Ferrer, J. & L.R. Malabarba. (2020). Systematic revision of the Neotropical catfish genus Scleronema (Siluriformes: Trichomycteridae), with descriptions of six new species from Pampa grasslands. Neotrop. Ichthyol., 18(2), Maringá 2020 Epub June 12, 2020.
is revised based on the re-examination of the type specimens and 1,713 newly collected specimens. Scleronema is diagnosed from other trichomycterids by the following unambiguous derived characters: fleshy flap at the base of the maxillary barbell; skin flap in the posterior margin of the opercle; articulation between the autopalatine and the vomer ventrally located, with the medial margins of the autopalatines very close to each other; and autopalatine with an interrupted or not interrupted ossified arch-shaped process on its dorsal surface forming a canal.
and S. operculatum are redescribed, S. angustirostre is considered a junior synonym of S. minutum , and six new species are described. A lectotype is designated for
. The type localities of S. angustirostre, S. minutum, and S. operculatum are reviewed in order to correct erroneous information cited in articles and catalogs subsequent to the original descriptions. Species of Scleronema are geographically distributed in the La Plata basin and Atlantic coastal drainages from Southern Brazil, Southern Paraguay, Northeastern Argentina and Uruguay. They inhabit rivers or streams with sand- or gravel-bottoms across the Pampa grasslands. We provide evidences to recognize two putative monophyletic units within the genus, namely the S. minutum species group and the S. operculatum species group, and discuss the distribution patterns of their species.
Identification key to the species of Scleronema (Ferrer & Malabarba, 2020):
1a. Body compressed; maxillary barbel with thinner portion shorter than wider one; fleshy flap at the base of the maxillary barbel located anteriorly, thick, prolonged up to the snout and with distal margin straight; posterior skin flap to opercle pointed and long; caudal fin with a vertical black bar distally (Fig. 1A) .................... 2 (Scleronema operculatum species group)
1b. Body roughly cylindrical; maxillary barbel with thinner portion longer than wider one; fleshy flap at the base of the maxillary barbel located posteriorly, thin, restricted to the maxilla and with distal margin rounded; posterior skin flap to opercle rounded and short; caudal fin lacking a vertical black bar (Fig. 1B) .................... 3 (Scleronema minutum species group)
Fig 1
2a. Lateral surface of body with a midlateral series of 6-9 rounded black blotches larger than opercle (Figs. 1A , 9, 11); tip of maxillary barbel extending between anterior and posterior margins of interopercle ....................
2b. Lateral surface of body with a midlateral series of 10-14 rounded black blotches smaller than or equivalent in size to opercle (Figs. 21, 22, 25A); tip of maxillary barbel never surpassing anterior margin of interopercle ....................
3a. Lateral surface of body with diffuse brown spots or rounded black blotches as large as or smaller than opercle .................... 4
3b. Lateral surface of body with rounded black blotches larger than opercle .................... 5
4a. Lateral surface of body with diffuse, scattered brown spots (Figs. 6, 7); infraorbital line of the laterosensory system with pores i10 and i11 and no additional pores associated ....................
4b. Lateral surface of body with rounded black blotches (Figs. 12, 13A); infraorbital line of the laterosensory system with pores i10 and i11 and additional pores associated (Fig. 5A) ....................
6b. Por s6 of the frontal canal of the laterosystem canal present (Fig. 5C-D) .................... 7
7a. Por s3 of the frontal canal of the laterosensory system absent (Fig. 5C); dorsal-fin origin located at vertical through origin of pelvic fin or slightly posterior ....................
7b. Por s3 of the frontal canal of the laterosensory system present (Fig. 5D); dorsal-fin origin located at vertical through half-length of pelvic fin ....................
