June 13, 2011
We describe a new genus and species of bagrid catfish from the Kreung Babah Rot drainage in northwestern Sumatra. This new taxon is distinguished from confamilials by the following combination of characters: anguilliform body, reduced supraoccipital posterior process, absence of first dorsal spinelet, first proximal dorsal-fin radial inserting on 4th vertebra, first dorsal-fin lepidotrich ossified into spine, anterior edge of pectoral spine smooth, adipose fin in contact with base of last dorsal-fin ray, anal fin with 26 rays, and caudal fin with 17 principal rays.
Holotype-based validation, redescription and continental-scale range extension of the South American catfish species Hypophthalmus oremaculatus Nani and Fuster, 1947, with additional information on Hypophthalmus edentatus Spix and Agassiz, 1829 (Siluriformes, Pimelodidae)
The heretofore little-known pimelodid species Hypophthalmus oremaculatus Nani and Fuster, 1947, from the río Paraná, Argentina is redescribed and validated based on examination of its recently found holotype and extensive comparative study of specimens of all nominal species of the genus. Specimens of Hypophthalmus from the Paraná Basin have often been mistakenly labelled as H. edentatus Spix and Agassiz, 1829, and H. oremaculatus has occasionally been considered a junior synonym of H. edentatus. Examination of the syntypes of H. edentatusreveals a long-mistaken concept of its diagnostic features in the original description based on Spix's inaccurate illustration. Hypophthalmus oremaculatus is common and widespread in the Paraná Basin, including the Upper Paraná system. This species is also widespread in the Amazon and Orinoco basins.
Hypophthalmus oremaculatus is distinguished from other species of the genus by the following combination of characters: caudal fin shallowly-forked, head broad and short, membrane of skin tying the innermost pelvic-fin ray to the edge of the urogenital-anal region, 55–59 total vertebrae, 3–6 vertebrae with separate and robust neural spines between the Weberian complex and first vertebra with contact between its neural spine and a dorsal-fin pterygiophore, long mental barbels usually extending to pectoral origin or beyond, and dorsal-fin origin approximately in line with anal-fin origin.
The anatomy and development of the siluriform pectoral-fin spine is described, illustrated and a terminology is suggested for its parts. Catfish pectoral-fin spines exhibit considerable diversity of size, shape, robustness, surface texture and, especially, details of the dentated or serrated anterior and posterior margins. This study illustrates the variety, and taxonomic and phylogenetic significance of pectoral-fin spine diversity in the South American goliath catfishes of the tribe Brachyplatystomini, family Pimelodidae, based on examination of spines of post-juvenile and adult specimens representing all eight living species of Brachyplatystoma and Platynematichthys. Unique pectoral-spine characters and character combinations serve to distinguish all eight species. Features of the pectoral-spines that change with growth are also described. Within the current phylogenetic framework of Pimelodidae, brachyplatystomines show character-state transformations and synapomorphies of the pectoral-fin spines that support hypotheses of monophyly for the subgenera Malacobagrus (B. rousseauxii, B. filamentosum, B. capapretum), and Goslinia (new usage) (B. platynemum, B. juruense), and also suggest a close relationship between B. tigrinum and subgenus Goslinia. Platynematichthys notatus and B. vaillantii retain relatively plesiomorphic features of the pectoral-fin spines.
A new species of electric knifefish of the genus Microsternarchus is described from the central basin of the rio Negro, Brazil. The new species is distinguished in external features from its single congener, Microsternarchus bilineatus, by the presence of a short caudal filament, a lower number of anal-fin rays, and uniform body pigmentation. Internally, features of the skeleton also distinguish the two species, in particular in the shape of the maxilla and antorbital.
This paper reports the results of a comparative study of the mandibular, hyoid, and pectoral musculature of South American Doradidae. Sixty-one species of Doradidae were examined including representatives of all the genera. Twenty muscles are described including their ontogenetic origin, function, area of origin and insertion, and parts. Seven muscles from the cranial region: adductor mandibulae, extensor tentaculi, levator arcus palatini, dilatator operculi, levator operculi, adductor operculi, and adductor arcus palatini; six muscles from the ventral region: intermandibularis, protractor hyoidei, hyohyoides inferioris, hyohyoidei abductores, hyohyoidei adductores, and sternohyoideus; and seven muscles from the pectoral fin: adductor superficialis, adductor profundus, abductor superficialis, abductor profundus, arrector ventralis, arrector dorsalis, and abductor rotator. Comparisons between Doradidae and other catfish families (e.g. Auchenipteridae, Aspredinidae) were made in order to understand and establish variations in position and shape of different muscles. A muscle not previously described for the pectoral fin of catfishes is described and named here as abductor rotator.
January 29, 2012
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