Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 20. 2002. (Budapest, 2002)

muster 1 Miodyromys aegerd Miodyromys aff. aegerd 12 % muster 2 14 82 % 17% muster 3 Miodyromys aegerd Miodyromys aff. aegerd muster 4 6% muster 5 Miodyromys aegerd Miodyromys aff. aegerd 17 % muster 7 Miodyromys aegerd Miodyromys aff. aegerd muster 6 The morphology of the Miodyromys material from Sámsonhaza refers to the descriptions of BAUDELOT (1972), ENGESSER (1972), MAYR (1979) and SACH (1999) in general outline. The special character of the Sámsonháza finds is the clear bimodal distribution of the M 1-2 molars (Figure 6, Figure 7 and 9). This bimodality can't be the result of the positional difference between the M

1 and the M

2 molars, because similarly considerable differences were not found between the dimensions and morphology of the two molars in the other Miodyromys populations, eg. in the materials of Sandelzhausen (MAYR 1972), Vermes 1-2 (ENGESSER et al. 1981), Puttenhausen (WU 1990) (Figure 7). The group of the M

1

"

2 molars with smaller dimensions of Sámsonháza evidendy refers to the species M. aegercii (BAUDELOT 1972). The systematic position of the larger Miodyromys aff. aegercii M

1

"

2 molars is uncertain. A M

2 molar with the same large sized measurements was published by AGUILAR (1980, Figure 8.) from Luc-sur-Orbieu determined as M. aegercii. In the immediate past a new large sized Miodyromys aegercii population was described from the Early Vallesian (MN 9) fauna of Nebelbergweg (KÄLTN & ENGESSER 2001). The average length and width dimensions of the M

1

"

2 molars of this material are very close to the corresponding measurements of the Miodyromys aff. aegercii M

1

"

2 finds from Sámsonháza (Figure 7). The coexistence of two or more Miodyromys species in the same fauna is very rare, eg. three Miodyromys species were described from the Late Orleanian (MN 5) fauna of Schellenfeld by ZlEGLER (1995). In Southern Germany and in Switzerland M. aegercii is very common in the upper part of the "Obere Süßwasser Molasse". The stratigraphie range of the species is MN6MN8 (DAAMS 1999). In Hungary there are no data of the occurence beyond Sámsonháza. In the prelirninary report (rTiR et al. 1998) the finds were determined as M. aegercii on the basis of few molars. 58% 8% Figure 9 — Morphological composition of the Miodyromys M

1

2 material of Sámsonháza, refering to the morphotypes (musters) of MAYR (1979). Family Muridae ILLIGER, 1811 Subfamily Cricetidae ROCHEBRUNE, 1883 Genus Megacricetodon FAHLBUSCH, 1964 Megacricetodon minor (LARTET, 1851) The measurements and the nomenclature with the methodology of the morphological study is after DAAMS & FREUDENTEiAL (1988 b). The individual measurements [in mm) and morphological characters are given in the enclosed Tables 1015. In the morphological descriptions the capitals in parentheses refer to the symbols of the morphotypes listed in the tables. M

1 (Figure 10: 1-6) — The morphology of the anterocone is uniform. It is slighdy subdivided by a shallow furrow, which never reaches the crown basis. It refers to the second type of DAAMS & FREUDENTPIAL (1988 b). The lingual part of the anterocone is smaller and rounded, the labial part is bigger, and transversally elongated. The labial spur of the anterolophule is short and directed obliquely backwards. It reaches the anterior wall of the paracone (B2, Figure 10: 1) or not (Bl, Figure 10: 3.). In some molars it is completely missing (C, Figure 10: 2-6). In one molar (Figure 10: 5) a longitudinal enamel ridge is developed between the labial spur of the anterolophule and the protolophule. The posterior ectoloph of the paracone is mainly developed as a short protuberance (B, Figure 10: 1-2). In 3 molars it reaches the