Browsing by Author "Provenzano, Francisco."
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Item The 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.Item New 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.