Taxonomy of the freshwater crab genus Neopseudothelphusa Pretzmann , 1965 ( Decapoda : Brachyura : Pseudothelphusidae ) , with the description of a new genus

The taxonomy of the genus Neopseudothelphusa Pretzmann, 1965 is revised based on the morphology of the male fi rst gonopod. A new genus, Culterthelphusa, is here proposed to receive Neopseudothelphusa simoni (Rathbun, 1905), while the genus Neopseudothelphusa is restricted to its type species, Neopseudothelphusa fossor (Rathbun, 1898). Illustrations of the fi rst gonopod of both genera are provided. key words Culterthelphusa, first gonopod, Kingsleyini, Neotropical region, macroinvertebrate fauna. CORRESPONDING AUTHOR Manuel Pedraza manupedrazam@gmail.com SUBMITTED 24 October 2016 ACCEPTED 28 December 2016 PUBLISHED 27 Abril 2017 Guest Editor Célio Magalhães DOI 10.1590/2358-2936e2017009


IntroductIon
In most pseudothelphusid crabs, the carapace morphology is quite uniform and distinction at generic and specific level is only possible using the morphological characteristics of the male first gonopod (Rodriguez, 1982;Rodríguez and Magalhães, 2005).Neopseudothelphusa was initially established by Pretzmann (1965) as a subgenus of Guinotia Pretzmann, 1965, to accommodate eight species.Nevertheless, the diagnostic characters provided by Pretzmann were little restrictive and, therefore, unsatisfactory for ascertaining the identity of Neopseudothelphusa.Rodriguez (1982) raised Neopseudothelphusa to full genus status, and transferred six of its eight species to other genera of Kingsleyini Bott, 1970, restricting it to two species: Neopseudothelphusa fossor (Rathbun, 1898) -its type species -and Neopseudothelphusa simoni (Rathbun, 1905).Even restricted to two species, Rodriguez (1982) acknowledged the artificiality of Neopseudothelphusa and justified the grouping of N. fossor with N. simoni merely on the basis of the proximity of their distribution limits in the Central Cordillera of Venezuela.
In a recent phylogenetic study of the Kingsleyini based on morphological characters (Pedraza, 2015), which included 49 out of 59 species currently known in the tribe, N. simoni and N. fossor were observed to exhibit remarkable differences in the morphology of their first gonopod.Therefore, a new genus, Culterthelphusa, is proposed herein to accommodate N. simoni, since the particularities in the morphology of its first gonopod do not allow its allocation in any other genus of Kingsleyini.Neopseudothelphusa is thus restricted to its type species, N. fossor.
Diagnosis.G1 with marginal process straight, flat; apex truncated, fused to crest of distal lobe of apical plate.Apical plate narrow, subtriangular; distal and proximal lobes well distinct, split by deep notch; distal lobe larger than proximal lobe.Strong subterminal bulge in lateral view, its margin uniformly rounded.

Genus Culterthelphusa n. gen.
Diagnosis.G1 with marginal process large; apex sharp, slightly curved laterally.Mesial process simple, straight, cultriform, about twice as large as the apical plate.Apical plate wide, subquadrate, apex slightly bent to sternal side; distal and proximal lobes totally fused to apical plate.
Etymology.The name Culterthelphusa is formed by the combination of the Latin word "cultratus", meaning knife, in reference to the shape of the mesial process of the first gonopod, which is unique in the tribe, with the suffix "thelphusa" for freshwater crab.The gender is feminine.
Remarks.Culterthelphusa n. gen. is established to accommodate C. simoni n. comb., formerly included in Neopseudothelphusa.Likewise, Culterthelphusa n. gen. is assigned to the tribe Kingsleyini as it shows the following diagnostic characters of the tribe: G1 with an apical plate projected beyond the opening of the spermatic channel; and G1 with basis widened along the sterno-abdominal axis.Culterthelphusa simoni n. comb. is unique in Kingsleyini in having the G1 with a simple mesial process, about three times longer than wide, cultriform in shape (Fig. 2A, C), and having the marginal process large, subtriangular and prolonged beyond the opening of spermatic channel (Fig. 2A, B).
Remarks.Culterthelphusa simoni n. comb.differs from Neopseudothelphusa fossor in the following characters of the G1: (i) the marginal process is slightly curved to the lateral side, the apex is sharp, prolonged above the opening of spermatic channel in C. simoni n. comb.(Fig. 2A) [marginal process straight, apex truncated and prolonged at the same level of the opening of spermatic channel in N. fossor (Fig. 1A)]; (ii) the apex of the marginal process is well distinct from the crest of the distal lobe of the apical plate in C. simoni n. comb.(Fig. 2B) [apex of marginal process fused to the crest of the distal lobe of the apical plate in N. fossor (Fig. 1B)]; (iii) the apical plate is large, wide, and subquadrate in C. simoni n. comb.(Fig. 2 A, B) [apical plate narrow and subtriangular in N. fossor (Fig. 1A, B)]; (iv) the distal and proximal lobes of the apical plate are indistinct in C. simoni n. comb.(Fig. 2B) [distal and proximal lobes of the apical plate well distinct, split by a deep notch in N. fossor (Fig. 1A-C)]; (v) there is a deep subterminal groove in sternal view, preceding the mesial process in C. simoni n. comb.(Fig. 2C) [sternal surface smooth, subterminal groove preceding the mesial process absent in N. fossor (Fig. 1C)]; (vi) the lateral surface is flat in the subterminal region, devoid of any subterminal bulge in C. simoni n. comb.(Fig. 2A-C) [strong subterminal bulge as seen in lateral view in N. fossor (Fig. 1A-C)]; (vii) the mesial process is about twice as large as the apical plate, and is cultriformin C. simoni n. comb.(Fig. 2A, B) [mesial process almost the same size of the apical plate, subquadrate, in N. fossor (Fig. 1A, B)].
The morphology of the G1 of Culterthelphusa simoni n. comb.closely resembles that of Prionothelphusa eliasi Rodriguez, 1980 and Microthelphusa racenisi (Rodríguez, 1966) since in these three species the apical plate is wide, subquadrate, and the distal and proximal lobes are complete fused.acknowledgMents I wish to thank Célio Magalhães and Marcos Tavares who encouraged and supported this study.I also thank Rafael Lemaitre (USNM) for a predoctoral fellowship and for providing working space and access to the Smithsonian collections, Karen Reed for helping with the collections, and the anonymous referees for their valuable suggestions and corrections.FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) provided financial support by way of the doctoral fellowship (2012/01334-7) conducted at the Museu de Zoologia, Universidade de São Paulo.