Choerolophodon pentelici (Gaudry F Lartet, 1856)

Tassy, Pascal, 2005, Proboscideans (Mammalia) from the late Miocene of Akkaşdağı, Turkey, Geodiversitas 27 (4), pp. 707-714 : 708-711

Choerolophodon pentelici (Gaudry F Lartet, 1856)

MATERIAL. — Left Dp2 (AK2-300); right dp3 (AK10- 2); right lunar (AK4-93); right lunar (AK6-89); left unciform ( AKA 29); left McIV and McV (AK2-93ab); right MtIII (AK11-68); left cuboid (AK14).

DESCRIPTION ( FIGS 1-6 )

The left upper second deciduous premolar (Dp2) AK2-300 ( Fig. 1 ) is fresh, comprising four main cusps forming two bunodont lophs. It belongs to an elephantoid of trilophodont grade. It bears two roots, a narrow anterior root and a larger posterior one.

The two anterior cusps are connected. The labial cusp (“paracone”) is the largest. The anterior cingulum is connected to the small lingual cusp (“protocone”). The two posterior cusps (the labial cusp – “metacone” – is the highest) are widely separated and the postcingulum does not form a loph. Small central conules are aligned to form a crest which connects the anterolabial cusp to the posterolingual one, that is, a contact between the posttrite anterior cusp and pretrite posterior cusp. This trait is present in Choerolophodon pentelici , including the Dp2 of the holotype cranium from Pikermi.

Measurements (mm): L = 34.3, W = 27.8 (second loph), H = 17.9 (“paracone”).

The right lower third deciduous premolar (dp3) AK10-2 ( Fig. 2 ) is slightly worn. It belongs to an elephantoid of trilophodont grade, with two lophids and an enlarged postcingulum. The enamel is heavily wrinkled, a character of milk teeth in general and especially marked on choerolophodont molars. The first loph is narrow, comprising two cusps, the labial one is anteroposteriorly enlarged, the lingual cusp is slighty displaced posteriorly compared to the labial, a choerolophodont character. In the interlophid a large posterior posttrite central conule connects the pretrite anterior central conule of the second lophid; a contact typical of choerolophodont dp3s.

The second lophid is transversely enlarged and separated from the inflated postcingulum by an entoflexus. No ectoflexus is marked.

All the characters described in this tooth match those of dp3s of Choerolophodon pentelici . The allocation of the Dp2 and the dp3 to C. pentelici is certain.

Measurements (mm): L = 47.0, W = 32.2 (second loph).

Two elephantoids are associated at Akkaşdagwı, so that the allocation of the postcranial bones remains tentative. On the basis of associated teeth and carpals and metacarpals in localities were only Choerolophodon pentelici is present, and thus belong without doubt to this species (Samos: Schlesinger 1917; Kayadibi, Garkın: Gaziry 1976), seven handbones and footbones from Akkaşdagwı are allocated to this taxon (comparisons with unpublished material on display in the Natural History Museum in Ankara were also helpful).

The two right lunars AK4-93 ( Fig. 3 ) and AK6- 89 show the same proportions as known lunars of C. pentelici with a strongly concave facet for the ulna. However, this bone is not especially modified in C. pentelici . The lunar AK6-89 is slightly narrower than AK4-93 but this does not change

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the overall shape. The two lunars have a wide strongly concave lateral facet for the ulna. Both lunars show an enlargement of the medial border for the trapezoid and lateral border for the unciform. The protruding anteromedial corner of AK6-89 is gnawed (probably by a hyaena).

The unciform AKA29 ( Fig. 4 ) has a rather vertical articular facet for the McV.

The metapodials (associated proximal parts of left McIV-McV AK2-93ab ( Fig.5 ) and the right MtIII AK11-68 ( Fig. 6 ) bear heavily marked rugosities where ligaments insert on the cranial face, just beneath the proximal articular facets. The contact between the McIV and the McV is anteriorly narrowed, because of the articulation with an enlarged unciform. The facet of the McV for the unciform is not much heightened but anteriorly deepened. In connection with the shape of the unciform (AKA29) it can be concluded that the McV is rather laterally oriented in C. pentelici .

The left cuboid AK14 shows two asymmetrical proximal articular facets. The calcaneal facet is much larger than the navicular facet. These two facets meet only in the center of the proximal face.

The MtIII AK11-68 has an oblique articular facet for the third cuneiform, heightened craniolaterally. This implies a third cuneiform with an asymmetrical distal surface.

Measurements (mm):

Lunar AK4-93: width = 146.0, depth = 125.3, height = 82.5.

Lunar AK6-89: width = 138.5, depth = 122.6, height = 72.3.

Unciform AKA29: width = 107.8, depth = 115.0, height = 93.0.

McIV AK2-93b: depth = 119.8, width = 87.6.

McV AK2-93a: depth = 97.0, width = 86.8.

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Cuboid AK14: width = 144.1, depth = 129.0, height = 53.0.

MtIII AK11-68: width = 95.9, depth = 111.0.

Figures

FIG. 1. — Choerolophodon pentelici (Gaudry & Lartet, 1856), left upper second deciduous premolar (Dp2) AK2-300, Akkaşdağı, Turolian, occlusal view. Scale bar: 1 cm. Photo D. Serrette (MNHN).

FIG. 2. — Choerolophodon pentelici (Gaudry & Lartet, 1856), right lower third deciduous premolar (dp3) AK10-2, Akkaşdağı, Turolian, occlusal view. Scale bar: 1 cm. Photo D. Serrette (MNHN).

FIG. 3. — Choerolophodon pentelici (Gaudry & Lartet, 1856), right lunar AK4-93, Akkaşdağı, Turolian; A, cranial view; B, distal view. Scale bar: 1 cm. Photo D. Serrette (MNHN).

FIG. 4. — Choerolophodon pentelici (Gaudry & Lartet, 1856), left unciform AKA29, Akkaşdağı, Turolian; A, cranial view; B, distal view. Scale bar: 1 cm. Photo D. Serrette (MNHN).

FIG. 5. — Choerolophodon pentelici (Gaudry & Lartet, 1856), left 4th and 5th Metacarpals (McIV and McV) AK2-93ab, Akkaşdağı, Turolian; A, cranial view; B, proximal view. Scale bar: 1 cm. Photo D. Serrette (MNHN).

FIG. 6. — Choerolophodon pentelici (Gaudry & Lartet, 1856), right third metatarsal (MtIII) AK11-68, Akkaşdağı, Turolian; A, cranial view;B, proximal view. Scale bar: 1 cm.PhotoD. Serrette (MNHN).