PALAEOECOLOGIC AND PALAEOBIOGEOGRAPHIC CHARACTER OF MIDDLE PLIOCENE NON-MARINE MOLLUSC FAUNAS FROM NORTH-WESTERN ITALY

Significant new records of rich Middle Pliocene nonmarine mollusc assemblages from the Piedmont basin (North-western Italy) have led to an update of the systematic position of some taxa known since the end of the 19th century. The recorded molluscs come from deposits belonging to the San Martino unit in the "Villafranchian type-area" (Villafranca d’Asti) and to Cuneo and Alessandria districts. Vertebrate remains referred to the Middle Pliocene Triversa Faunal Unit (Mammal Neogene zone MN16a) are often associated with molluscs. A detailed palaeoecologic and palaeobiogeographic picture of the Middle Pliocene aquatic and terrestrial mollusc faunas is outlined. The assemblages are characterised by a high degree of species diversity and by the dominance of land prosobranchs and pulmonates. The palaeoecologic character is related to the different sedimentary facies recognised in the lithostratigraphic units: hygrophilous land faunas in paleosols and dominant aquatic taxa in lacustrine-palustrine sediments. Thermophilous swampy and forest taxa point to warm-temperate and humid climate conditions. A high number of extinct taxa and a high rate of endemism are underlined. A Mio-Pliocene Central-western European origin is noticed for many species. In the Middle Pliocene a spreading of some terrestrial species took place from North-western Italy towards Central Italy. Some new extinct taxa, belonging to the families Aciculidae (Renea sp. 1) and Clausiliidae [Monoptychia (subgen. n.) sp. 1; Neostyriacasp. 1; Fusulus (Fusulus) sp. 1], are identified

THE MOLLUSCAN ASSEMBLAGES IN THE FLUVIO-LACUSTRINE SUCCESSION OF THE PLIO-PLEISTOCENE MUGELLO BASIN (TUSCANY, ITALY)

New geologic studies on the fluvio-lacustrine Mugello Basin (Florence, Italy) stimulated a revision of the continental molluscan assemblages known since the last century. The fluvio-lacustrine succession has been subdivided in four synthems composed of fluvio-lacustrine (Torrente Ensa synthem, STE) and alluvial deposits (Scarperia, Luco di Mugello and Sagginale synthems). Two progressive angular unconformities in the STE allowed to distinguish three depositional sequences (S1, S2 and S3) composed of fan-delta gravels and sands, lacustrine silty clays (S1 and S2) and alluvial-fan gravels and sands (S3). Molluscs have been collected in various localities where S1 and S2 fan-delta and lacustrine deposits are exposed. The paleoecologic analysis of the molluscan assemblages is in accordance with the fluvio-lacustrine environment inferred from facies analysis. Different types of humid habitats, ranging from swamps, ponds, to channel-related environments (banks, leeves etc.), and open woody habitats have been recognized. The presence of Villafranchian extinct taxa such as Prososthenia oblonga, Emmericia cf. umbra and Tournouerina belnensis is in general agreement with the vertebrate fauna collected in the fluvio-lacustrine deposits since the last century and referred to the Tasso and Farneta faunal units (Late Villafranchian). A detailed integrated analysis of a 15 m thick gravelly-silty facies section of the S2 sequence reveals alternating depositional conditions in the subaerial portion of the fan deltas. Following a relative rise of base-level (i.e the lake level) flood-channels were disactivated with the formation of a floodplain-like environment dominated by fine-grained deposition, where localized poorly-drained areas created favourable habitats for molluscan taxa loving humid conditions. The sourrounding zones were characterized by open forests inhabited by terrestrial taxa. Low-magnitude, overland flows mixed the molluscan faunas of the different biotopes. The cyclic arrangement of gravels and silty clays reflects high-frequency uplift/denudational cycles during which biotopes for the molluscan fauna were alternatively activated.   SHORT NOTE

THE SECTION OF TORRE PICCHIO (TERNI, UMBRIA, CENTRAL ITALY):A VILLAFRANCHIAN SITE RICH IN VERTEBRATES, MOLLUSCS,OSTRACODS AND PLANTS

Fluvial deposits of the S. Maria di Ciciliano Formation crop out near Montecastrilli (Terni), in the southwestern branch of the Tiberino Basin.  Many specimens of plants ("mummified" woods, fruits and seeds), freshwater molluscs, ostracods, vertebrate bones and coprolites were collected at Torre Picchio. This small outcrop contains a fairly rich record of fruits and seeds, among which about 50 species were identified; the most frequent invariably belong to submerged, floating and emergent aquatic herbs, possibly because these were buried not far from their place of growth, thus representing the ancient local vegetation.  The fruits and seeds of woody plants, including several exotic elements, were transported from neighbouring areas and indicate a paleoclimate similar to the present day, though slightly wetter.  Among molluscs, three distinct assemblages were found, indicating fluvial, swampy and lacustrine environment, respectively.  They contain taxa of biochronological interest, most of them typical of Early Pleistocene deposits (late Villafranchian), but making their first appearance in the Late Pliocene (Middle Villafranchian). One species, Margarifera (Pseudunio) auricularia, represents the oldest record everywhere, since it was known, so far, only from the Middle Pleistocene upwards.  As palaeoenvironmental indicators, the ostracods complete the information given by molluscs.  Vetrebrates are represented by large and small mammals, rare birds, reptiles, amphibians and some fishes.  A great number of coprolites was collected as well.  The mammal assemblage shows affinities with the Costa S. Giacomo and Olivola F. U. (Middle and Late Villafranchian, Late Pliocene). Mimomys medasensis, an Iberoccitane element, is signaled for the first time in Italy.  From the geological point of view, the S. Maria di Ciciliano Fm. is interfingering with the marine Chiani-Tevere Fm., which is mostly Santernian in age and lies unconformably on the Middle Pliocene cycle. Only in some areas representing a structural low, the continuous transition between the lower portion of this unit and Late Pliocene deposits may be observed before the heteropic episodes.  This fact suggests some inconsistencies between chronostratigraphy and biochronology in the examined area because some taxa indicate a latest Pliocene age.  A heterochrony in the extinction of some species of plants and animals is suggested as a possible solution to the problem.&nbsp

Late Messinian mollusks and vertebrates from Moncucco Torinese, north-western Italy. Paleoecological and paleoclimatological implications

The systematic analysis of more than 20,000 fossils (Vertebrata and Mollusca), recovered from the post-evaporitic Messinian (5.41-5.33 Ma) succession of Moncucco Torinese (NW Italy), resulted in the identification of 90 vertebrate and 65 mollusk taxa that provide additional information about the paleoecological context and the paleoenvironmental settings of NW Italy slightly before the Mio-Pliocene boundary. Our analyses indicate a landscape dominated by open woodlands within a mosaic environment also including closed canopy forests, grasslands, rocky outcrops and limited water edges. The wide spectrum of habitats may have had a prominent role in determining the high paleobiodiversity observed in the paleocommunity of Moncucco Torinese. Slight variations in the abundances of the most common rodent species over the investigated succession are probably related to local changes in the paleolandscape. From a paleoclimatic point of view, the overall information provided by the fauna indicates mesic conditions in a subtropical climate, which is also consistent with the interpretation derived from paleobotanical and sedimentological analyses for the latest Messinian of Northern Italy