Cremohipparion mediterraneum (Roth & Wagner, 1855)

Geraads, Denis, Spassov, Nikolaï, Hristova, Latinka, Markov, Georgi N. & Tzankov, Tzanko, 2011, Upper Miocene mammals from Strumyani, South-Western Bulgaria, Geodiversitas 33 (3), pp. 451-484 : 462-464

Cremohipparion mediterraneum (Roth & Wagner, 1855)

We refer to this species: a skull, FM-2028, that belongs to an adult animal with the protocon of P2 almost connected to the protoloph ( Fig. 6B ), and a partial skull, FM-2325, with unerupted M3. The nasal notch ends above the anterior part of P2, the facial crest ends above the posterior end of P4 (FM-2325) or the first half of M1 (FM-2028). The choanae reach the posterior half of M2. The preorbital bar is short (28 mm) and in both skulls the lachrymal bone does not reach the rim of the preorbital fossa.The preorbital fossa is large, moderately deep (about 10 mm), with moderate posterior pocket (about 7 mm). There is no trace of a canine fossa. The distance from orbit to facial crest is long: 29-32 mm. The infraorbital foramen is situated at the antero-ventral border of the preorbital fossa.The buccinator fossa is shallow.The muzzle of FM-2028 is short and narrow, with arc-shaped incisor series. The small size of the upper canine of FM-2028 suggests that it is from a female. The upper tooth row is slightly curved. The anterostyle of the P2 is elongate. The enamel plication is moderate, with 12-17 wide and shallow folds. The pli caballin is single, rudimentary on M1 and M2. The protocon is oval, with a thick, flattened lingual wall. The hypoglyph is shallow (on M1 and M2) to deep (on M3); only M3 has a labial sinus.

Cremohipparion mediterraneum is characterized by its medium size, a well-developed preorbital fossa located close to the orbit, and a narrow muzzle ( Koufos 1987a). After Bernor et al. (1996) the diagnosis is: medium size, presence of the three distinct facial fossae (preorbital, canine, and buccinator); short preorbital bar; lacrimal invading preorbital fossa; nasal notch above P2 mesostyle; skull relatively short; snout short and narrow; complex to moderate enamel plication. According to Vlachou & Koufos (2009) in all specimens of C. mediterraneum from Pikermi there exists an anterior, canine fossa, but the sample of the same species from Hadjidimovo-1 ( Hristova et al. 2002; Hristova 2009) consists of specimens with and without canine fossa. The same is true of the C. mediterraneum specimens from Karaslari ( Macedonia). Thus, at most, the diagnosis of the species could include the occasional presence of a canine fossa.

The species was described from several localities: Hadjidimovo, Perivolaki, Kemiklitepe A-B, Kalimantsi, Karaslari, Pikermi ( Koufos 1987a, b; Koufos & Kostopoulos 1994; Hristova et al. 2002; Hristova & Spassov 2005; Vlachou & Koufos 2006). There are some differences between the various samples. Most specimens of early C. mediterraneum from Hadjidimovo ( Bulgaria) and the one C. cf. mediterraneum from Perivolaki ( Greece) have a well-developed canine fossa and a larger preorbital fossa located closer to the orbit, as well as deeper nasal notch and a longer muzzle ( Hristova et al. 2002; Vlachou & Koufos 2006; Hristova 2009). The enamel plication of the Hadjidimovo sample is moderate to strong, with simple to double or multiple pli caballin. The later C. mediterraneum from Pikermi has a preorbital fossa situated slightly farther from the orbit and developed canine fossa (preserved only in PIK-259). The enamel plication is simple to moderate and the pli caballin is simple “very small and sometimes absent” ( Koufos 1987a).

The differences between skull FM-2028 on the one side and the samples from Perivolaki and Hadjidimovo on the other side lie in the shorter preorbital bar, the larger and much deeper preorbital fossa, the longer tooth row, the presence of a welldeveloped canine fossa in most of the skulls from Hadjidimovo and in the one from Perivolaki, and deeper nasal notch. FM-2028 closely resembles the hipparions from Pikermi, but differs from them in the longer palate and shorter preorbital fossa. The dimensions of FM-2028 are within the range of the Pikermi sample and they show the greatest similarity with it.

Another species with a preorbital fossa placed close to the orbit and the facial crest is C. moldavicum , described from the Northern Black Sea coast, Maragheh and AkkasdaĞI ( Gromova 1952; Forstén 1980; Bernor 1985; Watabe & Nakaya 1991; Krakhmalnaya 1996a, b; Forstén & Krakhmalnaya 1997; Krakhmalnaya & Forstén 1998; Koufos & Vlachou 2005). The differences between the Strumyani sample and samples of C. moldavicum from Taraklia (TAR-Moldavia) and Novoelisavetovka ( Ukraine, after Gabunia 1959), Maragheh ( Iran) and AkkasdaĞI ( Turkey) are in the absolute and relative dimensions and morphology of the preorbital fossa (in C. moldavicum it is sub-rhomboidal, larger and deeper), in the deeper buccinator fossa, narrower muzzle, and in different skull proportions. There are differences in the data about the sample from Novoelisavetovka. According to Gabunia (1959), the preorbital bar length ranges from 20 to 31 mm, but for Krakhmalnaya (1996b) it ranges from 22 to 44 mm; the distance from the facial crest to the preorbital fossa ranges from 16 to 27 mm after Gabunia, but from 21.4 to 45.2 after Krakhmalnaya, who might have mixed data from two different species. The sample from Novaya Emetovka-2 ( Ukraine) has longer skulls dimensions (400-414 mm), wider preorbital bar length (30-38 mm), larger (74-82 mm) and higher (48-57 mm) preorbital fossa. The specimens from Cherevichnoe are slightly smaller in overall size: tooth row length ranges from 123 to 134 mm and the distance from the anterior point of P2 to the most anterior point of the orbit is about 143- 150 mm versus 140 mm and 160.6 mm respectively for FM-2028 from Str-2.

The sample from Str-2 shares some similarities with “ Hipparion ” verae Gabunia, 1959. This species has similar skull size, close dimensions of the preorbital fossa, and in one specimen the position of the nasal notch is above the anterior end of P2 as in FM-2028. But some other features, such as less plicated tooth enamel, longer preorbital bar and longer distance between the preorbital fossa and the facial crest distinguish “ H.” verae from the Str- 2 specimens. The species was described also from the Republic of Macedonia ( Forstén & Garevski 1989), but our personal observations (L/H) do not confirm their species determination, as it seems that under this name these authors lumped H. brachypus and C. mediterraneum from Karaslari and H. brachypus from Basiboz.

Figures

FIG. 6. — Fossil mammals from the Miocene of Strumyani (SW Bulgaria): A, Hippotherium cf. brachypus (Hensel, 1862), lateral view of skull FM-2326; B, Cremohipparion mediterraneum (Roth & Wagner, 1855), lateral view of skull FM-2028;C, Hipparion dietrichi (Wehrli, 1941), lateral view of skull FM-2029. Scale bar: 20 cm.