1,720,991 research outputs found
Cetacei di Terra e di Mare, alle origini dei Cetacei. Mostra permanente realizzata presso il Museo di Storia Naturale e del Territorio, Università di Pisa
No full textEvolutionary trends in the Plio-Pleistocene icthyofauna of the Mediterranean Basin:nature, timing and magnitude of the extinction events
No full textTrends in standing diversity and turnover rates of Italian fish communities from the Late Pliocene to the Middle Pleistocene are analyzed on the base of a list of 197 taxa (represented by both ichthyoliths and otoliths) obtained through the study of 16 Italian fossil deposits with good chronostratigraphic resolution. Standing diversity shows a regular and positive trend, maintained by intense episodes of turnover, which have been recognized in Late Pliocene, Plio/Pleistocene boundary and Early/Middle Pleistocene boundary. On the contrary, an absolute stasis corresponds to the Early Pleistocene and an episode of extinction not balanced by originations characterizes the Middle Pleistocene. None of the observed episodes appear to be substantially selective: all environments are vulnerable, even if with different intensities, and the mechanisms of recharge seem to compensate the extinction. Evolutionary trends related to the biogeographic structure of the association are identified. In particular the most meaningful are: (1) the progressive loss of Indo-Pacific taxa; (2) the relative increase of endemic taxa; (3) the increase of Atlantic taxa; (4) the decline of cosmopolitan taxa. Among the causes responsible for these events, the influence of the Plio-Pleistocene climatic oscillations is important, even if the substantial non-selectivity of the events suggests the involvement of other mechanisms such as change of the circulation models and mechanisms of biotic interchang
Evolutionary dynamics in the fish faunas of the Mediterranean basin during the Plio-Pleistocene
No full textThe creation of a database including 243 taxa of teleostean fishes (ichthyoliths and otoliths) from the Lower Pliocene-Middle Pleistocene fossil record of the Mediterranean basin, allowed tracking of the diversity trend; assessment of origins, extinction, and turnover rates; and construction of hypotheses on the settlement mechanisms of the modern Mediterranean fish fauna. These processes have been analyzed with respect to two different time scales: the classic chronostratigraphic units and standard time units of equal duration (24 units of 200,000 years). In the Pleistocene, during the maximum intensity of glacial events and the most intense effects on the Mediterranean areas, the composition of the fish fauna had already developed a clear Mediterranean character (about 75% of the taxa). The residual elements (extinct and extramediterranean) underwent a further strong impoverishment at the Lower-Middle Pleistocene boundary with the Mediterranean component reaching 89.4%. On the basis of the observed trends, and particularly on the basis of the progressive changes in the taxonomic composition of these communities, from the upper Miocene to the present, the idea of a "paleomediterranean" fauna is discussed. © 2005 Elsevier Ltd and INQUA
Systematic and paleobiogeographical observations on the Gadid fish Gadiculus labiatus (Schubert, 1905)
No full textPassato e futuro della collezione osteologica di balene e delfini del Museo di Storia Naturale dell’Università di Pisa
No full textVengono descritte le principali tappe che hanno portato all'acquisizione della collezione osteologica di balene e delfini del Museo di Storia Naturale dell’Università di Pisa, una delle più importanti a livello europeo
Oreochromis lorenzoi a new species of tilapinae cichlid from the Late Miocene of Central Italy
No full textBiogeographical significance of nothern extraprovincial fishes in the Pliocene of Ecuador
No full textThe biogeographical relationships of a Pliocene (Globigerinoides fistulosus Zone) fish fauna are described. The data here presented show that the Ecuadorian fish fauna has a precise Panamic identity already in the Pliocene. Several (15) northern extraprovincial guests of Californian origin have been identified. The presence of Californian taxa in the Pliocene of Ecuador suggests the existence of faunal relationships between these two areas. The analysis of the California fossil record reveals that the faunal exchange occurred only via north-south. Two dispersal mechanisms have been pointed out by the authors: (1) the flow at lower latitudes of a branch of the California Current, and (2) the activation of coastal upwelling cells beginning from California area. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
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