Abstract
Two new species, Hypancistrus phantasma and Hypancistrus margaritatus, are described based on material from the Rio Negro drainage. Both species are distinguished from congeners by unique color patterns. Hypancistrus phantasma is described from the Rio Uaupes and differs from congeners by having a tan body with small dark spots (vs. dark with light spots or with saddles or stripes). Hypancistrus margaritatus is described from the Takutu River and differs from congeners by having densely-packed light spots on a dark brown background, with spots about the size of the nasal aperture (vs. sparse light spots either smaller or larger than the nasal aperture, or brown to black spots, saddles, or stripes).
Highlights
Hypancistrus margaritatus is described from a single specimen collected in the Takutu River, a tributary of the Rio Branco of the Rio Negro drainage
Hypancistrus phantasma appears most similar to H. inspector, as both species have large maximum sizes relative to other Hypancistrus species and share the presence of dark distal edges on the dorsal and caudal fins
Hypancistrus inspector is found in the upper Rio Negro, and H. phantasma is found in the Rio Uaupes, a tributary to the Rio Negro
Summary
Hypancistrus is a small genus comprising six species of loricariid catfishes in the tribe Ancistrini of the subfamily Hypostominae: H. zebra Isbrücker and Nijssen (1991), the type species from the Rio Xingu; H. inspector Armbruster (2002) from the Rio Negro; and H. contradens Armbruster et al (2007), H. debilittera Armbruster et al (2007), H. furunculus Armbruster et al (2007), and H. lunaorum Armbruster et al (2007), all from the Rio Orinoco. Different numbers of teeth on the dentary and premaxilla are found in many loricariids, so this character is not always diagnostic (Armbruster 2002). The genus is diagnosed by the unique presence of a wide anterior separation between the metapterygoid and the lateral ethmoid, and a sharply angled adductor palatini crest. It lacks the lateral wall of the metapterygoid channel (Armbruster 2002). Species of Hypancistrus are best distinguished from each other by their color pattern and cannot be separated by traditional morphometrics used in loricariids (Armbruster et al 2007). We describe two new species of Hypancistrus with spotted color patterns
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