PROC. BIOL. SOC. WASH. 107(4), 1994, pp. 160-111 DESCRIPTION OF MASTIGLANIS ASOPOS, A NEW PIMELODID CATFISH FROM NORTHERN BRAZIL, WITH COMMENTS ON PHYLOGENETIC RELATIONSHIPS INSIDE THE SUBFAMILY RHAMDIINAE (SILURIFORMES: PIMELODIDAE) Flavio A. Bockmann Abstract. —Mastiglanis asopos, a new genus and species of the neotropical catfish family Pimelodidae, is described from the Amazon basin, and rio Capim and its adjacencies, in northern Brazil. Its monophyly is supported by various autapomorphies in external and internal morphology, such as the first dorsal- and pectoral-fin elements filamentous distally, and the presence ofa remarkable osseous process at the anterior portion of the premaxilla. Mastiglanis shares unambiguously all diagnostic features proposed for the subfamily Rhamdiinae, and also those that delimit a subset called the Nemuroglanis sub-clade. Eleven new synapomorphies are proposed to corroborate the monophyly of the latter group. Additional character evidence supports a hypothesis placing Mastigla- nis as the sister group of the remainder of the Nemuroglanis sub-clade. Resumo. —Mastiglanis asopos, um novo genero e especie da familia Pime- lodidae e descrito para a regiao norte brasileira (bacia Amazonica e rio Capim e arredores). Seu monofiletismo e indicado por varios caracteres apomorficos observaveis na morfologia externa e interna, dentre os quais destacam-se: os primeiros elementos ("espinhos") das nadadeiras dorsal e peitoral extrema- mente alongados e a presenga de um notavel processo osseo na regiao anterior da premaxila. Mastiglanis compartilha todos os caracteres diagnosticos da subfamilia Rhamdiinae, assim como, todos aqueles que definem um subgrupo mais restrito chamado ^^Nemuroglanis sub-clade." O monofiletismo deste ul- timo e corroborado por onze novas sinapomorfias. Mastiglanis e provisoria- mente posicionado como grupo-irmao de todos os outros componentes do ^''Nemuroglanis sub-clade." The most recent account on the situation example of the above-mentioned situation, of the systematics of South American fresh- for it remained unknown until now in spite water fishes is that of Bohlke et al. (1978), of its distinctive external features and wide who estimated that a large portion of that distribution throughout the Amazonian ba- fish fauna, especially that from the Amazon sin. This paper describes this pimelodid cat- basin, remains undescribed and even un- fish as a new genus and species, and dis- known. In spite of the considerable progress cusses its relationships within a recently made since the publication of Bohlke et al.'s provided synapomorphy scheme of the paper, only recently have catfishes from the Rhamdiinae (Lundberg et al. 1991a). Ad- Amazon basin been dealt within a phylo- ditional new corroboration is given to a for- genetic context (e.g., Stewart 1986a, 1986b; merly suggested rhamdiine subset (Ferraris Ferraris & Mago-Leccia 1989; Pinna 1989). 1988) as well as a discussion about the ar- The fish herein studied is an illustrative rangement of the genera therein included. VOLUME 107, NUMBER 4 761 Material and Methods a plus sign. Pterygiophores, vertebrae, gill rakers, ribs, and branchiostegal rays were Morphometric values were taken with counted on cleared and stained specimens calipers and expressed to the nearest 0.1 only. Anatomical illustrations were sketched mm. All measurements are made point-to- using a Zeiss stereomicroscope with a cam- point on the specimens' left side whenever era lucida attachment. In the drawings, bone possible. Morphometric data are expressed is represented by stipple and cartilage by as proportions of standard length (SL), or open circles. head length (HL; all subunits of the cephalic Institutional abbreviations are: Califor- region, excepting the barbels which were ex- nia Academy of Sciences, San Francisco pressed in proportions of SL). Each pro- (CAS); Museu de Zoologia da Universidade portion is provided with its arithmetic mean, de Sao Paulo, Sao Paulo (MZUSP); Museu followed by the range and standard devia- Nacional do Rio de Janeiro, Rio de Janeiro tion. The number of specimens tallied in (MNRJ); Universidade Federal do Rio de counts is presented enclosed in parentheses. Janeiro, Rio de Janeiro (UFRJ); Departa- When meristics vary, the count for the ho- mento de Biologia Animal e Vegetal da lotype is indicated by an asterisk (*). Meth- Universidade do Estado de Rio de Janeiro, odology and terminology for measurements Rio de Janeiro (DBAV-UERJ), National followed Lundberg & McDade (1986), with Museum of Natural History, Smithsonian the following measurements added: prepel- Institution, Washington, D.C. (USNM). vic length, preadipose length, dorsal-fin base Comparative material examined (CS- length (taken as the gap between the inser- cleared and stained preparations).—Acen- tion point of the first and the last elements), tronichthys leptos, UFRJ 289 (1 ex., CS), maxillary-barbel length, outer- and inner- UFRJ 505 (1 ex., CS); Brachyglanis sp., mental barbel length, head depth (taken at MZUSP 45895 (1 ex., CS); Brachyplatysto- the vertical through the posterior margin of mafilamentosa, MZUSP 45896 (1 ex., CS); the fleshy opercular flap), head width (taken Brachyrhamdia meesi, UFRJ 397 (2 ex., CS); at its maximum width), fleshy interorbital Calophysus macropterus, MZUSP 26415 (1 distance (the space between the fleshy upper ex., CS), MZUSP 45904 (1 ex., CS); Cetop- orbital rims), preorbital length (measured sorhamdia iheringi, UFRJ 689 (2 ex., CS); from snout tip to anterior orbital rim), an- Cetopsorhamdia picklei, USNM 121218 (2 terior intemarial space, and length of first ex., paratypes, CS); Chasmocranus longior, and second branched rays of the dorsal and MZUSP 45909 (2 ex., CS); Chasmocranus pectoral fins. truncatorostris, UFRJ 322 (1 ex., CS), UFRJ Some paratypes of Mastiglanis asopos and 504 (1 ex., CS); Cheirocerus goeldi, MZUSP additional comparative material of Pime- 45905 (2 ex., CS); Gladioglanis conquis- lodidae were cleared and counterstained tador, MZUSP 45906 (2 ex., CS); employing the Taylor & Van Dyke (1985) Goeldiellaleques, MZUSP 45907 (1 ex., CS); technique, which provides a diflferential Heptapterus mustelinus, UFTU 291 (1 ex., staining of the skeletal system elements. CS); Hypophthalmus edentatus, MZUSP Vertebral counts included the first five ver- 43304 (1 ex., CS); Iheringichthys labrosus, tebrae transformed in the Weberian appa- UFRJ 690 (1 ex., CS), DBAV-UERJ 146 (1 ratus, and the compound caudal centrum ex.); Imparales mariai, USNM 121251 (1 (PUl+Ul) was counted as one. Principal ex., holotype); Imparales panamensis, caudal-fin ray counts included all branched USNM 293454 (1 ex., CS); Imparfinis min- rays plus one unbranched ray in each lobe, utus, MZUSP 39990 (1 ex., CS), UFRJ 320 following Hubbs & Lagler (1958). Counts (4 ex.); /. mirini, MZUSP 45899 (1 ex., CS); for each lobe, upper first, are separated by /. nemacheir, USNM 121 163 (2 ex., CS); /. 762 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON piperatus, CAS 63636 (1 ex., holotype); /. mesethmoid abruptly assuming a reversed schubarti, MZUSP 45897 (1 ex., CS); Im- direction at their mid-length; 8— an elon- parfinis sp. 1, MZUSP 45900 (1 ex., CS); gated metapterygoid; 9— a lamina at the an- Imparfinis sp. 2, MZUSP 45898 (1 ex., CS); terodorsal margin of the opercle; 10— rear Imparfinis sp. 3, UFRJ 393 (1 ex., CS); Lo- portion of opercular bone tapered and phiosilurus alexandri, UFRJ 042 (1 ex., CS); curved ventrally. Other characters consid- Megalonema platanus, MZUSP 45902 (1 ered plesiomorphic or of unknown polarity ex., CS); Megalonema sp., DBAV-UERJ 1 22 but still usefiil for identification include: eyes (1 ex., CS); Microglanis parahybae, UFRJ large; long maxillary barbels extending be- 693 (2 ex., CS); Nannoglanis bifasciatus, yond adipose-fin origin; mouth ventral; MZUSP 45903 (2 ex., CS); Nannorhamdia bones of cranial roof thin, lacking orna- stictonotus, UFRJ 292 (3 ex., CS); Nemu- mentation and connected via lap junctions roglanis sp., MZUSP 45908 (1 ex., CS); Par- (dentate sutures absent); well-developed su- apimelodus valenciennis, DBAV-UERJ 230 praoccipital process; and triangular pectoral (1 ex., CS); Phenacorhamdia boliviana, fins. MZUSP 42296 (2 ex., CS); Phenacorham- Type species.— Mastiglanis asopos, new dia sp., MZUSP 45901 (1 ex., CS); Pime- species. lodella lateristriga, UFRJ 503 (2 ex., CS); Etymology. —From the Greek mastix Pimelodella sp., UFRJ 502 (2 ex., CS); Pi- (mastigo, in latinized form) meaning whip, melodus maculatus, UFRJ 691 (2 ex., CS); in allusion to the filamentous elements of P. ornatus, DBAV-UERJ 934 (1 ex., CS); pectoral and dorsal fins; and glanis, the name Pseudopimelodus sp., DBAV-UERJ 1 18 (1 of the Greek catfish of Aristotle, a common ex., CS); Rhamdia sp., UFRJ 321 (3 ex., denomination for fishes of the order Silur- CS); Rhamdiopsis sp., UFRJ 708 (1 ex., CS). iformes. The last two letters of the word mastigo were suppressed for the sake of eu- phony. Gender masculine. Mastiglanis, new genus Diagnosis.— A small pimelodid catfish Mastiglanis asopos, new species displaying the suite of apomorphic char- Figs. 1, 2, Table 1 acters ascribed to the subfamily Rhamdi- inae (Lundberg, 1991a). It also exhibits all Diagnosis. —As for the genus. attributes that characterize a more restrict- Holotype. -MNRJ 12227, SL 65.9 mm, ed monophyletic unit called "Nemuroglanis Brazil, Para, Igarape Saracazinho, tributary sub-clade" (Ferraris 1988; see also Phylo- of rio Trombetas, near Porto Trombetas, genetic Relationships section