348 resultados para Faunas


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A continuous biostratigraphic sequence has been established, possibly from as low as the sedgwickii Biozone but certainly throughout the Telychian Stage (?sedgwickii, turriculatus, ?crispus, griestoniensis and crenulata biozones). Thirty-three taxa have been recorded, including the new genus Wandograptus wandovalensis sp. nov., the new species Pseudostreptograptus queenslandensis and the new subspecies Dictyonema paululum australis and Stimulograptus sedwickii loydelli. A number of species have been recorded from Australia for the first time: Dictyonema cf. geniculatum Bulman, Petalolithus kurcki (Rickards), Pristiograptus initialis (Kirste), Monoclimacis directa Zalasciewicz, Monograptus aff. distans (Portlock), Monograptus sartorius Törnquist, and Torquigraptus pragensis (Bouček). Nine forms have been left under open nomenclature. The type section for the Poley Cow Formation yields a griestoniensis biozone fauna close to the top, and this level can be correlated with a griestoniensis Biozone fauna in the Broken River crossing section, again just below the top of the formation. Further north, griestoniensis Biozone faunas have also been recognized, beyond Diggers Creek, and in the Quinton Formation at Top Hut, enabling a reliable time plane throughout the region. At Top Hut, the highest graptolitic strata yield a crenulata Biozone fauna; and stratigraphically lower sequences, referable to the ?sedgwickii, turriculatus and ?crispus biozones, have been established on the Broken River section. It is likely that a full Telychian (Upper Llandovery) sequence occurs in the Poley Cow and Quinton formations enabling accurate correlation with other parts of the world.

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Proceedings of the 1" R.C.A.N.S. Congress, Lisboa, October 1992

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A new species of terrestrial gastropod - Anadromus penai sp. nov. (Fam. Anadromidae) - is described from a set of composite moulds collected in reddish silts and clays of Campanian-Maastrichtian age, found in the lower pan of the Taveiro Formation (Taveiro, Coimbra, West Central Portugal). The known occurrences of this new species are restricted to the type locality. The main differences from other contemporaneous Anadromidae are the profuse spiral sculpture of the body-whorl, with 20-22 sub-equal, close, and regular ribs.

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Qualitative and quantitative collections of ants made in the region of Manaus, Brazil (evergreen tropical humid forest), and in western North Carolina, USA (deciduous temperate/wet forest), were undertaken to investigate. latitudinal patterns of ant diversity and community organization on regional and local scales. We have found to date 307 ant species in the Municipality of Manaus. Totals ranging from 134 to 270+ species have been reported in the literature for other tropical regions of less than 10,000km2. In contrast, temperate ant surveys generally report only SO to 150 species in similar or larger areas. Sampling at sardine baits set 10m apart on square grids, we found forest ecosystems near Manaus to be much richer and more diverse in ants than those sampled in North Carolina: 28 species vs. 5-10 species in 50 collections and 16 vs. 3 previously unrecorded species discovered with each doubling of sample size. Room's (1975a) results from climatically simllar Papua New Guinea forest agree closely with those from Manaus. We suggest that one important factor contributing to the increased diversity of tropical, omnivorous ants may be greater variety of nest sites available for specialization.

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Invasive species may carry with them parasites from their native range, differing from parasite taxa found in the invaded range. Host switching by parasites (either from the invader to native fauna or from native fauna to the invader) may have important consequences for the viability of either type of host (e.g., their survivorship, fecundity, dispersal ability, or geographic distribution). Rhabdias pseudosphaerocephala (Nematoda) is a common parasite of cane toads (Rhinella marina) in the toad's native range (South and Central America) and also in its introduced Australian range. This lungworm can depress host viability and is capable of infecting Australian frogs in laboratory trials. Despite syntopy between toads and frogs for up to 75 yr, our analyses, based on DNA sequence data of lungworms from 80 frogs and 56 toads, collected from 2008 to 2011, did not reveal any cases of host switching in nature: toads and native frogs retain entirely different lungworm faunas. All lungworms in cane toads were the South and Central American species Rhabdias pseudosphaerocephala, whereas Australian frogs contained at least four taxa (mostly undescribed and currently lumped under the name Rhabdias cf. hylae). General patterns of prevalence and intensity, based on the dissection of 1,315 frogs collected between 1989 and 2011 across the toads' Australian range, show that these Australian endemic Rhabdias spp. are widely distributed geographically and across host taxa but are more common in some frog species (especially, large-bodied species) than they are in others.

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Diversity patterns of ammonoids are analyzed and compared with the timing of anoxic deposits around the Cenomanian/Turonian (C/T) boundary in the Vocontian, Anglo-Paris, and Monster basins of Western Europe. Differing from most previous studies, which concentrate on a narrow time span bracketing the C/T boundary, the present analysis covers the latest Albian to Early Turonian interval for which a high resolution, ammonoid-based biochronology, including 34 Unitary Associations zones, is now available. During the latest Albian-Middle Cenomanian interval, species richness of ammonoids reveals a dynamical equilibrium oscillating around an average of 20 species, whereas the Late Cenomanian-Early Turonian interval displays an equilibrium centered on an average value of 6 species. The abrupt transition between these two successive equilibria lasted no longer than two Unitary Associations. The onset of the decline of species richness thus largely predates the spread of oxygen-poor water masses onto the shelves, while minimal values of species richness coincide with the Cenomanian-Turonian boundary only. The decline of species richness during the entire Late Cenomanian seems to result from lower origination percentages rather than from higher extinction percentages. This result is also supported by the absence of statistically significant changes in the extinction probabilities of the poly-cohorts. Separate analyses of species richness for acanthoceratids and heteromorphs, the two essential components of the Cenomanian ammonoid community, reveal that heteromorphs declined sooner than acanthoceratids. Moreover, acanthoceratids showed a later decline at the genus level than at the species level. Such a decoupling is accompanied by a significant increase in morphological disparity of acanthoceratids, which is expressed by the appearance of new genera. Last, during the Late Cenomanian, paedomorphic processes, juvenile innovations and reductions of adult size dominated the evolutionary radiation of acanthoceratids. Hence, the decrease in ammonoid species richness and their major evolutionary changes significantly predates the spread of anoxic deposits. Other environmental constraints such as global flooding of platforms, warmer and more equable climate, as well as productivity changes better correlate with the timing of diversity changes and evolutionary patterns of ammonoids and therefore, provide more likely causative mechanisms than anoxia alone.

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The author has made a study of an assemblage of fossils from the Blacktail Range near Dillon Montana with the purpose in view of attempting a correlation of that group with the fauna of the Big Snowy Group. Fossils have also been obtained from a limestone formation in northwestern Montana and from four different areas in the Amsden formation in central and western Mont­ana.

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Sites 759 through 764 were drilled during Ocean Drilling Program Leg 122 on the Exmouth and Wombat plateaus off northwest Australia, eastern Indian Ocean. Radiolarian recovery was generally poor due to unsuitable lithofacies. A few Quaternary radiolarian faunas were recovered from most of the sites. Rare and poorly preserved Oligocene and Eocene radiolarian faunas were recovered from Holes 760A, 761B, 761C, and 762B. Poorly preserved Cretaceous radiolarians occur in samples from Holes 761B, 762C, 763B, and 763C. Chert intervals from Cores 122-761B-28X, 122-761C-5R, and 122-761C-6R contain moderately well-preserved Cretaceous radiolarian faunas (upper Albian, mid- to upper Cenomanian, and mid-Albian, respectively). Rare fragments of Upper Triassic radiolarians were recovered from sections in Holes 759B, 760B, and 764A. The only well-preserved pre-Quaternary radiolarians are in lower and upper Paleocene faunas (Bekoma campechensis Zone) recovered from Site 761, Sections 122-761B-16X-1 to 122-761C-19X-CC. The composition of these faunas differs somewhat from that of isolated coeval Paleocene faunas from Deep Sea Drilling Project sites in the Atlantic, Gulf of Mexico, tropical Pacific, eastern Indian Ocean, and near Spain and North Africa, as well as from several on-land sites in North America, Cuba, and the USSR.