Iberomeryx parvus Gabunia, 1964

Métais, Grégoire, Coster, Pauline, Licht, Alexis, Ocakoğlu, Faruk & Beard, K. Christopher, 2023, Additions to the late Eocene Süngülü mammal fauna in Easternmost Anatolia and the Eocene-Oligocene transition at the periphery of Balkanatolia, Comptes Rendus Palevol 22 (35), pp. 711-727 : 716-717

cf. Iberomeryx parvus Gabunia, 1964

( Fig. 2 A-I, J-O)

REFERRED MATERIAL. — Sü-2002 , left p3 ; Sü-2003 , left p4; Sü-2005 , talonid of a left p4 ; Sü-2009 , right m1; Sü-2010 , lingual part of a right M1 or M2; Sü-2020 , left p4 ; Sü-2013 , right astragalus ; Sü-2014 , right astragalus .

LOCALITY. — Outcrop of unnamed rock unit consisting of c. 40 cm thick tuffite bed containing gastropod operculae superposed by c. 30 cm thick white silty limestone with silicified nodules exposed in a streambed roughly two km northwest of Süngülü, Ardahan Province, Turkey (de Bruijn et al. 2003: fig. 1). Latest Eocene according to de Bruijn et al. (2018, 2019).

DESCRIPTION

Dentition

The p3 is elongated with a small paraconid, and a hypoconid lower than the protoconid. A sharp crest joins the apex of the protoconid to the hypoconid, and is bifurcated distally, so that the two crests form a circular, postero-lingually opened depression. The paraconid of p4 is more pronounced than on p3, and the crest joining the paraconid to the protoconid corresponds to a wear facet.Two crests extend backward from the apex of the protoconid; the better expressed labial crest joins the distal border of the tooth, whereas the weaker lingual crest stops at the mid-point of the posterior half of the tooth, leaving the talonid distolingually opened.

The lower molar is brachyodont, and only the hypoconid is completely crescent-shaped. The trigonid is narrower than the talonid, and the protoconid is taller than the metaconid. The anterior fossa is widely antero-lingually open due to the absence of a premetacristid. The preprotocristid extends mesially and is notched; it forms the anterior-most part of the lower molars. The internal posprotocristid is lingually oriented and short, and it joins the very short and posterolabially oriented internal postmetacristid to form a cristid at the rear of the trigonid which is oriented toward the mesially oriented preentocristid. The external postprotocristid is very faint and extends toward the prehypocristid without connecting it because of transverse breakage of Sü-2009. The metaconid is rounded mesially and displays a short external postmetacristid. The combination of an external postprotocristid, an internal postprotocristid, an internal postmetacristid and an external postmetacristid forms a M-structure orΣ- structure which is characteristic of tragulids. The posthypocristid is short and lingually oriented. The entoconid is labio-lingually compressed and its distal side is rounded (devoid of any crest), thus leaving the posterior fossa open on its postero-lingual corner. There are both mesial and distal cingulids and an ectostylid on Sü-2009.

The fragmentary upper molar (Sü-2010) only preserves the lingual part. The relatively large size of the metaconule suggests it is either a M1 or a M2. The postprotocrista is short, straight, and postero-labially oriented whereas the preprotocrista is labially oriented. The premetaconulecrista extends labially. There is a strong cingulum surrounding the protocone and extending along the mesial border of the tooth; however, there is no protoconule as in Nalameryx ( Métais et al. 2009) .

Postcranials

Two astragali of similar size are referred to this small taxon on the basis of both their size and morphology. The astragali display non-aligned proximal and distal trochlea, the distal one being slightly rotated medially. The distal trochlea does not show any ridge separating the articular surfaces of the cuboid and the navicular. The astragalo-calcaneal facet is well-developed, and there is a deep fossa for the fibular condyle of the calcaneum. The distal astragalar facet is generally well-developed as it is in primitive Pecora ( Métais et al. 2016). The distal part of the internal malleolus facet is wide. Sü-2013 is slightly smaller than Sü-2014, but they are similar in morphology, and we attribute these slight metric differences to intraspecific variation.

Measurements

Provided in Table 1 for the dental material, and in Table 2 for postcranial material.

TAXONOMIC ATTRIBUTION

The dental material displays the characteristics of the genus Iberomeryx , and the astragali strongly resemble those reported from the early late Oligocene Kızılırmak Formation, central Anatolia, Turkey ( Métais et al. 2016). The genus Iberomeryx is known by three species: I. miaoi Mennecart, Aiglstorfer, Li, Li & Wang, 2021 recently described from material first identified as Lophiomeryx gracilis Miao, 1982 ( Mennecart et al. 2021) and restricted to the late Eocene beds of the Shinao Basin, southern China; I. minor (Filhol, 1882) is known from early Oligocene ( MP 23-24) localities of Western Europe ( Mennecart et al. 2011); I. parvus is known from the late Oligocene of Georgia ( Gabunia 1964) and Central Anatolia ( Métais et al. 2016). The material from Süngülü is identified as pertaining to I. parvus on the basis of the combination of these diagnostic features: lower molars lack a metastylid, and show a thin mesial cingulum, p4 with a distinct disto-lingual notch. However, the teeth of type material of I. parvus are higher crowned than that of the material from Süngülü which is also slightly smaller. Therefore, owing to these morphological and size differences, and pending additional fossil data, we prefer to refer our fossil material to Iberomeryx sp. cf. I. parvus .