Hipparion crassum Gervais, 1859

Montoya, Plinio, Ginsburg, Léonard, Alberdi, María Teresa, Made, Jan Van Der, Morales, Jorge & Soria, María Dolores, 2006, Fossil large mammals from the early Pliocene locality of Alcoy (Spain) and their importance in biostratigraphy, Geodiversitas 28 (1), pp. 137-173 : 137-173

publication ID	https://doi.org/ 10.5281/zenodo.5376630
persistent identifier	https://treatment.plazi.org/id/11352538-A705-FFF5-70AD-FA31026FFB8D
treatment provided by	Marcus
scientific name	Hipparion crassum Gervais, 1859
status

Treatment

Hipparion crassum Gervais, 1859 ( Fig. 10 View FIG )

MATERIAL EXAMINED. — Right P2; two right M1-2; two left M1-2; left p2; two left p3-4; right p3-4; left m1-2; a McIII fragment; 1st and a 2nd phalanges, both of the finger III ( MAA).

2433M, right P2; 2108M, left M1-2; 2126M, right M1-2; 2431M, left p3-4 ( MGM).

Six lower teeth that could belong to the same individual (right m1, m2, and m3 and left p4, m1 and m3) ( MNHN).

MEASUREMENTS. — See Appendix: Tables 9 and 10.

DESCRIPTION

The measurements follow the recommendations of the “ Hipparion Conference ”, New York 1981 ( Eisenmann et al. 1988) and all are expressed in millimeters.

Tables 9 and 10 show most of the dimensions and some of the characters of the dental remains from the different collections studied. The remains are not very numerous and a clear difference between the size of molars and premolars can be observed. Quite a lot of cement is generally preserved in all of them.

The upper dental remains ( Table 9) show some size differences that could reflect age differences of the animals (crown height), since their dimensions at the base of the crown (l/w) are more similar. Most of the teeth correspond to young adults. We could section them and study their characters at comparable wear degrees. The styles, are narrow, thin and well pronounced, both in molars and premolars, and are broader in premolars. Although the parastyle is not wide, it shows a groove-like notch. The protocone is oval, relatively small and sometimes with elongate or angular extremes when the wear is slight. With more advanced wear the protocone is clearly oval. The pli caballin has four or five folds (the only specimen that shows only one caballine fold corresponds to a little worn specimen that could not be sectioned because of its damaged state). The number of fossette folds is variable (Apre 5-6, Dpre 10-12, Apos 6-7 and Dpos 2). The hypocone shows a marked, more or less oval, open distal sinus (SD), that is oriented backwards.

The lower dental remains ( Table 10) show size differences between the teeth stored in Paris and those from other collections. The remains from the MNHN, which belong to the same individual, correspond apparently to a smaller Hipparion . The length of the right series m1-m3 is 67.1 mm. In the left series are preserved the p3-4, an m1-2 and an m3. The teeth stored in MGM and in the MAA, almost all of them premolars, correspond to a larger animal. Most of them belong to very young individuals, without signs of wear, but already adults. In section they show a typical design with an internal curl particularly in the postflexid, the presence of a protostylid, a median robust size, and an elongate and somewhat angular metaconid-metastylid bow. The linguaflexid is open and shallow in premolars and closer and sharper in molars. The ectoflexid extends inside and nearly reaches the linguaflexid in molars. This does not happen in premolars.

The scarce postcranial skeleton remains, are only those stored in the MAA. A fragment of McIII, attributed by Alberdi (1974: pl. 7, fig. 1) to Hipparion crassum , must correspond to Equus Linnaeus, 1758 , as pointed out by Eisenmann & Sondaar (1989) and Alberdi & Alcalá (1999). The assignation mistake could be due to the comparison with figure 1 of Depéret (1890). The dimensions of the 1FIII are: 1 = 62.2; 2 = 56.3; 3 = 31.7; 4 = 41.7; 5 = 32; 6 impossible to measure; 7 = 36.2; 8 = 22; 9 = 27.5; the dimensions of the 2FIII are: 1 = 44; 2 = 32; 3 = 36.4; 4 = 42.2; 5 = 27; 6 = 40. In addition there are a fragment of calcaneus and another fragment of a metapodial distal end, but they are so damaged that they do not yield any significant data.

DISCUSSION

The wear pattern of the upper teeth shows deep, complex and numerous lateral folds of the fossettes as is characteristic in Hipparion crassum . The protocone is oval and small if compared with the tooth; the pli caballin is complex (four or five more or less branched folds); the hypocone is oval, small and open, with a deep distal sinus, less deep as wear advances, and with a less marked lingual sinus that totally disappears with the wear. All this and the size of the teeth relate the material from Alcoy-Mina to a robust medium-sized Hipparion . In the same way, the morphology of the lower teeth, with a robust protostylid not always reaching the wear surface (because it is partly masked by the presence of cement), the angular and elongate metaconid-metastylid bow, the internal curl particularly in the postflexid, as well as the presence of pli caballin or ptycostilid more pronounced in premolars than in molars, also indicate a robust medium-sized animal.

Most of the studied teeth are homogenous and their dimensions are totally within the distribution of the remains from Serrat d’en Vaquer (Perpignan, Roussillon, France), the type locality of H. crassum . In Tables 9 and 10 are also included the dimensions of the remains from Dorkovo ( Thomas et al. 1986; Alberdi & Alcalá 1999), determined as Hipparion cf. crassum . The plots based on the dentition dimensions (length and width at the surface) show that the remains from Alcoy and Dorkovo are slightly smaller than those from the French localities of H. crassum , but the dimensions are very similar if taken at the base of the tooth. This is clearly observed when the upper molars (M1 and M2), on the one hand, and the lower molars (m1 and m2), on the other hand, are compared ( Figs 11 View FIG ; 12 View FIG ).

The comparison of the morphological characters of the dentition from Alcoy with those of other Pliocene populations of Hipparion , indicates that the upper dental remains have narrower and more pronounced styles (parastyle and mesostyle) than the rest of Spanish Pliocene forms studied by Alberdi & Alcalá (1999). This can be seen both in the parastyle and in the mesostyle, although the first one is generally wider than the second one, and both are wider in premolars than in molars. Also the protocone of the remains from Alcoy is comparatively smaller than that of other Spanish Pliocene forms in which it is elongate and larger, relative to tooth size. As for the lower teeth, in the Pliocene dolichopodial populations of Hipparion (and depending on the wear degree of the teeth), the ectoflexid crosses the isthmus and approaches the linguaflexid both in premolars and in molars, whereas in the remains from Alcoy this can only be observed in molars.

The lower teeth stored in the MNHN are apparently smaller and more slender than the specimens from Alcoy stored in the other institutions. But, as already mentioned, it can be observed in the plots ( Figs 11 View FIG ; 12 View FIG ) that the differences between the compared populations of Hipparion disappear when the utilized dimensions have been taken at the base of the teeth. The result is that these differences depend on the age of the animal and are not due to real size differences in the studied sample.

There are only two remains of the postcranial skeleton (1FIII and 2FIII). Both are robust and are within the range of variation of the phalanges of H. crassum from Perpignan and Le Soler (Lit de la Têt) ( Alberdi & Aymar 1995). On the other hand, they are identical, both in size and robustness to those of H. cf. crassum from Dorkovo ( Bulgaria).

All the mentioned characters indicate that these remains correspond to a robust medium-sized Hipparion with primitive (abundant and deep folds) and relatively brachydont cheek teeth. In addition, the only remains of the appendicular skeleton indicate a strong structure similar to that of Hipparion crassum , which characterizes the morphotype 4 of Alberdi (1989), who considered it as representative of the lower Ruscinian ( Alberdi 1986, 1989). This species was described by Depéret (1890: 76, 77) from Perpignan (Roussillon, France) placed by Mein (1990) and De Bruijn et al. (1992) in the upper Ruscinian (MN15). The structure and morphological characters of this Hipparion indicate a more covered environment and with a softer substratum than those of the Pliocene dolichopodial forms of the Iberian Peninsula ( Alberdi & Alcalá 1999). Besides this, the presence of a mastodont, Anancus Aymard, 1855 , an animal that feeds on branches and leaves and is generally associated with more wooded environments, could indicate a relatively covered environment on soft ground in the surroundings of the Alcoy site.

Family RHINOCEROTIDAE Owen, 1845