Pseudolithoxus anthrax can be diagnosed by color pattern from most Lasiancistrus: charcoal gray to black with white spots.  Pseudolithoxus anthrax differs from P. nicoi by the absence of a white band along the edge of the caudal fin, from P. dumus and P. tigris by the absence of bands in the caudal fin, and from Lasiancistrus sp. (see Discussion) by a greater dorsal base length to caudal depth ratio (2.9 - 3.5 vs. 2.1 - 2.2) and by usually having 5 anal-fin rays (versus 4; one specimen of P. anthrax examined has 4 anal-fin rays).

Body very dorsoventrally flattened with both ventral- and dorsal-surface flat.  Pectoral fins very elongate, pectoral-fin spine reaching anal fin in adults (only to anus in juveniles); very long, flexible odontodes present anterodistally on pectoral-fin spine.  Dorsal-fin spine weak; dorsal-fin spinelet supporting odontodes, v-shaped.  Dorsal fin short, folded dorsal fin not 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.  Opercle studded with moderately elongate, stout odontodes along ventral margin.  Cheek plates and opercle never with thin, whiskerlike odontodes.  Edge of snout anterior to evertible cheek plates with numerous hypertrophied odontodes.  Both males and females develop hypertrophied odontodes along snout margin and on distal tip of pectoral-fin spine.  Males develop greatly elongated anal fin.

Dorsal II 7-8 (usually 7), pectoral I 6, pelvic I 5, anal I 4-5 (anal-fin spine about half length of first branched ray; only one specimen with 4 branched rays). Teeth long and slender with large lateral and small mesial cusp; teeth 43-87 (47-64) per jaw ramus; tooth number tends to increase with standard length.  Lateral line plates 24-26 (26); dorsal plates 7-8 (8); interdorsal plates 6-7 (6); adipose-caudal plates 7-8 (7); folded dorsal-fin plates 11-14 (13); and postanal plates 12-14 (13).

Color in alcohol charcoal gray to black, with faint, small, sparse light spots on head, fin rays, fin spines, and body; in life, spots are brighter and more numerous (see photos in Weidner, 1996: 756).  Fins not with bands.  Five faint dorsal saddles often visible, first anterior to dorsal fin, second beginning at level of second dorsal fin ray, third below and slightly beyond posterior two rays of dorsal fin, fourth between dorsal and adipose fins, and fifth below and slightly beyond the adipose-fin membrane.  Abdomen slightly lighter than side, occasionally with light spots.  Ventral surface posterior to pelvic girdle colored as side.  Light spots usually present at the tips of caudal-fin spines.  White band never present at edge of dorsal or caudal fins.

Found in the Río Orinoco in Estado Amazonas and in the Ríos Caura and Aro of Estado Bolivar, Venezuela.

From the Greek anthrax for coal, in reference to the dark, coal-like color; treated as a noun in apposition.  Pseudolithoxus anthrax is referred to as Fliegerwels (flying catfish) in the German aquarium literature (Weidner, 1996) probably in reference to the long pectoral fins in adults.

LITERATURE CITED

Armbruster, J.W. and F. Provenzano. 2000.  Four new species of the suckermouth armored catfish genus Lasiancistrus (Loricariidae: Ancistrinae). Ichthyological Exploration of Freshwaters 11:241-254.

Armbruster, J. W. 1997. Phylogenetic relationships of the sucker-mouth armored catfishes (Loricariidae) with particular emphasis on the Ancistrinae, Hypostominae, and Neoplecostominae. Unpubl. Ph.D. dissertation, Univ. Illinois, Urbana-Champaign, 409 pp.

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

Armbruster, J. W. & M. Hardman. 1999. Redescription of Pseudorinelepis genibarbis (Loricariidae: Hypostominae) with comments on behavior as it relates to air-holding. Ichthyol. Explor. Freshwaters, 10: 53-61.

Armbruster, J. W. & L. M. Page., 1996. Redescription of Aphanotorulus (Teleostei: Loricariidae) with description of one new species, A. ammophilus, from the Río Orinoco basin. Copeia, 1996: 379-389.

Boeseman, M. 1968. The genus Hypostomus Lacépède, 1803, and its Surinam representatives (Siluriformes, Loricariidae). Zool. Verhand., 99: 1-89.

Heitmans, W. R. B., H. Nijssen, & I. J. H. Isbrücker. 1983. The mailed catfish genus Lasiancistrus Regan, 1904, from French Guiana and Surinam, with descriptions of two new species (Pisces, Siluriformes, Loricariidae). Bij. Dierk., 53: 33-48.

Isbrücker, I. J. H. 1980. Classification and catalogue of the mailed Loricariidae (Pisces, Siluriformes). Versl. Techn. Gegevens, Univ. van Amsterdam, 22: 1-181 pp.

Leviton, A. E., R. H. Gibbs, E. Heal, & C. E. Dawson. 1985. Standards in herpetology and ichthyology: Part I. Standard symbolic codes for institutional resource collections in herpetology and ichthyology. Copeia, 1985: 802-832.

Sabaj, M.H., J.W. Armbruster, and L.M. Page. In Press. Spawning in Ancistrus with comments on the evolution of snout tentacles as a novel reproductive strategy: larval mimicry. Ichthyol. Explor. Freshwaters.

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.

Weidner, T. 1996. Loricariiden aus Venezuela. DATZ 1996: 756.