PROC. BIOL. SOC. WASH. 99(2), 1986, pp. 328-334 SERRABRYCON MAGOI, A NEW GENUS AND SPECIES OF SCALE-EATING CHARACID (PISCES: CHARACIFORMES) FROM THE UPPER RIO NEGRO Richard P. Van Abstract.— Senabrycon magoi, a previously undescribed genus and species of scale-eating tetragonopterin characid, is described from the black waters of the Rio Negro system in the region of the Rio Casiquiare, Venezuela. The genus and species are unique in the combination of the presence of a series of out-wardly oriented teeth in the upper and lower jaws, the relatively low number of scales in a longitudinal series to the hypural joint, and in the limitation of pores for the laterosensory canal system of the body to the anteriormost scales of the lateral line. Scale-eating (lepidophagy) has been de-scribed as a significant food habit in a va-riety of both freshwater and marine fishes inhabiting diverse regions of the world (see Sazima 1983 for a review). Within the fresh-waters of the Neotropical realm, this spe-cialized food habit has been described for a number of species belonging to the order Characiformes. Neotropical characiforms of the family Characidae for which lepi-dophagy has been previously described in-clude Cataprion mento Miiller and Trosch-el (Kner 1860:34; Gosline 1951:54, Gery 1964:460) and Serrasalmus elongatus Kner (Goulding 1980:162) of the subfamily Ser-rasalminae, Exodon paradoxus Miiller and Troschel, Roeboexodon guanensis (Puyo), and the various species of the genus Roe-boides (Breder 1927:127; Gery 1964:459-460) all presently assigned to the subfamily Characinae, and Probolodus heterostomus Eigenmann (Roberts 1970:384; Sazima 1977:5 10) and Bryconexodon juruenae Gery (1980:1) of the subfamily Tetragonopteri-nae. These taxa, with the exception of Ser-rasalmus elongatus, are characterized by specialized dentition, typically consisting of everted teeth, often mammilliform in over-all shape, which form very irregular series along the outer margins of the jaws. The outwardly directed teeth function in dis-lodging scales from the host species, with the removed scales then being ingested di-rectly if taken into the mouth, or gathered from the water column or substrate if knocked free (Sazima and Machado 1982). Although these dental modifications are characteristic for, and very similar in, the majority of lepidophagous Neotropical characiforms, such distinctive teeth have been implicitly hypothesized to have arisen independently in the diverse lineages of scale-eaters which are presently assigned to four different subfamilies of the Characidae (but see also comments under "Relation-ships"). Recent collecting activities in the upper portions of the Rio Negro have revealed a previously undescribed genus and species of lepidophagous tetragonopterine characid described herein. This new form shares many of the dental modifications noted above as "typical" for lepidophagous Neo-tropical characiforms, but is quite distinc-tive in other attributes, most notably in its incompletely pored lateral line. Materials and methods.— AW measure-ments are given as proportion of standard length (SL) except for subunits of the head which are presented as proportions of head
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