Browsing by Author "Carvalho, Marcelo R. de."
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Item Freshwater stingrays of the Green River Formation of Wyoming (early Eocene), with the description of a new genus and species and an analysis of its phylogenetic relationships (Chondrichthyes, Myliobatiformes). Bulletin of the AMNH ; no. 284(New York, NY : American Museum of Natural History, 2004) Carvalho, Marcelo R. de.; Maisey, John G.; Grande, Lance.Freshwater stingrays from the Fossil Butte Member of the late early Eocene Green River Formation of Wyoming are reviewed, and a new genus and species of fossil stingray is described. †Asterotrygon maloneyi, n.gen., n.sp. is remarkably well preserved and is known from articulated skeletons of juveniles and adults, both males and females. It is distinguished from all Recent and fossil stingrays, including †Heliobatis radians from the same formation, by the unique presence of a dorsal fin covered with dermal denticles directly anterior to the caudal stings. Other characters that in combination distinguish the new fossil genus from all other stingrays include: retention of separate, individual vertebrae extending to the tail extremity instead of a cartilaginous rod posterior to caudal stings; dorsal surface of disc and tail covered by numerous, closely packed, minute denticles; tail relatively stout at base; and relative proportions of disc and tail. †Asterotrygon, n.gen. shares with certain stingray genera postorbital processes of neurocranium separated from a supraorbital process by a small notch in the supraorbital shelf, presence of both dorsal and ventral tail-folds posterior to caudal stings (and internally supported by rudimentary radial elements), and hyomandibulae separated from lower jaws by a gap that originally contained the hyomandibular-Meckelian ligament. A calcified angular cartilage between the hyomandibula and Meckel's cartilage is tentatively identified in †Asterotrygon, n.gen. as well. †Asterotrygon, n.gen. is unquestionably a stingray, presenting many myliobatiform synapomorphies including caudal stings on the dorsal aspect of tail, lack of jugal arches in neurocranium, a thoracolumbar synarcual cartilage posterior to scapulocoracoid, absence of thoracic ribs, and laterally expanded, shelflike postorbital processes. †Asterotrygon, n.gen. and †Heliobatis primitively retain a narrow and slightly arched puboischiadic girdle and primitively lack calcified rostral elements in adults. A phylogenetic analysis of 23 stingray genera, two outgroups, and 44 informative morphological characters resulted in 35 equally most parsimonious trees. The strict consensus reveals the following hierarchical structure: Hexatrygon + (†Asterotrygon, n.gen., Plesiobatis, Urolophidae + (Urotrygonidae + (†Heliobatis + (Potamotrygonidae + (amphi-American Himantura, Pteroplatytrygon, Himantura, Taeniura, Dasyatis + (Gymnuridae + Myliobatidae)))))). Our resulting tree has nodes in common with previous phylogenetic analyses of stingrays (e.g., Hexatrygon is the most basal stingray genus; gymnurids and myliobatids (pelagic stingrays) are well-supported sister-groups), but includes novel components, such as a clade that includes all dasyatid genera (as a polytomy) and the component Gymnuridae + Myliobatidae. 'Dasyatidae' is not monophyletic in any of the minimum-length trees obtained; Urolophidae (Urolophus and Trygonoptera) and Urotrygonidae (Urobatis and Urotrygon) are both monophyletic, but are not sister-groups. †Asterotrygon, n.gen. forms a clade with urolophids in 21 of the 35 equally most parsimonious trees. Successive approximations weighting adds only one additional node in relation to the strict consensus, which unites Pteroplatytrygon, Dasyatis, and Himantura sensu stricto (in a polytomy) with Gymnuridae + Myliobatidae. The resulting stingray phylogeny is at odds with previous phylogenies mostly regarding the affinities of amphi-American Himantura and Taeniura, which do not form a monophyletic group with the South American freshwater stingrays (Potamotrygonidae) in any of the minimum-length trees obtained. Similar to most elasmobranch groups, stingrays display much character conflict, and cladogram topologies are very sensitive to changes in character coding. Due to a high degree of character variation present in certain generic-level terminal taxa, a more fully representative species-level phylogeny is necessary to clarify the systematic importance of tail-fold configuration, ceratobranchial fusion patterns, and other characters discussed in our study. Three additional synapomorphies of stingrays were uncovered by our study, pertaining to the configuration of the basihyal, first pair of hypobranchial cartilages, and to the forward extension of the basibranchial copula. Our phylogenetic results imply the following biogeographic patterns: the relationships of †Asterotrygon, n.gen. demonstrate a strong Indo-west Pacific historical correlation, while †Heliobatis displays an affinity with the Americas; the node containing the greatest diversity of modern stingrays ('Dasyatidae' + (Gymnuridae + Myliobatidae)) evolved only after an American stingray lineage was established sometime earlier than the early Eocene; and potamotrygonids date at least from the late early Eocene, and not the Miocene, as previous studies have implied. The mechanism responsible for the invasion of the potamotrygonid ancestor into South America could indeed have been a marine transgression as advocated by other authors, albeit a much earlier (pre-Miocene) one, during either the late Cretaceous or the late Paleocene to early Eocene.Item Torpedo adenensis : a new species of electric ray from the Gulf of Aden : with comments on nominal species of Torpedo from the western Indian Ocean, Arabian Sea, and adjacent areas (Chondrichthyes, Torpediniformes, Torpedinidae). American Museum novitates ; no. 3369(New York, NY : American Museum of Natural History, 2002) Carvalho, Marcelo R. de.; Stehmann, Matthias, 1943-; Manilo, L. G. (Leonid Georgievich)A new species of electric ray of the genus Torpedo is described from the eastern Gulf of Aden, northwestern Indian Ocean. Torpedo adenensis, n. sp., is placed in the subgenus Torpedo due to the presence of small, knoblike papillae around its spiracles. It is distinguished from all other congeners by its unique dorsal coloration, consisting of a uniform reddish-, rusty-, or orange-brown without any distinctive spots, blotches, or reticulations. A unique combination of characters further distinguishes T. adenensis, including the proximity of the spiracles and eyes, the distance between the second dorsal and caudal fin, which is greater than the distance between the first and second dorsal fins, and the presence of an integumental flap in the clasper glans region. Torpedo adenensis is sexually mature when between 280 and 395 mm in total length, is known from specimens of both sexes, including adults and subadults, and is the only species of Torpedo unequivocally reported from the Gulf of Aden to date. Examination of further material, including type material, confirms that at least four other valid species of Torpedo occur in the western Indian Ocean, Red Sea, Arabian Sea, and adjacent gulfs: Torpedo panthera von Olfers, 1831, Torpedo sinuspersici Kämpfer in von Olfers, 1831, Torpedo fuscomaculata Peters, 1855, and Torpedo suessi Steindachner, 1898a . We have attempted to clarify the status and distribution of these species, and confirm that all four do not occur sympatrically. All four species may be distinguished on dorsal color pattern, but intraspecific variation in coloration and the proper limits of all four species remain to be precisely determined. Lectotypes are designated for T. panthera, T. fuscomaculata, and T. suessi. Torpedo smithii Günther, 1870 is confirmed as a junior synonym of T. fuscomaculata. Narcacion polleni Bleeker, 1866 is provisionally regarded as a junior synonym of T. sinuspersici, but it may eventually prove to be a valid species from Réunion. Torpedo zugmayeri Engelhardt, 1912 is either a junior synonym of T. sinuspersici or valid, but more material from off Pakistan needs to be examined to determine its taxonomic fate. Torpedo suessi has not been recorded since originally described from off Yemen in the southern Red Sea, but evidence for its possible occurrence off Sudan is presented. To serve as a reference for future studies, type material of T. panthera, T. fuscomaculata, T. polleni, T. smithii, and T. suessi is described and illustrated for the first time since their original descriptions. Torpedo panthera and T. adenensis share the derived presence of an integumental flap in the clasper glans region, forming a monophyletic species group.