Steindachneridion
Steindachneridion is a genus of South American pimelodid catfish (order Siluriformes). Taxonomy. 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. Two fossil species of "Steindachneridion" have been found. The first to be described, "S. iherengi" was first described to "Arius", but subsequently moved to "Steindachneridion"; though originally considered to be of Pleistocene age, it was later found to be actually of Oligocene age. The second fossil species to be described was "S. silvasantosi" . 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". Species. The currently recognized species in this genus are: Distribution and habitat. "Steindachneridion" species originate from South America and are restricted to eastern Brazilian coastal drainages, plus the upper Paraná and Uruguay River basins. "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. The large species of "Steindachneridion" always occur in swift-flowing, clear-water rivers running over large stony beds. These fish are naturally scarce in their habitats. Appearance and anatomy. "Steindachneridion" species are large fish, reaching 100 cm (40 in) in total length or more. "S. doceanum" reaches 42 cm (17 in) in standard length. "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 heads. They have long maxillary barbels that  extend to the base of their dorsal fins or adipose fins. 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 patterns 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 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. Of the six recognized species, all but "S. punctatum" are considered threatened by Brazil's Ministry of the Environment. 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 and to restore natural stocks in degraded habitats. Steindachneridion