Two new species of Leporinus Agassiz, 1929 (Characiformes: Anostomidae) from tributaries of the lower Amazon basin in Brazil

Abstract

Two new species of Leporinus (Characiformes, Anostomidae) are described. Both new species are diagnosed by having one dark blotch on midline of anterior portion of the flank (between opercle and pelvic-fin origin) surrounded by five to seven dark blotches; and a subinferior mouth with three premaxillary teeth. Leporinus multimaculatus, new species, is distributed in small and medium-sized tributaries of the rio Tocantins and rio Xingu basins, and also in the rio Jari and coastal drainages of Amapá state, whereas L. torrenticola, new species, is endemic to the rapids of the rio Xingu and its main tributaries. The number of scale rows around the caudal peduncle is the main feature distinguishing L. multimaculatus from L. torrenticola. Comments on the diagnostic features of the newly described species are provided. In addition, the phylogenetic position and generic assignment of the new species are discussed based on available information from recent morphological and molecular analyses.
Key words: Ostariophysi, Anostomoidea, Neotropics, taxonomy, systematics

Introduction

The Anostomidae includes 13 genera and approximately 150 valid species (Garavello & Britski, 2003; Birindelli & Britski, 2009; Garavello et al., 2014; Buns et al., 2014; Britski & Birindelli, 2016). The most diverse genus of the family is Leporinus, encompassing about 90 valid species (Garavello et al., 2014). The real diversity of the genus, on the other hand, is still far from being understood as new species are continuously being discovered and described (e.g., Feitosa et al., 2011; Birindelli & Britski, 2013; Burns et al., 2014), and as long-established species are subjected to taxonomic revisions (e.g., Britski et al., 2011; Britski et al., 2012). The phylogenetic relationships of the anostomids, including Leporinus, have been the subject of recent phylogenetic analyses based both on morphological (Sidlauskas & Vari, 2008) and molecular data (Ramirez et al., 2016).

During the 1990’s, P.M. Galetti Jr., P. C. Venere and collaborators studied the chromosomes of some Leporinus BIRINDELLI ET AL. 98 · Zootaxa 4178 (1) © 2016 Magnolia Press species, publishing several papers containing the first data on genetics of anostomids (Galetti et al., 1991; 1995). One of the taxa studied by them was an undescribed species from the Araguaia river basin in central Brazil. Those
species were sent to one of us (HAB) for identification and waited in the shelves of the MZUSP fish collection until now to be formally described. Since that time, several additional specimens of that same species and of another undescribed and closely related species were collected in distinct places of the Araguaia, Tocantins and Xingu basins. The present contribution aims to describe both new species diagnosing them from other congeners, and to discuss their phylogenetic placement and diagnostic characters.

Material and methods

Counts and measurements were taken according to Britski & Garavello (1978) and Winterbottom (1980). Standard length (SL) is expressed in mm and all other measurements are expressed as percentage of SL, except subunits of the head, which are expressed as percentages of head length. The lateral-line scale count included the pored scales extending onto the base of the median caudal-fin rays; counts of the horizontal scale rows above lateral line exclude the lateral-line scale and the middorsal scale row; counts of the horizontal scale rows below lateral line exclude the lateral-line scale row and include half a scale row when the pelvic-fin origin is immediately behind the middle of a scale. An asterisk indicates counts of holotypes. Weberian-apparatus vertebrae were counted as four elements and included in the vertebral counts; the compound caudal centrum (preural 1 + ural 1) of the caudal region was counted as a single element. The pattern of radii was defined on scales immediately above the lateral line row at the vertical through the dorsal-fin origin.

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