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Reis & Lehmann 2022. (3)

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). (Reis & 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).

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Loricariidae

Soth America: Rio Iriri at Cachoeira Grande, ca. 15 km upstream from confluence with rio Xingu, Piranhaquara, Pará, Brazil.

2.0cm. (¾ins)

22-26°c (71-79°f.)

6.5-7.2.

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.