Baryancistrus niveatus, photo by J.W. Armbruster
Baryancistrus demantoides Green Phantom Pleco, Photo by M.H. Sabaj
Baryancistrus has two described species, B. niveatus and B. longipinnis. Both have the posterior membrane of the dorsal fin expanded and it touches the adipose fin in B. niveatus but not in B. longipinnis. In addition, B. niveatus is covered in large white spots whereas B. longipinnis is either wihout spots or with small ones.
In addition, there are many undescribed species including the complex of species known in the pet trade as the gold nugget plecos. These usually have a white to orange band at the edges of the dorsal and caudal fins, although occasionally the real B. niveatus is seen under this name. Another species in the pet trade is the green phantom pleco (see photo above). Green phantom plecos are actually two species (one Baryancistrus and the other Hemiancistrus) from Southern Venezuela that we are describing.
The following is derived from Armbruster (1997).
Baryancistrus is not diagnosed by any unique characteristic. Characteristics considered synapomorphic for Baryancistrus include: a thin metapterygoid, a mesial, posterior facing ridge paralleling the anterior margin of the metapterygoid, seven or more infraorbital plates, a tall ridge on the lateral ethmoid for articulation with the metapterygoid, two large, perforated hemal spines anterior to the centrum in contact with the first anal fin pterygiophore, dorsal fin membrane expanded posteriorly and in contact with the preadipose plate, and a straight, tall posterior margin of the exposed coracoid process.
Baryancistrus is a small loricariid with the dorsal fin membrane enlarged posteriorly, contacting the preadipose plate in B. niveatus and the undescribed gold nugget and green phantom plecos. Color pattern is variable, but usually involves white to gold spots, occasionally with the dorsal and caudal fins edged in white to orange. Caudal fin is slightly emarginate. Three predorsal plates. Five rows of plates on the caudal peduncle. Abdomen naked.
Baryancistrus can be separated from all loricariids except Delturus,
Parancistrus, and Spectracanthicus by the presence of an enlarged, posterior membrane on the dorsal fin . Baryancistrus
can be separated from Spectracanthicus by having more than 26 teeth
and jaws that are long, nearly forming a straight line at union (vs. short,
forming an acute angle at union) from Spectracanthicus murinus by
having evertible cheek spines, from Parancistrus by lacking fleshy
folds on the skin around the dorsal fin, by having restricted gill openings
(the gill openings in Parancistrus are large), and by lacking plates
on the abdomen, and from Delturus by having only a single median
preadipose plate (vs. 3-4), evertible cheek plates, lack of a postdorsal
ridge, and lack of a very large naked area behind the pterotic-supracleithrum.
Amazon and upper Orinoco in tributaries of the Guyana and Brazilian Shields.
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.
Rapp Py-Daniel, L.H. 1989. Redescription of Parancistrus aurantiacus
1855) and a preliminary description of two new genera:
n.g. and Oligancistrus n.g. (Siluroidei; Loricariidae). Cybium