Abstract
Trichomycterus anhanga is described from the Amazon basin, northern Brazil. The species is diagnosed by the latero-sensory system which is restricted to LL1 and LL2, the pectoral fin with two branched rays, the absence of pelvic fins and girdle, the reduced jaws and pharyngeal dentition, the presence of six to seven interopercular odontodes, the absence of a lateral series of spots, the presence of a small dark spot on the ventral surface of the mandibular symphysis, the narrow comma-shaped palatine, the absence of procurrent rays anterior to the dorsal and anal fins, the position of insertion of the first dorsal-fin pterygiophore and the presence of a single pair of pleural ribs. Trichomycterus anhanga shares with T. hasemani and T. johnsoni a wide cranial fontanel which occupies most of the skull roof. Miniaturization as well as synapomorphies for the T. hasemani group are discussed.
Highlights
The Trichomycteridae is a large family of catfishes, widely distributed throughout most of cis- and trans-Andean South America, Panama and Costa Rica (de Pinna & Wosiacki, 2003)
Trichomycterus anhanga belongs to the clade referred to as the T. hasemani group
In a subsequent analysis (Wosiacki, 2002), the T. hasemani group was confirmed as monophyletic on the basis of several additional characters: 1- a wide fontanel that occupies most of the skull roof and is delimited by the frontal and supraoccipital; 2- the absence of the anterior portion of the infraorbital canal; 3- the first pectoral-fin ray much longer than the others; 4- the absence of branchiostegal rays on the posterior ceratohyal; and 5- a large posterior process of the palatine, partly forked and expanded distally
Summary
The Trichomycteridae is a large family of catfishes, widely distributed throughout most of cis- and trans-Andean South America, Panama and Costa Rica (de Pinna & Wosiacki, 2003) It is currently subdivided into eight subfamilies, of which Trichomycterinae is the only one which is not demonstrably monophyletic (Baskin, 1973; de Pinna, 1989, 1998; Wosiacki, 2002). Arratia (1990) and more recently Datovo & Bockmann (2010) proposed some putatively derived morphological characters for Trichomycterinae Those studies included neither Trichomycterus hasemani (Eigenmann) or T. johnsoni (Fowler), which form a monophyletic clade (Wosiacki, 2002) of markedly distinctive miniature species that is related to non-trichomycterine taxa (de Pinna, 1989, 1998). The new species is provisionally allocated in the genus Trichomycterus until its proper taxonomic assignment is established
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