The Skull of Quadruped and Bipedal Vertebrates. Djillali Hadjouis

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Figure 2.2. Diagrams showing the comparison of the average protoconic indices of the definitive superior jugal teeth of several horses from Europe and Africa (© Hadjouis). For a color version of the figure, see www.iste.co.uk/hadjouis/skull.zip

In his numerous works on Equidae, Eisenmann tried to give explanations on the cranial forms and those of the bones of the distal segments of fossil and current species. It is clear that on many interpretations, doubt persists in spite of everything, because morphological differences are also linked to genetic differences. Indeed, comparative analyses of the cranial remains of horses from the Middle Pleistocene of Europe (Mosbach, Caune de l’Arago and Lunel-Viel) show significant differences in the relative lengths of the snouts, which seemed to behave in the same way in other Pleistocene Caballines and behave in the same way in present-day ones. They could result from ecological adaptations (shortening of the snout in response to cooling) possibly leading to speciation (Eisenmann et al. 1985). Similarly, the European Quaternary horses, distinguished by the dimensions and proportions of their teeth and metacarpals, discriminate the large Antewürmian forms and the small ones from the Würm onwards. On the basis of the relative lengths of the protocones, this author defines three types with different sizes: type I with relatively long M1 and M2 protocones, adapted to a temperate climate; types II and III with short protocones, adapted to a cool or cold climate (Eisenmann 1991). The horse of the Saalian levels from Alfort 1 to Maisons-Alfort suggests that it belonged to the latter type (Hadjouis 1998a; Figure 2.2).

      2.1.2. A fossil horse in Africa: paleogeographic and biostratigraphic distributions

      Equus algericus (Bagtache et al. 1984) recognized in the Warthog Aterian deposit (Algiers, Algeria) (Bagtache and Hadjouis 1983; Bagtache et al. 1984; Hadjouis 1993, 2001, 2003a, 2003d; Hadjouis and Le Bihan 2014) was a caballine-type horse, measuring about 1.44 m at the withers, with stocky metapods and teeth with a wide and angular lingual groove and a very asymmetrical double loop typically caballine. It was found in the deposits of Ain Taya and Ain-Benian near Algiers, Oued Djebbana near Tébessa (Hadjouis 1993), Columnata in the Tiaret region (Chaid-Saoudi 1984), and Tit Mellil not far from Rabat (Hadjouis 1993), in Sidi Bou Knadel near Rabat, in El Mughara El Aliya near Tangier (Zouhri and Aouragh 1997) and in the Zouhra Cave in El Harhoura south of Rabat (Aouragh and Débénath 1999; Aouragh 2001); the latter are all dated to the Upper Pleistocene (Hadjouis 2001). Its reported presence at the Moroccan site to Homo erectus in Ain Maarouf near El Hajeb on the basis of a single tooth seems doubtful, especially since all the other Equidae remains have been attributed to the Equus mauritanicus (Geraads and Amani 1997).

      This horse appeared during the Upper Pleistocene and probably corresponding culturally to the Moustero-Aterian periods (Middle North African Paleolithic –32,000 to –16,000). The Algerian horse (E. algericus) was certainly of Euro-Asian origin since no acceptable ancestor in Africa can be found at present; all the Plio-Pleistocene horses of this continent being Stenonian.

The dispersion of horses to the Maghreb during the Upper Pleistocene was from a center of Euro-Asian origin. This East-West migration by land that took place during the last glaciation is well known to authors. Several Eurasian species had to follow the migration corridor along the Gulf of Sidra. This was notably the case for the wild boar (Sus scrofa), the Algerian red deer (Megaceroides algericus), the red fox (Vulpes vulpes) or the rhinoceros (Dicerhorinus hemithoecus). It seems likely that E. algericus took part in these successive waves. Its passage through the Moustero-Aterian material and Aterian sites thus seems quite logical. However, its absence in Epipaleolithic sites further complicates its status. While E. algericus did not appear in any of the Iberomaurusian and Capsian deposits in Algeria, its presence in this part of Africa would have been of short duration, which seems unlikely to us in view of the other Eurasian immigrants. Moreover, the Filfila deposit was not epipaleolithic (in the prehistoric sense), as has been pointed out by some, since no lithic industry or anthropic activity has been found there. It is a red clay fissure filling, corresponding rather to the periods of runoff resulting from the last glacial episodes (Ginsburg et al. 1968) and could be correlated to the Soltanian/Oulijian (isotopic stages 4 to 2) of the continental and marine chronologies of Morocco assuming that a Mediterranean/Atlantic correlation can be accepted (Texier et al. 1994). However, the presence of Ammotragus lervia at this site (if the determination is correct) gives this species an antiquity that has never before been raised. As for the presence of the Algerian horse in the Columnata Epipaleolithic (Iberomaurusian or Columnatian?), it rests on a distal end of a metacarpus, which in our opinion seems extremely limited without the association of sufficient dental and skeletal material to allow a distinction. However, the measurements nevertheless impose an approximation with the horses.

      Compared to the Equidae of the Zouhra Cave in Morocco, E. algericus from the Warthog deposit was smaller than the Moroccan form but with similar protoconic indices. As for the European species, we had already mentioned in a previous work (Bagtache and Hadjouis 1983) the similarity in proportions and size of the Algerian horse with Jaurens’ Equus gallicus (early recent Würm (Mourer-Chauviré 1980)), Solutrean (Prat 1968) and the horse from Torralba in Spain (Prat 1977). At the dental level, although the protocones are longer on P3/P4 than on M1/M2, its typological attribution (if this method were applied to vertebrates from Africa (Eisenmann 1991)) would be consistent with type 1, horses from temperate climates such as E. gallicus from Saint-Germain-de-la-Rivière, from Solutré and Combe-Grenal from Würm II (Guadelli 1987).

Concerning the horse (E. caballus or ferus), although its domestication dates back more than 3 millennia, known in Eastern Europe the species is determined with certainty in sites in France only in the Bronze Age. Sporadic remains of the wild form have been found in Neolithic sites of Val-de-Marne (Maisons-Alfort and Ivry-Grand-Ciel). The domestic species was attested to in the Gallic period by three forms of different sizes. The first one, with a slender shape, was a small horse with microdontia teeth. Its cranial, dental and skeletal characteristics bring it close to Iron Age horses with a height at the withers of 1.10 m. This size falls within the range of variation of average domestic horses of the Iron Age (between 1.10 m and 1.40 m) and therefore excludes the hybrid forms (bardot and mule), the pony and donkey. The second form had a height at the withers of 1.24 m also falling within this same variation, and the third, slightly larger, measured 1.39 m. These three forms of domestic horses nevertheless posed the problem of hybridization.

      2.1.3. The postural balance of Equidae

The Family Equidae reached during its evolution the maximum of its specialization by the development of its third digit (also in the Rhinoceros and Tapirs), the second and fourth being vestigial. The last phalanx ending in a powerful hoof supporting a body with symmetrical postural balance in each leg (Figure 2.4). The cephalo-caudal axis shows a template whose withers and rump illustrate a masterful structure reminiscent of the suspension bridge (Figure 2.3). In fact, the fore and rear-end are in a front-to-rear axis at equidistant height. The spine, from the first four thoracic vertebrae to the caudal vertebrae, shows a curvature with a lower concavity. The cantilevered head is positioned high, due to a verticalized cervical spine, exceeding in height the withers by five cervical vertebrae. Because of this balance, the gravitational forces have developed the same robustness in the fore and hind limbs, including both sexes. In spite of a little apparent sexual dimorphism on the bones, only the absence of canines in the mare constitutes a difference.

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