EQUIDAE, Gray, 1821

Mecozzi, Beniamino & Strani, Flavia, 2022, Equids from the late Middle Pleistocene to Early Holocene of the Apulia Peninsula (southern Italy): reassessment of their taxonomy and biochronology, Geodiversitas 44 (2), pp. 17-45 : 21-30

LATE MIDDLE TO LATE PLEISTOCENE APULIAN FOSSIL EQUIDAE

MELPIGNANO

The karst infilling deposits of Melpignano, locally known as “ventarole”, are located in the area of the village of Maglie. These karst deposits were firstly described by Mirigliano (1941), since then several Institutions, as the IsIPU and Italian Institute of Prehistory and Protohistory (IIPP), with the support of local Salentine Speleological groups, investigated this area ( de Lorentiis 1962; Cardini 1962a). The “ventarole” are generally filled with reddish sediments (called “terre rosse”) in the lower part, and brownish sediments (called “terre brune”) in the upper, particularly rich in vertebrate fossil remains ( Bologna et al. 1994) ( Fig. 1 ). The Equus sample was recovered from the “terre rosse” of the “ventarole” of Mirigliano, Cava Nuzzo and Cava Bianco.

Repository and studied material

MPUN Mirigliano collection – 17 upper teeth, 24 lower teeth;

Cava Nuzzo – PF 2 hemimandibles, 4 lower teeth ( Fig. 3C );

Cava Bianco – PF 17 upper teeth, 2 hemimandibles, 9 lower teeth.

SAN SIDERO

The “ventarole” of San Sidero are located along the state road (SS16) between the villages of Corigliano d’Otranto and Maglie. The first description of the deposit and its faunal assemblage was reported by Cardini (1962a). The mammal fauna from San Sidero was also studied by other authors ( De Giuli 1980, 1983; Petrucci et al. 2012; Iurino et al. 2013, 2015). Similarly to the Melpignano sediments, these “ventarole” include “terre rosse” layers in the lower part and “terre brune” layers in the upper part. The Equidae sample was collected from the “terre rosse” of the “ventarole” called SS6 and Cava L.

Repository and studied material

SS6 – IGF one skull ( Fig. 2A ), 11 upper teeth, 10 lower teeth ( Fig. 3A );

Cava L – PF five upper teeth, one hemimandible, six lower teeth.

GROTTA DI CAPELVENERE

The site, located near the town of Santa Caterina (Lecce), occurs in a Cretaceous limestone (Calcari di Melissano Formation) at 20 m a.s.l. and about 100 m from the current seashore. The cave was discovery in 1960 and was only partially excavated in 1971, 1974 and 1975 ( Borzatti von Löwenstern 1961; Giusti 1979, 1980). Outside the cave, a nearby conglomerate deposit at about 8 m a.s.l. has been referred to Tyrrhenian beach (MIS 5) ( Patriarchi 1980). The stratigraphic sequence can be divided into two main complexes separated from a speleothem: in the upper part, the brownish sediment, where domestic fauna, ceramics and artefacts appeared, has been referred to Iron age. Instead, in the lower part ten levels including vertebrate fossils and artefacts have been referred to Mousterian ( Borzatti von Löwenstern 1961; Giusti 1979, 1980; Patriarchi 1980). The studied sample comes from the lower part of the sedimentary succession.

Repository and studied material

IGF 18 upper teeth, five hemimandibles, 26 lower teeth.

GROTTA DELLE TRE PORTE

The fossiliferous site was discovered in 1936during a field survey of the IsIPU conducted by Gian Alberto Blanc ( Blanc 1958) ( Fig. 1 ). The coastal cave, located at Punta Ristola, includes three different saloons, but only two contained Pleistocene deposits, Antro del Bambino and Grotta Titti. The Equus material was collected from the level F of Antro del Bambino, associated to Middle Palaeolithic artefacts.

Repository and studied material

IsIPU eight upper teeth, one hemimandible, nine lower teeth.

GROTTA MARIO BERNARDINI

The cave located along the Ionian coast near the village of Santa Caterina, also known as Grotta di Santa Margherita, was discovered in 1961 ( Borzatti von Löwenstern 1970, 1971) ( Fig. 1 ). The stratigraphic succession consists of four main archeological levels: D, C, B and A, excepted for the top of the sequence, where ceramic and artefacts were referred to Iron and Bronze age ( Borzatti von Löwenstern 1970, 1971; Carmigiani & Romagnoli 2017). From the complex VI-III artefacts referred to Mousterian facies were found, whereas those from the complex II were attributed to Uluzzian ( Borzatti von Löwenstern 1970, 1971; Carmigiani & Romagnoli 2017). The volcanic material recovered in the top of complex IV (firstly indicated as ss) could be correlated with that found in the level G of the Grotta del Cavallo dated approximately to 109 100 ± 900 ka ( Sarti et al. 2002; Spinapolice 2008; Spinapolice 2018; Douka & Spinapolice 2012; Zanchetta et al. 2018). Instead, the volcanic material from the bottom of the complex II (initially indicated as ss) can be correlated with that found at the top of the level F of the Grotta del Cavallo dated approssimatively to 45700 ± 1 000 ka ( Sarti et al. 2002; Spinapolice 2008, 2018; Douka & Spinapolice 2012; Zanchetta et al. 2018). Albeit the mammal remains have never been studied in detail, a preliminary mammal list was provided byBorzatti von Löwenstern (1970, 1971). Equus is found from different levels (VI, IV, III, II), where also lithic artefacts referred to Middle Palaeolithic from the complexes VI-III and Upper Palaeolithic from the complex II were found ( Table 1 ; Appendix 1 ).

Repository and studied material

IGF 27 upper teeth, one hemimandible, 27 lower teeth.

GROTTA ULUZZO C

The cave is located in the Uluzzo Bay near the village of Nardò, opening into the Cretaceous limestone. The stratigraphic succession was described by Borzatti von Löwestern (1965, 1966) and Borzatti von Löwestern & Magaldi (1969). In particular, the green volcanic sand from the bottom of the complex II could be correlated with the tephra found at the top of the level F of Grotta del Cavallo, dated at 45700 ± 1000 ka by Zanchetta et al. (2018). Instead, the complex II-I transition, consisting of a grey volcanic sand, could be correlated with the Ignimbrite Campana (CI) identified at the bottom of the level C of Grotta del Cavallo, dated at 39 850 ± 140 ka Zanchetta et al. (2018). The presence of a reworked tephra in the top of the complex IV could represent a marker for the lower deposit. Further investigations needed to confirm the age of these volcanic levels. Moreover, Borzatti von Löwestern (1965, 1966) reported a preliminary list of the fossil mammals recovered from this locality. The studied sample come from the complex IV, III and II ( Table 1 ; Appendix 2 ). Whereas, artefacts from the complex IV and III were attributed to Middle Palaeolithic, instead those from the complex II to early Upper Palaeolithic.

Repository and studied material

IGF 21 upper teeth, two hemimandibles, 33 lower teeth.

CASTELLANETA

The Castellaneta deposit is a karst infilling into the Pleistocene Calcarenite (Monte Castiglione Formation) ( De Giorgi 1877). The fossil material was recovered during the geological survey in the area conducted by Cosimo De Giorgi in the 1870s. Albeit the author delegated the study of the collected sample to Ulderigo Botti, the remains from the karst fissure were never described.

Repository and studied material

ITCGC 28 upper teeth, 1 hemimandible, 28 lower teeth.

GROTTA DEI GIGANTI

The coastal cave, located between Punta Ristola and Punta Marchiello, was discovered by the Italian Institute of Human Paleontology during a field survey conducted by Gian Alberto Blanc in the 1930s ( Blanc 1958). The authors also reported a mammal faunal list.In addition, Alessio et al. (1978) attempted to carry out radiocarbon dating without success.However, the fossil material was found associated to Middle Palaeolithic artefacts.

Repository and studied material

IsIPU 12 upper teeth, 20 lower teeth;

ITCGC four upper teeth, three lower teeth.

GROTTA SANTA CROCE

The cave, located near the small village of Bisceglie, was discovered in the 1937 ( Segre & Cassoli 1987). The first systematic excavations directed by Luigi Cardini were carried out by Italian Institute of Human Palaeontology (IsIPU) dur - ing the 1950s ( Mallegni et al. 1987; Segre & Cassoli 1987; Boscato et al. 2006). The sedimentary succession includes several levels attributed to Middle and Upper Paleolithic and Neolithic ( Segre & Cassoli 1987; Arrighi et al. 2009; Ranaldo et al. 2017). Radiocarbon dated indicated an age of 24 900 ± 150 BP for the level B and 31 500 ± 400 BP for the level C ( Arrighi et al. 2009; Ranaldo et al. 2017). There are no radiocarbon dating results for levels H-D that are referred to MIS 5 and MIS 4, respectively ( Arrighi et al. 2009; Ranaldo et al. 2017). The fossil remains of mammals from the level D were studied by Segre & Cassoli (1987). Recently, new material also was discovered from this level and Equus ferus and Bos primigenius Bojanus, 1827 were identified ( Boscato et al. 2006). The studied material was recovered from the level D, associated with lithic artefacts attributed to Middle Palaeolithic.

Repository and studied material

IsIPU seven upper teeth, seven lower teeth.

GROTTA LACEDUZZA

The cave deposit, located near the village of San Michele Salentino, was discovered by the “Gruppo Speleologico Salentino Pasquale de Lorentiis” in 1970 ( Coppola 2005, 2012). The lower part of the sedimentary succession includes fossil remains of mammals and artefacts referred to Middle Palaeolithic. A preliminary mammal list was recently reported, including a rich sample of Meles meles ( Linnaeus, 1758) ( Mecozzi et al. 2019) . The Equus material was recovered from the lower part of the deposit, associated to Middle Palaeolithic artefacts.

Repository and studied material

MPCCSM nine upper teeth, 12 lower teeth.

GROTTA ZINZULUSA

The cave is located along the Adriatic coast near the town of Castro. In 1793, Francesco Antonio Del Duca, bishop of the diocese of Castro described the cave in a letter to Ferdinando IV, king of the Kingdom of the Two Sicilies. Nevertheless, the Pleistocene infilling deposit was presented only after a century from the discovery by Botti (1874). The cave consists of several saloons, where Pleistocene deposits were found ( Blanc 1962). The sedimentary succession can be divided in two complexes, the lower part, the level B6, where fossil remains of mammals and artefacts referred to Middle Palaeolithic were found, and the upper part, the levels B5-3 including fossil remains of mammals and artefacts referred to Upper Palaeolithic. The Equus material comes from the levels B5-3, where also artefacts referred to Middle Palaeolithic were found.

Repository and studied material

IsIPU B5-6 upper teeth, five lower teeth.

CARDAMONE

The karst infilling deposit was discovered by Cosimo De Giorgi in 1872 ( Botti 1890). The site is located in a region where several quarries are opened for the extraction of a Plio-Pleistocene calcarenite, and, unfortunately, the deposit was destroyed. The mammal assemblage from Cardamone, initially described by Botti (1890), was recently revised by Rustioni et al. (2003). Based on the presence of the wholly rhino ( Coelodonta antiquitatis (Blumenbach, 1799)) and the wholly mammoth ( Mammuthus primigenius (Blumenbach, 1799)) , the association was referred to “ Mammuthus-Coelodonta Faunal Complex” and chronologically attributed to climax of the Last Glacial Maximum (22-18 kyr).

Repository and studied material

IGF 16 upper teeth, 33 lower teeth;

ITCGC two crania ( Fig. 2B, C ), 13 maxillaries, 83 upper teeth, four hemimandibles, 112 lower teeth ( Fig. 3B ).

FONDO FOCONE The site, discovered during a survey conducted by Decio de Lorentiis in the early 1960s, is located near the village of Ugento. The first excavation campaign was carried out by Luigi Cardini ( Cardini 1962b). The fieldwork, direct by Eugenia Segre Naldini, continued during the 1970s, who opened a trench, 3 × 3 m, called “Trincea B” ( Cancellieri 2017). Fossil remains of mammals and the artefacts referred to Upper Palaeolithic (early Epigravettian) were found ( Cardini 1962b; Cancellieri 2017).

Repository and studied material

IsIPU one maxillary, 37 upper tooth, one hemimandible, 27 lower teeth.

SANTA MARIA D’ AGNANO – ESTERNO (SMA-ESTERNO)

The Grotta di Santa Maria di Agnano, located near the village of Ostuni, on the north-western margin of Risieddi promontory, was discovered during the 1960s by the Associazione Studi e Ricerche (Studies and Research Association) ( Coppola 2012). The excavations in the cave deposit started in 1991 and continued still today, whereas from 2007 the area outside the cave, known as SMA-esterno, was also investigated ( Coppola 1992, 2012; Vacca et al. 1992; Vacca & Coppola 1993; Baills 2015; Coppola et al. 2017; Chakroun et al. 2018). The fossil remains come from level 8, dated 25221-24549 cal BP and 26338-25779 cal BP, and levels 6A-4C dated 18013- 17587 cal BP and 16745-16401 cal BP with radiocarbon method (Renault-Miskovsky et al. 2011; Baills 2015).

Repository and studied material

MPCCSM level eight – 10 maxillary, 59 upper tooth, 35 hemimandibles, 67 lower teeth ( Fig. 3 D-E).

RESULTS

Equus samples from the late Middle Pleistocene to Early Holocene of AP show a large variation in dental dimensions and proportions. In particular, the length of P2 and M3 are highly variable both within and between samples (Appendices 3; 4; 7). On the contrary, the length of P 3-4 from San Sidero is closer (p- value> 0.05) to those from Cava Spagnulo, Grotta di Capelvenere, Grotta Mario Bernardini – II and Grotta Uluzzo C ( Appendix 7). The length of M1-2 from San Sidero is similar (p- value> 0.05) to those from Castellaneta, Fondo Cattìe, Grotta di Capelvenere, Grotta Mario Bernardini – III, Grotta Santa Croce, Grotta Zinzulusa, Melpignano and Tana delle Iene ( Appendix 7). As in the case of the upper teeth, even the length of P 2 and M 3 show a huge variability (Appendices 5; 6). The P 3-4 from San Sidero is closer (p-value> 0.05) to those from Grotta di Capelvenere, Grotta dei Giganti, Grotta Mario Bernardini – IV, Grotta delle Tre Porte, Grotta Zinzulusa and Tana delle Iene (Appendices 5; 6; 8). Whilst, the M1-2 from San Sidero is closer (p-value> 0.05) to Grotta Santa Croce, Grotta delle Tre Porte, Grotta Zinzulusa, Grotta Uluzzo C – II, Melpignano and Tana delle Iene (Appendices 5; 6; 8).

Considering the MIS chronology, the length of P2 and M3 of the sample from MIS 9-8 is larger only of samples from MIS 3 (P2, p-value <0.05; M3 p-value <0.05) and MIS 2 (P2, p-values <0.05; M3 p-value <0.05). Whilst, the length of P3-4 and M 1-2 of the sample from MIS 9-8 are larger than those from the late Middle Pleistocene (MIS 7) to Early Holocene (MIS 1) (p-values <0.05). In the lower dentition, the length of the teeth from MIS 9-8 are larger than those from Late Pleistocene (MIS 5) to Early Holocene (MIS 1) (p-values <0.05), whereas they are similar to those from late Middle to early Late Pleistocene (MIS 7-5) in the P2 (p-value> 0.05), P3-4 (p-value> 0.05) and M3 (p-value> 0.05) ( Fig. 5 , Table 3 ).

The protocone index of the Grotta di Capelvenere, Melpignano and San Sidero shows a trend closer to that reported for E. mosbachensis , with M3 value higher than M1-2 one and P3-4 value higher or sub-equal than M1-2 one ( Fig. 6 ). On the contrary, the pattern of the other samples is closer to that reported for E. ferus , with M1-2 value higher than both P3-4 and M3. Finally, the sample from Tana delle Iene and Grotta delle Mura possesses a well different values compared to the others, resembling those reported for Equus hydruntinus . In fact, in E. hydruntinus the values for P3-4 and M1-2 are significantly lower than those of both E. mosbachensis and E. ferus , whereas they are similar in P 2 and M 3 values.

Whereas, the postflexid index has been investigated, but no trend can be detected through the time and/or differences among the considered taxa ( Fig. 7 ).

Finally, in the standard bivariate plot of muzzle proportions ( Fig. 8 ), two groups can be recognized. The first includes the specimen from the fossiliferous sites referred to glacial stages ( Appendix 9), which display a large muzzle in relation to their length. An exception is the cranium of Equus ferus antunesi Cardoso and Eisenmann, 1989 from Fontainhas ( Portugal), where the muzzle is longest. The specimen from Cardamone falls in the variability of the glacial horses, and is similar to that from Cuane de l’Arago ( Fig. 8 ). A second group is composed by crania from deposits referred to interglacial stages, where the muzzle is narrow compared to its total length. The cranium from San Sidero falls in this variability.

DISCUSSION

The taxonomy of Middle to Late Pleistocene European Equus remains controversial ( Forstén 1991; van Asperen 2012). The large variability of the morphological features and biometric traits of caballoid horses has been the subject of controversy amongst many authors. No consensus exists on how to define this variability, as it is either treated as being intra-specific or inter-specific events ( Azzaroli 1983; Forstén 1988; Cramer 2002; van Asperen 2012). This unresolved taxonomic issue has led a proliferation of taxa, identified as either species or subspecies ( E. mosbachensis , E. steinheimensis Von Reichenau, 1915 , E. achenheimensis Nobis, 1971 , E. taubachensis Freudenberg, 1911 ) (see van Asperen 2012 for discussion). In the Italian fossil record, the specific attribution of the fossil samples from Middle Pleistocene sites reflects this uncertainty ( Equus altidens von Reichenau, 1915 , Equus aff. sussebornensis, Equus caballus ssp., E. cf. E. mosbachensis Equus caballus cf. mosbachensis and Equus sp. ) ( Berzi 1972; Caloi & Palombo 1987; Strani et al. 2018, 2019). Preliminary studies on Equus samples from several AP sites led to the identification of E. ferus from the deposits of Cardamone ( Rustioni 1998), Cava Spagnulo (Mecozzi et al. 2018), Grotta del Cavallo ( Sarti et al. 1998, 2002), Grotta Paglicci ( Boscato 1994), Melpignano ( Rustioni 1998) and Tana delle Iene ( Conti et al. 2010), whereas the previous taxonomic attribution of the material from San Sidero has been questioned. In the revision of the Middle to Late Pleistocene Equus material from Europe, Eisenmann (1991b) attributed the material from San Sidero to the large-sized Equus chosaricus , whereas other authors ( De Giuli 1983; Rustioni 1998) classified it as Equus ferus . Unlike, the results of the statistical analysis and the comparison of the protocone index carried out in this work allow to refer the material from San Sidero to E. mosbachensis .

In this scenario, the analysis of a relatively large sample of Equus fossils from late Middle to Late Pleistocene localities of AP allows us to reassess the taxonomy and the evolutionary trend of local horse species. Based on the results of the statistical analyses and the comparison of the protocone indexes, E. mosbachensis is identified for the first time from few Apulian fossiliferous sites, among which are included San Sidero, Melpignano and Grotta di Capelvenere. Equus mosbachensis possesses larger upper and lower teeth than those of E. ferus ( Figs 4 , 5 ; Tables 2 , 3 ) and different values of the P3-4, M1-2 and M3 protocone index ( Fig. 6 ). The Grotta di Capelvenere, Melpignano and San Sidero samples displays a M1-2 protocone index value lower than those both P3-4 and M3 ( Fig. 6 ). The taxonomic attribution to E. ferus of the material from other considered sites chronologically referred from late Middle Pleistocene (MIS 7) to the end of Late Pleistocene (MIS 2) is confirmed, based on the medium-size of the specimens and the values of the protocone index. In fact, besides displaying smaller upper and lower teeth than those of E. mosbachensis ( Figs 4 , 5 ; Tables 2 , 3 ), the protocone index in the materials of E. ferus displays M1-2 value higher than those both P3-4 and M3 ( Fig. 6 ). Furthermore, for the samples from Tana delle Iene and Grotta delle Mura, the protocone index differs. The values of P3-4 and M1-2 are much lower than those of caballoid horses. This atypical profile of IP index in the fossil materials of Tana delle Iene and Grotta della Mura could be due to the small size of the available samples.

Finally, following the literature, the postflexid index fails to discriminate Equus species from Middle to Late Pleistocene and no trend can be observed ( Fig. 7 ). In accordance with Boulbes (2010), the significant variation of the postflexid index could be related to tooth ontogeny (relative wear).

Whereas E. mosbachensis is widespread in Europe during the Middle Pleistocene, its presence in Italian Peninsula was quite scarce ( Gliozzi et al. 1997), and documented only from few sites: Cesi ( Ficcarelli et al. 1997), Venosa-Notarchirico ( Palombo & Alberdi 2017), Fontana Ranuccio ( Biddittu et al. 1979). In AP, the Mosbach horse is identified for the first time in a few localities, which unfortunately lack of absolute radiometric determinations. As for the European material, in the AP the Mosbach horse was well-distinct for its large teeth sized, which is larger to the wild horse ( E. ferus ) ( Figs 4 , 5 ; Tables 2 , 3 ) and display different values of the protocone index ( Fig. 6 ). According to several authors ( Guadelli 2007; Uzunidis 2017), the last occurrence of E. mosbachensis took place during the late Middle Pleistocene, probably during the MIS 6, although no general consensus was reached ( Boulbes & van Asperen 2019). However, the first historical appearance of E. ferus in AP is from Grotta del Cavallo during the early Late Pleistocene (<109 ka) ( Zanchetta et al. 2018). Therefore, a new dispersal of Equus species could have taken place during the late Middle Pleistocene. This possible scenario is consistent with the results of the aDNA analysis performed on E. ferus , which revealed that the wild horse originated at about 240.000 years ago (late Middle Pleistocene), differing therefore from the earlier form of Equus (George & Rider 1986) . Unfortunately, the taxonomic uncertainty for the Middle Pleistocene sample from Italian Peninsula record prevents an in-depth reconstruction of the caballoid horse lineage ( Berzi 1972; Caloi & Palombo 1987; Strani et al. 2018, 2019, Strani 2020).

The last occurrence of E. ferus in the Italian Peninsula took place during the end of Late Pleistocene to Early Holocene (18-9.1 ka BP). During the end of Late Pleistocene (16-12 ka BP), E. ferus was well diffused across the Italian Peninsula, as documented by Leonardi et al. (2018) at Grotta delle Mura, Grotta Paglicci, Palidoro, Romito and Vado Arancio.During the Early Holocene however, its presence was exclusively reported from Grotta delle Mura ( Bon & Boscato 1993) ( Leonardi et al. 2018). The radiometric dating of level 3 indicates an age ranging from 17913-1738 to 13009-12688 cal BP, whereas that of level 2 varies between 9451-9125 to 9527-8982 cal BP ( Leonardi et al. 2018; recalibrated using Oxcal v. 4.4, IntCal20 curve). Recently, new radiometric analysis has been performed on Grotta dei Cervi, which records the presence of E. ferus at 10175-9701 cal BP ( De Grossi Mazzorin & Montefinese 2017) (recalibrated using Oxcal v. 4.4, IntCal20 curve). A long gap was detected in the horse fossil record, between the occurrences from Grotta delle Mura and Grotta dei Cervi and those from the bronze age localities of Santa Rosa di Roviglio (4149-4112 to 3492-3355 cal BP) and Montale (4089-3057 to 3370-3219 cal BP) (recalibrated using Oxcal v. 4.4, IntCal20 curve). This gap has been interpreted as the local excinction of wild E. ferus , which was later reintroduced in the Italian Peninsula by recent human populations. This disappearance during the Early Holocene could be linked to a marked reduction of steppe- and tundra-like landscapes ( Leonardi et al. 2018).

The wild horse is a common element of the mammal assemblages from AP during the late Aurelian, showing a homogenous body size through the time. According to van Asperen (2012), size oscillations of E. ferus can occur in response to climatic change, with the specimens from glacial stages being smaller and more robust, possibly as an adaptation to colder environmental conditions ( Mayr 1956; James 1970; Lindstedt & Boyce 1985; Blackburn et al. 1999). On the contrary, interglacial horses could be larger with more slender limb proportions. Some populations of interglacial E. ferus can also be characterized by small and robust individuals (always less robust than glacial ones). The body-size of E. ferus of the Apulia region during the MIS 7-5 to MIS 2 is quite constant and no changes can be detected. According to van Asperen (2010), this stasis could suggest that the wild horse was in low competition for resources in a stable landscape constantly dominated by open-environments (i.e, steppe-like and/or grasslands). Another feature which could fluctuate as response to climatic change is the proportion of the muzzle, where the skulls from glacial stages possess a wide and short muzzle and vice versa ( Eisenmann 2014; Crégut-Bonnoure et al. 2018; Boulbes & van Asperen 2019). Moreover, there is no chronological differences among cranial proportions of caballoid horse through the Middle to Late Pleistocene of Europe ( Fig. 8 ), despite a possible evolutionary trend for explaining these different cranial proportions was proposed. Specimens from deposits attributed to glacial stages (n = 15) display a short and wide muzzle as in the cases of the Middle Pleistocene sites of Cuane de l’Arago (MIS 14-12) ( France) ( Eisenmann et al. 1985) and Igue des Rameaux (MIS 10-9) ( France) ( Uzunidis 2017) or Late Pleistocene ones of Coulet des Roches (MIS 2) ( France) (Crégut-Bonnoure et al. 2018), Jaurens (MIS 3) ( France) ( Guérin 1999) and Sirejol (MIS 3) ( France) ( Philippe et al. 1980) ( Appendix 9). Whereas, the crania from interglacial stages (n = 2) possess an elongated and narrow muzzle, as the specimens from Middle Pleistocene sites of Lunel-Viel (MIS 11) ( France) ( Bonifay 1980; Eisenmann et al. 1985) and Mosbach (MIS 13) ( Germany) ( Maul et al. 2000) ( Fig. 8 ; Appendix 9). An exception is represented by the cranium from Last Glacial (MIS 2; 22, 730 ± 835 ka) of Fontainhas ( Portugal), since its proportions fall outside the variability of the glacial caballoid horses ( Fig. 8 ; Appendix 9). The proportions of the two studied skulls, San Sidero and Cardamone specimens, corroborated the glacial/ interglacial separation. Indeed, the skull from Cardamone biochronologically referred to Last Glacial falls in the variability of the glacial group, representing one of the largest specimens ( Fig. 8 ; Appendix 9). Contrary, the proportions of the skull from San Sidero (MIS 9-8) differ from those of the glacial group, and are similar to those of Mosbach and Lunel-Viel ones ( Fig. 8 ; Appendix 9). Finally, considering the large variability of the skull size of caballoid horses during the Middle and Late Pleistocene, no evolutionary trend can be recognized. Nevertheless, based on the proportions of the muzzle, two groups are identified from the Middle to Late Pleistocene of Europe, which reflect an adaptation to climate (glacial and interglacial stages). Therefore, the proportions of the muzzle of caballoid horse clearly reveal important information on climatic conditions and palaeoenvironment.

Figures

FIG. 1. — Location of the considered Apulian sites: 1, Grotta Santa Croce; 2, SMA-esterno;3, Grotta Laceduzza;4, Castellaneta;5, Cardamone;6, Grotta Mario Bernardini - Grotta Uluzzo C - Grotta di Capelvenere; 7, San Sidero – Melpignano;8, Grotta Zinzulusa;9, Fondo Focone;10, Grotta dei Giganti Grotta delle Tre Porte.

FIG. 3. — Mandible of Equus from late Middle to Late Pleistocene of Apulia in labial (1), lingual (2) and occlusal (3) views:A1-A3, IGF16330,Equus mosbachensis von Reichenau,1903 from San Sidero;B1-B3, CC414,Equus ferus Boddaert,1785 from Cardamone; C1-C3, MPND396 (ex.Cur11),left hemimandible of Equus mosbachensis from Melpignano;D1-D3, C2 20b 77,right hemimandible from SMA-esterno;E1-E3, C2 20b 80,left hemimandible from SMA-esterno.Scale bars:5 cm.

FIG. 2. — Crania in right view from late Middle to Late Pleistocene of Apulia: A, IGF16329, cranium of male of Equus mosbachensis von Reichenau, 1903 from San Sidero;B, CC467,cranium of female of Equus ferusfrom Cardamone; C, CC468,cranium of male of Equus ferusBoddaert,1785 from Cardamone.Scale bars:5 cm

APPENDIX 1. — Schematic stratigraphic log of Grotta Mario Bernardini (modified from Borzatti von LÖwenstern 1970).

APPENDIX 2. — Schematic stratigraphical log of Grotta Uluzzo C (modified from Borzatti von LÖwenstern & Magaldi 1969).

FIG. 5. — Boxplot of the length of the upper teeth considered for chronology: A, second premolar (P2L); B, third-fourth premolar (P3-4L); C, first-second molar; (M1-2L); D, third molar (M3L). For the groups see Table 1.

FIG. 6. — Protocone index of the upper teeth of Equus species from the late Middle Pleistocene to Early Holocene sites of the Apulia. Abbreviations: see Table 1.

FIG. 7. — Postflexid index of the lower teeth of Equus species from the late Middle Pleistocene to Early Holocene sites of the Apulia.Abbreviations: see Table 1.

FIG. 8. — Standard bivariate plot of muzzle length (ML) and muzzle breadth at the posterior borders of I3 (MB) of caballoid horses from Middle to Late Pleistocene of Europe (Appendix 9). Symbol: square, Middle Pleistocene specimens; circle, Late Pleistocene specimens.

FIG. 4. — Boxplot of the length of the lower teeth considered for chronology: A, second premolar (P2L); B, third-fourth premolar (P3-4L); C, first-second molar (M1-2L); D, third molar (M3L). For the groups, see Table 1.