Spermophilinus besana Cuenca-Bescos, 1988

Hír, J., 2013, Early and Middle Miocene (MN 5 - MN 6) transitional rodent fauna from Litke (North Hungary, Nógrád County), Fragmenta Palaeontologica Hungarica 30, pp. 101-137 : 104-107

Spermophilinus besana Cuenca-Bescos, 1988

( Figs 2–5)

Material and measurements (mm) –

Description – D4 – Subtriangular outline, protuberant anterocone, strong and cingulum-like mesostyle, which closes the labial border of the central valley. High-developed transversal protoloph, lower developed oblique metaloph, which is connected to the protocone.

P4 – Ovoid outline, the anterocone is not so protuberant as the same structure in D4. The other morphological characters are similar to the deciduous upper premolar.

M1–2 – Subquadrat outline. Three cusps (protocone, metacone, paracone) and four lophs (anteroloph, protoloph, metaloph, posteroloph). All the lophs are connected to the protocone but this connection is weaker in the case of metaloph. The anteroloph is connected to the basis of the protocone in a low level. Three lophs are transversally directed, the lingual end of the metaloph is oblique. Anteroloph and posteroloph are less developed than protoloph and metaloph. Small mesostyle developed, which is connected to the paracone. Three closed sinuses (anterosinus, central sinus, posterosinus). Anterosinus and central sinus are elliptic, the posterosinus is narrow and its lingual end is anteriorly curved. The occlusal surface of M2 is wider than M1.

M3 – Subtriangular outline. Two cusps (the large protocone and a smaller, but higher paracone) and two lophs (anteroloph and protoloph). The anteroloph runs between the anterior bases of the two cusps. Protoloph is developed between the centres of these cusps. Anteroloph is lower developed. A narrow, transversal anterosinus is surrounded by the two lophs. A large central sinus is surrounded by the semicircular posteroloph. Special feature of the M3 from Litke 2 is the presence of a short metaloph ( Fig. 3).

p4 – Trapezoidal outline. Posterior part is broader than the anterior one. Four main cusps: protoconid, metaconid, anteroconid and hypoconid. The largest part of the occlusal surface is occupied by the large central basin. The posterolophid forms a continuous arch in the posterior and lingual margin of the molar from the hypoconid to the metaconid. The posterolingual angle is rounded.

m1–2 – Rhomboidal outline. Three main cusps: protoconid, metaconid and hypoconid. Anteroconid is small (2 out of 7 specimens) or missing (5/7). The posteroloph is continuous from the hypoconid to the metaconid. The posterolingual corner is rounded. The anterolophid is connected to the metaconid. The anterolophid-protoconid connection is variable: it is developed (4/7), ore those are divided by a narrow trench (1/7). The mesoconid is ridge-like, not so voluminous as the same cusp in S. bredai m1–2 molars from Felsőtárkány 3/2 locality. The metalophids are short (2/7) or missing (1/7). It reaches the anterolophid in specimen 2013.65. In this molar the protoconid, the metaconid, the anterolophid and the metalophid close a small basin. m2 is wider than m1.

m3 – Subtriangular outline, posteriorly narrowed. Three main cusps: protoconid, metaconid and hypoconid. Entoconid is incipient, only thickening of the posterolophid. Anterolophid-protoconid connection is developed (2013.66., 2013.69.), or there is a trench in the lingual side of the protoconid (2013.58.). The metalophid is missing (2013.58.) or short (2013.66., 2013.69.). Mesoconids are better developed than the same cuspulas in the m1–2.

Comments – Other species of the Spermophilinus genus: S. bredai (Von Meyer, 1848) ; S. turolensis de Bruijn et Mein, 1968 ; S. giganteus de Bruijn et al., 1970 ; S. minutus Shaohua et Li, 1982 . The distinction between S. besana and S. bredai is difficult and based on the dimensions and minor morphological characters. These morphological differences are listed by CUENCA-BESCOS (1988)and can be seen in Table 2.

ZIEGLER (2005) observed that these characters are difficult to use because of the high intraspecific variability. RUIZ-SANCHEZ et al. (2013) has shown that the development of the mesoconids of the lower molars is useful for the distinction. This method also seems to be applicable to the Hungarian material, because the mesoconids are less developed and ridge-like in the m1–2 from Litke, but well developed in the other Middle Miocene S. bredai samples (e.g. Hasznos, Sámsonháza, Felsőtárkány 3/2).

S. besana is regarded as an immigrant in Europe by DE BRUIJN (1998). He pointed out the first appearance in MN4, which is simultaneous or somewhat later than the arrival of Democricetodon . According to his opinion S. besana and D. franconicus are both of Asiatic origin and represent the same migration wave.

CUENCA-BESCOS (1988) described the presence of S. besana from the base of the Aragonian (local zone B) to the middle part of the Middle Aragonian (local zone D). The transition of S. besana – S. bredai took place during the time interval of the local zone D that refers to the middle part of the MN5 zone (RUIZ SANCHEZ et al. 2013). AGUILAR et al. (2010) described S. aff. bredai from the MN4 - MN5 transitional fauna of Blanquatére 1, although the published dimensions refer to S. besana .

In Switzerland Spermophilinus sp. primarily appeared in the fauna of Glovelier (MN4a) with Democricetodon franconicus . S. besana was not mentioned in the Swiss MN5 faunas, only Spermophilinus sp. or Spermophilinus aff. bredai were listed by KÄLIN & KEMPF (2009). Litke is the only known occurrence of the species in the Carpathian Basin.

A size increase of the Spermophilinus M1–2 through time is observed by DE BRUIJN (1995), but this size increase should not be used in fine biostratigraphical context. The mean dimensions of some selected Central European populations are given in a scatter diagram by HÍR et al. (2011, Figure 5).