1.1 – The zone, as defined in marine biostratigraphy, can not be identified dealing with continental faunas which have point distribution in space and time. Local Faunas are thus recognized in continental faunal sequences. Similar Locail Faunas make up a Faunal Unit which is defined by a type Local Fauna. Groups of Faunal Units form « Mammal Ages ». Boundaries among units can not be established and new units can be added in between.
Continental biostratigraphic criteria were discussed by Tedford, 1980 and Azzaroli, 1982. Tedford envisages Vertebrate Units as chronological entities drawn out of the embedding sediments, thus conceptually distinct from marine units that consist in rocks characterized by their paleontological content. There is no conceptual difference between biozone and faunal units since both are distinguished by the fossil content of rock bodies that are the expression of geologic time. The only but true difference is that the zone corresponds to a sedimentary continuum which enables the individuation of boundaries as physically existing surfaces. Faunal Units, instead, are not a sedimentary continuum in space and time, so boundaries are very difficult or, more often, impossible to be discriminated. Therefore correlations between continental and marine faunal sequences consist in projecting time segments, represented by the continental units, on the marine biostratigraphic scale.
1.2 – Still great confusion exists with regard to the established continental stratigraphies. Biostratigraphic scales in which faunal zones are distinguished by means of marine biostratigraphic statements applied to continental stratigraphy have been worked out. These subdivisions give a misleading impression of a continuous succession of faunal intervals.
2.1 – In the Italian Villafranchian « Mammal Age », the Triversa, Montopoli, Olivola, Tasso and Farneta Units can be distinguished. Other Italian local faunas, older and younger than the Villafranchian, can not stili be arranged in well defined faunal units. The pre-Villafranchian Local Faunas are Baccinello V3, Il Casino (upper lacustrine complex), Val di Pugna; the post-Villafranchian fossiliferous localities are far more numerous, but the exact chronological succession of most of them is still hard to establish.
The chronological gap between the Montopoli Unit and the Olivola Unit is covered by several French local faunas, such as Saint Vallier, Le Coupet and Chillac. Also the fauna of Tegelen, Holland, seems to be older than the one of Olivola. The Valle del Sacco and Collepardo (Anagni) fossil could stratigraphically be close to those of Saint Vallier.
2.2 – Baccinello V3 (Grosseto). The assemblage is characterized by Turolian (Tortonian p.p. – Messinian) forms together with elements that testify younger immigration events. Particularly meaningful is the occurrence of a leporid, indicated as aff. Hvpolagus, of a tapir and of a rhinoceros ascribed to Dicerorhinus  cf. megarhinus. The tapir testifies a return to umid climate as that of the Lower Ruscinian. The Baccinello V3 fauna represents the end of endemic conditions in Southern Tuscany and the final connection to the European continental area. Because of the association Baccinello V3 resembles Spanish, Libyan and South African local faunas that seem referable to the transition between the Turolian and the Ruscinian. Lorenz, 1968, assigns a Messinian age to the V3 level but the stratigraphy of Baccinello is still uncertain. Many correlations allow us to believe a correspondence of V3 with an initial phase of the marine Pliocene most probable.
2.3 – Il Casino – upper lignitic complex – (Siena). The faunal assemblage is poor; therefore detailed correlations with local faunas of the Mediterranean area are quite difficult. A Lower Ruscinian Age as that of the Montpellier Unit of Southern France can be inferred by the occurrence of Parabos cordieri and Sus minor, joined up with Tapirus arvernensis. The finding of Exaprotodon suggests a slightly older age than that of Montpellier. The relations with Baccinello V3 deserve deeper examination. Il Casino mammal deposits lie on gypsum beds ascribed to the Messinian or to part of it and underlie marine sediments assigned to the Globorotalia puncticulata Zone.
2.4 – Val di Pugna (Siena). The mammal fauna is very poor; anyhow the occurrence of Alephis lyrix and of a sirenid Felsinotherium gervaisi, more evolved than the Montpellier species, F. serresi, makes the correlation with the Perpignan Unit of Southern France most reliable. The mammal bearing marine sediments are referable to the Globorotalia puncticulata Zone. Suc, 1982, deems the Moltpellier and Perpignan faunas as belonging to a geologie horizon correlatable with the lower part of the Globorotalia crassaformis Zone. Taking in account also the stratigraphical data relevant to the following mammal units we believe more reasonable correlating the Perpignan Unit with the G. puncticulata Zone.

Significant macromammal local faunas between the Val di Pugna fauna and the following Triversa Unit faunal assemblage lack in Italy.
2.5 – Triversa Faunal Unit. The fauna comes from several sites along the Triversa and Triversola valleys nearby Villafranca d’Asti. Also the Local Faunas of Gaville and of the lignite mine of Santa Barbara, Upper Valdarno, of Barga and of Pieve Fosciana, in Garfagnana, and of Spoleto can be included into the Triversa Unit. Even the faunas of French localities, such as Vialette and Les Etouaires are surely referable to this same Faunal Unit. Baudet, Donville and Michaux assign to Vialette a radiometric age of 3.3 m.y. or younger, and anyhow not more recent than 2.6 m.y. In this lapse of time the paleomagnetic scale shows two negative events, Mammoth and Kaena, both comprised in the chrono-Gauss interval. Lindsay, Opdyke and Johnson, identified such negative events in the sediments that outcrop at one of the Triversa localities, Fornace RDB. Big size mammals suggest an increase of the forestal degrading that already began in the upper part of the previous unit. Such environmental alterations are well correlatable with the first climate cooling that took place about 3 m.y. ago. The Triversa continental deposits lie over, or, at least in part, laterally to the Pliocene marine sands of « Astian » facies that outcrop in the Asti area. Nearby Valleandona the occurence of Uvigerina cf. rutila was pointed out in a clayey level that underlies the « Astian » sands.
This Foram becomes extinct at the end of the G. puncticulata Zone in the Mediterranean basin. This datum also does not contradict the 3 m.y. assigned to the Triversa Unit.
2.6 – Montopoli Faunal Unit. It is essentially represented by the Montopoli (Pisa) Local Fauna, which must be considered the type fauna of the Unit. The Unit is characterized by the appearance of Equus and Mammuthus, while Zigolophodon and Tapirus seem disappeared. All this denotes a further forestal degrading and a marked increase of open spaces. The sediments that enclose the Montopoli mammals can be referred to the Middle Pliocene of Italian authors, that is to the Globorotalia crassaformis Zone.
According to several authors, the Triversa and Montopoli Units make up the Lower Villafranchian « Mammal Age ». However, because of their strong faunal change, faunal change clearly detectable at least in all Eurasia, it is advisable not to group these two Units into the same super-unit.
2.7 – Olivola Faunal Unit. It is characterized by the type Local Fauna collected at Olivola (Val di Magra) in an individual pocket of a fluvial deposit with thick gravel lenses. At Olivola, Canis etruscus and Pachycrocuta brevirostris are met for the first time in Italy. Some Upper Valdarno fauna were referred to the Olivola Unit; however, these are generally fossils of old collections with hagy indications relevantly to the collecting areas and without any geological reference. A Local Fauna that follows modern collecting criteria is that of Matassino; it is well correlable with the Olivola fauna. In order to date the Olivola unit, the fauna of Tegelen (Holland) should be taken under examination. The latter comes from clays with a Tiglian floral assemblage that comprises the Olduvai paleomagnetic event. The lack of genus Canis and of P. brevirostris, together with a higher primitivity of Mammuthus meridionalis and of Leptobos in the Tegelen fauna, lead to believe Olivola more recent. The migration of the dog and of the big hyaena could thus be related to the climatic cooling testified by the Eburonian flora that immediately follows the warm Tiglian phase.
2.8 – Tasso Faunal Unit. Only recently at Casa Frata near Terranova Bracciolini (Arezzo) a rich well representative fauna of the Tasso Unit assemblage was found. Therefore, the fauna of Casa Frata should be chosen as type Local Fauna of the Tasso Unit. The fauna novelties as a whole testify the persistence of degraded climatic conditions as those of the Eburonian phase. Thus the Tasso Unit is assumed correlatable with some interval of the upper part of the Globigerina cariacoensis Zone.
2.9 – Farneta Faunal Unit. This unit is not yet fully defined. It is used as gatherer of a group of faunas that come from various Italian localities (Selvella, Mugello, Imola, Crostolo, Leffe p.p., Gargano) that can generally be ascribed to the most recent phase of the Villafranchian. We can not tell if the Farneta Unit is still in the Eburonian phase or in a younger time. Mammals collected at Imola in littoral sediments overlying Hyalinea baltica bearing levels are referable to this unit. We can anyhow deem the Farneta Unit placed in a pre-Jaramillo phase since the French deposit of Le Vallonnet, characterized by a more modern fauna, showed a normai magnetisation referable to the Jaramillo event.
2.10 – Faunas just younger than those of the Farneta Unit are little known in Italy at present. The faunal renewal seems to pass through 3 following phases in which a progressive impoverishment of the Villafranchian facies components takes piace. In the first phase advanced Allophaiomys forms persist (Cava Sud and Viatelle near Verona, Monte Peglia in Umbria); the faunal assemblages are comparable with that of Le Vallonnet, mentioned above. In the second phase a micromammal fauna occurs devoid of Allophaiomys, with Mimomys savini and with macromammals mostly renewed but still with Villafranchian facies forms. The Italian Local Fauna that better exemplifies this second moment is that of Slivia. In the third phase the immigration of Arvicola takes piace; the Villafranchian facies forms are negligible. The Isernia fauna is typical of this period; radiometric dating and paleomagnetic surveys agree in assigning an age slightly older than 0.7 m.y.
In conclusion most of the faunal renewal in Italy seems to have occurred between 1.0 and 0.7 m.y. consistently with the Menapian cooling phase.

Download Article