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Fossil mollusk association from Isabela Island (Galápagos, Ecuador)
No full textIn this paper a fossiliferous assemblage coming from Puerto Villamil (Isabela, Galápagos) is examined. The sandy sediments chiefly contain a molluscan association besides arthropod pincers, spicules of siliceous sponges, sea urchin spines, barnacle plates, rare foraminifers and abraded fragments of corals and briozoa. The mollusk assemblage represents a subtidal community associated with coral reefs and is dominated by Panamic forms. The modern aspect of this fauna and the radiometric ages till now proposed suggest a Pleistocene age for the Villamil deposits, although the presence of the extinct species Pegophysema spherica, for the first time reported from Isabela, might indicate a Pliocene age
First cetacean fossil records from Ecuador, collected from the Mioocene of Esmeraldas Province
No full textCetacean fossils from Ecuador are reported for the first time on the basis of fragmentary remains referred to odontocetes, collected during our investigations of Neogene stratigraphic sequences out-cropping along the northern coast (Esmeraldas Province). One specimen was collected near Las Peñas village in the Lower-Middle Miocene sediments of the Viche Formation and consists of ear bones and mandibular fragments for sure belonging to Ziphiidae. It represents the oldest record of this family in the southeastern Pacific and one of the few records of this family in South America. The other fossil was collected near Rio Verde village in the Upper Miocene sediments of the Angostura Formation and consists of an isolated tooth exhibiting some ziphiid affinities
Paleontological and sedimentological observations on the Canoa Formation
No full textA succession of 150 m thick sediments, belonging to the Canoa Formation, was studied. Some specifications on past contradictory descriptions of the formation are provided. These sediments consist of a cycle of the first order and outcrop along the coast, south of Manta (Ecuador), between Punta Canoa and Quebrada El Mangle and have been attributed to a Late Pliocene age (Globigerinoides fistulosus Zone). The fossil assemblages are very rich and well differentiated: foraminifers, molluscs and otoliths (the latter being observed for the first time in this formation). On the basis of lithology and of sedimentologic and paleontologic characteristics, offshore/shoreface environments with foreshore episodes were recognized and a hypothesis for a possible geological evolution of the area was suggested
Paleontological and sedimentological observations on the Canoa Formation (Manabí Basin, Ecuador)
No full textPaleogene and Neogene foraminiferal biostratigraphy of the Monferrato and Epiligurian Succession (Northern Italy) - a synthesis of the most recent proposals
No full textPaleoecology and paleobiogeography of fossil mollusks from Isla Isabela (Galápagos, Ecuador)
No full textSandy sediments outcropping near Villamil (Isla Isabela, Galapagos) have yielded a fossil molluscan assemblage represented by 42 taxa (23 bivalves and 19 gastropods) and dominated by the lucinids Divalinga eburea and Pegophysema spherica. The paleocommunity developed on a inner subtidal sandy bottom no deeper than 30-40 m and located near reef habitats; the clear predominance of suspension over deposit feeders is in accordance with the sandy substrate, limiting the organic matter preservation in the seafloor. Although the presence of the fossil bivalve P. spherica might indicate a Pliocene age, the modern structure of the fauna and scant radiometric ages proposed to date seem to suggest a Pleistocene age. A biogeographic analysis highlights a large predominance of the Panamic component; the remaining mollusks include a significant endemic component and negligible percentages of forms from neighboring bioprovinces. Other than some differences in percentages, a similar biogeographic pattern results for the other fossil molluscan communities and the modern one of the archipelago. From a taxonomic point of view, most of the fossil and modern assemblages show a high ratio of gastropods to bivalves, whereas in the fauna discussed herein, bivalves are slightly predominant over gastropods
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