The genus Megantereon includes Plio-Pleistocene jaguar-sized, short limbed, dirk-toothed cats with a stoutly built postcranial skeleton, in which the robust distal limb bones indicate an ambushing hunting method. Taxonomy and evolution of this felid have been discussed in several papers issued during recent decades and different interpretations have been provided [7], [10], [12], [13], [16], [17], [22], [26] and [29]. Of particular concern is the debate on the taxonomy of the Old World Plio-Pleistocene Megantereon.

All the authors agree to refer Pliocene European specimens to M. cultridens. Different interpretations are proposed for Early Pleistocene European forms.

Turner [26] considered the differences recorded into the Eurasian and African sample of Megantereon as due to sexual dimorphism, comparing the data to those of the living leopard. Other authors [8] and [15] claimed a convergent evolution of the European samples of M. cultridens with the African M. whitei, due to the paleoclimatic and paleoenvironmental conditions prevalent at the end of Pliocene. They named this form M. cultridens adroveri [10] and [17].

Sardella [22] suggested the use of open taxonomy including the Early Pleistocene European specimens in Megantereon ex gr. cultridens (advanced form).

Martínez-Navarro and Palmqvist [12] and [13] suggested that the Early Pleistocene European Megantereon represent a dispersal of the African form M. whitei that replaced M. cultridens at the Plio-Pleistocene transition. This hypothesis seems to have recently reached a larger consensus [16].

The two species differ mainly in the following craniodental features: •

M. cultridens cheek teeth tend to be larger than those of M. whitei, and their proportions are different;

The Italian sample includes informative specimens. In particular, for several years the latest Pliocene Upper Valdarno fossils [6] and [7] constituted a rich basis for comparison in Megantereon studies. Megantereon remains have also been discovered in the Middle-Late Villafranchian faunal assemblages from the Late Pliocene sites of Collepardo, Olivola and Villa S. Faustino (previously referred to the Early Pleistocene), and the Early Pleistocene sites of Monte Argentario and Pirro Nord [1], [7], [9] and [22] (Fig. 1).

The Megantereon material from Monte Argentario, here referred to the species M. whitei, is represented by a right mandible with p4 and m1 (ARG34), part of a skull (ARG31, left dental and maxilla with teeth) and some elements of an articulated skeleton (ARG30) including the right upper canine, left mandible with teeth, an axis, and the left forelimb (humerus, ulna and radius, II to V metacarpal, first phalanges) (Fig. 2).

The upper incisors are strong: a diastema separates them from the upper canine. The upper canines are proportionally stronger than in the Tuscan specimens from Upper Valdarno. Such a feature seems to be typical of M. whitei and is even more evidenced in the specimen G1 from Pirro Nord [16] and [22] (Fig. 3).

P3 in ARG31 is reduced, P4 is posteriorly damaged (the carnassial blade is missing), but shows the typical morphology of the genus. The left hemimandible is almost complete. The mental profile is almost vertical, p3 is missing but, judging from the alveolus, was single rooted and reduced. Both p4 and m1 are quite well preserved.

Possibly some cervical vertebrae and the left forelimb of the animal are included in the rock block. At present all the measurements cannot be taken, because the bones are still included in the matrix. The restoration of the specimen will start within 2008 and hopefully new elements of the skeleton may be found. Comparison with the manus of M. cultridens from Sénèze [3] and M. whitei from Pirro Nord reveals great similarities. Metacarpals have strong diaphyses and quite long first phalanges, similar to those of extant felids. The humerus, ulna and metacarpals are much stouter and stronger in Megantereon than in Panthera, which is confirmed by the Monte Argentario specimens (Table 1). Such features of the forelimb of Megantereon are closely related to ambush behaviour [25]. The powerfully developed forelimbs suggest that this felid killed the prey (cervids and equids) biting them in the throat, after immobilizing them with the forelimbs [15] and [27]. A more detailed analysis on the postcranial skeleton of Megantereon is under progress and will point out further differences between M. cultridens and M. whitei.

The taxonomy of Megantereon is based mainly on craniodental features because of the scantiness of the fossil record. Valuable new data will be provided by the detailed study of the outstanding Chinese fossil sample [18] and by the analysis of the postcranial skeleton.

The Italian fossil record, and in particular the specimen from Monte Argentario, is interesting for both taxonomic and morpho-functional points of view. The available data suggest that the Early Pleistocene European dirk-toothed cats can be assigned to M. whitei that replaced M. cultridens at Plio-Pleistocene transition.

The dispersal of M. whitei into Europe occurred concurrently with other African species [11], [19] and [28]. The Levantine Corridor is the principal path of dispersal between Africa and Eurasia and it is evident that the influence of forms of African origin in the Early Pleistocene of the Levant, as at the ‘Ubeidiya site (Israel) [14] and [25], where the occurrence of (among others) Homo, Theropithecus sp., Hippopotamus gorgops, Kolpochoerus olduvaiensis, Pelorovis oldowayensis, Megantereon cf. whitei, Crocuta crocuta, is documented. However, only few of these African species expanded their range into northernmost regions of Eurasia. This group is composed together with M. whitei by T. oswaldi, Hippopotamus antiquus and, obviously, Homo [9], [18] and [20]. This assemblage (or representatives of this assemblage) has(ve) been partially found in western Europe, in Spain (Venta Micena, Fuente Nueva-3, Barranco León-5, Cueva Victoria and Incarcal), France (Sainzelles), Italy (Pirro Nord), Germany (Untermassfeld), Greece (Apollonia and Ravin de Voulgarakis) [9]. Monte Argentario provides further evidence of this assemblage in western Europe.