BIOCHRONOLOGY OF TERRESTRIAL MAMMALS AND QUATERNARY SUBDIVISIONS: A CASE STUDY OF LARGE MAMMALS FROM THE ITALIAN PENINSULA Maria Rita Palombo Dipartimento Scienze della Terra Università La Sapienza, CNR, Istituto di Geologia Ambientale e Geoingegneria, P.le Aldo Moro, 5 00185 Roma, Italy. E-mail: mariarita.palombo@uniroma1.it ABSTRACT: Palombo M.R., Biochronology of terrestrial mammals and Quaternary subdivisions: a case study of large mammals from the Italian peninsula (IT ISSN 0394-3356, 2009). Defining and subdividing the Quaternary on the basis of the mammalian fossil record from the continental realm is not a simple task due to the low degree of succession continuity and the scattered palaeontological evidence. Moreover, even if the approaches to the Quaternary are basically interdisciplinary and may combine many different chronological scales, establishing correlations between biochronology, biostratigraphy, chronostratigraphy, climatostratigraphy, and composite regional stratigraphy can often be very proble- matical. As far as biochronology is concerned, the marked geological, environmental and climatic diversity affecting different conti- nental regions makes a correlation based on biological events difficult. Indeed, “biochronological units” represent a time span during which faunas have a degree of taxonomic homogeneity and the corresponding “faunal complexes” have to be regarded as non- over- lapping and "ecologically adjusted groups of animals with specific geographic limits and chronological range" (TE D F O R D, 1970). Nevertheless, the stratigraphic lowest and highest occurrences of fossil remains (stratigraphic datum) within a given geographical area do not necessarily correspond to their actual first/last appearances (palaeobiological events) in time. This is due to diachroneity in palaeobiological events (i.e. local first and last appearances are strictly linked to dispersal, and the physical and biotic factors causing local evolution and extinctions) coupled with discontinuity in the continental sedimentary record, the rarity of deposits formed in a regime of virtually continuous sedimentation, the presence of important ecological barriers (that prevent some taxa from dispersing), environmental conditions (that affect the structure of palaeocommunities), and taphonomic and sampling biases. As a result, ongoing research, continuously yielding new data, make chronological frameworks thus far outlined, even if recent, open to significant impro- vements, and causing biochrons to be updated. This fact prevents any detailed biochronological framework from having widespread geographical significance. Thus, only higher ranking biochronological units (Land Mammal Ages, LMAs) - whose separation is based on palaeobiological events which have a wide territorial significance - could be useful for chronological correlations. Nonetheless, the transition between successive LMAs does not always correspond to the boundaries separating marine Series or Stages. For instance, the Villafranchian LMA approximately began with the Late Pliocene (Piacentian) and the transition from the early to the middle Villafranchian LMA happened around the Pliocene/Pleistocene (Piacentian/Gelasian) boundary, whereas the transition to the late Villafranchian took place during the latest Gelasian, and those from the Villafranchian to Galerian LMA and from the Galerian to Aurelian LMA respectively predated the beginning of the Middle and Late Pleistocene. RIASSUNTO: Palombo M.R., Biocronologia dei mammiferi terrestri e suddivisioni del Quaternario: l’esempio della faune a grandi mammiferi della penisola italiana. (IT ISSN 0394-3356, 2009). Definire e suddividere il Quaternario sulla base del record fossile dei mammiferi continentali non è un compito facile ed anche se gli approcci al Quaternario sono fondamentalmente interdisciplinari e tendono a combinare diverse scale cronologiche, stabilire correla- zioni tra biocronologia, biostratigrafia, cronostratigrafia, climatostratigrafia, e stratigrafia regionale è spesso problematico. Sebbene le unità basate su eventi biologici e climatici siano di largo uso nel Quaternario continentale, il loro status non è stato formalmente definito e questo alimenta dubbi nell’approccio metodologico e confusione tra teoria (dato Paleobiologico) ed operatività (dato stratigrafico). Dal punto di vista teorico, le " unità biochronologiche" rappresentano un lasso di tempo durante il quale le faune locali hanno un certo grado di omogeneità tassonomica ed i "complessi faunistici” che caratterizzano le singole unità devono essere considerati “non-over- lapping and ecologically adjusted groups of animals with specific geographic limits and chronological range" (TEDFORD, 1970). Tuttavia, l'’evidenza stratigrafica della prima e ultima presenza di un fossile nelle successioni affioranti in una determinata area geografica (dato stratigrafico) non corrisponde necessariamente all’effettiva prima e ultima comparsa di quel taxon nel tempo (evento paleobiologico). Ciò si deve alla diacronicità degli eventi paleobiologici (ad esempio gli eventi locali di comparsa e scomparsa sono strettamente legati rispettivamente alla dispersione ed ai fattori fisici e biotici che regolano diffusione ed estinzione), alla discontinuità del record sedimen- tario continentale, alla rarità di depositi formati in regime di sedimentazione continua, alla presenza di barriere ecologiche (che limita o impedisce la dispersione di alcuni taxa in certuni territori), alle condizioni ambientali locali (che influenzano la struttura delle Paleocomunita), a problemi tafonomici e di campionamento. Questi limiti rendono instabili schemi biocronologici dettagliati basati su un record fossile regionale, in quanto essi sono fortemente dipendenti dal progredire delle conoscenze sul campo. Fin dalla prima introduzione delle unità faunistiche (FUs) (Azzaroli 1977), sulle quale si fonda la biocronologia dei grandi mammiferi della penisola italia- na, il progredire delle ricerche e la scoperta di nuove faune ha portato sia alla ridifinizione e/o eliminazionedi alcune FUs sia alla crea- zione di nuove. Ne consegue che, proprio in funzione della possibilità di discriminare singoli bioeventi, ogni schema biocronologico delle faune italiane risulta quanto più dettagliato tanto meno stabile nel tempo, nonché difficilmente confrontabile con gli schemi pro- posti per l’Europa continentale. In realtà, l’utilizzo di unità biochronologiche di più alto rango (Land Mammal Age, LMA) - la cui separa- zione è basata su eventi paleobiologici validi a grande scala e cambi di struttura dei complessi faunistici – meglio si presta a correlazio- ni su vasta scala. La transizione tra successive LMA, tuttavia, non sempre corrisponde ai limiti che separano Serie e Stadi. Per esem- pio, il Villafranchiano inizia con il Pliocene superiore (Piacenziano), la transizione al Villafranchiano medio potrebbe coincidere grosso modo con il limite Pliocene/Pleistocene (Piacenziano / Gelasiano), ma il passaggio al Villafranchiano superiore avviene nel tardo Gelasiano, e le transizioni Villafranchiano/Galeriano e Galeriano/Aureliano precedono, rispettivamente, l'inizio del Pleistocene medio e superiore. Key words: Biochronology, Biostratigraphy, Plio-Pleistocene, Large Mammals, Itay. Parole chiave: Biocronologia, Biostratigrafia, Plio-Pleistocene, grandi Mammiferi, Italia. Il Quaternario Italian Journal of Quaternary Sciences 22(2), 2009 - 291-306 292 M.R. Palombo 1. INTRODUCTION Defining and subdividing the Quaternary on the basis of the mammalian fossil record from the continen- tal realm is not a simple task due to the low degree of succession continuity and the scattered palaeontologi- cal evidence. Moreover, even if the approaches to the Quaternary are basically interdisciplinary and can com- bine many different chronological scales, establishing correlations between biochronological, chronostrati- graphical, climatostratigraphical frames and composite regional stratigraphy can be problematical (concerning Italy, see e.g. DE GI U L I et al., 1983; RA V A Z Z I, 2003; PA L O M B O, 2004a; PA L O M B O & SA R D E L L A, 2007 and refe- rences therein). With regard to terrestrial fauna, especially mam- mals, diachroneity in palaeobiological events coupled with discontinuity in the continental sedimentary record, the rarity of deposits formed in a regime of virtually continuous sedimentation, the presence of important ecological barriers (that prevent some taxa from dis- persing), environmental conditions (that affect the structure of palaeocommunities), and taphonomical and sampling biases make the definition of isochronous boundaries, maybe of boundaries themselves, prob- lematical. Therefore, any biochronological framework is predisposed to change depending on new discoveries. During the latter half of the last century, study on the terrestrial mammals of the Italian peninsula was developed mainly on the basis of large-sized mam- malian taxa. The Italian mammal biochronological framework builds on the pioneering work of Azzaroli (AZZAROLI, 1977, 1982), who first introduced the “Faunal units”(FU’s) as “biochrons”, defined on the basis of all the species from selected local faunal assemblages (LFA’s). Like Land Mammal Ages (LMAs) which are the primary unit of North American vertebrate chronology (see TEAFORD,1970; LINDSAY & TEDFORD, 1990), FU’s rep- resent and are defined by typical associations of mam- malian taxa (biological entities), each living in non-over- lapping slices of time. As suggested by Lindsay (2003, pg. 222) for LMA’s, FU’s could be defined as “a rela- tively short interval of geological time that can be rec- ognized and distinguished from earlier and later such units (in a given region or province) by a characteristic assemblage of mammals”. Although sometimes criti- cised (e.g. GUERIN, 1982, 1990), FU’s are general con- cepts, especially used by the Italian scientific communi- ty. Since the time of the FU’s introduction, Italian palaeontologists have proposed new or revised some FU’s/LMA’s (see e.g. DE GIULI, et al. 1983, TORRE, 1987; AZ Z A R O L I et al., 1988; SA L A, et al., 1992; TO R R E, et al. 1992; CALOI & PALOMBO, 1990, 1996; GLIOZZI et al., 1997, PE T R O N I O & SA R D E L L A, 1999; PA L O M B O et al., 2004; PALOMBO, 2004a, 2007a; MASINI & SALA, 2007; PETRONIO et al ., .2 0 0 7 ) ( T abl e 1 ) . T h e i n t ro du c ti o n of n e w biochrons mainly depends on acquiring new data and discovering new fossiliferous assemblages, which makes possible, by means of ever more detailed bios- tratigraphical settings, increasingly accurate discrimina- tion between bioevents. This paper’s aim is to outline the pricipal prob- lems related to biostratigraphy/biochronology of large It a lia n ma mmal s, an d t o u pda t e t h e p rev i ou s biochronological schemes according to the most recent discoveries (Table 2.3). 2. ABOUT CHRONOSTRATIGRAPHY, BIOCHRO- NO LOG Y, B IOS TRA TIGR AP HY A N D RE LA TED ITEMS: A SHORT SKETCH As stated by Lindsay (2003) chronostratigraphy - the dominant method applied in the oceanographic- marine realm - and biochronology - the dominant method for the terrestrial realm - are the prime concep- tual methods for relating biological events to the geo- logical time scale. The chronostratigraphical concept was introduced by SCHENCK & MULLER (1941), who pro- pos ed a n ew ‘ ‘c h ro n os t r at ig rap h ical ’’ h i era rch y (System, Series, and Stage) for the stratigraphical rep- resent ation o f equiv alen t chr onolo gical in terv als (Period, Epoch, and Age). Recently, LINDSAY (2003, pg. 227) defined chronostratigraphy as: “the sequential ordering of geologic events, using biostratigraphic, iso- topic-radiometric, and paleomagnetic data”. The con- cept of biochronology dates back the beginning of the 2 0 th c en t u ry , wh en W I L L I A M S ( 1 90 1 ) d efin e d a “biochron” as the absolute time extent of a peculiar faunal or vegetal association. Later, TE I C H E R T ( 1 9 5 8 ) described biochronology as ‘‘the dating of geological events by biostratigraphical methods’’, but did not ch ar act er is e b io ch ro n o lo gi cal t e rms , s u c h as ‘‘biochronological unit’’, and concepts relative to the biostratigraphical ones. Due to that loose definition and to its ambiguous application, biochronology has never been discussed in any stratigraphical code (LI N D S A Y, 2003). Up to the present day, the operation of organis- i n g geological time on the basis of evidence provided by continental mammal faunas has continued to be a field plagued by interpretative and semantic confusion. BE R G G R E N & VA N CO U V E R I N G (1978, pag. 39) tried to avoid ambiguity defining biochronology as ‘‘the organi- zation of geological time according to the irreversible pr oces s of evo lut ion in th e o rganic con tin uu m’’. Su bs equ en t ly , L I N D S A Y (2 0 0 3 , pag . 2 2 7 ) def in ed biochronology as the “sequential ordering of biologic (and geologic) events, using morphologic differences that result from organic evolution (when applied to Earth history)”. On the other hand, it is widely known that the dis- cipline of biostratigraphy establishes the stratigraphi- cal ranges of the taxa remains within superimposed sections, and verifies the relative age of rocks using the fossil data. Biostrat igraphy is th e element of stratigraphy which focuses on “the distribution of fos- sils in the stratigraphical record and the organization of strata into units on the basis of their contained fos- sils” (SA L V A D O R, 1994, pag.55). But as claimed by SA L V A D O R ( 1994 , pag.55 ) biost rat igraphical units , including biozones, “vary greatly in thickness and geographic extent. ......The time they represent may likewise vary widely”. To avoid this issue, WA L S H (1998) defined the biochronostratigraphical units as “the sets of rock formed during biochrons, without ref- erence to any particular stratigraphic section”. As a result, a biochronological unit should be characterised and defined as a span of time defined by biological evidences (palaeobiological datum), while a biostrati- graphical unit as a body of rock strata defined by its fossil content (stratigraphical datum) (SC H O C H, 1989; SA L V A D O R, 1994). 293Biochronology of terrestrial mammals and quaternary subdivisions: ... 294 2.1. In search of a stable biochronological frame for the terrestrial large mammals: utopia or feasible undertaking? As defined above, “biochronological units” repre- sent a time span during which faunas are assumed to be characterised by taxonomical homogeneity and should be regarded as non- overlapping and an “eco- logically adjusted group of animals within specific geo- graphic limits and chronologic range” (TEDFORD, 1970). First/last appearan ce bioevents (palaeobiological events on which biochronology is based) have been the principal bases for establishing the chronological set- ting of continental mammalian faunas. However, the marked geological, environmental and climatic diversity affecting different continental regions, as well as the discontinuity in the continental sedimentary record, the rarity of deposits formed in a regime of virtually contin- uous sedimentation, the diachroneity in palaeobiologi- cal events (i.e. local first and last appearances are strictly linked respectively to dispersal, and the physical and biotical factors causing extinctions), taphonomical and sampling biases are responsible for the fact that the stratigraphical order of the highest and lowest occurrences (stratigraphical datum) of fossil remains of some taxa within a given geographical area, does not necessarily reflect the temporal order of the actual first/last appearances (palaeobiological events) of each taxon in time. Indeed, a stratigraphical discontinuity within a sedimentary succession (whether due to ero- sional phases or sedimentation lacking) corresponds to a time span during which palaeobiological events do not yield a stratigraphical record. Moreover, fossil remains of taxa characterising a given biochronological unit do not necessarily appear in each section because they were absent from the depositional environment for ecological or taphonomical factors. Therefore, the time range of a paleobiological entity (either in general or in a given geographical area) cannot be unquestionably established by its fossil evidence. The lowest and high- est stratigraphical records of a taxon, respectively cor- respond to the time “ante” or “post quem” when it actually originated and became extin ct (PA L O M B O 2004a). Accordingly, it should be appropriate to dis- criminate taxon longevity from time slice of its fossil record, e.g. first/last historical appearance bioevents (FHA/LHA = First/Last Historical Appearance) from “known data” of lowest and highest occurrences in a local stratigraphical section (LlSDk/HlSDk = local Lowest/Highest known Stratigraphical Datum) (WA L S H, 1998; PA L O M B O & SA R D E L L A, 2007). On the other hand, mammalian biochronology is actually founded on fossil records available in the continental rocks, FHA/LHA bioevents can only be inferred from the lowest/highest occurrences of fossil remains in fossiliferous levels, maybe based on more than one continental stratigraph- ical section. Hence, new discoveries may substantially change the chronological extent of already defined biochrons. Indeed, the finding of a/some taxon/a (whose LHA/LHA were already regarded as markers of a biochrons) in significantly older/younger extends the theoretical time range of such a biochron, without changing its theoretical definition. As a result, ongoing research, continuously providing new data, makes chronological frameworks thus far outlined, even if recen t, open to s ignificant improv emen ts. Some biochrons, consequently, will require revisions and updated definitions. 3. FAUNAL TURNOVERS, BIOCHRONS AND QUA- TERNARY SUBDIVISIONS During the Pliocene and Pleistocene a series of cli- matic cycles caused latitudinal displacements of vege- tation and biomes in Europe and exerted great influ- en ce o n disper sal and dispers ion of mammalian species. As a result, the composition of regional faunas changed because of origination/ extinction and disper- sal bio even t s . O n t h e I t alian p enin s u la, climat ic changes were a driving factor, at least as far as the two most important detectable faunal renewals are con- cer n ed: t h e Ear ly t o M idd le Vil la fra n ch ia n L M A (Piacentian to Gelasian, ~2.7–2.5 Ma) and Early to Mi ddl e G al eri an L M A, t r an s it i on ( l at es t Ear ly Pleistocene, ~1.1–0.8 Ma). Faunas changed also at the end of the Gelasian (Middle to Late Villafranchian tran- sit ion ) and at th e en d of t h e M iddle Pleis to cen e (Galerian to Aurelian transition), but to a lesser degree (PALOMBO, 2007b and references therein). 3.1 The beginning of the Villafranchian and the warn- ing signs of the already called “Glacial Pliocene” The list of early Villafranchian taxa have been established on a number of LFA’s from Piedmont (sev- eral localities in the Villafranca d’Asti area) and central Italy (e.g. Lower and Upper Valdarno, Arcille, Spoleto). Palaeomagnetic data at Fornace R.D.B. (Villafranca d’Asti) (LINDSAY et al., 1980, 1995) as well paleomagnet- ic calibration of the long sedimentary sequence out- cropping at Santa Barbara quarry (lignitic lacustrine silty clays and sands, Meleto clays of Castelnuovo dei Sabbioni Lower Synthem of the Upper Valdarno basin) (TORRE et al., 1996; BERTINI & ROION, 1997; NAPOLEONE et al., 2003; GHINASSI et al., 2004) illustrate that, at about 3.2 Ma, the faunal association regarded as typical of the early Villafranchian was already present on the Italian peninsula. The early Villafranchian LMA (Triversa FU) retains subtropical affinities typical of Ruscinian mammals, which lived during the Early Pliocene, the most recent interval with a climate definitively warmer than today. Pach y d er ms , mid dle s i zed Ar t io da ct y la, an d Perrissodactyla, mainly browsers or mixed-feeders inhabiting dense or clear forest, were still present along with arboreal/scansorial viverrids and arboreal omni- vo r es , s u ch a s Me sop it h ec u s mon s pess u la n u s, Parailurus hungaricus and Ursus minimus. On the other hand, the appearance of some taxa, such as Leptobos s t e n o m e t o p o n a n d St ep h an o rh i n u s je an vi re ti ( = Stephanorhinus elatus) (Table 3), perhaps more linked to wooded parkland environment, testified to a change in faunal structure which can be correlated with the cli- matic cooling, which occurred at about 3.2/3.1 (KM2 isotopic stage) (Table 2). 3.2 Early to Middle Villafranchian and the Piacentian to Gelasian transition The following Montopoli FU is based on rich fauna from a site near Montopoli (Lower Valdarno, Tuscany), M.R. Palombo 295 Table 2 - Integrated chronological scheme for the Middle Pliocene to Late Pleistocene large mammalian record of the Italian peninsula. Biochronology of terrestrial mammals and quaternary subdivisions: ... 296 found in a fossiliferous level at the top of a shallow- water marine sequence of Late Pliocene age (BENVENUTI et al., 1995), calibrated with the Gauss/ Matuyama tran- sition (LI N D S A Y et al. , 1980). The Montopoli FU should correspond to the MN16b zone and was traditionally included in the Early Villafranchian LMA (Table 1), but the marked faunal turnover characterising the transition from the Triversa FU to the Montopoli FU recommends reg ar di n g it as t h e bas al u n i t o f t h e Mi dd le Villafranchian (Caloi & Palombo 1990, 1996). The faunal renewal from Triversa to the Montopoli FU can be regarded as a true turnover phase, due to the high per- centage of last and new appearances, but also to the important structural changes in the faunal complexes, in both the herbivore and carnivore guilds. This is con- sistent with the significant global changes characteris- ing the Piacentian to Gelasian transition (actually the beginning of the Quaternary as proposed by several authors, see e.g. BOWEN & GIBBARD, 2007), with the per- manent ice-sheet growth in the Northern Hemisphere, the first major influx of ice-rafted debris in the middle latitudes of the North Atlantic, the onset of extensive loess deposition in China around the Gauss/Matuyama boundary (marine isotopic stage, MIS, 104 to 100) (see inter alios RU D D I M A N et al., 1989; DI N G et al., 1997; SHACKLETON, 1997; PARTRIDGE, 1997a, b; RIO et al. 1998; BO W E N & GI B B A R D, 2007 and recently ratified by the International Commission on Stratigraphy, GI B B A R D & HE A D, 2009), the profound changes in Eurasian flora assemblages (see inter alios ZA G W I J N, 1974; GR I C H U K, 1997; SU C et al., 1997). Bioevents behind this faunal change (e.g. the so-called “elephant-E q u u s e v e n t ” , Lindsay et al., 1980 ) likely occurred close to t he Piacentian- Gelasian boundary, driven by climatic cool- ing, as well as by the effects of changes in the Earth cli- mate system: 19-23 ka cycles were superseded pro- gressively by a 41-ka rhythm (orbital obliquity periodici- ty) accompanied by moderately increased amplitude climatic oscillations. The resulting increase in aridity and more intense seasonality triggered vegetation to reconstruct (SUC et al., 1995, and references in Bertini, 2003) and caused the disappearance of most forest- dwelling taxa, especially small carnivores and arboreal- scansorial taxa, whereas new large grazers (the horse Equ u s liven zoven si s) , mixed feeders ( a pr imitiv e Mammuthus meridionalis, the medium-size Gazella bor- b o n i c a) or even browsers (the deer Eucladoceros fal- coneri) appeared (Table 3). The taxonomical composition of the Montopoli FU resulted primarily from the dispersal, mostly from Eastern Europe, of large to medium-sized herbivores, while evolutionary substitutions within surviving phyletic lineages were rather negligible. The faunal change indi- cates that forests gradually gave way to more open environments (including A r t e m i s i a steppe), alternating with warm temperate deciduous forests (see Bertini, 2003). Indeed, from an ecological point of view, the Triversa faunal complex, which had a relatively high fre- quency of frugivores, developed in environments rather similar to those of modern forests, whereas the struc- ture of the Montopoli faunal complex shows some affi n it i es w it h t h o s e of mo de rn bu s h - w oo dl an d (P A L O M B O & G I O V I N A Z Z O, 2 0 0 6 , P A L O M B O 2 0 0 7 b ) . Moreover, this event can be considered as the begin- ning of a dispersal phase leading to a progressive increase in standing richness during the subsequent Pli o cen e an d u p t o t h e be gi n n in g o f t h e Ear ly Pleistocene. A temperate interlude occurred between 2.5 and 1.8 Ma; during this phase the Mediterranean climate was established permanently in southwestern Europe. A progressive faunal renewal took place, and some dis- persal/origination bioevents led to a moderate faunal structural reconstruction of late middle Villafranchian fauna. Two FU’s have been proposed as characterising this time slice, the “Saint Vallier” and the Costa San Giacomo FU (Table 1), but the Italian “Saint Vallier” FU is loosely defined as being based on sporadic finds of taxa that also occur in the LFA’s assigned to the Costa San Giacomo FU. Accordingly, the author is inclined to consider the Italian late middle Villafranchian LFA’S as belonging to only one FU. The “Costa San Giacomo” name is here retained despite the priority of “S a i n t Vallier”. This is because of the rich fossil record of the corresponding LFA (Costa San Giacomo, Anagni, Latium), as well to stress the significance of the appear- ance on the Italian peninsula of a wolf-like canid closely related to Canis etruscus (a primitive representative of this phyletic lineage might be already present in the early Villafranchian Vialette LFA, LACOMBAT et al., 2008). As here redefined, the Italian Costa San Giacomo FU should roughly correspond to the MN 17”zone”. The faunal composition is similar to that of the preceding u n it as re ga rd s t h e pr es en ce o f t ax a s u ch as “Pseudodama” lyra, Eucladoceros tegulensis, Gazella borbonica, or long-surviving taxa such as the cheetah, Acin o n yx pa rd in en s is, t h e h u n t in g h ya en a Chasmaporthetes lunensis and the proboscidean A . a r v e r n e n s i s , but renewed because of the first appear- ance, among others, of the middle-sized horse E q u u s stenonis, the goat Gallogoral meneghini, and the spiral horned antelope Gazellospira torticornis, all parkland dwellers, as well the large-sized and slender legged boar Sus strozzii. The presence in the Costa San Giacomo of Canis aff. C etruscus bears witness that the so-called “wolf- event” (AZ Z A R O L I 1983, 1995) was already in progress. The carnivore guild renewal was a gradual phenomenon (SARDELLA & PALOMBO 2007, PALOMBO et al., 2008), which developed throughout the latest Gelasian and the earli- est Calabrian and involved several large and middle- sized carnivores, such as the powerful scavenger, Pachycrocuta brevirostris, the jaguar-like P a n t h e r a gombaszoegensis (= Panthera onca toscana according to HEMMER et all., 2003), the cooperative foraging canid, Lycaon (Xenocyon) falconeri, as well the coyote-like (but see OL I V E, 2006) Canis arnensis (PA L O M B O et al. , 2008 and references therein). 3. 3 The Lat e Vi ll af ran chi an and the Ge la sia n- Calabrian boundary The latest Gelasian faunal renewal involved both carnivores and herbivores: most Pliocene and Early Gelasian species disappeared, particularly among her- bivores, and new carnivores and herbivores progres- sively appeared (Table 3). The renewal from the middle to late Villafranchian LMA, should be regarded as a dis- persal phase (more than an actual turnover), which developed before and after the Gelasian-Calabrian boundary, and came to an end during the earliest Early M.R. Palombo 297Biochronology of terrestrial mammals and quaternary subdivisions: ... Calabrian, (PA L O M B O, 2004b, 2007a, b). The dispersal phase primarily involved carnivores, since among new taxa none belong to species which evolved in loco, whereas new appearances among herbivores were principally linked to the emergence of new species within pre-existing phyletic lineages (e.g. M a m m u t h u s , Equus, Eucladoceros, “Pseudodama” and large bovids of subgenus Leptobos), and subordinately, to immigra- tion of large ruminants, mainly mixed feeders (e.g. Procamptoceras and Praevibos). These faunal changes indicate that forests or woodlands gradually gave way to more open en v iron men t s (in clu ding A r t e m i s i a steppe), but alternating with warm-temperate decidu- ous forests. The gradual faunal reconstruction from the latest Gelasian to Early Calabrian took form within an interval of climatic transition, and was possibly driven both by climatic worsening (moderate average cooling MIS 70 to58), and modification of internal competitive dynamics, the latter depending on the disappearances of some pre-existing key taxa and ensuing availability of ecological niches (PALOMBO, 2007b). After AZ Z A R O L I (1977) the late Villafranchian, at this time considered as coincident with the early Pleistocene (s e n s u AG U I R R E & PA S I N I, 1985), would include three FU’s: Olivola, T and F (Table 1). Subsequently, a more recent, fourth FU, Pirro was added, and the end of the late Villafranchian was dropped before the Jaramillo sub- chron (Table 1). LFA’s assigned to the Olivola and Tasso FU’s are well-known from the Upper Valdarno Basin, where fossil-bearing sediments of two stratigraphically superimposed units are exposed (DE GI U L I & MA S I N I, 1 9 8 7 ; TO R R E, 1987; AZ Z A R O L I et al., 1988). Magnetostrati- graphy of these fossiliferous stratigraphical successions provides chronological constraints for Olivola plus the Tasso FU: in the Upper Valdarno area, LFA’s assigned to the Tasso FU have been correlated to the top of the Olduvai subchron (NA P O L E O N E et al., 2003), which is around the GSSP of the Gelasian-Calabrian boundary (La Vrica Section; AG U I R R E & PA S I N I, 1985), whereas LFA’s of the Olivola FU (e.g. Matassino and Poggio Ros so LFA’s) are “inferred as pre-Olduvaian, not younger than 2.0 Ma.” (NA P O L E O N E et al. , 2003, pag. 308). The t ruct ure of th e faunal complexes of t he Olivola and Tasso FU’s are not very dissimilar, the latter being different essentially for the appearance, among others, of Lycaon (Xenocyon) falconeri (already present in the latest Pliocene Spanish fauna of Fonelas P-1, GA R R I D O, 2008), Equus stehlini (= Equus senezensis stehlini, according to ALBERDI et al., 1998) and the stout bovid Leptobos vallisarni. Praeovibos is also recorded in the Casa Frata LFA, whereas Gallogoral, Gazellospira a n d Procamptoceras were not reported (Table 3). The occurrence of Hippopotamus antiquus in the Tasso FU is doubtful, since hippopotamuses from Valdarno (already ascribed to the Tasso FU), was probably retrieved from fossiliferous layers younger than those of the Montervarchi succession (NA P O L E O N E et al., 2003). On the other hand, the occurrence in the same strati- graphical layer of H. antiquus and Leptobos aff. furtivus at Piano dei Cavalieri (Rieti basin, Latium) (MASINI 1989, GE N T I L I & MA S I N I, 2005), needs to be confirmed (see SE G R E N A L D I N I & V A L L I a n d r ef ere n ces t h e rei n ) . Accordingly, faunas assigned to OL I V O L A and TA S S O FU’s seem to be part of the same, progressive faunal renewal, and the hypothesis that they could represent a single FU cannot be ruled out. 3.4 The end of the Villafranchian LMA and the dawn of the Galerian LMA During the subsequent Early Pleistocene (Farneta, Pirro and Colle Curti FU’s) (Table 2) an important ren ewal of fau nas occu rr ed: mos t of t he t yp ical Villafranchian taxa disappeared or became rare while scattered bioevents led to the appearance of new species, either newcomers or ones evolved from pre- existing taxa (Table 3). The previously mentioned in cr eas e i n div er s it y t h r ou g h ou t t h e ea rl y l at e Villafranchian (mainly via migrations and dispersal events) had possibly altered the palaeocommunity equilibria, and climate changes possibly removed key- stone species causing new in tra- and inter-guild dynamics, leading mammalian communities to signifi- cantly reconstruct (PALOMBO, 2007b). This is the reason wh y, despite the progressive appearance of new species (most of which will survive in the early Middle Pleistocene), last appearances prevailed, leading to a progressive reduction in diversity from Farneta to Colle Curti FU’s (Table 3). 3.4.1 Farneta and Pirro FU’s Differences in taxonomical composition and struc- ture between Tasso and the following Farneta FU are mainly related to changes in the herbivore guild and mirror the spread of open environments due to the decreas e in average t emperatu re, along wit h t he increase in dryness (BE R T I N I, 2003; SU C & PO P E S C U, 2 0 05 ) . Fo r in s t an ce , r h in o cer o se s s i mil ar t o Stephanorhinus hundsheimensis were the possible eco- logical substitutes for Stephanorhinus etruscus. T h e larger, mixed-feeder Praemegaceros obscurus replaced the browser Eucladoceros, and a more specialised form replaced the mixed-feeder “Pseudodama” nesti. It is worth noting that BR E D A & MA R C H E T T I (2007) doubtfully reported ?Eucladoceros ex gr. ctenoides-dicranios and ?Megaloceros obscurus from the main brown coal level (subunit 5) of the biogenetic unit of Leffe Formation (Bergamo, Northern Italy), but the actual co-occurrence of these large deer needs to be fully substantiated. Among carnivores, Megantereon whitei, a saber-tooth cat of African origin, first appeared. The faunal renewal between the Farneta and Pirro FU (Table 2) is marked by the appearance of some arriving African taxa, such as the large H i p p o p o t a m u s antiquus (MAGRI et al., 2009), and (doubtfully) the cerco- pithecid T h e r o p i t h e c u s, a mixed-feeding genus whose extant species inhabits the high grasslands of Ethiopia and Eritrea (RO O K et al., 2004, but see PA T E L et al., 2007). This evidence of African immigration to south- ernmost Europe stresses the importance of “out of Africa” migratory waves, which occurred approximately around 1.6/1.3 Ma (MA R T I N E Z- NA V A R R O, 2004). Other immigrants had an Asian/European origin, as the ovi- bovine M e g a l o v i s and the rather stout bovine B i s o n (Eobison) degiulii, the latter replacing the slender lepto- bovines. Among perissodactyls, the middle-sized, slen- der limbed Eq uu s alt iden s an d th e larg er E q u u s s u e s s e n b o r n e n s i s were certainly present, whereas Equus stehlini is no longer recorded (see AL B E R D I & PALOMBO, in press for a discussion). Among carnivores the middle-sized bone crusher Canis mosbachensis first appeared and Lycaon (Xenocyon) lycaonoides sub- stituted the less advanced L. falconeri. The dispersal of 298 M.R. Palombo Homo in the Italian peninsula is testified by the finding of lithic implements in the karstic network of Pirro Nord, the local eponym of the Pirro FU (AR Z A R E L L O et al. , 2007). All in all, forest-dwelling taxa dwindled, whereas sp ecie s i nh a bit i ng pr air ies , s av an n a or st e ppes increased in percentage. The prevalence of dry and open environments at the time of the Pirro FU (and Colle Curti FU as well) is confirmed by the great struc- tural compatibility of these faunas with those of present day savanna/bushland habitats (PA L O M B O, 2007b). Nevertheless, forest areas were still rather abundant, and woodlands spread in the more temperate and humid climatic phases, as evidenced, for instance, by the presence of the browser moose Cervalces carnutu- r u m in the subunit 7 of Leffe Formation (Bergamo, Northern Italy) (BREDA & MARCHETTI, 2005, 2007), which deposited s hort ly befo re th e Jaramillo Subchron (MUTTONI et al., 2007). The occurrence at Pietrafitta (Umbria, central Italy) of a vole close to Microtus (Allophaiomys) ex gr. M. ruf- fo i, a nd o f Micro tu s (All oph aiomys) ch alin ei a n d Mimomys pusillus in a large mammal fauna whose taxo- nomical composition and structure is consistent with that of the the Farneta FU (GE N T I L I et al., 1996; BA R I S O N E et al. ,2006; PA L O M B O & GI O V I N A Z Z O, 2006), as well the presence at Pirro Nord of a more evolved M i c r o t u s ( A l l o p h a i o m y s ) ex gr. M. ruffoi, provide a correlation of the Farneta and Pirro FU with the earliest Biharian (Early Biharian I, MA S I N I & SA L A, 2007). Accordingly, and taking into account magnetostratigraphical dating of Tuscan LFA’s assigned to Olivola plus the Tasso FU, the Farneta and Pirro FU’s developed during the pre-Jaramillo Early Pleistocene, but the actual chronological extent of each FU is based only on biochronological estimates. 3.4.2 Colle Curti FU and the beginning of the Mid Pleistocene revolution (MPR) The transition from the Early to Middle Pleistocene, Mid-Pleistocene revolution (MPR) (from about 1.2 to 0.6 Ma) marks a fundamental change in the Earth’s climate system (MA S L I N and RI D G W E L L, 2005) and represents a major episode in mammalian fauna reorganisation over the course of the Cenozoic. Orbital obliquity at 41-ka cycles was superseded progressively by a 100-125-ka rhythm, sustained by four-five precessional cycles, and accompanied by increased amplitude climatic oscilla- tions (Table 2). Glacial phenomena intensified, tempera- ture and moisture dropped notably, vegetational “exot- ic” essences, quite common in earlier floras, progres- sively disappeared and sustained climatic changes pre- vented these floral elements from becoming re-estab- lished (BERTINI, 2003). These changes spurred a shift in environments and constrained the geographical diffu- sion of a number of taxa, allowing dispersal waves that drove the reorganisation of large mammal communities. Community rebuilding came to an end during the beginning of the Middle Pleistocene with the disappear- ance of the last surviving Villafranchian species, such as Pachycrocuta brevirostris and Panthera gombazsoe- gensis (Table 3). Thus, at the time of MPR, fauna was charact eris ed by t he pres ence of lon g su rv iv in g Villafranchian taxa and by a progressive increase in taxa, which also persisted into the Middle Pleistocene. Such a framework of “mixed faunal elements” was regarded by authors either as a “transitional fauna” (BO N I F A Y, 1978; AZ Z A R O L I et al., 1988) or a distinct biochron (e.g. Protogalerian sensu Caloi & Palombo, 1995, Epivillafranchian sensu Kahlke 2007 and previous papers; ‘latest Villafranchian’ sensu Koufos, 2001 or ‘Final Villafranchian’ SPASSOV, 2003). On the other hand, if Middle Pleistocene faunas are clearly to be consid- ered as ‘modern’ when compared to those from the Villafranchian (PA L O M B O, 2004b), which criteria should be used to define the ‘theoretical’ boundary between the Villafranchian and the following Galerian LMA? According to GL I O Z Z I et al. (1997) (Table 1), the begin- ning of the Galerian LMA would be conventionally mar ked by t h e app ear an ce , a mon g o t h er s , o f Praemegaceros verticornis, which is first recorded in Italy at the Colle Curti LFA (Colle Curti FU, late Early Pleistocene, Jaramillo Subchron, COLTORTI et al., 1998). This giant deer has been recently found in the Spanish Fuente Nueva 3 and the Barranco Leon LFA, dated at about 1.3 Ma (AG U S T Í & MA D U R E L L, 2003), which retain several Villafranchian taxa, as does the Colle Curti LFA. Moreover, the Pirro Nord (latest Villafranchian) and the Colle Curti LFA’s exhibit a relatively high coefficient of similarity (PA L O M B O & VA L L I, 2005). Consequently, the Col le C u rt i L F A s t il l l oo k s cl o se r t o th e lat es t Villafranchian LFA’s than to the ensuing typical Galerian ones, despite the LlSDk of Praemegaceros verticornis, Cervalces latifrons (BREDA & MARCHETTI, 2005), and pos- sibly of subgenus B i s o n , the significant reduction in biodiversity shown by carnivores, as well as the innova- tive characteristics of the arvicolids (SA L A & MA S I N I, 2007). All in all, the the Pirro and Colle Curti FU’s corre- spond to a time slice during which the Villafranchian were gradually but not completely displaced by some typical Galerian large mammals foreshadowing the coming of a new age. This evidence encourages a redefinition of the Galerian LMA (cf. PA L O M B O, 2004a and references therein, KAHLKE, 2007). 3.5. The MPR accomplishment and the onset of typi- cal Galerian mammalian faunas As above mentioned, the faunal renewal leading to the typical Galerian faunas finds its origin in two distinct trends: 1) the progressive reduction in richness charac- terising late Early Pleistocene faunas (from the Farneta to the Colle Curti FU’s), 2) the subsequent dispersal and the progressive spread in Italy of taxa from Eastern and Central Europe, that triggered a rapid increase in diversity at the beginning of the Middle Pleistocene (Slivia FU) (PALOMBO 2007b and references therein). It is noteworthy that this faunal change involved both carni- vore and herbivore guilds at various times. The most important change in the former had already taken place prior to the Jaramillo Subchron, at the Pirro–Colle Curti FU’s transition, with the disappearance of some large taxa, either flesh-eaters or bone-breakers, such as large canids and felids (Table 3) (PALOMBO et al., 2008 and references therein). This is the starting point for a reversal in the proportion of carnivores versus herbi- vores: indeed, across the Early to Middle Pleistocene (Slivia FU), the faunal renewal was strongly biased in favour of large herbivores, while the carnivore guild changed at a slower pace. Taxa dispersed from Eastern and Central Europe reached the Italian peninsula in succession, thus leading an important and relatively 299Biochronology of terrestrial mammals and quaternary subdivisions: ... rapid increase in diversity at the beginning of the Middle Pleistocene. These changing faunas represent a majo r l ar ge m ammal com mu n it y re or ga n is at i on throughout the Quaternary. This dispersion phase was probably triggered by notable climatic changes that cor r es po n d t o t he o n s et o f t h e p ro n ou n c ed glacial–interglacial fluctuations as observed in the marine isotope record during the late Early Pleistocene (MIS 25 to 22-20), while the progressive increase in diversity is seen as a consequence of the ensuing onset of w et t er cli mat i c co n dit i on s ( s ee P A L O M B O & GI O V I N A Z Z O, 2006 and references therein). Instead of replacing any one species, these taxa enriched the her- bivore guild, as well as the large mammal community as a whole (Palombo, 2007b and references therein). Even if, on a larger temporal scale, the progressive modification in the structure of large mammal faunas of th e I tali an penin s ula began befo re t h e Jar amill o Subchron, it was shortly before the Early to Middle Pleistocene boundary that the major renewal and important ecological reorganisation of faunal complex- es took place (PALOMBO, 2007b). Throughout the course of time (Table 3), the local app ear an ces o f se v era l pa ch y der ms (E l e p h a s (Palaeoloxodon) antiquus, Mammuthus trogontherii, Stephanorhinus kirchbergensis, Stephanorhinus hemi- t o e c h u s), large (Megaloceros savini, Praemegaceros solilhacus), and medium-sized deer (Capreolus capreo- lus suessenbornensis, Cervus elaphus acoronatus a n d possibly Dama clactoniana), as well as large (Hemibos galerianus, Bos primigenius) and middle-sized bovids (Ovis ammon antiqua, Hemitragus bonali), together with caballine horses (Equus mosbachensis), all mainly mixed feeders or grazers, inhabiting open landscapes, bushlands or wooded grasslands, brought about a major change in the herbivore guilds (PALOMBO, 2007b). Among carnivores, Crocuta crocuta first appeared (Ponte Galeria 2 LFA, PG2 sequence, about 750-650ka, MILLI & PALOMBO, 2005 and references there in), where- as some other large carnivores, active hunters that were both flesh-eaters and scavengers [such as Ursus deningeri, Panthera fossilis, Isernia LFA, about 600 ka (COLTORTI et al., 2005); a hyaena, Hyaena prisca, whose taxonomical identification is still matter of debate at the Ponte Galeria 3 LFA (see CA L O I & PA L O M B O, 1980; PA L O M B O et al., 2008; TU R N E R et al., 2008), PG3 about 650-550 ka ( MI L L I & PA L O M B O, 2005); Panthera pardus, Valdemino Cave LFA, Isernia FU (SA L A, 1992) and Isernia LFA (SALA, 2006) ], had their lowest stratigraphi- cal occurrence even later. These species, together with S. hundsheimensis, Equus altidens, E. suessenbornen- sis, P. verticornis and B. shoetensacki are eponymous of the “typical” Galerian faunas. Most authors recognise in the “middle” Galerian (sensu Gliozzi et al., 1997) two FU’s, Slivia and Isernia which are clearly differentiated by the small mammals: Mymomys savini (Slivia LFA) and Arvicola mosbachen- sis (Isernia LFA). The small mammal association found at the archaeological site Isernia La Pineta (Molise), represents the oldest Toringian fauna recorded in Italy to date (SALA & MASINI, 2007) and represents the main renewal of small mammals throughout the Galerian LMA. PE T R O N I O and SA R D E L L A (1999) proposed the intro- duction of the Ponte Galeria FU (Table 1), by these authors regarded as intermediate in taxonomical com- position, and in age as well, between the Slivia and Isernia FU’s. This, because of the persistence of Pachycrocuta brevirostris and Panthera gombaszoe- g e n s i s in the Slivia FU, the exclusive occurrence of Hemibos galerianus in the “Ponte Galeria FU” and the appearance of Bos primigenius in the Isernia FU. Nevertheless, Slivia and Ponte Galeria 2 LFA’s would be assumed to be part of the same FU due to the uncertain identification of some herbivores from Slivia LFA, and the assumption that carnivores absent from the Ponte Galeria CU have in fact been found in the Slivia LFA. Unfortunately, there are no stratigraphical constraints for the age of the Slivia FU, even if it can be cor relat ed with the Lat e Bih arian , which rou ghly extends from 0.95 to 0,6 Ma, due to the occurrence of M. savini associated with that of Microtus (Steno- c r a n i u s) and Microtus (Terricola). Conversely, in the Roman basin, the integrated mammal biostratigraphy and sequence stratigraphy approach represents a valid tool to identify and to correlate physical and biological events. The biochronological and sequence-strati- graphical scheme proposed for the Ponte Galeria area, highlights that the sequence stratigraphical framework can constrain the possible chronological interval in which a bioevent, even if local, occurred (see MI L L I & PALOMBO, 2005). The transition from the middle to late Galerian (Fontan a Ranuccio FU) possibly occurred around 550–500 ka, due to the absolute age available for the LFA’s ascribed to Isernia FU (Notarchirico and Isernia LFA’s , estimated age about 600 ka by LE F É V R E & RAYNAL, 1999; Lefévre et al., 1999; and COLTORTI et al., 2005, respectively), and the Fontana Ranuccio FU (Fontana Ranuccio LFA, estimated age about 458 ka, BIDDITTU et al., 1979). D u ri n g t h e la te m idd le G ale ri an ( Fo n t an a Ranuccio FU), “Villafranchian” taxa were not yet record- ed and the number of very large herbivores diminished (Table 3). The occurrence of “Galerian” equids and megacerines is doubtful and the specialised and slight- ly larger H. antiquus was replaced by H i p p o p o t a m u s a m p h i b i u s an d, amo ng car ni vo res , Ursu s a rct os appeared as well as Felis silvestris (Table 3). In the second half of the Middle Pleistocene, increasingly different habitats supported increasingly varied faunas (cf. TR I A N T I S et al., 20 03), with new dynamic interspecific relationships. In fact, with the end of the Galerian (Fontana Ranuccio FU) and the transi- tion to the following Aurelian LMA, the most flexible species became the dominant group, the percentage of browsers increased and fauna progressively acquired modern characteristics (PALOMBO 2007b and references therein). 3 .6 The A ur e li a n L MA an d the Mi ddl e t o l at e Pleistocene boundary GLIOZZI et al. (1997) proposed the Aurelian as a new LMA, differing from the Galerian LMA because of the appearance of taxa that constitute the core of the mod- ern mammalian fauna, whereas some “Galerian”species (such as horses, megacerine deer, m e d i u m - s i z e d , bovid Ovis ammon antiqua and Hemitragus bonali, and large bovide, Bison shoetensacki) were no longer pre- 300 M.R. Palombo sent. According to GL I O Z Z I et al. (1997), three distinct, main faunal complexes could be detected: early, middle and late Aurelian, characterised by an increase in the percentage of modern taxa. The early and middle Aurelian were subdivided on the basis of faunal differ- ences between two already created FU’s, Torre in Pietra and Vitinia (CA L O I and PA L O M B O 1990, 1996, but see below), while for the late Aurelian (MIS 5-2) no char- acteristic FU’s have correctly been designated due to the monotonous taxonomical composition of the last interglacial faunas, as well the only sporadic occur- rence of the so called “cold taxa” during the last Glacial (but see PETRONIO et al, 2007). 3.6.1 The Aurelian LMA and the question of Vitinia FU The Torre in Pietra and Vitinia FU’s have been defined on the basis of palaentological and stratigraphi- cal evidence collected in the Roman Basin (CALOI et al., 1998; but cf. PALOMBO et al., 2004 and references there- in). Along the Latium coast, rich LFA’s (Torre in Pietra, La Polledrara di Cecanibbio, Collina Barbattini, Castel di Guido, Malagrotta) have been recovered either from fossiliferous deposits of the Aurelia Formation (CONATO et al., 1980) or the PG6 sequence, both correlated with MIS 9 (MILLI & PALOMBO, 2005). In these LFA’s, assigned to the Torre in Pietra FU the LlSDk of Canis lupus, Ursus spelaeus and Megaloceros giganteus is reported. In the same area, LFA’s uncovered in fossiliferous lev- els of the Vitinia Formation (CONATO et al., 1980) or PG7 sequence (MILLI, 1997), correlated with MIS 7 (e.g. Torre in Pietra upper levels, Vitinia level e, Cerveteri) (PALOMBO et al., 2003 and references therein) were previously ascribed to the Vitinia FU’s (CA L O I & PA L O M B O, 1995; CALOI et al., 1998) essentially because of the abundance of a primitive fallow deer, Dama dama tiberina ( l o c a l l y associated with the pre-existing larger Dama dama clactoniana), as well the appearance, among others of Cervus elaphus with features similar to those of modern red deer and of Equus hydruntinus. Nevertheless, the structure and the taxonomical composition of the Torre in Pietra and Vitinia faunal complexes are similar (PALOMBO & MUSSI, 2001; PALOMBO 2004), thus the divi- sion into two FU’s seems to be based on weak palaen- tological data, moreover new stratigraphical evidences call for a revision of these biochrons. In the 1990’s, two LFA’s, Sedia del Diavolo and Monte delle Gioie (today, no longer exposed due to of the intense urbanization of Rome after World War II), were assigned to the Vitinia FU due to the abundance of Dama dama tiberina remains in the alluvial deposits overlaying the “Tufo lionato” (a lithified pyroclastic flow deposit from Albani Volcanic Complex, dated 355 ka by KARNER et al., 2001) where also Equus hydruntinus was found (CA L O I & PA L O M B O, 1995). CA L O I et al., (1998) correlated these bone-bearing deposits with the Vitinia Formation (MIS 7), but recently the overlain ash flow has been dated at 285 ± 1 ka (MARRA & ROSA, 1995; KARNER et al., 2001). Following this new chronological data, the deposition of the fluvio-lacustrine sediments overlaying the “Tufo lionato” at Sedia del Diavolo, occurred approximately during the time span between 355 and 285 ka (PALOMBO et al., 2004). Accordingly, the LlSDk Dama dama tiberina in Italy is documented in deposits correlated with the MIS 9, thus th e Vitinia FU can not be cons idered a valid biochron. The LFA’s previously ascribed the Torre in Pietra and the Vitinia FU’s have to be included in a sin- gle FU (named Torre in Pietra FU for priority reason) (Table 1). Summarizing, several bioevents characterised the beginning of the Torre in Pietra FU, as well as the beginning of the Aurelian LMA (subdivided into early and late Aurelian) as here redefined: for instance Canis lupus first appeared as well as Ursus spelaeus that sub- s t i t u t e d U. deningeri, Megaloceros giganteus, Dama dama “tiberina, and Bubalus murrensis (PALOMBO, 2007 and unpublished data), the “steppe horse E. hydrunti- nus dispersed along the Italian peninsula. Furthermore, some new medium-sized taxa appeared, when more severe, arid climatic oscillations favoured the spread of “mountain” bovids (Capra ibex and Rupicapra) towards the southernmost regions of the Italian peninsula, whereas Galerian megacerine deer and horses, O v i s ammon antiqua and Bison shoetensacki are no longer recorded (Table 3). All in all, with the end of the Galerian (Fontana Ranuccio FU) and the transition to the Aurelian (Torre in Pietra FU), the most flexible species became the domi- nant group, the percentage of browsers increased and fauna progressively acquired modern characteristics. This is consistent with a moderate woodland expansion under increasingly mild climatic conditions characteris- ing the interglacial phases, as well as the increase in north to south and east to west climatic gradients lead- ing to the fragmentation of Italian habitats. The structure of Aurelian mammalian faunas was fully attained long before the beginning of the beginning Late Pleistocene, thereby the transition from Galerian to Aurelian LMA predated the Middle to Late Pleistocene boundary. 3.6.2 The Late Pleistocene The Last Interglacial LFA’s did not substantially dif- fer fr om t h o s e r eco rd ed d u ri n g t h e lat e Mi dd le Pleistocene. The rare species Bubalus murrensis is no longer present, while modern fallow and red deer sub- stitute the late Middle Pleistocene subspecies, but the cor e o f t h e earl y Au r elian fau na s kee ps ro u gh ly unchanged. Although the Last Glacial phase caused a remarkable shift in the vegetational cover and in the distribution of mammals in Europe, minor changes characterised the transition from the Last Interglacial to the Last Glacial faunal complexes on the Italian penin- sula (PALOMBO, 2007b). During the last Glacial, the fau- nal biodiversity increased with the arrival of some “cold” species, such as the typical, Mammuthus primi- g e n i u s, the woolly rhinoceros Coelodonda antiquitatis, the elk Alces alces, inhabiting a “mammoth steppe”-like environment extending throughout the Eastern Po Valley (GALLINI & SALA, 2001). Mammoth and woolly rhi- noceros, as well the wolverine, Gulo gulo, reached the Tyrrhenian coast (Latium) and were widespread in the south-eastern part of the Italian peninsula, where Alopex lagopus is also recorded, while Rangifer taran- d u s o nly reached th e wes tern mo st geog raphical boundary of the Italian coast ( CA L O I & PA L O M B O, 1995; SA L A, 2005). The spread of “cold” species across the Italian peninsula was profoundly conditioned by micro- climate and physiography, and the taxonomical compo- 301Biochronology of terrestrial mammals and quaternary subdivisions: ... sitio n and st ruct ure of L FA’s cou ld v ary greatly , depending on the geographical position of fossiliferous sites. That, coupled with the high percentage of extant species, prevent any FU to be fairly defined. Moreover, the faunal assemblages were progressively depleted of some long-surviving Galerian species. Pachyderms wer e mo s t aff ect ed by cl ima t ic d et er io ra t io n . H i p p o p o t a m u s survived only until the end of the MIS 5a, whereas Elephas antiquus occurred also during MIS 4 and S t e p h a n o r h i n u s was still present during MIS 3, while Panthera spelaea survived till the beginning of the Holocene (BOSCHIAN et al., 1995). All in all, the mammal faunas on the Italian main- land maintained “temperate-cool” characteristics even during the cold-arid peaks of the Last Glacial. Broad- leaved wooded release “refugial” areas always existed on the Tyrrhenian side of the peninsula, while the cli- mate on the Adriatic side was probably drier. Therefore, some “warm” species remained on the Italian peninsula longer than elsewhere, and turnovers in successive communities were less dramatic than in northern Europe. With the deglaciation phase at the beginning of the Ho locen e, dramatic mois tu re and vegetation change led to marked changes in mammalian faunas, particularly in their abundance, leading to the megafau- na extinction. 4. CONCLUSION Several evidences show that, at least as far as the Italian peninsula is concerned, global climatic changes are a contributing factor, especially in the first appear- ances of large mammals. This permitted the dispersal of new taxa, because mammals frequently reacted to the Plio-Pleistocene climate changes, expanding their distribution area or migrating rather than by evolving and producing new species. Climate change, via migrations and dispersal events, caused diversity bursts but altered palaeocommunity equilibria, leading to new intra- and inter-guild dynam- ics. We can also hypothesize that cause-and-effect relationships between climatic oscillations and faunal changes may be the cumulative result of the responses of individual species and that climatic changes could h av e ca u s ed th e r emo va l o f key s t o n e s p eci es . Accordingly, migratory responses to climate change and physical-environmental disturbances, together with biotical interactions mainly contributed to faunal evolu- tion in successive phases by discrete bioevents, maybe diachronous even in a restricted geographical area such as the Western Europe. This fact prevents any detailed biochronological framework from having wide geographical significance and predisposes it to change in the light of new findings. This is, e.g., the case of weakly defined FU’s such as the Italian “Saint Vallier” (GL I O Z Z I et al., 1997) and the Vitinia (CA L O I & PA L O M B O, 1990) FU’s, which stratigraphical evidences forced its deletion. Moreover, increasing palaeontological and stratigraphical data sometimes leads us to better dis- criminate bioevents, highlighting the gradual renewal between successive biochrons, but blurring their clear identification as in the case of the Olivola and Tasso FU’s. Thus, only higher rank biochronological units (Land Mammal Ages, LMAs) - whose separation is based on palaeobiological events which have a wide territorial significance - could be useful for chronologi- cal correlations. Nonetheless, the transition between successive LMAs does not always correspond to the boundaries separating marine Series or Stages. For instance, the Villafranchian LMA approximately began with the Late Pliocene (Piacentian) and the transition from the early to the middle Villafranchian LMA hap- pened around the Pliocene/Pleistocene (Piacentian/ Gelasian) boundary, whereas the transition to the late Villafranchian took place during the latest Gelasian, and those from the Villafranchian to Galerian LMA and from the Galerian to Aurelian LMA respectively predated the beg in n i n g o f t h e M idd le an d L at e Pl eis t o cen e . Concerning the Villafranchian to Galerian LMA transi- tion, from what has been previously reported on the biochronological patterns of large mammals, it possibly occurred close to MIS 25, where CI T A & CA S T R A D O R I (1995, but see CI T A et al. , 2006) previously proposed lowering the Early to Middle Pleistocene Boundary. 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