Pseudacanthicus leopardus, Photo by M.H. Sabaj
The following is an excerpt from Armbruster (1997).
Pseudacanthicus is diagnosed by two unique characteristics: a
well-developed ridge ventrally on the hyomandibula and dorsolateral processes
of the tripus connecting near the base of the main body of the tripus.
Other characteristics considered synapomorphic for Pseudacanthicus are:
a bladelike first epibranchial, reduction of the levator arcus palatini
crest, a ventral process on the preopercle for articulation with the canal
plate, a highly angled maxilla, a metapterygoid condyle of the lateral
ethmoid that is only slightly raised, a wide ventral process of the sphenotic,
and a tall tripus.
Species of Pseudacanthicus are large, spiny loricariids with a diverse range of color patterns. Color is from light to dark gray, often with black spots. The fins and body may have red sections or a red wash. Abdomen covered in small plates in adults. Tail is forked, but without filaments. Four or more predorsal plates. Five rows of plates on the caudal peduncle. Pterotic-supracleithrum not enlarged. Jaws short, forming an acute angle at union; teeth few and stout. Adipose fin present.
P. histrix has incredibly elongated odontodes that form
a brush on the anterior margin of the pectoral fin spine in breeding males
(Burgess, 1989), but dimorphism has not been reported for the other species.
Pseudacanthicus can be separated from all hypostomines except Pogonopoma obscurum, the Acanthicus group, Pterygoplichthys, the Chaetostoma group (Chaetostoma, Cordylancistrus, Dolichancistrus and Leptoancistrus), and an undescribed Pseudancistrus by having eight or more dorsal-fin rays and from Pogonopoma, the Chaetostoma group and Pseudancistrus by having sharp odontodes forming keels on the lateral plates (vs. maximally weak keels in Co. platycephalus). Pseudacanthicus can be separated from Acanthicus by having an adipose fin and dentaries forming an angle of 90 degrees or less 9vs. almost straight), from Acanthicus and Megalancistrus by having a small pterotic (vs. a very large pterotic and an associated increase in the size of the swim bladder), from Megalancistrus by usually having eight to nine dorsal-fin rays (vs. 10-11, occasionally nine), from Leptoancistrus by lacking fimbriae on the upper lip, having more than two premaxillary teeth, and by having an oval lower lip (vs. round), and from Pterygoplichthys by having eight or nine dorsal-fin rays (vs 10 or more, rarely nine), a crescent shaped opercle (vs. triangular), a small stomach (vs. a stomach that fills almost the entire abdominal cavity), and by having the keel odontodes stout (vs. long if present)
The Orinoco, the Guyanas, the Negro, and the lower Amazonian tributaries.
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. University of Illinois, Urbana-Champaign. 409 pp.
Burgess, W.E., 1989. An atlas of freshwater and marine catfishes, a
preliminary survey of the Siluriformes. T.F.H. Publications, Neptune City,
New Jersey. 784 pp.