Pseudolithoxus tigris is diagnosed by the presence of numerous, black bars on the body and head.  Among other loricariids, only some undescribed Panaque Eigenmann and Eigenmann have a similar color pattern, but they have less than 15 large, spoon shaped teeth per jaw ramus (vs. 30+ thin teeth per jaw ramus).

Body very dorsoventrally flattened with both ventral- and dorsal-surface flat.  Extremely hypertrophied odontodes present anterodistally on pectoral-fin spine.  Dorsal-fin spine weak; dorsal-fin-spinelet supporting odontodes, v-shaped.  Dorsal fin short, folded dorsal fin just barely reaching median, unpaired preadipose plate.  Caudal fin weakly forked, lower lobe longer than upper.  Eyes mostly dorsal.  3 rows of plates on caudal peduncle.  Pterotic-supracleithrum bordered posteriorly at lateral line by small naked area ventrally and small plate dorsally.  Abdomen without plates.  Cheek odontodes hypertrophied, numerous, and set on evertible plates; odontodes fold into groove underneath opercle when relaxed.  Edge of snout anterior to evertible cheek plates with numerous hypertrophied odontodes.  Opercle studded with moderately elongate, stout odontodes along ventral margin.  Cheek plates and opercle never with thin, whiskerlike odontodes.  Pectoral fins not elongated, but only small individuals examined.

Dorsal fin II 7; pectoral fin I 6; pelvic fin I 5; anal fin I 5 (anal-fin spine about half length of first branched ray). Teeth long and slender with large lateral and small mesial cusps; teeth 35-49 (42-49) per jaw ramus; tooth number increases with size.  Lateral line plates 23-24 (23); dorsal plates 7-8 (7); interdorsal plates 4-5 (5); adipose-caudal plates 7-8 (8); folded dorsal-fin plates 11-12 (12); and postanal plates 11-12 (12).

Color in alcohol consists of numerous alternating dark brown and tan to orange bars.  Tan bars generally much thinner than dark bars, bars often squiggly or interconnecting.  Tan bars continue onto head where they form interconnecting lattice.  Dark spots present on fin spines and rays making fins appear banded.  Abdomen white; lower surface posterior to pelvic girdle tan.

Known from the upper Río Orinoco and the Río Ventuari.

Pseudolithoxus tigris probably matures at a small size.  The holotype is only 49.2 mm SL, yet the snout and pectoral-fin spine odontodes are greatly elongated.  In similarly sized specimens of the other species of Pseudolithoxus, the snout and pectoral-fin spine odontodes are just beginning to develop and cannot be described as hypertrophied.

Pseudolithoxus tigris may actually represent more than one species.  One specimen from near the type locality (MBUCV V-17557) has a similar color pattern to the type specimens, but the tan bars are wider than the dark bars, it appears to have a slightly deeper body (dorsal-pectoral length 26.1% SL vs. 21.2 - 25.3% SL), and the eyes that are more lateral.  Specimens from the upper Río Ventuari (MBUCV V-16843) appear to have the same body shape as the types; however, they are old, faded specimens whose identity could not be confirmed.  The specimens of MBUCV V-17557 and MBUCV V-16843 were not used in the morphometric analyses.  We defer splitting P. tigris into other species until more specimens become available.

From the Latin tigris for tiger in reference to the tigerlike markings; treated as a noun in apposition.

Holotype.  MBUCV V-17546, 49.2 mm SL; Venezuela, Estado Amazonas, backwater of Río Orinoco behind sand playa ca. 0.5 hr. upstream from Isla Temblador, 03°04íN 66°28íW, B. Chernoff, W. G. Saul, H. Lopez, J. Fernandez, O. Castillo, M. E. Antonio, & J. Moreno, 10 March 1987.

Paratypes.  All collection: Venezuela, Estado Amazonas.  ANSP 161496, 1, 28.8 mm SL, collected with holotype. - MBUCV V-23086, 2, 33.1 - 34.8 mm SL, Río Ventuari, S side of river ca 0.5 hr. (ca. 12 km) above mouth in Río Orinoco, Laguna Pavón, 04°04íN 66°56íW, A. Machado, B. Chernoff, & J. Wheeler, 24 January 1991. - MBUCV V-23107, 1, 21.8 mm SL, Río Orinoco at Isla Cupoven, rapids and rocks, A. Machado & B. Chernoff, 29 January 1991.

Non-types.  Venezuela, Estado Amazonas: MBUCV V-16843, 1, 93.6 mm SL, Río Hacha, a tributary of the Río Ventuari, 04°40íN 65°20íW, I. Rodriguez et al., 22 February 1972. - MBUCV V-17557 (50.7 mm SL), Río Orinoco, creek between the island and the beach, just downstream from Quiritare, (Quiritare is at 03°02íN 66°04íW), B. Chernoff, H. Lopez, J. Fernandez, and W. G. Saul, 11 March 1987. - Colombia, Departmento Meta: MAC-PAY 01555,1, 61 mm SL, Río Tomo (Río Orinoco drainage), Aceiticos, approximately 5 km from Centro Administrativo del INDERENA, western margin of the Río Orinoco.

LITERATURE CITED

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Armbruster, J. W. 1998. Phylogenetic relationships of the suckermouth armored catfishes of the Rhinelepis group (Loricariidae: Hypostominae). Copeia 1998: 620-636.

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Taylor, W. R. & G. C. Van Dyke. 1985. Revised procedures for staining and clearing small fishes and other vertebrates for bone and cartilage study. Cybium 9: 107-119.

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