SESS 0_retro e indice edi.pub Il Quaternario Italian Journal of Quaternary Sciences 24, (Abstract AIQUA, Roma 02/2011), Congresso AIQUA Il Quaternario Italiano: conoscenze e prospettive Roma 24 e 25 febbraio 2011 THE EARLY TO EARLY MIDDLE PLEISTOCENE STENONOID HORSES FROM ITALY María Teresa Alberdi1 & Maria Rita Palombo2 1Departamento de Paleobiología. Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain 2Dipartimento di Scienze della Terra, Universita` degli Studi di Roma ‘‘La Sapienza’’, and CNR- Istituto di Geologia Ambientale e Geoingegneria, Roma, Italy Corresponding author: M.R. Palombo ABSTRACT: Alberdi, M.T., Palombo M.R., The Early to early Middle Pleistocene stenonoid horses from Italy. (IT ISSN 0394-3356, 2011) At least five stenonoid horses have been recorded in the Early to early Middle Plestocene Italian faunal assemblages: Equus livenzovensis, Equus stenonis, Equus stehlini, Equus altidens and large sized equids generally referred to as the so-called “Equus ex gr. E. bressanus - E. suessenbornensis”. Equus altidens and Equus suessenbornensis are a rather long surviving species, ranging in age from the latest Villafranchian (Pirro FU) to the late Galerian, and are sometimes found together in the same local faunal assemblage. This study mainly focuses on these two species. RIASSUNTO: Alberdi, M.T., Palombo M.R, Gli equidi stenonoide del Pleistocene inferiore e medio inferiore dell’Italia. (IT ISSN 0394-3356, 2011) Almeno cinque specie di equidi stenonoidi sono presenti in Italia durante il Pleistocene inferiore e medio inferiore: Equus livenzovensis, Equus stenonis, Equus stehlini, Equus altidens ed equidi di grande taglia generalmente riferiti al cosiddet- to gruppo di “E. bressanus - E. suessenbornensis”. Equus altidens e Equus suessenbornensis sono sicuramenti presenti in Italia, almeno dal tardo Villafranchiano fino al Galeriano superiore, spesso associate nello stesso giacimento. Questo studio è principalmente centrato sull’esame critico di queste due specie. Key words: Equus altidens, Equus suessenbornensis, Pleistocene, Italy Parole chiave: Equus altidens, Equus suessenbornensis, Pleistocene, Italia  1. INTRODUCTION Fossil representatives of the genus Equus are re- corded from several Italian localities, dating from the Early to early Middle Pleistocene. Various spe- cies and subspecies are reported in the literature (see e.g. AZZAROLI, 1965, 1979,1990,1999; DE GIULI, 1972; ALBERDI et al., 1988; CALOI & PALOMBO, 1990; CALOI, 1995, 1997; FORSTEN, 1999; and references in those papers), but their taxonomy, phylogenetical relationships and chronological distribution are still a matter of de- bate. At least five stenonoid horses have been re- corded: Equus livenzovensis, Equus stenonis, Equus stehlini, Equus altidens and large sized equids generally referred to as the so-called “Equus ex gr. E. bressanus - E. suessenbornen- sis”. Equus livenzovensis was a large horse whose scanty remains were found in deposits dated to the beginning of the Pleistocene (Middle Villafran- chian, Montopoli FU). Equus stenonis first reported a short time later (Costa San Giacomo FU) is the most common equid in the early late Villafranchian local faunal assemblages (LFAs) (Olivola, Tasso FU), while the actual chronological range of the small stenonoid horse Equus stehlini is uncertain, due to the controversial identification of some specimens already ascribed to E. stenonis and/or E. altidens (cf. ALBERDI et al. 1998; FOSTERN 1999). Advanced stenonoid equids, by some au- thors ascribed to Equus altidens are reported in LFAs of Farneta FU (e.g horses from Selvella, Tuscany = E. cfr. stenonis in DE GIULI 1987; = E. stenonis ssp., in CALOI & PALOMBO, 1990; Equus altidens in CALOI, 1995). Equus altidens and Equus suessenbornensis were rather long surviving species, sometimes found together in the same LFA. Their remains have been found in Italy in LFAs ranging in age from the latest Villafranchian (Pirro FU, ALBERDI & PALOMBO, in press) to the late Galerian. A horse possibly close to E. suessenbornensis is also re- ported from an early Aurelian LFA by CAPASSO BARBATO & GLIOZZI, (1995). This study mainly focuses on these two species. Equus altidens REICHENAU, 1915 E. altidens is a slender horse, more so than in the other stenonoid species, including the most related species E. senezensis (ALBERDI et al. 1998). The protocone shows a variable shape, flattened or indented lingually, occasionally lacking a heel, while the distal part is more protruding than in E. stenonis. Scholars are divided about the origin and 141 - 143 142 the phylogenetic relationship of E. altidens be- cause of differing opinions about the actual taxo- nomical and phylogenitical value of some features typically shown by this species. Most authors con- sider it a “stenonoid” horse, close to or originated from the Equus stenonis lineage (cf. ALBERDI et al. 1998). Others believe E. altidens to have been a new Early Pleistocene settler coming from Africa (=Equus numidicus, GUERRERO-ALBA & PALMQVIST 1997), or to be part of a “non- stenonian” widely dispersed group, which includes Early to Middle Pleistocene slender horses, sharing some features such as short protocone, long metaconide, a not very deep lingual grove, and developed stylides (EISENMANN 2004). The main morphological traits, especially those shown by teeth, support the hy- pothesis that E. altidens could be part of a stenon- oid lineage related to E. stenonis. The subspecies E. a. granatensis has been regarded by some au- thors as an advanced subspecies of E. stenonis, but a revision of stenonoid horses performed by ALBERDI et al. (1998) demonstrated that “E. ste- nonis grantensis”, “E. grantensis” and specimens regarded as intermediate (Equus granatensis- altidens) can be confidently ascribed to E. altidens. Equus suessenbornensis WÜST, 1900 E. suessenbornensis is a large and robust horse, but smaller than E. major (=E. bressanus). The teeth are morphologically close to E. altidens but the enamel of upper cheek teeth show a more complicated pattern. Moreover, the teeth of E. suessenbornensis share some morphological traits with the teeth of caballine horse (e.g. a long proto- cone with concave lingual borders, and larger mesostyles and grooves on the premolars at least somewhere along the crown). On the molars, the styles are simple or faintly grooved. The lower cheek teeth show cingular structures as pro- tostylids. The preflexid and postflexid are slightly folded. The phylogenetical relationship of this species have been a matter of debate. Some authors con- sider E. suessenbornensis a descendant of E. ma- jor (GROSSOUVRE & STEHLIN 1912; FORSTEN 1999). Others consider it an archaic caballoid or a true horse (GROMOVA 1949). MUSIL (1969, 1992) re- jected any affinity between E. suessenbornensis and E. stenonis, while NOBIS (1971). SAMSON (1975) and AZZAROLI (1984) considered it close to or direct descendant of the latter. Actually, E. sues- senbornensis might be regarded as intermediate or convergent to the stenonoid horses (cf. ALBERDI et al. 1998). Some features of E. suessenbornensis look like caballoid equids (GROMOVA & DUBROVO 1975) and some among the most advanced vari- ants of the species show dental characteristics too derived for a stenonoid horse. In point of fact, the species belongs to the phyletic lineage of E. major- E. suessenbornesis and likely originated from the E. livenzovensis clade, and could be regarded as a ‘stenonoid horse’. In Italy, E. suessenbornensis is mainly known from early Middle Pleistocene LFAs, albeit scanty re- mains have been reported from few early Galerian (late Early Pleistocene) LFAs. The time of the first appearance of the species in Europe is uncertain. In Italy, some cheek teeth, whose morphology and dimensions are close to those of E. suessen- bornensis, were found in the 17th century near Bucine (Val di Chiana, Tuscany). As discussed by AZZAROLI (1984), their stratigraphical position is unclear, but the hypothesis that they might have been retrieved from sediments of early Pleistocene age, widely outcropping in the area, cannot ruled out. If this is so, E. suessenbornensis might be part of the species recorded in the Farneta faunal unit (late Villafranchian). The presence in the late Early Pleistocene of Equus suessenbornensis is con- firmed by findings in the Pirro Nord karst network (ALBERDI & PALOMBO, in press). 2. REMARKS Equus altidens and Equus suessenbornensis were a rather long surviving species, recorded in Italy from the latest Villafranchian to the Galerian, sometimes found together in the same LFA. The two equids probably differentiated in ecology and the notable differences in size likely prevented any interspecies competition. For instance, E. altidens, and E. suessenbornensis were both present in LFAs dating to the Early Plestocene (e.g. in Italy in the Pirro Nord LFA, Alberdi & Palombo, in press; in Spain in the Fuente Nueva-3, Barranco León-5 and Huéscar-1 LFAs, ALBERDI, 2010) as well as to the early Middle Pleistocene (e.g in Italy in the LFAs of Ponte Galeria, ALBERDI & PALOMBO, in press, and Venosa Loreto, ALBERDI et al., 1988, as well as in some LFAs in the surroundings of Ve- rona, CALOI & PALOMBO 1991; in Spain in the Cúl- lar de Baza-1 LFA, ALBERDI, 2010). In Italy, as in Spain¸ E. altidens is definitely more abundant than E. sussenbornensis, while in Central Europe (e.g. Süssemborn, Germany) both species are equally represented. The relative abundance of these spe- cies varies according to the environmental charac- teristics, especially the vegetation cover and pro- ductivity, of the localities in which they were found. Available data suggest that, consistently with their ecological requirements, E. altidens, might have differentiated even in a rather restricted geographic region, whilst E. suessenbornensis, did not un- dergo any important local differentiation. Alberdi M. T.& Palombo M. R. 143 Ms. received: Testo ricevuto il REFERENCES ALBERDI M.T. (2010) - Estudio de los caballos de los yacimientos de Fuente Nueva-3 y Barranco León-5 (Granada). En I. Toro, B. Martínez-Navarro y J. Agustí (Eds.) "Ocupaciones humanas en el Pleistoceno infe- rior y medio de la Cuenca de Guadix-Baza". Arqueol. 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