Hypancistrus phantasma, Tan, Milton & Armbruster, Jonathan W., 2016

Tan, Milton & Armbruster, Jonathan W., 2016, Two new species of spotted Hypancistrus from the Rio Negro drainage (Loricariidae, Hypostominae), ZooKeys 552, pp. 123-135 : 124-127

Taxon classification Animalia Siluriformes Loricariidae

Hypancistrus phantasma sp. n. Figure 1

Holotype.

MZUSP 116531, 123.3 mm SL, Amazon Basin, Rio Negro drainage: Rio Uaupes, Taracua, 0.1°N, 68.46667°W, 14 Feb 1924, D. Melin and A. Vilars.

Paratypes.

NRM 16880, 3, 92.5-105.46 mm SL, same data as holotype; NRM 39344, 1, 101.3 mm SL, same locality as holotype, 19 Feb 1924, same collectors as holotype.

Diagnosis.

Hypancistrus phantasma can be distinguished from congeners by a color pattern consisting of a tan base coloration with black spots vs. a color pattern consisting of a dark base coloration and light spots (as in Hypancistrus contradens , Hypancistrus inspector , Hypancistrus lunaorum and Hypancistrus margaritatus ) or a color pattern consisting of saddles, vermiculations, bands, or stripes (as in Hypancistrus furunculus , Hypancistrus debilittera , and Hypancistrus zebra ).

Description.

Morphometric data given in Table 1. Counts are variation observed in paratypes. Largest specimen examined 123.3 mm SL. Ventral surface from anus to head largely lacking plates in adults. Small plates present in skin ventral to pectoral girdle, anteromesially to gill opening, and on ventrolateral margins of thorax extending posteriorly from insertion of pectoral-fin spine towards insertion of pelvic-fin spine. Extent of small ventral plates correlated with body size, with larger specimens having larger ventral plated areas with plates ventral to pectoral girdle joining medially, and ventrolateral abdominal plates extending further posteriorly. Lateral plates unkeeled except ventral plate row with moderately elongate odontodes forming one or two keel-like rows on caudal peduncle, and mid-ventral plate row bent above pectoral girdle forming ridge continuous with cleithrum. Cheek plates with 23-49 hypertrophied odontodes. Frontal, infraorbitals, nasal, preopercle, compound pterotic, and suprapreopercle supporting odontodes. Small ridge of opercle covered in smallest paratype (92.5 mm SL), exposed in remaining specimens; if exposed, zero to six odontodes present.

Caudal fin emarginate, lower lobe longer than upper. Ventral surface flat. Head tall. Snout short. Vertical through anterior margin of orbit about half-way between vertical through anterior margin of snout and vertical through posteromedial tip of supraoccipital. Head with steep angle in profile, roughly 45° from tip of snout to anterior margin of eye. Body depth increases gradually from anterior margin of eye to dorsal-fin origin, then decreases gradually from dorsal-fin origin to posterior insertion of adipose fin; caudal-peduncle depth increases slightly from insertion of adipose fin to origin of caudal fin.

Supraorbital crest low. Orbital opening oriented at less than 45°from sagittal plane. Interorbital isthmus between supraorbital crests flat. Supraoccipital crest low. Eye large with iris operculum. Gill opening restricted in L-conformation, with half of opening vertical and opening laterally and half of opening horizontal and opening ventrally.

Dorsal-fin spine short; depressed dorsal fin reaching anterior edge of or slightly beyond preadipose plate. Depressed pectoral-fin spine reaching beyond base of pelvic-fin rays; depressed pelvic-fin spine reaching beyond posterior insertion of anal fin. Dorsal fin II,7; caudal fin I,14,I; dorsal procurrent caudal-fin spines four to five, four in holotype; ventral procurrent caudal-fin spines four to five, four in holotype; anal fin i3-4 (one paratype examined with 3 anal-fin rays); pectoral fin I,6; pelvic fin i,5. Fin spines and rays supporting odontodes. Odontodes more elongate distally on pectoral-fin spine and ventrally on pelvic-fin spine than at base of pectoral- and pelvic-fin spines.

Lips papillose, forming oral disk less than half width of head. Maxillary barbels long (reaching past posterior edge of lower lip when extended posteriorly), thin, and pointed; barbel rugose proximally, almost smooth distally.

Median plates 24; mid-dorsal plates 22-24 (24 in holotype, mode 23); mid-ventral plates 24; rows of plates on caudal peduncle five. Dentary teeth two to three (two in holotype), teeth long and wide; premaxillary teeth four to seven (six in holotype), thinner and shorter than dentary teeth. In new teeth, medial cusps longer and wider than lateral cusps; in worn teeth, medial and lateral cusps of approximately the same length and width. Central buccal papilla absent.

Color. Specimens preserved in 70% alcohol with tan base color and small brown spots. Tan base coloration largely uniform, with paler region between orbits, posterior to orbit, and extending posterior to cleithrum. Naked areas white, including ventral surface and areas surrounding origins of pectoral- and pelvic-fin spines. Small brown spots evenly spaced on head. Brown spots on body larger than spots on head, increasing slightly and gradually in size posteriorly. Brown spots on body more closely spaced anteriorly and more distantly spaced posteriorly; on imaginary vertical-oblique lines through the spots, four to five spots occurring per line anteriorly diminishing to two spots per line posteriorly. No spots ventral to an imaginary line between origin of pelvic-fin spine and origin of dorsal caudal-fin spine. Fin rays tan, fin membranes of paired fins and anal fins hyaline. Dorsal-fin rays tan; dorsal-fin membrane tan at base, gradually fading to dark brown band at the distal edge. Caudal-fin membrane on lower lobe transitioning to brown posteriorly. Dark spots present on pectoral-fin rays, pelvic-fin rays, and dorsal-fin rays. Faint white, round spots on dorsal and caudal fins; on dorsal fin, white color more apparent on brown fin membranes than on rays. Odontodes on cheek and fin spines straw-colored with dark brown tips.

Range.

Only known from Taracuá of the Rio Uaupes, a tributary of the Rio Negro drainage (Fig. 2).

Etymology.

The specific epithet phantasma is Latin for “phantom,” and refers to its elusiveness (the described specimens represent the only known specimens, despite nearly a century passing since their collection) and its pale body coloration. It is treated as a noun in apposition.