what is the boundary for the quaternary period and

Quaternaire, 18, (1), 2007, p. 35-53
WHAT IS THE BOUNDARY FOR THE QUATERNARY PERIOD
AND PLEISTOCENE EPOCH?
THE CONTRIBUTION OF TURNOVER PATTERNS
IN LARGE MAMMALIAN COMPLEXES
FROM NORTH-WESTERN MEDITERRANEAN TO THE DEBATE
䡲
Maria Rita PALOMBO*
ABSTRACT
Assuming that the Quaternary has to be recognized as a formal chronostratigraphic/geochronological unit (having a Sub-Erathem/Sub-Era
rank, as recommended by the International Commission on Stratigraphy (ICS), or better a System/ Period rank, as suggested by several scientists),
what boundary should be chosen? Should the lower boundary of the Quaternary coincide with the base of the Gelasian Stage (2.6 Ma) as proposed
by the ICS? If so, should the Quaternary and Pleistocene lower boundaries be the same or should be different?
To contribute to the debate, the Villafranchian large mammal fossil record from the North-Western Mediterranean region have been revised
in order to correlate the diversity and structural dynamics of reconstructed faunal complexes with the changes in environmental conditions occurring from the Middle Pliocene to the Early Pleistocene.
According to the results obtained, two major faunal renewals are detectable at the transition from the early to middle Villafranchian
[~2.7-2.5 Ma, about at the time of the transition from the Middle (Zanclean Stage) to the Late Pliocene (Gelasian Stage)], and from the middle to late
Villafranchian (~2.0-~1.9 Ma, shortly before the official Plio-Pleistocene boundary). The faunal renewal from the early (V1) to the middle (V2)
Villafranchian faunal complexes (that means from the MN16a “zone”/Triversa FU to MN16b “zone”/Montopoli FU) is linked to the Middle Pliocene climate worsening, in turn related to the onset of bipolar glaciations followed by glacial-interglacial cycles of moderate amplitude (orbital periodicity of 41 ka). The resulting increase in aridity and more intense seasonality caused the disappearance of several forest-dwelling taxa,
especially small carnivores and arboreal-scansorial taxa, whereas new large grazers, mixed feeders or even browsers appeared. This renewal (already called the “Equus-elephant event”) can be regarded as a true turnover phase, due to the high percentage of last and new appearances, and to the
important ecological structural changes in faunal complexes, involving mainly the herbivore guild. These faunal changes indicate that forests or
woodlands gradually gave way to more open environments (including Artemisia steppe) alternating with warm-temperate deciduous forests. Moreover, this event can be considered as the starting point for a dispersal phase leading to a progressive standing richness increase during the following
Pliocene (middle Villafranchian, V3). Around 2.0-1.8 Ma (late Villafranchian, V4), despite the extinction of some small browsing and grazing
ruminants, diversity notably increased due to the progressive appearance of a number of carnivores. Indeed, the so-called “wolf-event” involved
several large and small Carnivora, such as the powerful scavenger Pachycrocuta brevirostris, the jaguar-like Panthera gombazsoegensis, and cooperative foraging canids. On the other hand, minor phyletic adjustments and some new appearances (especially grazers) affected herbivore guild.
This relatively long dispersal phase, and correlated moderate turnover pulses, seems to be less important than the early/middle Villafranchian
renewal phase, especially as far as France and the Italian peninsula are concerned. As a result, taking into account the importance of faunal renewal
at the Middle to Late Pliocene transition, it seems more reasonable to extend the base of the Pleistocene downwards from 1.81 Ma (official
Plio/Pleistocene boundary) to 2.6 Ma (base of Pliocene Gelasian Stage). Accordingly, the base of the Gelasian seems to be the most appropriate
lower boundary for both the Quaternary Period and Pleistocene Epoch.
Key-words: Quaternary, Pleistocene, Large mammals, North Western Mediterranean.
VERSION FRANÇAISE ABRÉGÉE
QUELLE LIMITE POUR LE QUATERNAIRE ET LE PLÉISTOCÈNE ? L’APPORT DE L’ÉTUDE DU RENOUVELLEMENT DES FAUNES À
GRANDS MAMMIFÈRES DE LA MÉDITERRANÉE NORD OCCIDENTALE DURANT LE PLIOCÈNE MOYEN ET SUPÉRIEUR ET LE
PLÉISTOCÈNE INFÉRIEUR
INTRODUCTION
La plupart des chercheurs conviennent que le Quaternaire devrait être reconnu comme une unité chronostratigraphique/géochronologique
formalisée, Sub-Erathème/Sub-Ere, comme cela a été recommandé par la Commission Internationale pour la Stratigraphie (ICS) (cf. Clague, 2005,
2006) ou mieux Système / Période, comme suggéré par plusieurs chercheurs. Mais, il n’existe pas encore d’accord au sujet de cette unité. La limite
inférieure du Quaternaire devrait-elle coïncider avec la base de l’étage Gélasien (2.6 Ma), comme cela a été proposé par l’ICS ? Si oui, les limites inférieures du Quaternaire et du Pléistocène devraient-elles coïncider ou bien devraient-elles être différentes ?
* Dipartimento di Scienze della Terra, Università “La Sapienza”, CNR – Istituto di Geologia Ambientale e Geoingegneria, Piazzale A. Moro,
5 – 00185 ROMA, Italy. E-mail : [email protected]
Manuscrit reçu le 08/07/2006, accepté le 09/10/2006
36
Pour contribuer au débat et en rappelant que le « Pléistocène » et le Quaternaire ont été créés en s’appuyant sur des donnés soit paléontologiques, soit climatiques (ex. Desnoyers, 1829 ; Lyell, 1833, 1839 ; Reboul, 1833 ; Agassiz, 1840 ; Forbes, 1846), les faunes à grands mammifères de
la région méditerranéenne nord-occidentale ont été révisées dans le but d’envisager quels ont été les changements les plus importants des complexes
fauniques (fluctuations de la diversité et changement de la structure) qui se sont produits durant le Pliocène moyen et supérieur et le Pléistocène inférieur, lorsque d’importants changements climatiques ont modifié l’environnement.
Le renouvellement des faunes et de la structure des paléocommunautés et leurs rapports avec les changements globaux du climat ont été
considérés. En particulier, la dynamique des deux plus importants « turnovers » du Villafranchien, l’“elephant-Equus event” (Lindsay et al.,1980)
(qui s’est déroulé grosso modo entre la fin du Zancléen et le début du Gélasien), et le « wolf event » (Azzaroli, 1983 ; Palmqvist, 1999 ; Sardella &
Palombo, 2007), auparavant placé au début du Pléistocène, a été analysée dans le but d’envisager lequel des deux était le plus remarquable, en précisant si et de quelle façon le climat et les changements de l’environnement avaient entraîné le renouvellement des faunes.
En effet, écologistes et également évolutionnistes ont débattu depuis longtemps du rôle que les changements du climat ont et ont eu sur l’évolution de la faune, et il semble que nous n’ayons pas encore trouvé d’accord. Les modèles les plus importants – tel que le « Stationary model » (Rosenzweig, 1975) et les théories qui privilégient le rôle de l’environnent (Vrba, 1992, 1995 ; Brett & Baird, 1995), ou par contre les modèles et les
théories qui regardent comme plus important la compétition intra- et inter-spécifique (Red Queen Hypothesis, Van Vallen, 1973 ; Bell, 1982 ; Prothero 2004) ; ou, enfin les hypothèses dont la vision est un peu plus complexe (“Coevolutionary disequilibrium Model”, Graham & Lundelius,
1984) ou stochastique (Court Jester Hypothesis, Barnosky 2001) – semblent être à la fois confirmés ou réfutés par les donnés paléontologiques.
D’autre part, si le climat et les changements de l’environnement ont causé le renouvellement des faunes, soit par migration, soit par apparition et extinction, les variations dans la structure des paléocommunautés devraient être en accord avec ces changements du climat.
Dans ce but, nous avons analysé les turnovers et les variations en richesse, diversité et structure écologique, des complexes faunistiques à
grands mammifères du Pliocène moyen et supérieur et du Pléistocène inférieur de la zone méditerranéenne nord occidentale.
MATÉRIAUX ET MÉTHODE
Les listes fauniques de 112 faunes locales (LFAs) d’Espagne, de France et d’Italie, les plus riches ou les plus irréfutables au point de vue
chronologique, ont été révisées aussi bien que la taxonomie et la distribution chronologique des espèces (fig. 1, tab. 1 et 2). Des complexes faunistiques proches des « paléocommunautés » ont été déterminés également à l’aide d’analyses multivariées (analyses de cluster), permettant de reconnaître des complexes fauniques (FCs) cohérents au point de vue chronologique et écologique (biochrones). Ces complexes peuvent être regardés
comme des « block of coordinated stasis » (sensu Brett & Baird 1995 ; Bret et al., 1996), puisqu’on assume que, pendant le temps qu’ils renferment,
aucun turnover ne se produisit (cf. Palombo, 2005, sous presse et références bibliographiques citées).
Les méthodes de Harper (1975) et Foote (2000) ont été utilisées pour calculer la richesse standardisée et la diversité, celles de Torre et al.
(1999) et Foote (2000) pour calculer l’index de turnover entre deux FCs successives et les taux d’apparition et d’extinction dans chaque FC
respectivement.
RÉSULTATS
L’analyse de similitude montre l’évidence d’une séparation plus importante entre le LFAs du Villafranchien inférieur et moyen qu’entre
celles du Villafranchien moyen et supérieur.
Les valeurs des indices de turnover calculés à la transition entre deux FCs successives confirment le caractère progressif du renouvellement
qui se développe durant le Pliocène supérieur. Les taux d’apparition et d’extinction soulignent d’un côté ce turnover, et de l’autre mettent en évidence la phase de dispersion qui se déroule pendant le Pliocène supérieur (bien que d’une façon différente en chaque région), lorsque les nouvelles
apparitions sont toujours plus nombreuses que les extinctions. En revanche, une phase de disparitions progressives et de réduction de la biodiversité
caractérise le Pléistocène inférieur. Cette tendance est confirmée par les fluctuations de la diversité et de la richesse qui augmentent durant le
Pliocène final, atteignant leur maximum au début du Pléistocène inférieur.
En ce qui concerne l’habitat, les taxons qui préfèrent un milieu forestier, bien que plus nombreux en Italie qu’en Espagne, diminuèrent durant le Pliocène et le Pléistocène inférieur. Parmi les herbivores, on peut remarquer la diminution des brouteurs, lorsque les « mixed-feeders » deviennent plus nombreux, peut-être à cause d’une fragmentation plus importante du milieu. Le début du Pliocène moyen est marqué aussi par la
disparition des taxons de petite taille et l’apparition de mammifères de grande taille.
DISCUSSION
D’après les résultats obtenus, durant le Pliocène moyen et supérieur et le Pléistocène inférieur, les renouvellements majeurs sont détectables
à la transition entre les complexes fauniques du Villafranchian inférieur (V1 FC) et du Villafranchien moyen ancien (V2 FC) (~2.7-2.5 Ma), et entre
le complexes du Villafranchien moyen (V3 FC) et supérieur (V4 FC) (~2.0-1,9 Ma). Le premier peut être mis en relation avec le début des glaciations bipolaires, suivi par des cycles glaciaire/interglaciaire d’amplitude modérée (périodicité orbitale de 41 ka), qui favorisent des variations du
climat et du milieu. La saisonnalité plus marquée et une augmentation de l’aridité causent la disparition de plusieurs taxons de milieu forestier, des
petits carnivores et des espèces « scansorial » ou arboricoles, alors que des herbivores de grande taille, « mixed-feeders » ou bien brouteurs, apparaissent. Ce renouvellement (“elephant-Equus event” Lindsay et al., 1980) peut être considéré comme un vrai turnover, et marque aussi un changement de la structure des complexes fauniques, qui affecte surtout la guilde des herbivores/frugivores. De plus, cet événement peut être considéré
comme le point de départ de la phase de dispersion qui mène à une augmentation progressive de la richesse pendant le Pliocène supérieur (Villafranchien moyen,V3 FC, et début du Villafranchien supérieur, V4 FC). En effet, au début du Pléistocène inférieur, en dépit de l’extinction de quelques
broyeurs ou tondeurs d’herbe de taille moyenne, la diversité acquiert son maximum en raison de l’apparition progressive pendant le Pliocène supérieur de plusieurs carnivores (“wolf event”, Azzaroli, 1983 ; Palmqvist et al., 1999 ; mais voir aussi Sardella & Palombo, 2007), tel que des canidés
solitaires ou chassant en groupes, et Pachycrocuta brevirostris et Panthera gombazsoegensis. Une situation équivalente (un turnover suivi par une
phase de dispersion), mais beaucoup plus accentuée, caractérise aussi le turnover de la fin du Pléistocène inférieur (Palombo et al., 2005 ; Palombo
& Valli, 2005 avec références). Ces deux turnovers sont précédés par une phase plus ou moins prolongée de réduction de la diversité, pendant laquelle les extinctions prévalent (Palombo, 2005, 2007). Il semble que les turnovers les plus importants se produisent d’une façon cyclique et qu’ils
marquent le début d’une période caractérisée d’abord par la prévalence des apparitions de nouveaux taxons, puis par une réduction de la diversité.
Les plus importants changements de faune semblent être déclenchés ou favorisés par les variations les plus importantes du climat et de la végétation,
lorsque la structure des communautés va être aussi bâtie progressivement par la compétition intra- et inter-guilds.
CONCLUSION
Le renouvellement faunique qui se réalise au passage entre Villafranchien inférieur et moyen (Pliocène moyen et supérieur) semble être plus
important que la restructuration du début du Pléistocène inférieur. En réalité, le renouvellement qui marque le passage entre Villafranchien moyen
et supérieur arrive au cours du Pliocène tardif. En outre, le turnover au passage Pliocène moyen– Pliocène supérieur (début du Gélasien) marque le
début d’un cycle de renouvellement faunique qui se terminera à la fin du Pléistocène inférieur. Les données relatives aux faunes à mammifères de la
zone méditerranéenne nord occidentale indiquent donc que le Gélasien pourrait être considéré comme le premier étage du Pléistocène et le début du
Quaternaire.
Mots-clés : Quaternaire, Pléistocène, Grands mammifères, zone méditerranéenne nord occidentale.
37
1 - INTRODUCTION
In the revised geological time scale (Gradstein et al.,
2004), it has been propose to extend the Neogene System (Period) up to the present, de facto deleting the
“Quaternary”. Actually, when in 1985 the Plio-Pleistocene boundary was formally defined (Aguirre & Pasini,
1985), the status of the Quaternary within the
chronostratigraphical scale remained undefined and
later was never formally resolved. Pillans (1998, 2004)
proposed the Quaternary should be redefined as a Subsystem (Subperiod) of the extended Neogene System
(Period), and that its base be defined at the base of the
Pliocene Gelasian Stage at 2.6 Ma, opening a new debate (e.g. Ogg, 2004; Pillans & Naish, 2004; Clague,
2005, 2006). In point of fact, paleontological and
climatic peculiarities of the “Quaternary” were
recognized since the beginning of the 19th century (e.g.
Desnoyers, 1829; Lyell, 1833, 1839; Reboul, 1833;
Agassiz, 1840; Forbes, 1846) and “Quaternary” has
been traditionally considered to be an interval of
climate worsening during which climate had oscillating extremes. Currently a formal decision on the
“Quaternary” status is pending. Anyhow, assuming
that the Quaternary is to be recognized as a formal
chronostratigraphic/geochronological unit (having a
Sub-Erathem/Sub-Era rank, as recommended by the
International Commission on Stratigraphy (ICS), or
better a System/ Period rank, as suggested by several
scientists), what boundary should be chosen? Should
the lower boundary of the Quaternary coincide with the
base of the Gelasian Stage (2.6 Ma) as proposed by the
ICS? If so, should the Quaternary and Pleistocene
lower boundaries be the same or should be different?
According to the ICS proposal (Clague, 2005, 2006),
the base of the Quaternary becomes 2.6 Ma, but the
base of the Pleistocene remains at 1.8 Ma, as ratified in
1985 (Aguirre & Pasini, 1985). On the other hand, it is
worth mentioning that the base of the Gelasian corresponds to the beginning of significant global
changes: for instance the first major influx of ice-rafted
debris, in the middle latitudes of the North Atlantic, or
the onset of extensive loess deposition in China around
the Gauss/Matuyama boundary (marine isotopic stage
MIS104, Ding et al., 1997; Shackleton, 1997; Partridge, 1997a, b; and reference therein) coincided with
a profound change in the Eurasian flora and faunal assemblages (for instance Zagwijn, 1974; Grichuk, 1997;
Lindsay et al., 1980; Steininger et al., 1985; Azzaroli et
al., 1988). Shackleton (1997, p. 34) pointed out that the
lower part of the proposed Upper Pliocene Gelasian
Stage approximates the culmination of a series of cycles over which the intensity of the glaciations gradually increases (“glacial” stages 104, 102 and 100
represent clearly defined events; they are succeeded by
less well-defined fluctuations). Accordingly, since the
global change that occurred at MIS 104, several authors have considered the lower boundary of the
Gelasian Stage as a more appropriate lower boundary
for the Pleistocene Period.
In point of fact, the Gelasian corresponds to the beginning of significant evolution not only of Earth climatic system but also of the biosphere. As a matter of
fact, during the Pliocene and Pleistocene, large mammal species and “palaeocommunities” have turned over
several times, moreover a plentiful literature debates
whether these taxonomical and structural changes in
the course of time are more greatly influenced by biotic
interactions (for instance Prothero, 1999, 2004), or by
random perturbations to the physical environment (for
instance “Court Jester hypotheses”, Barnosky, 2001).
Actually several models have been proposed that
emphasised the role of density-dependent factors
(Rosenzweig 1975) or changes in the physical environment (Vrba, 1992, 1995, 2000; Brett & Baird, 1995).
On the other hand, following to the “Red Queen hypothesis”– in this Macroevolutionary (Van Valen,
1973) and Microevolutionary (Bell, 1982) sense,
changes in equilibrium may be due to the internal dynamics of competitive relationships, and do not necessarily predict a close interdependence between major
climatic changes and evolutionary events. Actually,
due the fact that climate change removes keystone species causing changes in interactions between species
and the restructuring of ecosystems (“Coevolutionary
disequilibrium Model” by Graham & Lundelius,
1984), the internal dynamics of competitive relationships might also have played an important role in mammalian fauna evolution (see e.g. Alroy et al., 2000;
Prothero, 2004). As regards to the Plio-Pleistocene
boundary and taking into account the climatic changes
characterizing the Pliocene and those at the beginning
of the Pleistocene, when, and for what reason were
faunal communities most significantly reconstructed?
In the middle latitudes of the North Atlantic, the first
major influx of ice-rafted debris around the
Gauss/Matuyama boundary coincided with a profound
change in the Eurasian flora assemblage and with a reorganisation of mammalian communities. This important biotic event, linked to the Middle Pliocene climate
worsening, in turn related to the onset of bipolar glaciations, has been already recognized (the so-called “elephant-Equus event” Lindsay et al., 1980; Steininger
et al., 1985; Azzaroli et al., 1988), and has been chosen
as the boundary between the early and middle
Villafranchian (Caloi & Palombo 1996). The profuse
changes in flora and fauna during this event have
prompted several authors to propose placing the
Plio-Pleistocene boundary here (cf. inter alios Alberdi
et al., 1997; Kolfschoten & Gibbard, 1998; Suc et al.,
1997 and the references therein).
After the Middle Pliocene climate worsening, in the
time span included between the Reunion normal magnetic episode and the Olduvai magnetostratigraphic
event, a slight decrease in temperature altered the vegetation, at least in the Western Mediterranean area,
giving rise to more open environments (Suc et al.,
1995; Torre et al., 2001). Moreover, at the transition
from the middle to the late Villafranchian (~2.0-1.9 Ma)
a further faunal renewal can be detected, involving the
38
Tab. 1: Biochronological range of selected Carnivora and Primata of the North-Western Mediterranean, dating from the Middle Pliocene to the Early Pleistocene.
Habitat. Taxa inhabiting: O = open environments, grassland, steppe or savanna; W = forests and closed woodland; Wc = open woodland, bushland and wooded Mediterranean-type vegetation; W-Wc = miscellaneous woodland;
Wc-O, O-Wc = flexible taxa, which can live in shrubland or open woodland, as well as in more open landscapes, or at the edge of both;
Feeding behaviour: Br = browser; B-G = mixed-feeder Gr = grazer; Fr = Frugivore; Om = omnivore; C = carnivores.
Body mass: BM1 I = <10 kg; BM2 =10-60 kg; BM3=60-200 kg; BM4 =200-1000 kg; BM5= >1000 kg.
(*) Authors disagree on tassonomy, systematic and phylogenetical relashionships of the Plio-Pleistocene deer belonging to the so-called Dama-like group (see inter alios Azzaroli, 1992; Di Stefano & Petronio, 1998, 2003; Pfeiffer,
1999, 2005; Croitor, 2001, 2005; Croitor & Bonifay, 2002; van der Made, 1999; Valli et al., 2006 for a discussion).
Tab.1 : Chronologie des principaux Carnivores et Primates de la zone méditerranéenne nord occidentale durant le Pliocène et le Pléistocène inférieur.
Habitat. Taxons habitant : O = des environnements ouverts, prairie, steppe ou savane ; W = des forêts plus ou moins fermée ; Wc = des forêts ouvertes, bushland, milieu à végétation de méditerranéen boisée ; W-Wc = des forêts
claires et prairies boisées ; Wc-O, O-Wc = taxons ubiquistes à large valence écologique, qui peuvent habiter des shrublands ou des milieux boisés ouverts aussi bien que des milieux ouverts peu boisés ou au bord des deux ;
Diète : Br = brouteur; B-G = animaux qui changent de brouteur à tondeur d’herbe avec la saison ou occasionnellement; Gr = tondeurs d’herbe; Fr = Frugivores; Om = omnivores; C = carnivores.
Masse corporelle : BM1 = <10 kg ; BM2 =10-60 kg ; Kg BM3=60-200 ; BM4 =200-1000 kg ; BM5 = >1000 kg.
(*) L’appartenance générique des cervidés de taille moyenne du Plio-Pléistocène rapportées au groupe génériquement nommé « Dama-like » est assez discutée (voir inter alios Azzaroli, 1992 ; Di Stefano & Petronio, 1998, 2003 ;
Pfeiffer, 1999, 2005 ; Croitor, 2001, 2005 ; Croitor & Bonifay, 2002 ; van der Made, 1999 ; Valli et al, 2006).
39
40
Tab. 2: Biochronological range of selected Perissodactyla and Artiodactyla of the North-Western Mediterranean, dating from the Middle Pliocene to the Early Pleistocene.
Abbreviations as in Tab. 1
Tab. 2 : Chronologie des principaux Périssodactyles et Artiodactyles de la zone méditerranéenne nord occidentale durant le Pliocène et le Pléistocène inférieur.
41
42
dispersal of a canid closely related to Canis etruscus
(the already called “wolf-event”, first defined by
Azzaroli, 1983, but see Palmqvist et al., 1999; Sardella
& Palombo, in press for a discussion). This event was
supposed to be connected with the climatic changes occurring at the end of the Pliocene and regarded as a
signal of the transition to the Pleistocene.
Thus the question is: what was the most important
faunal turnover? Is it the Middle to Late Pliocene renewal or the Late Pliocene to Early Pleistocene one?
To contribute to the debate, the large mammal fossil
records from North-Western Mediterranean region
have been revised in order to analyse the diversity and
structural dynamics of reconstructed faunal complexes
in the light of the changes in environmental conditions
occurring from the Middle Pliocene to the Early
Pleistocene.
2 - MATERIAL AND METHODS
Biochronological ranges of 149 Pliocene and Early
Pleistocene taxa, whether commonly found at Spanish,
French and Italian sites or having a particular
biochronological significance, have been revised and
carefully reassessed (tab.1 and 2).
2.1 - FAUNAL COMPLEX DETECTION
To better outline the chronological distribution of
species in the NW Mediterranean region, it is imperative to define a common chronological framework
matching Spanish, French and Italian local
biochronological schemes (MN, MNQ, MmQ and
FUs) already erected on the basis of selected
palaeobioevents, as well as on the evolutionary stage
displayed by taxa belonging to a well-defined phyletic
lineage or on typical taxa associations (Mein, 1975,
1990, 1998; Azzaroli, 1977, 1982; Guérin, 1982, 1990;
Agustí, 1986; Bruijn et al., 1992; Agustí et al., 1987,
2001; Gliozzi et al., 1997; van Dam, 2001; Palombo,
2005).
Disparities among Spanish, France and Italian fossil
records increase the well-known difficulties in establishing correlations among local faunal complexes
(FCs) (Palombo, 2005; Palombo & Sardella, 2007).
Moreover, the comparison is often problematic because of the actual disparities in the composition of local faunal assemblages (LFAs) (due to discontinuities
in the stratigraphic record, to taphonomical biases, and
to the fact that only a small part of the whole fossil record is actually known), the uncertain chronology of
some classic LFAs (see for instance Pastre, 2004) as
well as different opinions regarding the taxonomic
determinations of some taxa.
Given these considerations, to re-assess the Middle
Pliocene-Early Pleistocene mammalian complexes of
the NW Mediterranean region, a multivariate analysis
has also been performed. 112 LFAs (lists of the species
identified from the fossil remains retrieved at a given
site, and/or recovered from the same stratigraphic horizon; 20 from Spain, 46 from France, 46 from Italy)
ranging in age from the Pliocene to the Middle Pleistocene (Ruscinian to early Aurelian land mammal ages,
LMAs, sensu Gliozzi et al.,1997; Palombo, 2004,
2005) have been selected because of their unusually
complete faunal record, their richness, or because they
are the only representatives of a biochron. Selected
Ruscinian (MN14-15) and Galerian plus Aurelian
LFAs have been considered for comparison purpose.
Similarities have been evaluated based on the Jacquard binary coefficient, and of cluster analysis performed using the UPGMA method (NTSYS-PC
programme, version 2.0, Rohlf, 1998). According to
this method, each member of a cluster has equal weight
at all levels of clustering (cfr. Hazel, 1970; Shi, 1993).
Taxa occurring in a very few faunas are not relevant for
this type of quantitative analysis, even if characteristic
of a well-defined span of time. The cophenetic correlation coefficient (CCC) was computed as a measure of
distortion (Farris, 1969). Preference was shown for
the Q-Mode dendrogram, particularly suitable in
biochronologically-oriented studies (Hazel, 1970).
2.2 - BIOCHRONOGICAL SETTING
The Plio-Pleistocene biochronology of large mammals from North-Western Mediterranean region has
been re-assessed taking into account the results of similarity analysis as well as the regional data supplied by
the empirical documentation of the stratigraphical
ranges of fossils in local sections. From the Pliocene to
the Early Pleistocene, the following FCs have been
considered (fig. 1):
- R= Ruscinian, including the Early Pliocene LFAs
already ascribed to MN14-15. We have chosen to
consider these faunas as a group due to the very poor
fossil record of French and Italian LFAs belonging
respectively to MN14 and MN15 “zones”.
- V1= Villafranchian 1, corresponding to the Middle
Pliocene LFAs already ascribed to MN16a or
Triversa FU (early Villafranchian sensu Palombo et
al., 2003).
- V2= Villafranchian 2, including the early Late Pliocene LFAs ascribed to MN16b or Montopoli FU
(early middle Villafranchian sensu Caloi &
Palombo, 1996).
- V3= Villafranchian 3, to which the Late Pliocene
LFAs such as the Spanish and French LFAs belonging to MN17 and the Italian ones already attributed
to “Saint Vallier”/Collepardo and Costa San
Giacomo FUs have been ascribed. We have chosen to
include the latter FU in this faunal complex,
although in the Costa San Giacomo LFA (Italy) a
true “Canis” of C. etruscus group lowest occurred
side by side with typical middle Villafranchian taxa
(Rook & Torre, 1996) due to The compositional affinity shown by these FUs.
43
taxa, together with a stock of Villafranchian faunal
elements. Such LFAs have been considered as “transitional faunas” in previous works (Bonifay 1978;
Azzaroli et al., 1988 and references there in) or as
Epivillafranchian faunas (cf. Kahlke, 2005) or as
representative, as far as Italy is concerned, to the beginning of the Galerian MA. G1 includes the LFAs
referable to MmQ2 (here MmQ2b), MNQ20 “zone”
and Colle Curti FU.
As suggested by the “minimum census technique”
(Rosenzweig & Taylor, 1980; Stucky, 1990), ‘rangethrough’ or Lazarus taxa (Barry et al., 1995; Maas et
al., 1995) have been assumed to occur in intervals
where they were actually not found, provided that they
can be identified in preceding and successive intervals.
2.3 - FAUNAL COMPLEX CHARACTERISATION
Three main approaches have been used to explore the
palaeoclimatic significance of faunal evolutionary
changes: shifts in diversity; shifts in origination/immigration and extinction rates (turnover, dispersal, extinction phases); shifts in relative abundance of
specific ecological categories.
2.3.1 - Diversity and Richness
Fig. 1: Biochronological scheme of Spain, French and Italian faunal
complexes.
Fig. 1 : Schéma biochronologique des complexes faunistiques
d’Espagne, de France et d’Italie.
- V4= Villafranchian 4, including the latest Pliocene
and earliest Pleistocene LFAs (early late Villafranchian sensu Gliozzi et al., 1997). We choose to include in the same FC the assemblages previously
referred to Olivola and Tasso FUs (Azzaroli et al.,
1988; Gliozzi et al., 1997) for two reasons: the scantiness of French and Spanish fossil record in this interval (roughly corresponding to MNQ18 and
MmQ-1 biozones), and the compositional affinities
shown by the latest Pliocene-earliest Pleistocene
Italian LFAs (Palombo, 2005).
- V5= Villafranchian 5, including the Early Pleistocene renewed LFAs referred to Farneta and Pirro
FUs, and to MNQ 19 and MNQ2 (herein MNQ2 a)
“zones”. Even in this case, we group together different LFAs not only due to the paucity of the fossil record in some regions, but for the substantially similar composition.
- G1= Galerian 1, including the late Early Pleistocene
LFAs. They are characterised by a few “Galerian”
Richness (herein considered as a proxy of the γ diversity, which measures the overall diversity for different
ecosystems within a region, Whittaker, 1972) can be
measured by the total number of taxa actually or potentially occurring in each biochronological interval. Nevertheless, the richness of a single time interval may be
overestimated when first local appearances have been
considered as occurring at the beginning of the interval
and the taxa that disappeared as persistent up to the end
of it, whereas they might not actually overlap in time.
In order to reduce this bias, and since taxonomic diversity relates to origination/immigration and extinction/emigration rates, data have been analysed using
the methodology developed by Foote (2000) calculating “Total Diversity” and “Estimated mean standing
diversity” as well as “Diversity minus singletons”.
[“Total Diversity” (Ntot) = NFL + NbL + NFt + Nbt; and
“Estimated mean standing diversity” (Nemd) = Ntot –
No/2 – Ne/2; “Diversity minus singletons” (NDmS) = +
NbL + NFt + Nbt; where No (Number of originations) =
NFL + NFt; Ne (Number of extinctions) = NFL + NbL;
NFL = taxa that exist only in the interval; NbL = taxa that
originate before the interval but go extinct within it;
NFt = taxa that originate in the interval and persist beyond it; Nbt = taxa that originate before the interval and
persist beyond it].
Moreover, it is possible to standardise the number of
taxa that potentially occur at a given time interval by
considering species richness at the midpoint of each
time interval as standing richness value calculated according to Harper’s method (Harper, 1975) [Standing
Richness (Nsr) = Nbda + Nrt + ½ (Nf + Nl– No) where
Nsr = number of taxa that potentially occur at a given
44
time interval, Nbda = number of species present before-during and after the faunal unit, Nrt = number of
species present before and after but not in the faunal
unit, Nf = number of first appearances, Nl = number of
last appearances, No = number of taxa confined in the
interval].
2.3.2 - Faunal Renewal
Actually, species richness patterns strictly relate to
origination and extinction rates, thus richness changes
and turnover patterns are closely connected. Increases
or decreases in richness indicate respectively dispersal
or extinction events, whereas a change in taxonomical
composition between two successive biochrons can be
regarded as a true faunal turnover when changes in species composition result from the concurrent extinction
of existing species and replacement by the immigration/origination of new species. Both speciation and
immigration have been treated as first appearances
(= ‘lowest occurrences’ in the local stratigraphic succession) and extinctions or migration as last appearances (= ‘highest occurrences’ in the local stratigraphic succession) (cf. Palombo, 2005 for a discussion). To compute origination and extinction rates, a
taxon is assumed to have originated within the
biochron where it is first observed, while a taxon is assumed to have become extinct within its last observed
biochron. Per-taxon rates of origination (ORpt) and extinction (ERpt) are calculated as ORpt = (NFL +
NFt)/Ntot/∆t, and ERpt = (NFL + NbL)/Ntot/∆t following
Foote (2000) (∆t = span of time).
Faunal renewals can also be estimated from the number of extinctions and new occurrences at the end of a
biochron and at the beginning of the successive one.
Turnover indices (TI) are calculated using the first appearance (FA) and last appearance (LA) percentages
(% FA = FA / RM x 100) (% LA = LA / RM × 100) that
have normalised the LA and FA using a running mean
[RM = N – (FA + LO) / 2], as in Torre et al. (1999) [TI =
(% FA + % LA) / 2]. Using this method, faunal complexes have been considered as “blocks of coordinated
stasis” (sensu Brett et al., 1995, 1996); thus taxa were
assumed to be present during the whole time span corresponding to the biochron in which they first /last appeared (even if this was not necessarily true).
2.3.3 - Taxon-Free Characterisation of Faunal
Complexes
“Palaeocommunity” types were established, assigning species to several ecological categories by means
of feeding behaviour, preferred habitat and body mass
(Taxon-free characterization, Damuth, 1992).
Feeding behaviour has been inferred on the basis of
skull and mandible morphology, the extension of masticator muscle insertions, hypsodonty index, relative
dimensions of premolar and molar rows, occipital bone
and condylus inclination, apophysis of dorsal vertebra
length and inclination, etc. (see Palombo, in press and
references there in).
Herbivores were separated into grazers (Gr, concentrating feeding on grasses and sedges), browsers (Br,
concentrating feeding on leaves, seeds, shoots, etc.,
with a reduced amount of grasses), and mixed-feeders
(MF, taxa which on a seasonal, regional or occasional
basis, eat grass or leaves, bark, seeds, etc. indifferently). The trophic categories of frugivores (Fr) and
omnivores (Om) have been considered as a single
group. Carnivora consuming more than 10% of flesh
are included in “Carnivores” (C).
Three major ecological habitat groups were retained
encompassing taxa inhabiting: 1) forests and closed
woodland (W); open woodland, bushland and wooded
Mediterranean-type vegetation (Wc); miscellaneous
woodland (W-Wc); 2) open environments, grassland,
steppe or savanna (O); as well as 3) more flexible taxa,
which can live in shrubland or open woodland, or even
in more than one landscape or at the edge of two
different ones (Wc-O, O-Wc).
Body mass, the most useful describer of species
adaptations in fossil species, was considered a proxy of
body size, according to Gingerich et al., (1982). Body
mass was estimated using different allometric equations, tested as the most adequate for each taxon (see
Palombo, in press; Palombo & Giovinazzo, 2007).
The following categories have been utilised: BM1 =
<10 kg; BM2 =10-60 kg; BM3=60-200 kg; BM4 =
200-1000 kg; BM5= >1000 kg.
Palaeosynecological analysis was based on the relative abundance of ecological categories for each faunal
complex.
3 - RESULTS
3.1 - SIMILARITY
Clustering of the entire dataset based on species occurrence from the Pliocene to the middle Pleistocene
(fig. 2) clearly divides local faunal assemblages (LFAs)
into two main groups: cluster A with Pliocene-Early
Pleistocene LFAs (from the Ruscinian up to the late
Villafranchian, pre-Jaramillo event) and cluster B with
Middle Pleistocene LFAs (Galerian and early Aurelian
sensu Gliozzi et al., 1997; but see Palombo, 2005).
However, the Italian LFAs correlated with the
Jaramillo event (early Galerian, sensu Gliozzi et al.,
1997) fall within the group made up of the “late
Villafranchian” Spanish and French LFAs highlighting
the main gap separate that occurs between the Italian
“archaic” and “modern” fauna (cf. Palombo, 2005).
Within cluster A, two sub-clusters can be detected:
the first, A1, includes in separate groups the Ruscinian
(A11) and the early Villafranchian (A12) LFAs; the
second (A2) includes the middle-late Villafranchian
ones. The gap dividing A1 from A2 is definitely more
important than the separation between middle (A211)
and late (A212) Villafranchian LFAs. It is worth mentioning that the latest Villafranchian LFAs (as well as
45
Fig. 2: Dendogram for 112 Spanish (20) French (46), and Italian (46)
local faunal assemblages (Q-mode) based on un-weighted data of 149
species. Cophenetic correlation coefficient = 0.9467.
Spain: Layna = Layna-MN15; Villaroya = Villaroya MN16a; Helago =
Huel-MN16b; La Puebla de Valverde = PVal-MN16b; Fonelas = Fonelas-MmQ1; Cueva Victoria = Cvict-MmQ2; Venta Micena; Venta del
Moro = VentaMMmQ2; Quibas = Quibas-MmQ2; Barranco Leon =
BLeon-MmQ2; Fuente Nueva 3 = FNueva-MmQ2; Ponton de la Oliva =
POliva-MmQ2; Huescar = Huescar-MmQ3; Atapuerca TD4 =
AtTD4-MmQ3; Atapuerca TD6 = AtTD6-MmQ3; Cullar de Baza = CullarBaza-MmQ4a; Torralba = Torr-MmQ4b; Ambrona = Ambr-MmQ4b;
Atapuerca TD10= AtTD10-MmQ4b; La Solana del Zamborino = SolZam-MmQ4b; El Congosto = Cong-MmQ4b
France : Montpellier, yellow sands = Mont-14; Montpellier, Palais de
Justice = Just-14; Celleneuve = Celle-14; Trévoux = Tré-14; Saint Laurent des Arbres = SLA-14; Perpignan = Perp-15; Autrice = Autr-15; Vialette = Vial-16; Les Etuaires = Et-16; Chagny = Cha-16; Roca Neyra =
Roc-17; Saint Vallier = StVal-17; Pardines = Pard-17; Saint Vidal =
SVid-17; La Rochelambert = Lamb-17; Corneillet = Corn-17, Chilhac =
Chil-17; Montoussé 5 = Mt5-18; Le Coupet = LCop-17; Senèze =
Sen-18; Peyrrolles = Pey-19; Blassac la Gironde = Blas-19; Sartenette =
Sart-20; Le Vallonet = Vallo-20; Sainzelles = Sz-20; Saint Prest =
SPrest-20; Durfort = Durf-20; Sohleilac = Sol-21; L’Escale = Esc-22;
Vergnac =Verg-22; Nautire = Naut-22; Céou-22; Caune de L’Arago, lower complex = AraI; Caune de L’Arago, middle complex 1 =AraII;
Caune de L’Arago, middle complex 2 = AraIII; Aldène = Ald-23;
Burg-23; Montoussé 3 = Mt3-23; Lunel Viel = LunV-23; Combe-Grenal
= CGren-23; Verchizeuil = Verz-23; Orgnac = Or3-24; Pech d’Aze =
Az7-24; La Fage = Fag-24; Cedres =Cedr-24; Grotte du Lazaret =
LazIII-24
Italy : Val di Pugna = Pugna-MN15; Ponzano di Magra =Ponz; Barga,
Pieve Fosciana = Barga; Triversa = Tr; Gaville, Santa Barbara =
Gav./Barb-Tr; Montopoli = Montop-Mo; Valle Catenaccio = V.Caten.-Mo; Colle Pardo = C.Pardo-Mo; Costa San Giacomo = C.Giacomo-CsGTorre Picchio = T.Picchio-CsG; Quercia = Quercia-CsG;
Olivola = Olivola-OT; Upper Valdarno (already ascribed to Olivola FU)
= Valdarno1-OT; Poggio Rosso = PoggioRos-OT; Matassino = Matassino-OT; Casa Frata = CasaFrata-OT; Casa Sgherri = C.Sgherri-OT; Faella = Faella-OT; Fontana Acetosa = F.Acetosa-OT; Upper Valdarno
(already ascribed to Tasso FU) = Valdarno2-OT; Bacino Tiberino =
B.Tiberino-OT; Monte Riccio = Mt.Riccio-OT; Pantalla = Pantalla-OT;
Mugello = Mugello-Fa; Val di Chiana = ValChiana-Fa; Selvella = Selvella-Fa; Pietrafitta = Pietrafita-Fa; Pirro Nord = Pirro-Pr; Colle Curti =
C.Curti-CC; Cava Redicicoli = Redicicoli-Pr; Slivia = Slivia-Sl; Ponte
Galeria 2 = P.Galeria-Sl; Pagliare di Sassa = Sassa-Sl; Valdemino = Valdemino-Is; Isernia La pineta = Isernia-Is; Cesi = Cesi-Is; Notarchirico =
Notarch-Is; Venosa Loreto= Loreto-Fr; Fontana Ranuccio = Ranuccio-Fr; Visogliano = Visogliano-Fr; Sedia del Diavolo = S.Diavolo-TP;
Torre in Pietra, lower level = T.Pietra-TP; Capri Quisisana = CapriQ-TP;Bucine = Bucine-TP; Torre in Pietra, upper level = T.Pietra2-TP; Campo Verde = Cverde-TP
Tr = Triversa FU; Mo = Montopoli FU; CsG = Costa San Giacomo FU;
OT = Olivola+Tasso FU; Fa = Farneta FU; Pr = Pirro FU; TP = Torre in
Pietra FU.
Fig. 2 : Classification hiérarchique (dendrogramme-Q) des 112 faunes
locales espagnoles (20), françaises (46) et italiennes (46) du Pliocène et
Pléistocène inférieur et moyen basée sur 149 espèces. CCC = 0,9467.
46
the Italian LFAs ascribed to Colle Curti FU) set separately, confirming the renewal characterising the second part of the Early Pleistocene (A22).
Within cluster B, a gap clearly separates two other
groups: B1 (late Early Pleistocene and early Middle
Pleistocene, early Galerian and the most archaic middle Galerian LFAs) and B2 (Middle Pleistocene, middle
and late Galerian, early Aurelian LFAs). B1 subcluster
includes French LFAs which have been calibrated with
the Jaramillo event or LFAs considered very close in
age to it (Huescar, Spain) as well as the Italian Ponte
Galeria LFA, probably because of the presence of exclusive taxa such as Hemibos galerianus (Martinez
Navarro & Palombo, 2004) and of the long-surviving
Villafranchian herbivores, such as the medium-sized
cervids belonging to the “Pseudodama” group (but see
Di Stefano & Petronio, 2003). Interestingly, this
sub-cluster set together Italian and French localities
that in separate analyses set with the latest
Villafranchian and Galerian (early Middle Pleistocene)
LFAs respectively. This fact highlight the “transitional” character of latest Early Pleistocene LFAs
confirmed by the persistence of several Villafranchian
taxa together with new taxa that will survive until the
following middle Pleistocene.
On the whole, the results obtained seem to indicate
that, although the heterogeneity of the fossil record in
each region does not enable us carry out analyses on the
basis of a comparable number of LFAs for each interval
(for instance, large mammalian faunas are poorly represented in the Ruscinian fossil record of Italy and the
late Villafranchian record of Spain and France), the
main clusters emphasise on the significance of the middle to late Pliocene faunal reconstruction.
3.2 - DIVERSITY AND RICHNESS
The trend of total diversity (Ntot), measured on the
basis of species occurrences in the faunal complexes
defined above (fig. 3), reveals that periods of lower
diversity alternating phases of an average species increase occurred throughout the whole Plio-Pleistocene. A decrease in Ntot characterised the transition
from the Middle to Late Pliocene (early, V1-MN16a, to
middle, V2-MN16b, Villafranchian). The following increase in number of species during the Late Pliocene
(middle Villafranchian, V3-MN17) was more gradual
and was eventually completed at the beginning of the
Early Pleistocene (early late Villafranchian, V4), when
a peak in Nemd and Nsr can also be detected (fig. 3).
During the following Early Pleistocene (latest
Villafranchian-Early Galerian sensu Gliozzi et al.,
1997, V4-G1), richness decreased reaching a minimum
at the end of the Early Pleistocene. This late Early
Pleistocene negative peak was followed by a significant increase in the number of species at the transition
to the Middle Pleistocene (middle Galerian sensu
Gliozzi et al., 1997, G2).
It is worth noting that the declining in biodiversity at
Middle (V1) to Late Pliocene (V2) transition is possibly related to the dwindling of forest dwellers. This
tendency is less evident or disagrees with the trends of
forest dwellers’ Nemd and Nsr (fig. 3) because of following Harper’s (1975) and Foote’s (2000) methods the
number of taxa confined in the interval are underestimated. On the other hand, the high values of Ntot, Nemd
and Nsr characterising the North-western Mediterranean region at the beginning of the Early Pleistocene
were mainly related to the increase in ubiquitous taxa
(fig. 3).
3.3 - FAUNAL RENEWAL
The general trend shown from the Middle Pliocene to
the Early Pleistocene in biodiversity is confirmed by
trends in origin/extinction rates (fig. 4). At transition
from the Middle to Late Pliocene (from V1 to V2), the
number of last appearances was greatly enhanced,
leading to a moderate extinction phase that mainly involved forest dwelling taxa (fig. 5), followed by a dispersal period, during which first appearances (open
landscape dwelling and, subordinately, ubiquitous
taxa, fig. 5) clearly prevailed.
For most of the Early Pleistocene extinctions, once
again prevailed. This period was followed by a new dispersal phase at the transition to the middle Pleistocene,
leading to the increase in diversity mentioned above
(fig. 3, 4).
The trend in turnover indexes calculated at the transition between two successive biochrons (fig. 6) shows
two important faunal renewals at the early to middle
Villafranchian (V1 toV2+V3) (first mainly involving
forest dwellers and later ubiquitous taxa), and at the
early to the middle Galerian (sensu Gliozzi et al., 1997)
(G1-G2) transition. The highest turnover indexes correspond to extinction bioevents characterising the
Early Pleistocene (V4 and V5) and especially concern
ubiquitous taxa (fig. 6).
Accordingly, four different phases ensued in a rather
cyclical way: an “extinction” phase took place during
the Early and Middle Pliocene (Ruscinian and early
Villafranchian), followed by a dispersal phase during
the Late Pliocene (middle and Earliest Villafranchian);
a new extinction phase took place during the ensuing
early Pleistocene, even if the faunal complexes
(V5-G1) were relatively static. At the transition to the
Middle Pleistocene new appearances again prevailed.
3.4 - CHANGES IN ECOLOGICAL STRUCTURE
OVER TIME
Even if faunal renewal is related to extinctions, origination/immigration and local evolution affecting faunal richness, it does not always imply structural
reconstruction of mammal communities. Changes in
community structure can, however, be detected during
the whole time-span examined here.
47
120
90
80
100
70
60
80
50
60
40
40
30
20
20
10
0
0
R
V1
V2
V3
Richness
V4
V5
G1
G2
R
V1
V2
V3
Total Diversity
Estimated mean standing diversity
Standing richness
60
V4
V5
G1
G2
Total Diversity minus singletons
60
Richness
Diversity
50
50
40
40
30
30
20
20
10
10
0
R
V1
V2
Forest dwellers
V3
V4
Open landscape dwellers
V5
G1
G2
0
R
Ubiquitous taxa
V1
V2
Forest dweller
V3
V4
Open landscape dwellers
V5
G1
G2
Ubiquitous taxa
30
35
Estimated mean diversity
Standing richness
30
25
25
20
20
15
15
10
10
5
5
0
0
R
V1
V2
Forest dwellers
V3
V4
Open landscape dwellers
V5
G1
Ubiquitous taxa
G2
R
V1
V2
Forest dweller
V3
V4
Open landscape dwellers
V5
G1
G2
Ubiquitous taxa
Fig. 3: Trends of diversity from the Middle Pliocene to the Early Pleistocene in the North-Western Mediterranean faunal complexes and in ecological categories established on the basis of the preferred habitat.
Standing richness value calculated according to Harper’s method (1975) [Standing Richness (Nsr) = Nbda + Nrt + ½ (Nf + Nl– No) where Nsr = number
of taxa that potentially occur at a given time interval, Nbda = number of species present before-during and after the faunal unit, Nrt = number of species
present before and after but not in the faunal unit, Nf = number of first appearances, Nl = number of last appearances, No = number of taxa confined in the
interval].
“Total Diversity”, “Estimated mean standing diversity” and “Diversity minus singletons”, calculated according to Foote’s (2000) method. [“Total Diversity” (Ntot) = NFL + NbL + NFt + Nbt; “Estimated mean standing diversity” (Nemd) = Ntot – No/2 – Ne/2; “Diversity minus singletons” (NDmS) = + NbL + NFt + Nbt;
where No (Number of originations)= NFL + NFt; Ne (Number of extinctions) = NFL + NbL;NFL = taxa that exist only in the interval; NbL = taxa that originate before the interval but go extinct within it; NFt = taxa that originate in the interval and persist beyond it; Nbt = taxa that originate before the interval and persist
beyond it].
Fig. 3 : Variation de la diversité des complexes fauniques de la zone méditerranéenne nord occidentale durant le Pliocène moyen et supérieur et le Pléistocène inférieur établie d’après l’habitat préféré.
Valeur de la richesse standardisée calculée d’après la méthode de Harper (1975) [Richesse Debout (Nsr) = Nbda + Nrt + ½ (Nf + Nl – Aucun) où Nsr =
nombre de taxons potentiellement présents durant l’intervalle de temps examiné, Nbda = nombre de taxons présents avant, pendant et après l’intervalle
de temps examiné, Nrt = nombre de taxons présents avant et après mais pas dans l’intervalle de temps examiné, Nf = nombre de premières apparitions,
Nl = nombre de dernières apparitions, No = nombre de taxons confinés dans l’intervalle].
Diversité totale, diversité moyenne estimée et Diversité moins singletons, calculées d’après la méthode de Foote (2000). [“Diversité totale” (Ntot) = NFL +
NbL + NFt + Nbt ; “diversité moyenne estimée” (Nemd) = Ntot – No/2 – Ne/2 ; “Diversité moins singletons” (NDmS) = + NbL + NFt + Nbt ; où No(Nombre d’apparitions) = NFL + NFt ; Ne (Nombre d’extinctions) = NFL + NbL ; NFL = taxons qui existent seulement dans l’intervalle du temps examiné ; NbL = taxons qui sont
présents avant l’intervalle de temps examiné mais qui disparaissent durant cet intervalle ; NFt = taxons présents dans l’intervalle de temps examiné et persistant dans l’intervalle suivant ; Nbt = taxons présents avant et après l’intervalle de temps examiné].
During the Middle Pliocene (early Villafranchian,
V1) distribution by habitat type for large mammals and
by feeding behaviour for categories of herbivores did
not noticeably differ from that typically recorded in
modern forest or scrubland environments: forestdwellers dominated, and among the herbivores, browsers attained their maximum percentage, along with the
trophic category of frugivores and omnivores (fig. 7).
Starting from the Late Pliocene until the Early Pleistocene (middle and late Villafranchian, V2-V5), the
frequency of taxa inhabiting forest woodlands progressively decreased, whereas taxa suggesting open
environments and more arid climatic conditions progressively augmented, especially during the Early
Pleistocene, reaching their maximum at the end of the
late Villafranchian (V5) (fig. 7). Actually, the late
48
Fig. 4: Trends in origination and extinction rates in the North-Western Mediterranean faunal complexes from the Middle Pliocene to
the Early Pleistocene.
Origination (ORpt) and Extinction (ERpt) rates calculated according to
Foote’s (2000) method (ORpt = (NFL + NFt)/Ntot/∆t, and ERpt = (NFL +
NbL)/Ntot/∆t ; ∆t = span of time).
Fig. 4 : Taux d’apparition et d’extinction durant le Pliocène moyen et
supérieur et le Pléistocène inférieur calculés à partir des complexes
fauniques de la zone méditerranéenne nord occidentale.
Taux d’apparitions (ORpt) et d’ extinctions (ERpt) calculés d’après la
méthode de Foote (2000) (ORpt = (NFL + NFt)/Ntot / t, et ERpt = (NFL +
NbL)/Ntot / t ; t = intervalle du temps).
Fig. 6: Faunal renewals from the Middle Pliocene to the Early Pleistocene of North-Western Mediterranean faunal complexes (above)
and in the ecological categories established on the basis of the
species’ preferred habitat (below).
Turnover indices (TI) = (% FA + % LA) / 2; % FA = FA / RM x 100;
% LA = LA / RM x 100; FA = first appearance; LA = last appearance;
RM (running mean) = Ntot – (FA + LA) / 2.
Fig. 6 : Renouvellements des complexes fauniques de la zone méditerranéenne nord occidentale et des catégories écologiques établies d’après l’habitat préféré (en bas) durant le Pliocène moyen et supérieur et
le Pléistocène inférieur
Indices de renouvellement (TI) = (% FA + % LA) / 2 ; % FA = FA / RM x
100 ; % LA = LA / RM x 100 ; FA = première apparition ; LA = dernière
apparition ; RM (running mean) = Ntot – (FA + LA) / 2.
Early Pleistocene (V5) was the time span during which
the lowest frequency of forest-dwelling taxa has been
found. Moreover, starting from the Late Pliocene (V3),
grazer frequency progressively increased, reaching its
maximum during the latest Villafranchian (V5), when
browsers reached their minimum.
It is worth noting that mixed feeders were the dominant category, and reached their maximum at the beginning of the Late Pliocene, starting to decrease only at
the beginning of the Middle Pleistocene (G2), when
grazers slightly augmented along with open landscape
and forest dwellers, possibly due to the occurrence of
more diversified environments.
Fig. 5: Trends in origination and extinction rates (following Foote,
2000), from the Middle Pliocene to the Early Pleistocene, in the ecological categories established on the basis of the preferred habitat of
species characterising the North-Western Mediterranean faunal
complexes.
Fig. 5 : Taux d’apparition et d’extinction estimés à partir des catégories
écologiques établies d’après l’habitat préféré par les taxons des complexes fauniques de la zone méditerranéenne nord occidentale durant le
Pliocène moyen et supérieur et le Pléistocène inférieur.
A comparison of body mass categories (fig. 7) shows
an average decrease in small taxa (BM1 < 60 kg) from
the early (V1) to middle Villafranchian (V2), when medium-sized species (BM3) became dominant. Mediumsized species were particularly frequent during the late
Early Pleistocene (late Villafranchian, V4-V59),
whereas larger mammals (BM4) and pachyderms
(BM5) were especially frequent during the middle
49
Fig. 7: Bar charts of species frequency in each ecological category established on the basis of the species’ preferred habitat, feeding habit and
body mass in the North-Western Mediterranean faunal complexes from the Middle Pliocene to the early Middle Pleistocene.
Fig. 7 : Fréquence des espèces dans chaque catégorie écologique établie d’après l’habitat préféré, la diète, et la masse corporelle des complexe fauniques de la zone méditerranéenne nord occidentale durant le Pliocène moyen et supérieur et le Pléistocène inférieur.
Villafranchian (V2) and the Galerian (G1-G2). These
trends substantially agree with environmental data.
4 - DISCUSSION
As mentioned above, ecologists and evolutionists
have been concerned mainly with problems related to
climatic influence on faunal renewal, and two central
questions have been widely debated. Could progressive
changes in the composition of mammal faunal complexes (fluctuations in biodiversity, biomass, changes
in frequency between forest- or woodland-dwellers
and more open environment dwellers, of browsing,
grazing and mixed-feeder ungulates, etc.) be interpreted as a response to climate changes (which in turn
paralleled significant changes in temperature, moisture
and vegetational cover)? Are intrinsic biotic controls
more important than extrinsic environmental controls
as regards faunal renewal? The results obtained support
the argument that, in the North-western Mediterranean
region and during the time span considered here, the
most important faunal renewals occurred at the transition from the early to middle Villafranchian (Middle to
Late Pliocene, ~2.7-2.5 Ma) and from the early to middle Galerian, (latest Early to Middle Pleistocene
~1.1-0.7 Ma). A progressive faunal renewal also took
place during the latest Pliocene (middle to late
Villafranchian transition). As expected, more or less
significant changes in faunal taxonomical composition
(leading to biochron distinction) correspond to faunal
structural reconstructions.
However, which among the above mentioned faunal
renewal was most affected by climatic and environmental changes? The faunal renewal from the early to
middle Villafranchian faunal complexes and the ensuing (V2 – V3) reorganisation of palaeocommunities
was probably driven by the Pliocene climate worsening, in turn related to the onset of bipolar glaciations
and changes in the periodicity and amplitude of the glacial-interglacial cycles (orbital periodicity of 41 ka,
deMenocal & Bloemendal, 1995). The resulting increase in aridity and more intense seasonality (Suc et
al., 1995) caused the disappearance of forest-dwelling
taxa, especially small carnivores and arborealscansorial taxa, whereas new large grazers, mixed
feeders or even browsers appeared.
This renewal (already called “elephant-Equus
event”, Lindsay et al., 1980; Azzaroli, 1983; Azzaroli
et al., 1988) can be considered as the starting point for a
dispersal phase leading to a progressive diversity increase during the following Pliocene and up to the beginning of the Early Pleistocene. These faunal changes
indicate that forests or woodlands gradually gave way
50
to more open environments (including Artemisia
steppe), alternating with warm-temperate deciduous
forests. Indeed, from an ecological point of view, early
Villafranchian faunal complexes developed in environments slightly resembling those of modern forests,
especially due to the relatively high frequency of
frugivores and the presences of scansorial species (especially Carnivora), whereas the middle Villafranchian
faunal complexes show more affinities with modern
bush-woodland. The faunal renewal was primarily due
to immigration, mainly from Eastern Europe, of large
and medium-sized herbivores, both grazers and
mixed-feeders, but also very large browsers (such as a
primitive Mammuthus), while evolutionary substitutions within surviving phyletic lineages were rather
negligible (tab. 1 and 2). The dispersion of incoming
herbivores is consistent with the spread of grassland
and Artemisia and Ephedra steppe during “glacial”
phases, while closed forests gave way to warm-temperate deciduous or coniferous forests during the “interglacial”, under more arid global conditions. Moreover,
during the late Pliocene, the appearance of cooperative
foraging ubiquitous canids and, perhaps, the powerful
scavenger hyaenid Pachycrocuta brevirostris, inhabiting more or less open environment, affected the
carnivore guild. Indeed, the already-called “wolfevent” (Azzaroli, 1983, 1995; Palmqvist et al., 1999),
possibly a more gradual phenomenon than previously
believed, had already been completed at the beginning
of the Early Pleistocene (Palombo, 2005; Sardella &
Palombo, 2007). The latest Pliocene dispersal phase
primarily involved carnivores, since among new taxa
none belong to species which evolved in loco (tab. 2),
whereas new appearances among herbivores were principally linked to the origination of new species within
pre-existing phyletic lineages [such as Mammuthus,
Equus, Eucladoceros, “Pseudodama” (=Axis Rusa
after Di Stefano & Petronio, 2003) and some Leptobos]
and subordinately to immigration of large ruminants
both browsers and mixed feeder (e.g Cervalces,
Praevibos) (tab. 2).
Accordingly, around 2.0-1.8 Ma (beginning of the
late Villafranchian), the diversity peaked, despite the
extinction of some small browsing and grazing ruminants. The Early Pleistocene faunal reconstruction was
possibly affected both by climatic worsening and modification of the internal dynamics of competitive relationships, also depending on the disappearances of
some pre-existing key taxa and ensuing available
empty niches (Walker & Valentine, 1984; Rosenzweig
& McCord, 1991). During the late Early Pleistocene,
the drop in temperature, along with an increase in dryness, undoubtedly led to the spread of wooded grassland and savanna, especially in the southernmost
region (for instance the Iberian and Italian peninsulas).
The increase in grazers and the appearance of new taxa
inhabiting grasslands, and among other of
Theropithecus, a mixed feeder primate dwelling in
open landscapes (Martinez-Navarro et al., 2005; Rook
et al., 2005), is consistent with this environmental
change. This evidence of African immigration to
southernmost Europe stresses the importance of “out of
Africa” migratory waves, taking place approximately
around 1.6 /1.3 Ma (Martinez Navarro, in press). Subsequently, the diversity dropped and a new faunal renewal took place at the end of the Early Pleistocene.
Actually, the so-called “Galerian mammal turnover
pulse” (Rodriguez et al., 2004) started approximately
when glacial maxima attributed to massive Northern
Hemisphere ice sheets (Suc et al.,1995; Shackleton,
1995) became more extreme, representing a major
community reorganization in the Western Mediterranean area (see e.g. Azanza et al., 1999, 2000, 2004;
Palombo, 2005, in press and references therein;
Palombo & Valli, 2005).
5 - CONCLUSION
According to the results obtained, it seems that the
most important faunal renewals, due both to immigrations and extinctions, can be linked to major global climatic changes (noticeably cold-shift oscillations).
These turnovers are preceded by more or less prolonged phases during which diversity decreased, but
represent a starting point for a dispersal phase, leading
to a progressive enhancement of faunal diversity.
Moreover, it seems that the most important turnovers
occurred in a quasi-cyclical way, each cycle corresponding to a faunal reconstruction made up of a period
of prevailing appearances and by a successive phase of
predominant extinctions, leading to a reduction in
diversity.
The most important changes in faunas seem to be
triggered by important climatic and vegetational
changes, whereas the structure of the communities to
be progressively reassessed by inter- and intra-guilds
competition.
As a result, what are the implications for “Quaternary” and Pleistocene boundaries? Actually, the faunal
renewal from the early to the middle Villafranchian
(from V1-MN16a to V2-MN16b) can be correlated
with the beginning of significant evolution not only of
the Earth’s climatic system but also of the biosphere
corresponding to the dawn of the Gelasian. Moreover,
taking into account on the one hand that the transition
to the Late Pliocene marks the beginning of a more period of increasing of faunal diversity coupled with
changes in community structure, and that on the other
hand the tassonomical and structural changes characterising the Early Pleistocene faunas, depend on the
previous dispersal phase, and correlated moderate turnover pulses, the middle to late Villafranchian transition
seems to be less important than the early to middle
Villafranchian renewal phase, as far as the NorthWestern Mediterranean faunas are concerned.
Accordingly, it seems more reasonable to extend the
base of the Pleistocene downwards from 1.81 Ma (official Plio/Pleistocene boundary) to 2.6 Ma (base of Pliocene Gelasian Stage). Hence, the base of the Gelasian
51
seems to be the most appropriate lower boundary for
both the Quaternary Period and Pleistocene Epoch.
ACKNOWLEDGEMENTS
Thanks are due to Prof. C. Guerin and J-F. Pastre for their useful
comments.
The English version was revised by Dr. Mary Groeneweg, English
Language Lecturer at Cagliari University. Work supported by MIUR
60% grants 2005 Prof. M.R. Palombo (“Evoluzione degli ecosistemi
continentali dell’Italia peninsulare durante il Plio-Pleistocene: un
approccio multidisciplinare”).
REFERENCES
AZZAROLI A., DE GIULI C., FICCARELLI G., & TORRE D.,
1988 - Late Pliocene to Early Mid-Pleistocene mammals in Eurasia: Faunal succession and dispersal events. Palaeogeography,
Palaeoclimatology, Palaeoecology, 66, 77-100.
BARNOSKY A.D., 2001 - Distinguishing the effects of the red
queen and Court Jester on Miocene mammal evolution in the northern Rocky Mountains. Journal of Vertebrate Paleontology, 21
(1), 172-185.
BARRY J.C., MORGAN M.E., FLYNN L.J., PILBEAM D.,
JACOBS L.L., LINDSAY E.H., RAZA S.M., & SOLOUNIAS
N., 1995 - Patterns of faunal turnover and diversity in the Neogene
Siwaliks of Northern Pakistan. Palaeogeography, Palaeoclimatology, Palaeoecology, 115, 209-226.
BELL G., 1982 - The Masterpiece of Nature: The Evolution and Genetics of Sexuality. University of California Press, Berkeley, 635 p.
BONIFAY M.F., 1978 - Faunes de transition du Pléistocène moyen
de France. Bulletin du Museum d’Anthropologie et Préhistoire de
Monaco, 22, 5-15.
AGUIRRE E., & PASINI G., 1985 - The Plio-Pleistocene boundary.
Episodes, 8 (2), 116-120.
BRETT C.E., & BAIRD G.C., 1995 - Coordinated stasis and evolutionary ecology of Silurian to Middle Devonian faunas in the
Appalachian Basin. In D.H. Erwin & R.L. Anstey (ed.), New
Approaches to Speciation in the Fossil Record. Columbia University Press, New York, Pennsylvania, 285-315.
AGUSTI J., 1986 - Synthèse biostratigraphique du Plio-Pléistocène
de Gaudix-Baza (province de Granada, sud-est de l’Espagne).
Geobios, 19, 505-510.
BRETT C.E, IVANY L.C., & SCHOPF K.M., 1996 - Coordinated
stasis: an overview. Palaeogeography, Palaeoclymatology, Palaeoecology, 127, 1-20.
AGUSTÍ J., CABRERA L., GARCÉS M., KRIJGSMAN W.,
OMS O., & PARÉS J.M.. 2001 - A calibrated mammal scale for
the Neogene of Western Europe. State of the art. Earth-Science Reviews, 52, 247-260.
BRUIJN DE H., DAAMS R., DAXNER-HÖCK G., FAHLBUSCH
V., GINSBURG L., MEIN P., & MORALES J., 1992 - Report of
the RCMNS working group on fossil mammals, Reisensburg 1990.
Newsletter Stratigraphy, 26, 65-118.
AGUSTÍ J., MOYÀ-SOLÀ S., & PONS J., 1987 - La sucesión de
mamíferos en el Pleistoceno inferior de Europa: proposición de
una nueva escala bioestratigráfica. Paleontologia i Evolution, 1,
287-295.
CALOI L., & PALOMBO M.R., 1996 - Latest Early Pleistocene
mammal faunas of Italy, biochronological problems. Il Quaternario, 8 (2), 391-402.
AGASSIZ L., 1840 - Etudes sur les Glaciers. Jemt & Gassmamm
Neuchâtel, 346 p.
ALBERDI M.T., AZANZA B., CERDEÑO E., & PRADO J.L.,
1997 - Similarity relationship between Mammal faunas and
biochronology from latest Miocene to Pleistocene in Western
Mediterranean area. Eclogae Geologicae Helvetiae, 90, 115-132.
ALROY J., KOCH P.L., & ZACHOS J.C., 2000 - Global climate
change and North American mammalian evolution. In D.H. Erwin,
& S.L. Wing (ed.), Deep Time. Palaeobiology supplement, 26 (4),
259-288.
AZANZA B., ALBERDI M.T., & PRADO J.L., 1999 - Large mammal diversity and turnover patterns during the Plio-Pleistocene in
Western Mediterranean Area. Revista de la Sociedad Geológica de
España, 12 (1), 113-122.
AZANZA B., ALBERDI M.T., & PRADO J.L., 2000 - Large mammal turnover pulses correlated with la test Neogene glacial trends
in the northwestern Mediterranean region. In M.B. Hart (ed.), Climates: Past and Present. Geological Society Special Publications,
London, 161-171.
AZANZA B., PALOMBO M.R., & ALBERDI M.T., 2004 - Large
mammal turnover pulses and palaeoclimate changes from the Miocene to the Late Pleistocene in Italy. Rivista Italiana di Paleontologia e Stratigrafia, 110 (2), 531-545.
AZZAROLI A., 1977 - The Villafranchian Stage in Italy and the
Plio-Pleistocene Boundary. Giornale di Geologia, 41, 61-79.
AZZAROLI A., 1982 - Remarques sur les subdivisions chronologiques du Villafranchien. Actes Colloque “Le Villafranchien Mediterranéen”, Lille 9-10 décembre 1982, 1, 7-14.
AZZAROLI A., 1983 - Quaternary mammals and the “End-Villafranchian” dispersal event A turning point in the history of Eurasia. Palaeogeography, Palaeoclimatology, Palaeoecology, 44,
117-139.
AZZAROLI A., 1992 - The cervid genus Pseudodama n.g. in the
Villafranchian of Tuscany. Palaeontographia Italica, 79, 1-41.
AZZAROLI A., 1995 - The ‘Elephant-Equus’ and the ‘End-Villafranchian’ events in Eurasia. In E.S. Vrba, G.H. Denton, T.C. Partridge & L.H. Burckle (ed.), Paleoclimate and Evolution with
Emphasis on Human Origins. Yale University Press, New Haven
and London, 311-318.
CLAGUE J., 2004 - Status of the Quaternary. Quaternary Science
Reviews, 24, 2424-2425.
CLAGUE J., 2006 - Status of the Quaternary: Your opinion sought.
Quaternary International, 144, 99-100.
CROITOR R.V., 2001 - Functional morphology and ecology of fossil deer of Italy in conditions of climate aridisation. Journal of
Morphology, 248.
CROITOR R.V., 2005 - Early Pleistocene small-sized deer from the
mediterranean area. In H. de Lumley, F. Lacombat & P.E. Moullé
(ed.), Abstracts Coll. Cadre biostratigraphique de la fin du Pliocène et du Pléistocène inférieur (3 Ma à 780 000 ans) en Europe
méridionale. Tende 20-22 mai 2005, 63-64.
CROITOR R.V., & BONIFAY M.F., 2002 - Etude préliminaire des
cerfs du gisement Pléistocène inférieur de Ceyssaguet
(Haute-Loire). Paleo, 13, 129-144.
DAMUTH J.D., 1992 - Taxon-free characterization of animal communities. In A.K Behrensmeyer., J.D. Damuth, W.A. Dimicheli,
R. Potts, H. Sues & S.L. Wing (ed.), Terrestrial ecosystems
through time. University of Chicago Press, Chicago and London,
183-203.
DEMENOCAL P.B., & BLOEMENDAL J., 1995 - Plio-Pleistocene climatic variability in subtropical Africa and the paleoenvironment of hominid evolution: A combined data model approach.
In E.S. Vrba, G.H. Denton, T.C. Partridge & L.H. Burkle (ed.), Paleoclimate and Evolution with Emphasis on Human Evolution.
Yale University Press, New Haven, 262-288.
DESNOYERS J., 1829 - Observations sur un ensemble de dépôts
marins plus récents que les terrains tertiaires du bassin de la Seine,
et constituant une formation géologique distincte; précédées d’un
aperçu de la non-simultanéité des bassins tertiaires. Annales de
Sciences Naturelles, Paris, 402-491.
DI STEFANO G., & PETRONIO C., 1998 - Origin and relationships among the Dama-like cervids in Europe. Neues Jahrbuch für
Geologie und Paläontologie Abhandlungen, 207, 37-55.
DI STEFANO G., & PETRONIO C., 2003 - Systematics and evolution of the Eurasian Plio-Pleistocene tribe Cervini (Artiodactyla,
Mammalia). Geologica Romana, 36 (2000-2002), 311-334.
52
DING Z., RUTTER N.W., & LIU T., 1997 - The onset of extensive
loess deposition around the G/M boundary in China and its palaeoclimatic implications. Quaternary International, 40, 53-60.
the Bighorn and Crazy Mountains Basins, Wyoming and Montana
(USA). Palaeogeography, Palaeoclimatology, Palaeoecology,
115, 181-207.
FARRIS J.S., 1969 - On the Cophenetic Correlation Coefficient. Systematic Zoology, 18, 279.
MARTINEZ NAVARRO B., & PALOMBO M.R., 2004 - Occurrence of Indian genus Hemibos (Bovini, Bovidae, Mammalia) at
the Early-Middle Pleistocene transition in Italy. Quaternary
Science, 61, 314-317.
FOOTE M., 2000 - Origination and extinction components of taxonomic diversity: general problems. In D.H. Erwin, & S.L. Wing
(ed.), Deep Time. Palaeobiology supplement, 26, 74-102.
FORBES E., 1846 - On the connection between the distribution of
existing fauna and flora of the British Isles, and the geological
changes which have affected their area, especially during the
epoch of the Northern Drift. Great Britain. Geological Survey Memoir, 1, 336-342.
GINGERICH P.D., SMITH B.H., & ROSENBERG K., 1982 Allometric scaling in the dentition of primates and prediction of
body weight from tooth size in fossils. American Journal Physical
Anthropology, 58, 81-100.
GLIOZZI E., ABBAZZI L., AMBROSETTI P., ARGENTI P.,
AZZAROLI A., CALOI L., CAPASSO BARBATO L., DI
STEFANO G., ESU D., FICCARELLI G., GIROTTI O.,
KOTSAKIS T., MASINI F., MAZZA P., MEZZABOTTA C.,
PALOMBO M.R., PETRONIO C., ROOK L., SALA B.,
SARDELLA R., ZANALDA E., & TORRE D., 1997 - Biochronology of selected Mammals, Molluscs, Ostracods from the
Middle Pliocene to the Late Pleistocene in Italy. The state of the
art. Rivista Italiana di Paleontologia e Stratigrafia, 103 (3),
369-388.
GRADSTEIN F.M., JAMES G., OGG J.G., & SMITH A.G., 2004
- A Geological Time Scale 2004. Cambridge University Press,
500 p.
GRAHAM R.W., & LUNDELIEUS E.L. JR., 1984 - Coevolutionary disequilibrium and Pleistocene extinctions. In P.S. Martin &
R.G. Klein (ed.), Quaternary Extinctions, a Prehistoric Revolution. University of Arizona Press, Tucson, 223-249.
GRICHUK V.P., 1997 - Late Cenozoic change in flora in extra-tropical Eurasia in the light of palaeomagnetic stratigraphy. In E. Van
couvering (ed.), The Pleistocene boundary and the beginning of
the Quaternary. Cambridge University Press, 104-113.
GUÉRIN C., 1982 - Première biozonation du Pléistocène européen,
principal résultat biostratigraphique de l’étude des Rhinocerotidae
(Mammalia, Perissodactyla) du Miocène terminal au Pléistocène
supérieur de l’Europe occidentale. Geobios, 15, 593-598.
GUÉRIN C., 1990 - Biozones or Mammal Units? Methods and Limits in Biochronology. In E.H. Lindsay, V. Fahlbush & P. Mein
(ed.), European Neogene Mammal Chronology. Plenum Press,
New York, 119-130,.
HARPER C.W. JR., 1975 - Standing diversity of fossil groups in
successive intervals of geologic time: A new measure. Journal of
Paleontology, 49, 752-757.
HAZEL J.E., 1970 - Binary Coefficients and Clustering in Biostratigraphy. Bulletin geological Society of America, 81, 3237-3252.
KAHLKE R.D., 2005 - Late Early Pleistocene mammal faunal communities in Europe: mixture of acquaintance or unique assemblages? In H. de Lumley, F. Lacombat & P.E. Moullé (ed.), Abstracts
Coll. Cadre biostratigraphique de la fin du Pliocène et du Pléistocène infèrieur (3 Ma à 780 000 ans) en Europe méridionale. Tende
20-22 mai 2005, 19.
KOLFSHOTEN Van T., & GIBBARD P.L., 1998 - The dawn of the
Quaternary, an introduction. Mededelingen Nederlands Instituut
voor Toegepaste Geowetenschappen TNO, 60, 13-17.
LINDSAY E.H., OPDYKE N.D., & JOHNSON N.M., 1980 - Pliocene dispersal of the horse Equus and Late Cenozoic mammalian
dispersal events. Nature, 287, 135-138.
LYELL C., 1833 - Principles of Geology, Being an Attempt to
Explain the Former Changes of the Earth’s Surface by Reference
to Causes Now in Operation, vol. III. John Murray, London, 398 p.
LYELL C., 1839 - Eléments de Géologie, Pitois-Levrault, Paris, 648
p.
MAAS M.C., ANTHONY M.R.L., GINGERICH P.D.,
GUNNELL G.F., & KRAUSE D.W., 1995 - Mammalian generic
diversity and turnover in the Late Paleocene and Early Eocene of
MARTINEZ-NAVARRO B., CLARET A., SHABEL A.B.,
PÉREZ-CLAROS J.A., LORENZO C., & PALMQVIST P.,
2005 - Early Pleistocene “hominid remains’’ from southern Spain
and the taxonomic assignment of the Cueva Victoria phalanx.
Journal of Human Evolution, 48, 517-523.
MARTIRNEZ-NAVARRO B., in press - Hippos, pigs, bovids, saber-toothed tigers, monkeys and hominids dispersals during Late
Pliocene and Early Pleistocene times through the Levantine Corridor. In N. Goren-Inbar & J.D. Speth (ed.), Proceedings of the
conference “Human Paleoecology in the Levantine Corridor”.
Oxbow Books, Oxford.
MEIN P., 1975 - Résultats du groupe de travail des vertébrés : biozonation du Néogène méditerranéen à partir des Mammifères. Report
Activity RCMNS working groups, Bratislava, 78-81.
MEIN P., 1990 - Updating of MN zones. In E.H. Lindsay, V. Fahlbusch & P. Mein (ed.), European Neogene Mammal Chronology.
Plenum Press, New York, Nato ASI Ser., 180, 73-90.
MEIN P., 1998 - Biochronologie et phases de dispersion chez les Vertébrés cénozoïques. Bulletin de la Société géologique de France,
170 (2), 195-204.
OGG J., 2004 - Introduction to concepts and proposed standardization of the term “Quaternary”. Episodes, 27 (2), 125-126.
PALOMBO M.R., 2004 - Guilds of large mammals from the Pliocene to the Late Pleistocene in Italian peninsula. In E. Baquedano
& S. Rubio (ed.), Homenaje a Emiliano Aguirre. Zona Archeologica 4 (2 Paleontologia) Museo Arqueológico Regional, Madrid,
372-391.
PALOMBO M.R., 2005 - Biochronology of the Plio-Pleistocene
mammalian faunas of Italian peninsula: knowledge, problems and
perspectives. Il Quaternario, 17 (2/2), 2004, 565-582.
PALOMBO M.R., in press - Large Mammal Guilds on the Italian
Peninsula from the Pliocene to the Late Pleistocene: new methodological approaches. Courier Forschungsinstitut Senckenberg.
PALOMBO M.R., AZANZA B., & ALBERDI M.T., 2003 - Italian
mammal biochronology from Latest Miocene to Middle Pleistocene: a multivariate approach. Geologica Romana, 36, 335-368.
PALOMBO M.R., & GIOVINAZZO C., 2006 - What do cenograms tell us about mammalian palaeoecology? The example of
Plio-Pleistocene Italian faunas. Courier Forschungsinstitut Senckenberg, 256, 215-235.
PALOMBO M.R, RAIA P., & GIOVINAZZO C., 2005 - Structural
changes in mammalian communities of Italian peninsula. In M.J.
Head & P.L. Gibbard (ed.), Early-Middle PleistoceneTransitions:
The Land-Ocean Evidence. Geological Society, London, Special
Publications, 247, 251-262.
PALOMBO M.R., & SARDELLA R., 2007 - Biochronology versus
Biostratigraphy: a true dilemma or a false trouble? The example of
the Plio-Pleistocene large mammalian faunas from the Italian peninsula. Quaternary International, 160, 30-42.
PALOMBO M.R., & VALLI A.M.F., 2004 - Remarks on the biochronology of mammalian faunal complexes from the Pliocene to
the Middle Pleistocene in France. Geologica Romana, 37,
145-163.
PALOMBO M.R., & VALLI A.F.M., 2005 - Large mammal fauna
turnover at Early-Middle Pleistocene transition in France. In M.J.
Head & P.L. Gibbard (ed.), “Early-Middle Pleistocene transitions: the land-ocean evidence”. Geological Society, London,
Special Publications, 247, 263-276.
PARTRIDGE T.C. (ed.), 1997a - The Plio-Pleistocene Boundary.
Quaternary International, 40, 100 p.
PARTRIDGE T.C., 1997b - Reassessment of the position of the
Plio-Pleistocene boundary: is there a case for lowering it to the
Gauss-Matuyama palaeomagnetic reversal? Quaternary International, 40, 5-10.
53
PASTRE J.F., 2004 - Le cryptotéphra de Saint Vallier : comparaison
avec d’autres retombées pyroclastiques du Mont-Dore issues de
gisements Plio-pléistocènes mammaliens du Massif Central.
Implications chronostratigraphiques. Geobios, 37, 44-57.
PFEIFFER T., 1999 - Die Stellung von Dama (Cervidae, Mammalia) im System plesiometacarpaler Hirsche des PleistozansPhyllogenetische Rekonstruktion-Metrische Analyse. Courrier
Forschungsinstitut Senckenberg, 211, 1-218.
PFEIFFER T., 2005 - The position of Dama (Cervidae, Mammalia)
in the system of fossil and living deer from Europe – phylogenetical analysis based on the postcranial skeleton. In E. Crégut-Bonnoure (ed.), Les ongulés holarctiques du Pliocène et du
Pléistocène. Quaternaire, h.s., 2, 39-57.
PILLANS B., 1998 - Proposal to redefine the Quaternary. Episodes,
20 (1), 1.
PILLANS B., 2004 - Proposal to redefine the Quaternary. Episodes,
27 (2), 127.
PILLANS B., & NAISH T., 2004 - Defining the Quaternary. Quaternary Science Reviews, 23, 2271-2282.
PROTHERO D.R., 1999 - Does climatic change drive mammalian
evolution? GSA Today, 9, 1-7.
PROTHERO D.R., 2004 - Did impacts, volcanic eruptions, or climate change affect mammalian evolution? Palaeogeography, Palaeoclimatology, Palaeoecology, 214 (3), 283-294.
REBOUL H., 1833 - Géologie de la période Quaternaire et introduction a l’histoire ancienne. F.G. Levrault, Paris, 222 p.
RODRÍGUEZ J., ALBERDI M.T., AZANZA B., & PRADO J.L.,
2004 - Body size structure in north-western Mediterranean
Plio-Pleistocene mammalian faunas. Global Ecology & Biogeography, 13 (2), 163.
ROHLF F.J., 1998 - NTSYSpc: numerical taxonomy and multivariate analysis system, version 2.02h. Exeter Software, Setauket,
NY.
ROOK L., MARTIRNEZ-NAVARRO B., & HOWELL F., 2005 Occurrence of Theropithecus sp. in the Late Villafranchian of Southern Italy and implication for Early Pleistocene “out of Africa”
dispersals. Journal of Human Evolution, 47 (4), 267-77.
ROOK L., & TORRE D., 1996 - The latest Villafranchian early Galerian small dog of the Mediterranean area. Acta Zoologica Cracoviensia, 39, 427-434.
ROSENZWEIG M.L., 1975 - On continental steady states of species diversity. In M.L. Cody & J.M. Diamond (ed.), Ecology and
evolution of communities. Belknap Press of Harvard University
Press Cambridge, 121-140.
ROSENZWIG M.L., & MCCORD R.D., 1991 - Incumbent replacement: evidence for long-term evolutionary progress. Paleobiology, 17 (3), 202-213.
SHI G.R., 1993 - Multivariate data analysis in palaeoecology and palaeobiogeography A review. Palaeogeography, Palaeoclimatology, Palaeoecology, 105, 199-234.
STEININGER F.F., RABEDER G., & RÖGL F., 1985 - Land
Mammal Distribution in the Mediterranean Neogene: A Consequence of Geokinematic and Climatic Events. In D.J. Stanley, &
F.C. Wezel (ed.), Evolution of the Mediterranean Basin. Raimondo Selli Commemoratio. Springer Verlag, 559-571.
STUCKY R.K., 1990 - Evolution of land mammal diversity in North
America during the Cenozoic. Current Mammalogy, 2, 375-432.
SUC J.P., BERTINI A., COMBOURIEU-NEBOUT N., DINIZ F.,
LEROY S., RUSSO-ERMOLLI E., ZHENG Z., BESSAIS E.,
& FERRIER J., 1995 - Structure of West Mediterranean vegetation and climate since 5.3 Ma. Acta Zoologica Cracoviensia, 38
(1), 3-16.
SUC J.P., BERTINI A., LEROY S.A.G., & SUBALLYOVA D.,
1997 - Towards the Lowering of the Pliocene/Pleistocene Boundary to the Gauss/Matuyama Reversal. Quaternary International,
40, 37-42.
TORRE D., ROOK L., & FICCARELLI G., 1999 - The mammal
fauna turnover in Italy at the Early to Middle Pleistocene transition. In G. Gibert, F. Sanchez, L. Gibert & F. Ribot (ed.), The Hominids and their environment during the Lower and Middle
Pleistocene of Eurasia. Museo de Prehistoria y Paleontologia “J.
Gibert”, Orce, 541-548.
TORRE D., ABBAZZI L., BERTINI A., FANFANI F.,
FICCARELLI G., MASINI F., MAZZA P., & ROOK L., 2001 Structural changes in Italian Late Pliocene. Bollettino della Società Paleontologica Italiana, 40 (2), 303-306.
VALLI A.M.F., CARON J.B., DEBARD E., GUÉRIN C.,
PASTRE J.F., ARGANT J., 2006 - Le gisement paléontologique
villafranchien terminal de Peyrolles (Issoire, Puy-de-Dôme,
France) : résultats de nouvelles prospections. Geodiversitas, 28
(2), 297-317.
VAN DAM J.A., 2001 - The Upper Miocene Mammal record from
the Teruel-Alfambra region (Sapin). The MN system and continental Stage/Age concepts discussed. Jounal of Vertebrate Paleontology, 21 (2), 367-385.
VAN VALEN L., 1973 - A new evolutionary law. Evolutionary Theory, 1, 1-30.
VAN DER MADE J., 1999 - Ungulates from Atapuerca TD6. Journal
of Human Evolution, 37 (3-4), 389-413.
VRBA E.S., 1985 - Environment and evolution: alternative causes of
the temporal distribution of evolutionary events. South African
Journal Science, 81, 229-236.
VRBA E.S., 1992 - Mammals as a key to evolutionary theory. Journal
of Mammalogy, 73, 1-28.
ROSENZWEIG M.L., & TAYLOR J.A., 1980 - Speciation and diversity in Ordovician invertebrates: filling niches quickly and carefully. Oikos, 35, 236-243.
VRBA E.S., 1995 - On the Connections between Paleoclimate and
Evolution. In E.S. Vrba, G.H. Denton, T.C. Partridge & L.H.
Burckle (ed.), Paleoclimate and Evolution with Emphasis on Human Origins. Yale University Press, New Haven and London,
24-45.
SARDELLA M., & PALOMBO M.R., 2007 - The Pliocene- Pleistocene boundary: which significance for the so called “Wolf
Event”? Quaternaire, 18 (1), 63-69.
VRBA E.S., 2000 - Major features of Neogene mammalian evolution
in Africa. In T.C. Partridge & R.R. Maud (ed.), The Cenozoic of
southern Africa. New York, Oxford University Press, 277-304.
SHACKLETON N.J., 1995 - New Data on the Evolution of Pliocene
Climatic Variability. In E.S. Vrba, G.H. Denton, T.C. Partridge &
L.H. Burckle (ed.), Paleoclimate and Evolution, with Emphasis on
Human Origins. Yale University Press, London, 242-248.
WALKER T.D., & VALENTINE J.W., 1984 - Equilibrium models
of Evolutionary Species diversity and the number of empty niches.
American Naturalist, 124 (6), 887-899.
SHACKLETON N.J., 1997 - The Deep-Sea Sediment Record and
the Pliocene-Pleistocene Boundary. Quaternary International, 4,
33-36.
WHITTAKER R.H., 1972 - Evolution and measurement of species
diversity. Taxon, 21, 213-251.
ZAGWIJN W.H., 1974 - The Pliocene-Pleistocene boundary in western and southern Europe. Boreas, 3, 75-97.