11 resultados para bivalve molluscs


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The state of research on the evolution of marine bivalve taxonomic diversity of the Mediterranean Pliocene is analysed. The following assertions are discussed: 1) The Early Pliocene malacofauna is characterized by a high number of warm-water taxa and a high taxonomic diversity with respect to that of the present time. 2) The first appreciable extinction event in the Mediterranean Pliocene approximates or just follows the FO of Globorotalia bononiensis. 3) The second appreciable extinction event is between the LAD of Discoaster tamalis and the LAD of Discoaster surculus . 4) A third minor extinction event is penecontemporaneous with the FO of Globorotalia inflaia. Taking into account the available data on the Pliocene extinction events it has been possible to distinguish 4 different molluscan units with different climatic-oceanographic significance.

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The state of research on the evolution of marine bivalve taxonomic diversity of the Mediterranean Pliocene is analysed. The following assertions are discussed: 1) The Early Pliocene malacofauna is characterized by a high number of warm-water taxa and a high taxonomic diversity with respect to that of the present time. 2) The first appreciable extinction event in the Mediterranean Pliocene approximates or just follows the FO of Globorotalia bononiensis. 3) The second appreciable extinction event is between the LAD of Discoaster tamalis and the LAD of Discoaster surculus. 4) A third minor extinction event is penecontemporaneous with the FO of Globorotalia inflata. Taking into account the available data on the Pliocene extinction events it has been possible to distinguish 4 different molluscan units with different climatic-oceanographic significance.

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Thesis submitted to the Faculdade de Ciências e Tecnologia to obtain the Master’s degree in Environmental Engineering, profile in Ecological Engineering

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Revista Española de Paleontologia 19 (2), 229-242

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Guernet & Lauverjat (1986) described a new species, Neocyprideis lusitanicus, from sediments deposited near Aveiro, Portugal. For these authors, some associated fossils (Molluscs, planktonic Foraminifera) indicated a Pliocene age. That seemingly was the first record of Neocyprideis in post-Miocene sediments in Europe. A recent study of Upper Cretaceous material from the same region showed an abundant Neocyprideis fauna, associated with Charophyta. These Neocyprideis could be assigned without any doubt to N. lusitanicus. Therefore, N. lusitanicus appears as an Upper Cretaceous species, reworked in much later sediments, not Pliocene but Quaternary, as indicated by the planktonic Foraminifera assemblage. This interpretation is supported by: 1 - the incompatibility of the Neocyprideis (restricted to lacustrine-lagoonal environments) with abundant planktic Foraminifera; 2 - the occurrence of N. lusitanicus with Charophytes and non marine, cretaceous vertebrates but without the same Foraminifera. Neocyprideis lusitanicus is a valid species, clearly different from the other late Cretaceous species (N. coudouxensis and N. murciensis) as well as the Early Miocene described species (N. aquitanica, N. janoscheki).

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This communication deals with the less known research activities on Palconlology by Octávio da Veiga Ferreira, since just after he became a member of the staff of the Serviços Geológicos de Portugal. These activities lasted for about 25 years (1951-1975, eventually up to 1987). Besides much field and laboralory work, Veiga Ferreira produced (alone or in collaboration} 38 papers. These concern vertebrates, echinoids, pectens and other molluscs, and malacostraca, as well as some papers of a more general or divulgation character. Studied fossils range from Jurassic to Quaternary, and from continental Portugal to Santa Maria Island (Azores), the Madeira Archipel and Angola. Veiga Ferreira is author of much valid work. He generously helped others as well. A bibliography for his paleontological papers is provided.

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This paper describes a high-resolution stratigraphic correlation scheme for the early to middle Miocene Lagos-Portimão Formation of central Algarve, southern Portugal. The Lagos Portimão-Formation of central Algarve is a 60 m thick package of horizontally bedded siliciclastics and carbonates. The bryozoan and mollusc dominated biofacies is typical of a shallow marine, warm-temperate climatic environment. We define four stratigraphic marker beds based on biofacies, lithology, and gamma-ray signatures. Marker bed 1 is a reddish shell bed composed predominantly of bivalve shells in various stages of fragmentation. Marker bed 2 is a fossiliferous sandstone / sandy rudstone characterized by bryozoan masses. Marker bed 3 is also a fossiliferous sandstone with abundant larger foraminifers and foliate bryozoans. Marker bed 4 is composed of three distinct layers; two fossiliferous sandstones with an intercalated shell bed. The upper sandstone unit displays thickets of the bryozoan Celleporaria palmate associated with the coral Culizia parasitica. This stratigraphic framework allows to correlate isolated outcrops within the stratigraphic context of the Lagos-Portimão Formation and to establish high resolution chronostratigraphic Sr-isotopic dating.

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The sub-fossil fauna from the Late Quaternary marine deposits of Santa Maria is made of more than 50 species of gastropods and bivalves, 19 of them collected recently and for the first time in the northern coast of the island (Lagoinhas Bay). The sub-fossil shells are found in deposits of beach sands, situated 2-3 meters above the present low tide. The carbonated sands from the basal part of the succession yield an autochthonous association of borers dominated by the bivalve Myoforceps aristata (Dillwin, 1817). Upwards, the marine sands contain concentrations of beach drift shells, including well-preserved supratidal and intertidal gastropods, among them a large number of Rissoidae. The bivalve fauna is dominated by disarticulated valves of Ervilia castanea (Montagu, 1803), a small infaunal coloniser of mobile sandy substrates. The composition of the fauna is made essentially of West European species, many of them common to the West Coast of Portugal. However, a few "warm guests" with West African or Caribbean affinities were also found, suggesting a close relation with some of the "Tyrrhenian" warm associations found in the Western Mediterranean.

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Silveirinha, a rich site for mammals and other vertebrates, yielded some molluscs, charophytes and ostracods. The latter are described here. Eight species were recognized. Two of them, Ilyocypris lusitanicus n. sp. and Cypris silveirinhaensis n. sp. are new. Other, unnamed species may be ascribed to Cyclocypris? and Cypria? besides a further four undeterminate Cypridacea. The Ostracod association is typical for limnic environments and is compatible with intertropical conditions. Cypris silveirinhaensis suggests an Eocene, and especially a lower Eocene age.

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Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente – Perfil Engenharia Ecológica

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Dissertação para obtenção do Grau de Mestre em Tecnologia e Segurança Alimentar