The Aspredinidae are known as banjo catfishes due to their overall body shape, a depressed head and slender caudal peduncle which somewhat resembles a banjo. They occur throughout the tropical rivers of South America. Local names for aspredinids include "banjaman" or "banjo-man" (Guyana), "croncron" (French Guiana), "rabeca" (Brazil), and "guitarillo" (Venezuela). Banjo catfishes maybe found in habitats ranging from shallow backwaters to deep river channels to tidal estuaries. In general, most species are cryptically pigmented, benthic and sluggish unless disturbed. Many are semi-fossorial, during the day often resting just beneath the substrate surface.

Approximately 6O extant species of banjo catfishes have been described. A large proportion of these species are now considered subjective junior synonyms of earlier described species. As currently recognized the family contains approximately 35 nominal species placed in 13 genera. In addition there are several undescribed species mostly in the genus Bunocephalus. Despite the relatively small number of species in this family as compared to other catfish families, aspredinids are quite diverse in their morphology. They range from miniature armored species such as Hoplomyzon papillatus, less than 20 mm in length, to large elongate species such as Aspredo aspredo, reaching up to 380 mm in length.

Aspredinids are a highly derived group of catfishes and display some very unusual features. Their skin is completely keratinized and covered with tubercles. Periodically the entire outer layer of skin is shed just like that of amphibians and reptiles (Friel, 1989).

This SEM micrograph shows rows of enlarged tubercles which run longitudinally along the bodies of aspredinids. The light spots covering the tubercles are unicellular keratinized processes called unculi (Roberts, 1982). The horizontal field of view of this image is 1.68 mm.

While aspredinids can swim by typical undulatory movements, they can also use jets of water thrust from their opercular openings to skip along the substrate. When agitated, some species produce audible stridulatory sounds by repeatedly abducting and adducting their pectoral spines.

Very little is known about the general ecology of aspredinids. Based on little published work and personal observation, most aspredinids appear to be generalized omnivores and their stomachs often contain aquatic invertebrates, terrestrial insects and organic debris. One notable exception are members of the genus Amaralia. Based on stomach contents they appear to feed on the eggs of other catfishes (Friel, 1992).

Few specifics are known about reproduction of aspredinids. Parental care is known with certainty in one clade which contains Pterobunocephalus, Platystacus, Aspredo, and Aspredinichthys. Females of this clade carry their developing embryos attached to the ventral surface of their bodies. In Pterobunocephalus, the eggs are directly attached to the body whereas in Platystacus, Aspredo, and Aspredinichthys they are attached to fleshy stalks, called cotylephores, which grow out from the female (Friel, 1994). These develop seasonally and may function in the exchange of materials between the mother and her developing embryos (Wetzel, Wourms, & Friel, 1997).

This Neotropical family of catfishes is found throughout the tropical rivers of South America (Magdalena, Orinoco, Amazon, São Francisco and Paraguay-Paraná), a few rivers west of the Andes (Atrato, San Juan, and Patia) and in brackish and marine waters between the Orinoco and Amazon River deltas.

View Aspredinidae Tree

modified from Friel (1994).

As already mentioned, aspredinids are highly derived catfishes and their monophyly is well supported by many apomorphies. Some of these including: laminar processes of the pterotics directed laterally; vomer absent; mandibular lateralis canal does not enter lower jaw; opercle "L" shaped, resembles a branchiostegal ray; opercular apertures reduced to ventral slits; 5 or fewer branchiostegal rays; dorsal lamina of Weberian complex contacts dorsal surface of body; hemal canal forms de novo by vertebra 7 without a transformation series of rib parapophyses; abdominal vertebral with peg and socket articulations; parapophyses for ribs reduced or absent; 10 or fewer principal caudal-fin rays; expanded bases on outermost caudal-fin rays; muscles on the ventral surface of the pectoral girdle highly reduced or absent; basipterygia without anterior arms; posterior cartilage of basipterygia reduced; mental barbel bases reduced; rows of unculiferous tubercle present on body; and loss of alarm cells & fright reaction. For a complete list of synapomorphies see Friel (1994).

Friel's (1994) phylogenetic revision of the aspredinids revealed that the traditionally recognized subfamily Aspredininae is not the sister group to all other Aspredinidae but is nested higher up in the phylogeny of aspredinids. Furthermore, the subfamily Bunocephalinae sensu Myers (1960), tribe Bunocephalini sensu Myers (1960), Dysichthys sensu Mees (1988, 1989) and Aspredo sensu Mees (1987) are paraphyletic taxa. Major taxonomic and nomenclatural changes are necessitated as a result of this new phylogeny. Species originally placed in Bunocephalus Kner, 1855 and recently transferred to Dysichthys Cope, 1874 by Mees (1988, 1989) are reassigned to Pseudobunocephalus Friel 2008, Pterobunocephalus Fowler, 1943, and Bunocephalus Kner, 1855. In addition, several genera are synonymized. Petacara Böhlke, 1959 is a junior subjective synonym of Pterobunocephalus Fowler, 1943; Dysichthys Cope, 1874 is a junior subjective synonym of Bunocephalus Kner, 1855; and Bunocephalichthys Bleeker 1858 and Agmus Eigenmann, 1910 are junior objective synonyms of Bunocephalus Kner, 1855.

The phylogenetic relationship of the Aspredinidae to other catfishes remains controversial. Prior ideas on relationships are briefly summarized. Günther (1864) first suggested a relationship between the Aspredinidae and a clade containing the Neotropical loricarioids and the Asian Sisoridae. A relationship with loricarioid catfishes was also suggested by Chardon (1968). However Baskin (1972) and Howes (1983) both reviewed Chardon's evidence and concluded that the Aspredinidae are not closely related to loricarioids. Ferraris (1989) suggested that the Asian Akysidae are the sister group to the Aspredinidae. Mo (1991) placed the Aspredinidae either basal to or in a polytomy with a clade containing the Afro-Asian Clariidae, the African Amphiliidae, Neotropical loricarioids, and Asian sisoroids (Amblycipitidae, Akysidae and Sisoridae). Pinna (1993) placed the Aspredinidae in a polytomy with Amblycipitidae, Akysidae, Sisoridae, Amphiliidae and loricarioids. Chen (1994) placed the Aspredinidae as the sister group to Asian sisoroids. More recently, Pinna (1996) now places the Aspredinidae within the currently recognized Asian Sisoridae. Friel (unpublished) reanalyzes all prior evidence presented by others along with new character information and finds two equally parsimonious placements for the Aspredinidae. The sister group to the Aspredinidae are either the Asian sisoroid catfishes as has been suggested by others or the doradoid catfishes (the African Mochokidae, and the Neotropical Doradidae, Centromochlidae and Auchenipteridae). A most recent molecular phylogney (Sullivan et al. 2006) supports the hypothesis that aspredinids are the sistergroup to a clade containing the Neotropical Auchenipteridae and Doradidae.