A new genus has been erected,
Rhinotocinclus, (2022) with the type species
of Parotocinclus longirostris Garavello,
1988. Abstract: A new genus of Hypopopomatinae
armored catfish is described from the northern portions
of South America, namely the Amazon, Orinoco and Guianan
coastal drainages. The new genus is diagnosed from
all remaining hypoptopomatines by having the canal
cheek plate on the ventral surface of the head posteriorly
elongated and contacting the cleithrum, in addition
to other features that distinguish the new genus from
specific genera. Five new species are described and
18 species currently allocated in Parotocinclus,
Hisonotus, and Curculionichthys
are transferred to the new genus and rediagnosed.
Parotocinclus amazonensis and P. aripuanensis
are considered junior synonyms of P. britskii.
The secondary sexual dimorphism of the members of
the new genus is detailed and illustrated. Morphological
characters are used to delimit four phenotypic groups
of species that might have phylogenetic significance,
which still have to be properly tested. A key to the
species is offered and diagnoses, illustrations, and
distribution maps are provided for all species (Reis
& Lehmann 2022).
Description: Rhinotocinclus marginalis
is distinguished from all congeners, except for R.
bockmanni, R. dani, R. hera,
R. pentakelis, and R. loxochelis
n. sp. by having the dominant colour pattern formed
by dark bars on body well separated and distinct (vs.
dominant colour pattern formed by wide dark bars partially
coalesced or closed together, or formed by a dark
stripe from the snout tip, through the eye and extending
to end of caudal peduncle); having two separate light
lines from snout tip diverging to each nostril (vs.
light lines on snout absent, Y- or V-shaped); and
by having teeth with yellow cusps (vs. cusps light
ochre or brown). Rhinotocinclus marginalis
is further distinguished from R. britskii,
R. discolor, R. eppleyi, R.
isabelae, R. kwarup, R. longirostris,
R. pilosus, R. polyochrus, R.
variola, and R. yaka by lacking an adipose
fin (vs. adipose fin present). Rhinotocinclus
marginalis is further distinguished from congeners,
except R. bockmanni, R. dani, R.
loxochelis n. sp., and R. pentakelis,
by having small platelets at adipose-fin position
(vs. small platelets absent). Rhinotocinclus marginalis
is distinguished from R. bockmanni by lacking
a triangular dark spot at the dorsal-fin membrane
(vs. dorsal-fin dark spot present), and by having
a conspicuous dark bar 2 on body (vs. bar 2 absent
or inconspicuous). It is distinguished from R.
hera by having small platelets at adipose-fin
position (vs. small platelets absent) and yellow teeth
cusps (vs. light ochre cusps); and from R. pentakelis
by the shallower caudal peduncle (9.1–10.1%
vs. 10.1–11.7% SL and 23.3–26.3% vs. 26.6–29.7%
HL). Rhinotocinclus marginalis is further
distinguished from R. loxochelis n. sp. by
the regularly arranged dark bars on body (vs. dark
bars on body somewhat fragmented and inclined, such
that they connect to form a zig-zag pattern), the
shallower caudal peduncle 9.1–10.1% vs. 10.3–11.2%
SL) and shorter pectoral-fin spine (26.7–30.3%
vs. 30.4–32.1% SL); and from R. dani
by the dark bars on body barely passing lateral dark
stripe (vs. dark bars 2 and usually 3 reaching to
the ventral midline), and fewer premaxillary (12–18,
mode 16; Tab. 1) and dentary (11–16, mode 13;
Tab. 2) teeth (vs. more numerous premaxillary, 19–28,
mode 21, and dentary, 16–22, mode 19, teeth).
& Lehmann 2022).
Etymology: Rhinotocinclus masc.,
from the Greek ????s (Rhinos), beak, snout and Otocinclus,
a genus of Hypoptopomatinae, in allusion to the conspicuous
and elegant snout of most of its species. The specific
name of marginalis from the Latin margo,
meaning margin, and -alis, in allusion to the distribution
of the species in the northern margin of the Brazilian
Shield. An adjective (Reis
& Lehmann 2022).
South America:Rio Iriri at Cachoeira Grande, ca. 15 km
upstream from confluence with rio Xingu, Piranhaquara,
Reis RE, Lehmann A.
P. A new genus of armored catfish (Siluriformes:
Loricariidae) from the Greater Amazon, with a review
of the species and description of five new species.
Neotrop Ichthyol. 2022.