Taxonomic review of the genus Erythrocricus Schubart, 1962 (Diplopoda, Spirobolida, Rhinocricidae)

Abstract. We review the genus Erythrocricus Schubart, 1962 based on the type material of the species Erythrocricus sanguineostriatus (Schubart, 1962). We propose a new diagnosis, redescribe the type species, and propose a new synonymy and a new combination. In addition, a male-based key to both species recognized, including Erythrocricus electrofasciatus (Schubart, 1957), comb. nov. ex. Rhinocricus, is given.


Introduction
The order Spirobolida Bollman, 1893 with more than 1000 described species is divided into three suborders, Spirobolidea Bollman, 1893, Trigoniulidea Attems, 1909and Rhinocricidea Brölemann, 1913(Enghoff et al. 2015. Rhinocricidea has only the family Rhinocricidae Brölemann, 1913 which is the largest family in the order Spirobolida with more than 575 species and 30 genera (Marek et al. 2003;Pitz & Sierwald 2010;Enghoff et al. 2015). These genera are grouped into three subfamilies, Rhinocricinae Brölemann, 1913, Oxypyginae Chamberlin, 1922and Poecilocricinae Schubart, 1962. The genus Erythrocricus Schubart, 1962 represents one of the Brazilian genera of the subfamily Rhinocricinae. The genus was proposed by Schubart (1962) as a subgenus of Rhinocricus Karsch, 1881, based on the shape of the gonopods and a transverse red line in the dorsal part of the metazonites of the body rings. Two species were described, the type species Rhinocricus (Erythrocricus) sanguineostriatus Schubart, 1962 from the states of São Paulo and Goiás and Rhinocricus (Erythrocricus) miniatostriatus Schubart, 1962 from the state of Goiás. In the description of both species, Schubart (1962) described the great similarity between them, with the difference based only on details of the red coloration. Hoffmann (1980) raised Erythrocricus to the genus level but did not justify the proposed new status or whether he examined the species of the genus. In the present study, we revise the genus Erythrocricus. The type species Erythrocricus sanguineostriatus Schubart, 1962 is considered a senior synonym of Erythrocricus miniatostriatus (Schubart, 1962), and the species Rhinocricus electrofasciatus (Schubart, 1957) is transferred to the genus Erythrocricus. A redescription of these species, based on fresh specimens and the type material, is presented. In addition, a key to males of the genus and new illustrations of the species are presented.

Material and methods
The examined material is deposited in the institutions indicated below (curators in parentheses). The specimens are preserved in 70% ethanol. For the examination of taxonomic characters, measurements and illustrations of the gonopods, we used a stereo microscope with a measuring eyepiece coupled to a drawing tube. Photographs were taken with a Motic SMZ171 stereo microscope camera in conjunction with a Motic Moticam 5+ digital imaging system software. To edit images, we used CorelDRAW Graphics Suite X5. For the gonopod terminology and external characters, we followed Enghoff et al. (1993), Koch (2015) and Rodrigues et al. (2020).

Distribution
Occurring in the Atlantic forest (state of São Paulo), Cerrado biome (state of Goiás), and in the Amazonian and Pantanal biomes (Mato Grosso) of Brazil.

Key to species of Erythrocricus (based on males)
1. Red coloration on collum, telson and all metazonites as a transverse red line dorsally ( (Schubart, 1958) comb. nov.
Erythrocricus sanguineostriatus (Schubart, 1962 the red coloration on body rings wich in E. sanguineostriatus is present dorsally and in E. miniatostriatus dorsally and ventrolaterally. Our examination of the type species revealed that there is no significant difference either in external morphology or the structure of the gonopods between the species. Still, during examination of fresh specimens, we observed that the differences in the red coloration, seems to reflect only intraspecific variation.

Diagnosis
Erythrocricus sanguineostriatus (Schubart, 1962) resembles E. electrofasciatus (Schubart, 1957) comb. nov. by the shape of the anterior gonopod (Figs 2A, 5A) with a triangular sternite having the medial portion distally rounded and the anterior gonopod wider than long but differs by the telopodite of the anterior gonopod with a reduced lobe in posterior view (Fig. 2B), and the red coloration presented as a transverse red line on all metazonites, collum and telson (Fig. 1B, D-F) and a rounded process of the coxae of leg pair 3 of the male (Fig. 1C).   Coloration (in 70% alcohol) (Fig. 1). Antennae and legs dark brown. Collum red with yellowish margins. Prozonites grey; metazonites in dorsal portion with transverse red line on all body rings, posterior margins whitish. Telson red.

Diagnosis
Erythrocricus electrofasciatus resembles E. sanguineostriatus in the characteristics cited above for the diagnosis of E. sanguineostriatus but differs by the general coloration (Fig. 4) and by the transverse red line only on the posterior metazonites. Coxae of leg pair 3 with a pointed apex (Fig. 4B); the telopodite of the anterior gonopod is well developed in posterior view (Fig. 5B), the external branch of the posterior gonopod lamellated and narrow, distally long and slender (Fig. 5C). (Schubart, 1957).

Distribution
Known from Serra do Cachimbo, states of Pará, and state of Mato Grosso.

Discussion
Currently, two species are known to compose the millipede genus Erythrocricus, which is distributed in the Central-West and Southeast regions of Brazil. According to Schubart (1962), the genus is "purely Brazilian". As suggested by Schubart (1962), the genus Erythrocricus resembles Rhinocricus in the external morphology and gonopods. However, our review of the specimens revealed that details of the gonopods support the status of the genus as proposed by Hoffman (1980). Based on this examination, we proposed a new diagnosis for the genus. This work contributes to the knowledge of the full genus Erythrocricus because we provided more and new information from both males and females of the species and solved internal taxonomic problems.