Rhinelepis is diagnosed by: a large plate between the opercle
and the pterotic-supracleithrum (15-1); two canal plates (16-2); an enlarged
sixth infraorbital bone that forms the entire posterior margin of the orbit
(18-1); a sphenotic that does not contact the orbit externally (22-1);
a cleithrum that is flattened ventromesially (26-1) and that is shaped
like a trapezoid (27-1); and expanded gill openings (35-1).
Rhinelepis is large and heavily plated, but develops plates on
the abdomen late in ontogeny when compared to Pseudorinelepis. Rhinelepis
is generally charcoal gray with no markings. The head is long and
flat (Armbruster and Page, 1997; Table 2). The fins are short; the
adipose fin is absent although the raised pre-adipose plate is often present.
The gill openings are much larger than in most other loricariids.
There is a large plate between the opercle and the pterotic-supracleithrum.
The cheek lacks elongate odontodes. Dorsal II-7, pectoral I-6, pelvic
I-5, anal 6 (1 unbranched, 5 branched), caudal I-14-I. 22-25 lateral
line plates, 6-7 plates under the base of the dorsal fin, 9-12 plates in
the depressed dorsal fin, 13-14 postdorsal plates, 10-11 postanal plates,
and 43-57 teeth per jaw ramus. Morphometrics given in Table 2.
Rhinelepis can be distinguished from most other loricariids by the combination of a loss of the adipose fin, a well developed dorsal fin spinelet (vs. a small, rectangular spinelet or no spinelet in Hemipsilichthys, Pareiorhaphis, Kronichthys, Pareiorhina, and Corymbophanes andersoni),
a large plate between the opercle and the pterotic-supracleithrum, expanded
gill openings, 6 anal fin rays, and a coracoid that is exposed ventrally.
Within the Rhinelepis group, Rhinelepis differs from all
others by the presence of expanded gill openings and presence of a plate
between the opercle and the pterotic-supracleithrum. In addition,
Rhinelepis differs from P. wertheimeri by the absence of an adipose fin, a completely plated abdomen in adults, no elongate cheek odontodes, and the following morphometric features (Table 2): a larger predorsal length/SL ratio (0.430-0.473 vs. 0.366-0.413), a larger head length/SL ratio (0.347-0.396 vs. 0.265-0.326), a larger snout length/SL ratio (0.210-0.243 vs. 0.155-0.179), a larger interorbital width/SL ratio (0.182-0.194 vs. 0.112-0.136), a smaller dorsal-caudal length/SL ratio (0.298-0.338 vs. 0.342-0.396), and a larger head depth/SL ratio (0.214-0.243 vs. 0.155-0.190); from P. parahybae by a completely plated abdomen in adults and the following morphometric features (Table 2): a larger predorsal length/SL ratio (0.430-0.473 vs. 0.373-0.400), a larger head length/SL ratio (0.347-0.396 vs. 0.304-0.326), a larger snout length/SL ratio (0.210-0.243 vs. 0.176-0.193), a larger interorbital width/SL ratio (0.182-0.194 and 0.120-0.137), a smaller postanal length/SL ratio (0.203-0.241 vs. 0.260-0.289), a smaller dorsal fin length/SL ratio (0.195-0.212 vs. 0.235-0.256), a larger head depth/SL ratio (0.214-0.243 vs. 0.155-0.190), and a larger cleithral width/SL ratio (0.286-0.333 vs. 0.233-0.275); from P. obscurum by having seven dorsal-fin rays (vs. eight to 11); and from Pseudorinelepis by the absence of tall ridges on the pterotic-supracleithrum, a lack of keels on the lateral plates, presence of a longer, lower head (Armbruster and Page, 1997), and the following morphometric features (Table 2): a larger snout length/SL ratio (0.210-0.243 vs. 0.138-0.176), a larger interorbital width/SL ratio (0.182-0.194 vs. 0.124-0.166), a smaller thorax length/SL ratio (0.151-0.207 vs. 0.258-0.317), a smaller postanal length/SL ratio (0.203-0.241 vs. 0.260-0.289), and a smaller dorsal fin spine length/SL ratio (0.185-0.229 vs. 0.236-0.342).
Three described species, Rhinelepis aspera from the Rio São Francisco, and R. paraguensis and R. strigosa from the Rio Paraná. Rhinelepis is also present in the Rio Paraíba and in a reservoir near Fortaleza in Ceará (marked by ? below). The population in Ceará is likely to be an introduction because the region is very dry and the large river habitat preferred by Rhinelepis is not naturally present. I have also examined a specimen of Pterygoplichthys etentaculatus from this reservoir. Pterygoplichthys etentaculatus is also thought to be restricted to the Rio São Francisco (Weber, 1992) where it is sympatric with Rhinelepis.
The question mark refers to a potentially introduced population of Rhinelepis.
Armbruster, J.W. 1998. Phylogenetic relationships of the suckermouth armored catfishes of the Rhinelepis group (Loricariidae: Hypostominae). Copeia 1998:620-636.
Weber, C. 1992. Révision du genre Pterygoplichthys sensu lato (Pisces, Siluriformes, Loricariidae). Revue fr. Aquariol., 19:1-36.