1,721,029 research outputs found
Littiofauna pliocenica della Sez. Stuni e suoi rapporti con l'ittiofauna plio-pleistocenica della Vrica (Crotone-Calabria)
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The origin of biogeographic segregation in the copper shark (Carcharhinus brachyurus): an integrative reconstruction based on neontological and paleontological data
No full textNowadays, the copper shark Carcharhinus brachyurus Günther, 1870 displays an antitropical, disjunct distribution in marginal-marine environments of both the hemispheres. Differing from other species of Carcharhinus, C. brachyurus inhabits temperate rather than tropical coastal waters, and its dispersal abilities are strongly conditioned by the presence of habitats suitable as nursery grounds. Here we analyze, through well-defined geological timeslices, the global fossil record of C. brachyurus in order to identify the main biogeographic dynamics that led to the present-day biogeographic segregation pattern of this requiem shark species. By integrating a thorough review of the paleontological literature with the results of recent phylogeographic analyses on extant copper shark populations, our study provides a first integrated reconstruction of the historical distributional patterns of this shark species that allows for proposing the identification of some dispersal trajectories as well as of a number of key events in the paleobiogeographic history of C. brachyurus. Our research supports the notion that the present-day distributional pattern of C. brachyurus is the product of historical biogeographic processes and events that might be traced back to an early Miocene East Pacific-central West Atlantic center of origin and likely reflect major changes in the global ocean system (including the closure of major seaways and the emergence of new oceanic circulation patterns)
Data matrix codes: Experimental use in a museum exhibition
No full textThe application of the data matrix codes to the exhibition «Back to the past - A 500 million-year trip to Monti Pisani» is here presented. Reading these codes with the camera-equipped smartphones permits to visualize information and pictures about eight specimens that lived in the Monti Pisani 217 million-year ago (Triassic). The innovative application of this technology provides a new and exciting way to visit the Museum exhibitions through an interactive experience
Until Panama do us part: New finds from the Pliocene of Ecuador provide insights into the origin and palaeobiogeographic history of the extant requiem sharks Carcharhinus acronotus and Nasolamia velox
No full textThe extant blacknose shark Carcharhinus acronotus is a small-sized, tropical to warmtemperate carcharhinid shark occurring along the western Atlantic coasts from North Carolina (USA) through the Gulf and Caribbean regions to Uruguay. Here, we report on two carcharhinid teeth from lower Pliocene (4.07–3.76 Ma) strata of the Upper Onzole Formation exposed in the vicinities of Camarones (northwestern Ecuador). These specimens are assigned to C. acronotus, of which they apparently represent the first occurrence in the Pacific Ocean. The blacknose shark is regarded as the sister group of the whitenose shark Nasolamia velox, an idiosyncratic carcharhinid that currently inhabits the eastern Pacific coasts from Baja California (Mexico) to Peru; furthermore, the divergence between C. acronotus and N. velox has been recently estimated at about 3.7 Ma, which matches well the final phases of formation of the Isthmus of Panama. In light of these data, our Ecuadorian specimens might document an early Pliocene phase in which the newly originated C. acronotus occurred West of the then-fading Panamanian Seaway, possibly as a consequence of occasional dispersal through the latter. Alternatively, they might represent the teeth of an as yet unnamed C. acronotus-like carcharhine, from which the the morphologically conservative C. acronotus and the highly autapomorphic N. velox later arose by vicariance as the Isthmus of Panama rose. A survey of the fossil record of these two taxa does not falsify either hypothesis. Further research on the fossil chondrichthyans from the Cenozoic marine successions of Ecuador will hopefully shed new light on this issue and, more generally, on the role played by the closure of the Panamanian Seaway as a macroevolutionary trigger in the late Cenozoic marine realm
Basin physiography and tectonic influence on sequence architecture and stacking pattern: Pleistocene succession of the Canoa Basin (central Ecuador)
No full textFacies, shell bed features, and sequence stratigraphic framework for the shallow-marine Pleistocene upper Canoa and Tablazo Formations are presented, based on outcrop data from the southern coast of Cabo San Lorenzo, Ecuador. Sediments of this succession exhibit a distinct cyclic pattern, consisting of a stack of eight depositional sequences likely developed under the main control of orbitally induced sea-level changes. As a rule, within the studied interval an idealized cyclothem is composed of a transgressive systems tract (TST) and a highstand systems tract, whereas deposits attributable to the lowstand and falling-stage systems tracts are not present. Transgressive lithosomes may be defined by estuarine deposits interposed between the sequence boundary and the ravinement surface and by upward fining shoreface to inner-shelf facies successions above the ravinement (backstepping shelf wedge). Notwithstanding the different synsedimentary tectonic and climatic regimes, the Ecuadorian cyclothems share basic patterns of condensation and facies assemblages with other roughly coeval cyclothemic successions around the world.
At a multicycle time scale, tectonics influenced the long-term trend of the relative sea-level changes and consequently the large-scale stratigraphic organization. Owing to the continued tectonic uplift of the area, successive high-frequency depositional sequences are nested to form a longer-order falling-stage sequence set
Did the Mediterranean marine reflooding precede the Mio-Pliocene boundary? Paleontological and geochemical evidence from upper Messinian sequences of Tuscany, Italy
No full textThe events related to the Messinian salinity crisis are among the most deeply investigated of Earth's history. According to the current hypothesis of Neogene paleogeographic evolution, approximately 5.5 Ma ago, after evaporitic sedimentation and before the Mio-Pliocene boundary, the Mediterranean was characterized by the widespread development of non-marine environments inhabited by molluscs and ostracods of brackish affinity. The Messinian post-evaporitic deposits that testify such a dramatic environmental change are commonly referred to as 'Lago-mare' and have been reported from several outcrops and boreholes throughout the entire Mediterranean basin. The origin of 'Lago-mare' conditions is commonly interpreted as the result of the synergistic effect of both the humid climatic conditions and change of the drainage patterns at the Mediterranean scale, with the capture of Paratethyan brackish waters. A few recent studies, however, suggest that such a scenario probably represents an oversimplification of the original context, from both a paleogeographical and paleoenvironmental point of view. Unfortunately, the results of these studies have never been commonly accepted and the proposed evidences have been considered questionable. In this paper we describe the fish assemblages from the 'Lago-mare' deposits of two localities, Cava Serredi and Podere Torricella, located in the Neogene hinterland basins of Tuscany, central Italy. These assemblages consists of a mixture of marine euryhaline and stenohaline taxa suggesting that the depositional environments were characterized by permanently open connections with a marine basin filled with normal marine waters. In order to better define the paleontological significance of these upper Messinian fish assemblages, the oxygen, carbon and strontium isotopic composition of fish otoliths and other fossils has been measured. These isotopic compositions are strongly indicative of the presence of normal marine conditions close to the depositional environments testified by the sedimentary sequences, thereby implying that the interpretation of the geochemical results are consistent with those derived from the paleoecological analyses of the fish assemblages. Based on the integrated paleoichthyological-geochemical approach discussed in this paper it is possible to unambiguously demonstrate that normal marine rather than fresh- or brackish waters were present in the Mediterranean at least during the upper part of the 'Lago-mare' event, providing an unquestionable evidence that the marine refilling of the basin preceded the Mio-Pliocene boundary. © 2007 Elsevier B.V. All rights reserved
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