Browsing by Author "Schaefer, Scott Allen, 1958-"
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ItemThe Lithogeninae (Siluriformes, Loricariidae) : anatomy, interrelationships, and description of a new species. American Museum novitates, no. 3637.(New York, NY : American Museum of Natural History., 2008) Schaefer, Scott Allen, 1958-; Provenzano, Francisco.A new species of the loricariid genus Lithogenes Eigenmann, 1909, is described on the basis of 84 specimens captured from a single locality in the upper Río Orinoco drainage of southern Venezuela. The new species is only the third representative of the subfamily Lithogeninae to be recognized in the 100 years since the discovery of the type species, L. villosus, and is the only lithogenine known from more than a handful of specimens. This new material provides the basis for a comprehensive review of lithogenine systematics, comparative anatomy, and interrelationships. Lithogenes wahari, new species, shares with its congeners the dermal plates of the trunk comprised of three paired series, presence of a bifurcate levator arcus palatini crest and expanded lateral lamina of the hyomandibula, and the palatine sesamoid not reaching the nasal capsule, thus confirming its placement in Lithogenes among the Loricariidae. The new species is diagnosed among congeners by the absence of odontodes on the proximal portion of the ventral surface of the first pelvic-fin ray (vs. ventral pad covered with embedded odontodes along entire length) and thickened skin of the pelvic pad forming extensive ridges; accessory premaxillary teeth absent; anal fin with intense pigment band along base and diffuse spot at midlength of fin rays (vs. pigment band at base absent, fin rays dusky, without distinct spot). Characters useful for distinguishing lithogenine species are reviewed; revised diagnoses and descriptions are provided for the two previously described species in light of new character evidence. A detailed comparative analysis of the osteology and myology of L. wahari is presented and discussed relative to homologous conditions observed more broadly among the loricarioid catfishes. Of particular importance are aspects of musculoskeletal anatomy that are hitherto unknown for lithogenines, and aspects of sexual dimorphism and the anatomy of the reproductive and digestive systems that are unique or unusual among loricariid catfishes. A phylogenetic analysis of relationships among species based on morphological characters places the two Guyana Shield species (L. villosus and L.wahari) as sister taxa on the basis of four synapomorphies. Both species share reduction in the width and extent of the jaws, resulting in the derived reduction in the numbers of teeth carried by the jaw elements. Evaluated with respect to the geographic distribution of the species, the pattern of phylogenetic relationships suggests an ancestral widespread distribution for the Lithogeninae throughout the Guyana Shield plus the Caribbean and eastern Andean foreland basin of northern South America, followed by vicariance and subsequent divergence of populations now isolated in the coastal mountains of northern Venezuela and the Guyana Shield region. Lithogenine catfishes share a number of unique features with astroblepid catfishes that are not observed to occur in other members of the Loricariidae, such as the morphology of the pelvic fins, specialized pelvic musculature, and associated adaptations for climbing. Evaluated against the evidence supporting their phylogenetic placement as the sister group to all other Loricariidae, exclusive of the Astroblepidae, these shared similarities suggest that the association with rocky habitats of headwater stream systems and the ability to climb vertical surfaces may represent ancestral conditions for the lineage leading to the astroblepid plus loricariid catfishes. ItemNew and noteworthy Venezuelan glanapterygine catfishes (Siluriformes, Trichomycteridae), with discussion of their biogeography and psammophily. American Museum novitates ; no. 3496(New York, NY : American Museum of Natural History, 2005) Schaefer, Scott Allen, 1958-; Provenzano, Francisco.; Pinna, Mário C. C.; Baskin, Jonathan N.Four new species of the trichomycterid subfamily Glanapteryginae are described from the Río Orinoco basin of Venezuela. Two new species each in Pygidianops Myers 1944 and Typhlobelus Myers 1944 represent the first documented occurrence of these genera in Venezuela, and for Pygidianops the first occurrence outside the Río Negro basin. The new species were captured from sand-bottom habitats in two disparate locations in the Orinoco River basin and display a remarkable suite of reductive features, such as loss of eyes, fins, and pigment, and reductions or absence of laterosensory canals and odontodes. Pygidianops cuao, n.sp. from the Río Cuao, a clear-water tributary of the upper Orinoco River, is diagnosed from its congeners by the presence of diminutive eyes and a triangular skin flap at the corner of the mouth. Pygidianops magoi, n.sp., known from near the delta of the Orinoco River, is diagnosed from its congeners by the absence of pectoral and anal fins, presence of four laterosensory pores, and nine or ten caudal-fin rays. Typhlobelus guacamaya, n.sp. from the Río Cuao is diagnosed relative to its congeners by the presence of three branchiostegal rays, posterior naris absent, lack of pleural ribs, and is further distinguished from both T. ternetzi and T. macromycterus by the absence of eyes and from T. lundbergi by the presence of three laterosensory canal pores. Typhlobelus lundbergi, n.sp. from the lower Orinoco is diagnosed by the presence of four laterosensory canal pores and further distinguished from T. ternetzi and T. macromycterus by the absence of eyes. We review the characters useful in diagnoses of Pygidianops and Typhlobelus among trichomycterid catfishes and discuss morphological patterns in the diversification of the Glanapteryginae. Species of Pygidianops and Typhlobelus are known only from the rivers draining the Guyana and Brazilian shields, yet within these areas they occupy all major water types. Such broad ecological range suggests that the geographic distribution of species of these two genera are not limited by water type. That observation, plus their common occurrence in the ubiquitous shallow sand-bottom habitats of the larger rivers of the shield regions of northern South America, indicate that species of Pygidianops and Typhlobelus may be expected to occur throughout the entire Amazon and Orinoco basins. The evolution of habitat preference in glanapterygines seems to follow a trend toward increased specialization for interstitial environments. The degree of psammophilic adaptation in species of Pygidianops and Typhlobelus is remarkable, without parallel in siluriforms and perhaps in any other freshwater fishes. We describe the physical characteristics of the sand and review the suite of morphological specializations for life in interstitial sand that are shared by these species, such as loss or reduction of certain structures and presence in these species of paired metapleural keels along the ventral edges of the abdomen formed by a long ridge of stiffened integument, underlain by well-differentiated medial infracarinalis muscles, that are superficially similar to the metapleural folds of sand-dwelling cephalochordates and other interstitial organisms. ItemNew cascudinhos from southern Brazil : systematics, endemism, and relationships (Siluriformes, Loricariidae, Hypoptopomatinae). American Museum novitates ; no. 3254(New York, NY : American Museum of Natural History, 1998) Reis, Roberto E.; Schaefer, Scott Allen, 1958-"Epactionotus, a new genus of the loricariid catfish subfamily Hypoptopomatinae with three new species, and a new species of Eurycheilichthys are described from southern Brazil. Epactionotus is diagnosed among genera of the Hypoptopomatinae by the posterior position of the dorsal fin and morphology of its internal supports and by absence of an expanded fleshy flap on the dorsal surface of the first pelvic-fin ray of males. The three Epactionotus species are each endemic to a very limited geographic area along the Atlantic coast of southern Brazil. Epactionotus bilineatus n. sp. is restricted to the rivers Maquiné and Tres Forquilhas in northeastern Rio Grande do Sul State, E. itaimbezinho n. sp. is endemic to the rio Mampituba along the border between Rio Grande do Sul and Santa Catarina States, and E. gracilis n. sp. is endemic to the rio Araranguá drainage of southern Santa Catarina State. These new species are distinguished based on morphometric comparisons, color pattern, and arrangement of abdominal platelets. Eurycheilichthys limulus n. sp. is described from the upper reaches of the rio Jacuí drainage in Rio Grande do Sul State. This new species shares with its sole congener, E. pantherinus, a single synapomorphy, presence of seven branched pectoral-fin rays, and is distinguished from it by a more narrow body, head and dorsal trunk with series of longitudinal light stripes, versus scattered dark blotches, and presence of an accessory ceratobranchial flange and filamentous gill rakers, versus absence of those features in E. pantherinus. In addition to the presence of longitudinal stripe coloration and accessory teeth, these four species also share with several other, but not all hypoptopomatines, a peculiar slitlike morphology of the skin at the base of the pectoral-fin spines, the function and biological significance of which is unknown"--P. . ItemA new species of Hisonotus (Siluriformes, Loricariidae) of the upper Río Uruguay Basin. American Museum novitates ; no. 3333(New York, NY : American Museum of Natural History, 2001) Aquino, Adriana E.; Schaefer, Scott Allen, 1958-; Miquelarena, Amalia María.A new species of the hypoptopomatine genus Hisonotus (Loricariidae) is described from a small tributary of the upper río Uruguay basin near the border between Uruguay and Brazil. The new species can be distinguished from all other congeners by the following combination of characters: (1) presence of serrae along distal two thirds of posterior margin of pectoral-fin spine (versus serrae absent, posterior margin smooth); (2) odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow odontode-free area covered by pad of soft tissue; (3) caudal peduncle short (27-34% SL, versus > 34% SL) and deep (13-15% SL, versus < 13% SL); (4) eye large (15-19% HL, versus < 13% HL); and (5) caudal-fin pigmentation, when well defined, dark brown with a pair of whitish blotches on upper and lower lobes. The significance of the distribution of the new species is discussed relative to the degree of endemism of other fish groups in the Uruguay basin. ItemRelationships of Lithogenes villosus Eigenmann, 1909 (Siluriformes, Loricariidae) : evidence from high-resolution computed microtomography. American Museum novitates ; no. 3401(New York, NY : American Museum of Natural History, 2003) Schaefer, Scott Allen, 1958-The unusual neotropical freshwater catfish Lithogenes villosus Eigenmann, 1909 was described from a single specimen collected in 1908 at Aruataima Falls, a cataract of the upper Potaro River of Guyana, as a new genus and species of the armored catfish family Loricariidae. There are no subsequent published reports of additional specimens. Lithogenes villosus is unusual among the armored loricariid catfishes in being nearly naked, or unplated. The dermal plates which typically encase the head and body of other representatives of the Loricariidae are restricted in Lithogenes villosus to three paired series of small plates on the posterior portion of the trunk, plus a set of three plates on either side of the lateral cheek. Its taxonomy has been debated largely because it is intermediate in morphology between the armored loricariids and the naked astroblepids; these two families are presently regarded as sister groups among the larger assemblage of Neotropical loricarioid catfishes. Nijssen and Isbrücker (1987, Revue Française d'Aquariologie et Herpétologie 13: 93-98.) transferred Lithogenes villosus, without comment or justification, from the Loricariidae to the Astroblepidae, and several recent presentations have renewed the controversy surrounding Lithogenes relationships by asserting that Lithogenes is well supported as the sister group of the Astroblepidae. Lithogenes has not been subjected to a thorough systematic investigation because it is thus far known only from the holotype, a situation that precludes rigorous comparative anatomical survey via traditional, destructive methods. Given its unusual morphology and putative basal position among the loricariids, ultimate resolution of Lithogenes relationships is crucial to resolving several issues in siluriform systematics. In this study, three-dimensional reconstructions of computed tomography (CT) scans of the holotype made at 13-mm resolution revealed details of internal anatomy informative of its relationships. Parsimony analysis of 41 characters obtained from the CT reconstructions, gross examination of external features, and previously published characters surveyed among loricarioid and outgroup catfishes indicated that Lithogenes shares a rich suite of derived characters with loricariids, most notably the presence of a mesethmoid condyle, posterior placement of the nasal capsule, closed pterotic aperture, lateral ethmoid lamina, and metapterygoid contacting the lateral ethmoid, and is the sister group of all other loricariids, exclusive of astroblepids. Evaluation of this dataset revealed that support for alternative relationships was considerably worse. A sister-group relationship between Lithogenes and astroblepids occurred in less than 1% of 10,000 bootstrap replicate trees and required 7 additional steps relative to the shortest, most parsimonious tree. A sister-group relationship between astroblepids and loricariids, exclusive of Lithogenes villosus, was not observed among the bootstrap replicates; forcing this topological constraint required nine additional steps relative to the shortest tree. Although Lithogenes villosus shares several morphological similarities with astroblepids, most of these represent symplesiomorphy and are therefore not indicative of relationships. ItemSystematics of the genus Hypoptopoma Günther, 1868 (Siluriformes, Loricariidae). (Bulletin of the American Museum of Natural History, no. 336)(American Museum of Natural History., 2010) Aquino, Adriana E.; Schaefer, Scott Allen, 1958-The systematics of Hypoptopoma Günther (1868a) is revised based on comprehensive evaluation of specimen collections and a phylogenetic analysis of the species. The genus Hypoptopoma comprises a distinctive assemblage of loricariid catfishes distributed in the lowland drainages of tropical, subtropical, and temperate latitudes of South America to the east of the Andes. Hypoptopoma is uniquely diagnosed among genera of the Loricariidae on the basis of the presence of a laterally expanded nuchal plate. Members of the genus can be further distinguished from all other loricariids, except the hypoptopomatin genus Oxyropsis, by the depressed head with eyes placed ventrolateral and visible from below. Hypoptopoma is further distinguished from all other Hypoptopomatini, including Oxyropsis, by the caudal peduncle posterior to the base of the anal fin ovoid in cross section and deeper in the dorsoventral axis. All species of Hypoptopoma, except H. spectabile, can be further distinguished among loricariids by the presence in adult stages of a column of variably enlarged and flattened odontodes positioned along the posterior margin of the trunk plates. Individuals of several Hypoptopoma species attain the largest body size for the subfamily Hypoptopomatinae, with standard length reaching 105 mm. Species of Hypoptopoma typically occur in streams of slow to moderate current and muddy to sandy bottom with marginal emergent vegetation. Based on verified specimen records, the species is distributed in the Río Amazonas basin, including the Ucayali, Madeira, and Tapajos rivers, as well as in the rivers east to the Ilha Marajo drainage (Para, Brazil), in the Tocantins and smaller coastal river drainages in northeastern Brazil (Mearim), the upper Río Orinoco basin, the Essequibo and Nickerie river basins of the Guiana Shield, and in the ríos Paraguay and lower Paraná. There are no records of Hypoptopoma in the Río Uruguay, the Atlantic coastal drainages of Uruguay and Brazil south of Rio Mearim (Maranão), the upper Paraná, and Rio São Francisco systems. Fifteen species are recognized in Hypoptopoma, seven of which are newly described herein. Phylogenetic analysis of Hypoptopoma species, based on analysis of 26 characters drawn from aspects of external morphology and internal osteology, recovered a well-supported but incompletely resolved nested set of clade relationships that suggests a widespread ancestral distribution for the group in central Amazonia, plus at least four instances of divergence of a species having a peripheral distribution from an Amazonian sister group. Relationships at the basal node were unresolved. There was insufficient evidence to resolve the relationships among H. baileyi, n. sp., of the Madeira river basin, an unresolved clade comprised of H. guianense Boesemann, 1974, of the Essequibo and Nickerie basins in Guyana and Surinam; H. psilogaster Fowler, 1915, of the upper Amazon basin in Brazil and Peru; and H. thoracatum Günther, 1868a, of the upper and middle Amazon basin; and a well-supported clade that includes all other Hypoptopoma species. The latter clade was supported by four synapomorphies and includes H. brevirostratum, n. sp., of the upper Amazon basin in Brazil and Peru, H. muzuspi, n. sp., of the Tocantins basin, and a more restricted clade supported by six character-state changes comprising the remainder of the subfamily. Two species, H. spectabile (Eigenmann, 1914) of the upland Amazon and upper Orinoco river basins of Venezuela, Colombia, Ecuador, and Peru and H. sternoptychum (Schaefer, 1996a) of the lowland reaches of the Amazon River, formerly placed in the genus Nannoptopoma Schaefer, 1996, represent a clade most closely related to a nested subset of Hypoptopoma species. These former Nannoptopoma species are reassigned to Hypoptopoma, thus rendering the former generic name a subjective junior synonym of Hypoptopoma. Hypoptopoma bianale, n. sp., of the upper Amazon River basin in Brazil and Peru represents the sister group to a largely unresolved clade comprised of H. inexspectatum (Holmberg, 1893a) of the Paraguay-Paraná basin, H. steindachneri Boulenger, 1895, of the upper Amazon basin in Brazil and Peru, H. gulare Cope, 1878, of the upper Amazon basin, H. machadoi, n. sp., of the Orinoco basin, and a clade comprised of H. elongatum, n. sp., of the lower Tapajos and lower Trombetas rivers plus H. incognitum, n. sp., of the middle Amazon basin, Tocantins, and Mearim rivers. A key to the species of Hypoptopoma is provided. ItemSystematics of the genus Otothyris Myers 1927, with comments on geographic distribution (Siluriformes, Loricariidae, Hypoptopomatinae). American Museum novitates ; no. 3222(New York, NY : American Museum of Natural History, 1998) Garavello, Julio C.; Britski, Heraldo A.; Schaefer, Scott Allen, 1958-"A revision of the genus Otothyris Myers, 1927, is presented on the basis of collections from the coastal river systems of southeastern Brazil. Otothyris is diagnosed among genera of the loricariid subfamily Hypoptopomatinae on the basis of autapomorphies of the cranial skeleton and caudal fin. Three new species are described and compared with the three nominal species of Otothyris, which are herein redescribed: Rhinelepis lophophanes Eigenmann and Eigenmann, 1889, is transferred to Otothyris under a new combination; Otocinclus cephalacanthus Ribeiro, 1911, and Otothyris canaliferus Myers, 1927, are junior synonyms of Otothyris lophophanes; we designate a lectotype from among the type series of O. canaliferus. Otothyris juquiae, n. sp. is described from the Juquiá River of the Ribeira de Iguape basin, São Paulo State; Otothyris rostrata, n. sp. is described from the coast of Rio Grande do Sul State; Otothyris travassosi, n. sp. is described from the isolated coastal rivers of Espírito Santo State. The species are compared by multivariate statistical analysis of morphometric characters, which distinguishes O. lophophanes and O. juquiae from O. rostrata and O. travassosi on the basis of variables with highest loadings on head depth, head width, and orbit diameter. We offer comments on the endemic distribution of the genus Otothyris in southeastern Brazil"--P. .