head, trunk and fins.

Hopliancistrus xikrin

is distributed in medium- to small-sized tributaries of the lower portion of Rio Xingu basin, and is diagnosed by absence of contact between the transverse process of the first dorsal-fin pterygiophore and the transverse process of the second pterygiophore.

Hopliancistrus xavante

is distributed in the tributaries of upper Rio Xingu basin, and is diagnosed by having a thick skin covering the nuchal plate; by having large white spots on trunk and fins; and by the possession of five branched anal-fin rays. An osteological description and a key for species identification are also provided.

• 1. Four branched rays on the anal-fin. .....
  Hopliancistrus tricornis
  (Tapajo´s basin)
  • 1’. Five branched rays on the anal-fin. .....2
• 2. Head, trunk, and fins covered by conspicuous yellowish-white small dots of similar size and uniformly spaced. .....
  Hopliancistrus wolverine
  (middle Xingu basin)
  • 2’. Head and trunk covered by yellowish-white somewhat faint spots of varying sizes along the body, smaller in the snout and head and larger towards caudal fin. .....3
• 3. Nuchal plate covered by thick skin, lacking exposed odontodes (Fig 7F); caudal peduncle depth 11.5–12.9% of SL; nasal bone plate broad, length approximately equal width, sometimes slightly triangular (Fig 2B). .....
  Hopliancistrus xavante
  (upper Rio Xingu)
  • 3’. Nuchal plate exposed and ornamented by odontodes (Fig 7A–7E); caudal peduncle depth 10.0–11.3% of SL; nasal bone plate narrow, length approximately two times width (Fig 2A). .....4
• 4. Preserved specimens with overall dark coloration on body and fins; fins uniformly darkened
  with inconspicuous black spots. .....
  Hopliancistrus xikrin
  (tributaries of middle Xingu basin, not on main channel)
  • 4’. Preserved specimens with overall brown coloration with irregular and inconspicuous pale blotches; fins with conspicuous black spots on rays. .....
    Hopliancistrus munduruku
    (upper Rio Jamanxim and Rio Curua´)

Jools wrote: 20 Jan 2021, 22:44 In addition, L171 = H. xikrin and L361 = H. munduruku.

Jools

LDA015

Hopliancistrus wolverine

Hopliancistrus xikrin