Palaeotragus rouenii Gaudry, 1861

Kostopoulos, Dimitris S. & Saraç, Gercek, 2005, Giraffidae (Mammalia, Artiodactyla) from the late Miocene of Akkaşdağı, Turkey, Geodiversitas 27 (4), pp. 735-745 : 739-742

Palaeotragus rouenii Gaudry, 1861

MATERIAL EXAMINED AND MEASUREMENTS (in mm). — Upper toothrow (AK3-298): LP2-M3 = 123.0, LP2- P4 = 53.0, LM1-M3 = 72.7, LP2 = 15.5, WP2 = 15.3, LP3 = 15.8, WP3 = 18, LP4 = 17.1, WP4 = 17.1, LM1 = 23.1, WM1 = 22.5, LM2 = 24.8, WM2 = 26, LM3 = 26.5, WM3 = 25.8; lower toothrow (AK12- 78): Lp2-m3 ≈ 129.0, Lp2-p4 ≈ 49.0, Lm1-m3 = 77.0, Lp3 = 17.0, Wp3 = 10.1, Lp4 = 18.5, Wp4 = 12.2, Lm1 = 22.5, Wm1 = 15.4, Lm2 = 24.5, Wm2 = 16.4, Lm3 = 30.5, Wm3 = 15.3; proximal part of radius (AK5-392): DT prox = 88.2, DAP prox = 50.0; part of metacarpal III+IV (AK6-86): DT prox = 65.0, DAP prox = 48.0, DT diaph = 34.4, DAP diaph = 41.0; (AK6-87): DT prox = 56.6, DAP prox = 38.4; tibia (AK4- 236): DT dist = 67.5, DAP dist = 51.7; talus (AK3-197): L lat = 76.2, L med = 69.0, DT dist = 50.0; (AK5-184): L lat = 80.0, L med = 72.0, DT dist = 49.5.

DESCRIPTION ( FIGS 5 ; 6 )

The teeth are small, brachyodont and with finely rippled enamel ( Fig. 5 ). The upper premolar row represents 72.9% of the molars, while the same ratio is estimated about 63-65 for the lower dentition.

Upper toothrow ( Fig. 5A )

P2 is simple with a rudimentary hypoconal spur, directed strongly backwards. The parastyle is well developed. The paracone rib is strong and is placed anteriorly. A weak cingulum is present anterolingually ( Fig. 5A ). P3 is morphologically similar to P2, but with stronger hypoconal spur, tending to form a hypoconal islet. The parastyle and the lingual cingulum are also stronger than in P2. P4 is more symmetrical than P2 and P3. In occlusal view there is a well formed hypoconal islet ( Fig. 5A ). The paracone rib is strong and situated centrally on the labial wall, while both the parastyle and the metastyle are less developed. A weak cingulum appears along the lingual surface. All the molars have moderate to well developed styles and ribs. The posterior flange of the paracone does not confine with the mesostyle. The protocone of M1, 2 is angular and slightly constricted lingually ( Fig. 5A ). A strong hypoconal spur is present in all upper molars and especially in M3, which also bears a weak protoconal fold. The cingulum is weakly developed both on the lingual and labial faces. A very short basal pillar is also present.

Lower toothrow ( Fig. 5B )

p3 is highly molarized with strongly elongated metaconid, parallel to the anteroposterior axis of the tooth and extremely shortened talonid. The elongated endoconid is independent from the metaconid in early wear. The reduced endostylid is obliquely settled. Labially, a well developed furrow separates the bulgy hypoconid from the strong protoconid. The parastylid is well defined ( Fig. 5B ). p4 is also molariform ( Fig. 5B ). Its metaconid is long and the parastylid thinner than in p3. The endoconid is well distinct and oblique. The endostylid is longer than in p3 and placed lingually. On the labial wall, the trigonid is distinguished from the bulgy talonid by a deep furrow. The first molar shows a weak anterior fold. A rudimentary basal pillar, a well developed metaconid and a strong metastylid (especially on the m2, 3) are present in all molars. The third lobe of m3 is relatively small, elliptical and bicuspid ( Fig. 5B ).

Postcranials

The poor postcranial material ascribed to this form does not allow major observations. The preserved part of the metacarpal clearly shows dolichopodial morphology. The external articular groove of the distal trochlea of the tibia is shorter than the internal one. The plantar face of the talus lacks the depression for the external tendon of the cubonavicular and its external face is quite flat.

DISCUSSION

Palaeotragus is a well known genus from the so-called Greco-Iranian province and Eurasia in general, while its distribution area extends also to Africa. Nonetheless, the phylogenetic relationships among the referred late Miocene species are not always clear and the species synonymy appears sometimes to be confused (see Bohlin 1926; Bosscha-Erdbrink 1977; Hamilton 1978; Geraads 1986, 1994; Gentry et al. 1999). Overlooking the palpable nomenclature problems, it is evident that most of the Turolian Palaeotragus could be grouped in two size categories:

– a group of small-sized and slender-limbed forms, represented mainly by the type species of the genus P. rouenii Gaudry, 1861 from Pikermi ( Greece) and its allies ; and

– a group of larger and stouter forms, principally represented by P. coelophrys (Rodler F Weithofer, 1890) , originally described from Maragha ( Iran). The contemporaneous Palaeotragus microdon (Koken, 1885) from China (mainly from Loc. 116 of Kansu; Bohlin 1926) is considered to be very similar to P. rouenii ( Bohlin 1926; Bosscha- Erdbrink 1977; Geraads 1986). Nevertheless, P. microdon presents ossicones in both sexes while P. rouenii females appear to be “hornless” ( Bohlin 1926; Geraads 1974). Moreover, the lower dentition of P. microdon presents a comparatively shorter premolar row than that of P. rouenii (the index [premolar/molar row lengths% ranges

110

between 57-62 [n = 7s in the first species and between 63-73 [n = 5s in the second one; Fig. 6 ) and its limb proportions are slightly different (more slender limb bones, stouter tali, etc.). Therefore, we regard P. microdon as a distinct species.

Except for the ossicone and skull morphology (which anyway are not available in the Akkaşdagwı collection) P. coelophrys differs from P. rouenii in its larger size and dental dimensions ( Fig. 6 ), simpler dental morphology, more robust and less dolichopodial limbs ( Bohlin 1926; Geraads 1974, 1978). Moreover, the p3 of P. coelophrys has an independent metaconid, while the p3 of P. rouenii presents a strong molarization on the lingual wall.

The small size, the molarized p3 and p4, the bi-cuspid talonid of m3, the weakly developed cingula and basal pillars on the molars and the slender limbs of the Akkaşdagwı form rule out the association with P. coelophrys and related forms, and match P. rouenii and P. microdon . Moreover, the “premolar/molar ratio” values for the Akkaşdagwı specimens are larger than those of P. microdon and within the known range of P. rouenii .

The original comparison with P. rouenii from RPl, NKT, DIT ( Greece; LGPUT), PIK ( Greece; MNHN, BMNH), Samos ( Greece; MGL, BMNH, AeMNH) and KTD ( Turkey; MNHN), does not exhibit important morphological or metrical differences ( Fig. 6 ). Nevertheless, the accessory features of the dentition (labial and lingual cingula, basal pillars, spurs, etc.) seem to become less significant in the younger samples of the species. Although the value of this “smoothening” cannot be systematically or chronologically appreciated because of the insufficient data, the Akkaşdagwı P. rouenii seems to be closer to the later Turolian forms than to the early ones.

Figures

FIG. 5. — Palaeotragus rouenii from Akkaşdağı, Turkey, occlusal view; A, upper dentition; B, lower dentition. Scale bar: 2 cm.

FIG. 6. — Scatter diagram “Length P2-P4 against Length M1-M3 (p2-p4/m1-m3)” of Palaeotragus rouenii, Akkaşdağı, Turkey (N) in comparison with other late Miocene Palaeotragus species (data from Bohlin 1926; Geraads 1974, 1978; and pers. data). Abbreviation: DIT, Dytiko 3, Axios valley, Greece.