Thalassictis spelaea ( Semenov, 1988 )

Bonis, Louis de, 2005, Carnivora (Mammalia) from the late Miocene of Akkaşdağı, Turkey, Geodiversitas 27 (4), pp. 567-589 : 575-576

Thalassictis spelaea ( Semenov, 1988)

Ictitherium spelaeum Semenov, 1988: 46 ; 1989: 66.

Thalassictis spelaea – Werdelin F Solounias 1991: 47.

MATERIAL. — Right half mandible (AKK-114) with p1-m1.

A right hemi-mandible (AKK-114) with p1-m1 differs from all the other carnivores from Akkaşdagwı. The size is similar to that of Ictitherium viverrinum but the morphology is clearly different. DESCRIPTION ( FIG. 8 )

The corpus mandibulae is destroyed in the lingual face and the roots of the teeth are visible. It was quite shallow. The teeth are unworn but the enamel of p3 to m1 is marked by weathering. The premolars are larger and larger from p1 to p4. The p1, one-rooted, is small and the crown is slightly buccolingually flattened and slightly asymmetrical, the mesial part being a little small- er and more steeply inclined than the distal one. The p2 has a tiny lingually situated mesial accessory cuspid and a distal one followed by a tiny cingulum. The p3, almost symmetrical, has two developed accessory cuspids, the distal one with a cingulum lingually enlarged. The p4 is also symmetrical with two, mesial and distal, very well developed accessory cuspids, trefoil or felid-like profile, and a more developed distal cingulum ( Fig. 8 ). The m1 has a high trigonid with the protoconid clearly taller than the paraconid and a reduced metaconid. A cingulum runs buccaly along the trigonid and the metaconid. The talonid is moderately reduced. The hypoconid is on a thin crest running from the distal face of the protoconid and joining distally the end of the cingulum together with a hypoconid small crest which is separated by a small notch from the tiny entoconid. The latter is separated from the metaconid by a deep notch.

COMPARISONS

Some late Miocene hyaenid genera, Chasmaporthetes Hay, 1921 , Lycyaena Hensel, 1861 , Miohyaenotherium Semenov, 1989 , Metahyaena Viranta F Werdelin, 2003 , Palinhyaena Qiu, Huang F Guo, 1979 and Thalassictis , can be compared to the carnivores from Akkaşdagwı.

All the species of Chasmaporthetes are larger, more robust with robust dentition.

The type species of Lycyaena , L. chaeretis ( Gaudry, 1861) , comes from the Greek locality Pikermi and is larger than AKK-114 (m1 = 26.6 mm). In the mandible ( Gaudry 1861: pl. 15, figs 1, 2) the premolars, p3 and p4, are a little relatively taller but have the same accessory cuspids. We note that the mesial cuspid of the p4 is more developed in the specimen itself than in the Gaudry’s drawing. The morphological characters of m1 match very well with AKK-114, particularly the pattern of the talonid. Nevertheless the metaconid of L. chaeretis is more reduced and the talonid is shorter (21.6% of the total length versus 26.3%). These two features are derived characters. Other species of Lycyaena are far larger than AKK-114.

Miohyaenotherium bessarabicum (Simionescu, 1937) , sole species of the genus, has a p3 without mesial accessory cuspid and the same cuspid in p4 is relatively smaller. The talonid of m1 is shorter (21.4 to 23.4% versus 26.3%) and the p4 is shorter relative to m1.

Metahyaena confector Viranta F Werdelin, 2003 differs by the lack of accessory cuspids in p2 and p3, by the conical shape of the main cuspid of p4 and the greater width of the m1 talonid.

The premolars of Palinhyaena are taller, there is no accessory cuspid in p3 and the mesial accessory cuspid of p4 is relatively smaller. The metaconid of m1 is more reduced and the talonid is shorter (21% versus 26.3%).

Two species of Thalassictis , T. robusta and T. spelaea , match AKK-114 by the size and the depth of the mandible under p3-p4 is quite the same. The two species have developed accessory cuspids on the premolars, more developed in T. spelaea . The proportions of the m1 are similar to those of AKK-114. I identify this mandible as Thalassictis spelaea despite the difference in the geological age, Vallesian for T. spelaea and Turolian for AKK-114.

Figures

FIG. 8. — Thalassictis spelaea (Semenov, 1988), fragment of right mandible p1-m1, Akkaşdağı, late Miocene (Turolian), Turkey; A, buccal view; B, lingual view. Scale bar: 1 cm.