Temporal range: Oligocene - Recent
C. H. Eigenmann & R. S. Eigenmann, 1919
The first species of the genus, S. parahybae, was described in 1877 by Franz Steindachner under the name Platystoma parahybae. Later, Carl H. Eigenmann and Rosa Smith Eigenmann described Steindachneridia, named for Steindachner, for this species and for S. amblyurum (designated as the type species) in 1888. The next year, Eigenmann and Eigenmann described S. doceanum. In 1918, Miranda Ribeiro described S. scriptum and S. scriptum punctatum; later, S. punctatum was studied and considered to be a species of its own. However, because Steindachneria was already being used, these fish were transferred to Steindachneridion in 1919. The most recent species, S. melanodermatum, was described by Garavello in 2005. This genus currently includes six extant species.
There are two fossil species of Steindachneridion. The first fossil species to be described, S. iherengi (Woodward, 1898), was first described to Arius, but subsequently moved to Steindachneridion; though originally considered to be of Pleistocene age, it has later been argued that it is actually of Oligocene age. The second fossil species to be described was S. silvasantosi Figueiredo & Costa-Carvalho, 1999.
The phylogenetic placement of Steindachneridion and its relationship to other Pimelodid genera is unresolved. These fish have been classified with Sorubim-like fish such as Brachyplatystoma and Pseudoplatystoma. They have also been classified as being more closely related to Phractocephalus and Leiarius.
There are currently six recognized species in this genus: 
- Steindachneridion amblyurum (C. H. Eigenmann & R. S. Eigenmann, 1888)
- Steindachneridion doceanum (C. H. Eigenmann & R. S. Eigenmann, 1889)
- Steindachneridion melanodermatum Garavello, 2005
- Steindachneridion parahybae (Steindachner, 1877)
- Steindachneridion punctatum (A. Miranda-Ribeiro, 1918)
- Steindachneridion scriptum (A. Miranda-Ribeiro, 1918)
Distribution and habitat
Steindachneridion species originate from South America and are restricted to eastern Brazilian coastal drainages, plus the upper Paraná and Uruguay River basin. S. amblyurus originates from the Jequitinhonha River basin. S. doceanum originates from the Doce River basin. S. melanodermatum originates from Iguaçu River in Brazil. S. parahybae originates from Paraíba do Sul and Jequitinhonha River basins. S. punctatum originates from the upper Paraná River and the Uruguay River basins. S. scriptum originates from the Uruguay River.
Appearance and anatomy
Steindachneridion species are large sized fishes, reaching 100 centimetres (40 in) TL or more. S. doceanum reaches 42 cm (17 in) SL. S. melanodermatum reaches a length of about 53.2 cm (21 in) SL. S. punctatum reaches about 70 cm (28 in) SL.
These fish have relatively small eyes and head. They have long maxillary barbels that extend to the base of the dorsal fin or the adipose fin. The adipose fin is relatively long and straight, and its base is longer than the base of the anal fin. Pectoral and dorsal fin spines are short. Most of these species have light grayish or brownish ground color pattern combined with dark brown, vermiculated dark stripes or spots; however, S. doceanum has reticulations over its body instead of spots, and S. melanodermatum is unique in the genus for its dark brown ground color. S. amblyurum differs from other members of this species by having a rounded caudal fin instead of a caudal fin that is notched.
Relationship to humans
Steindachneridion species suffer intense anthropogenic pressure, through modification to their habitat and due to overfishing; consequently, some of them are highly endangered and practically extinct in various parts of their original areas of distribution. Due to their economic importance as a food source, some aquaculture stations are currently developing programs for captive propagation of Steindachneridion species. Fish produced by these programs would be used in fish farms as well to restore natural stocks in degraded habitats.
- Garavello, Julio Cesar (2005). "Revision of genus Steindachneridion (Siluriformes: Pimelodidae)" (PDF). Neotropical Ichthyology 3 (4): 607–623. doi:10.1590/S1679-62252005000400018.
- Swarça, Ana Claudia; Fenochhio, Alberto Sergio; Cestari, Marta Margarete; Dias, Ana Lúcia (2005). "First chromosome data on Steindachneridion scripta (Pisces, Siluriformes, Pimelodidae) from Brazilian rivers: Giemsa, CBG, G-, and RE banding" (PDF). Genet. Mol. Res. 4 (4): 734–741. PMID 16475119.
- Froese, Rainer, and Daniel Pauly, eds. (2012). Species of Steindachneridion in FishBase. February 2012 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Steindachneridion amblyurus" in FishBase. May 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Steindachneridion doceanum" in FishBase. May 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Steindachneridion melanodermatum" in FishBase. May 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Steindachneridion parahybae" in FishBase. May 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Steindachneridion punctatum" in FishBase. May 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Steindachneridion scripta" in FishBase. May 2007 version.