Eomyidae, Winge, 1887
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publication ID |
https://doi.org/ 10.5252/g2010n2a3 |
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DOI |
https://doi.org/10.5281/zenodo.10543989 |
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persistent identifier |
https://treatment.plazi.org/id/03E18794-0F0B-7243-CC83-FA47FC87F92B |
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treatment provided by |
Marcus |
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scientific name |
Eomyidae |
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Eomyidae gen. et sp. indet. ( Fig. 9 View FIG E-G)
MATERIAL. — Left M1 ( BSO 1975 XXII 858), Fig. 9E View FIG ; right?P4?M1/2 ( BSP 1975 XXII 857), Fig. 9F View FIG ; right M2 ( BSP 1975 XXII 853), Fig. 9G. View FIG
LOCALITY. — Möhren 20 ( Germany); Early Oligocene ( MP 21).
TEETH SIZE. — Measurements are given in Table 11.
DESCRIPTION
General characteristics: large buno-lophodont Eomyidae with longitudinally elongated paracone and metacone opposed to rounded lingual tubercles; long mesoloph fused with the paracone, entoloph more or less interrupted behind the mesoloph; synclinal I very long on M2.
Two teeth present a clearly unknown morphology. The large right M2 is clearly wider than long and conspicuously reduced posteriorly. The crests are massive and cusps weakly developed; the difference on cusps development between labial and lingual part is weaker than in other Bavarian eomyids.
Paracone and metacone are stretched longitudinally and the paracone is fused with the labial extremity of the mesoloph. Protocone and hypocone are rounded lingually and hollowed on their labial face. Th e sinus reaches the middle of the tooth and is slightly oblique antero-labially. The labial anteroloph is very long, starting directly on the anterior arm of the protocone with a right angle, so that syncline I extends over about two thirds of the tooth. Protoloph and mesoloph are roughly parallel and have the same length as anteroloph so that synclines I and II are equal in length. In relationship with the long sinus, syncline III is shorter and opens labially. Th e metaloph, slightly oblique, joins the anterior arm of the hypocone, which is a little antero-labially orientated. Th e posteroloph is well developed and, with wear, joins the metacone and the posterior arm of the hypocone and, with further wear, its lingual part. Syncline IV is a little shorter than the anterior synclines. The entoloph is faintly interrupted behind the mesoloph.
The two other teeth display some variations; they are more quadrate with round angles.
– The pattern of the left M1 is very similar to that of the M2 but the anteroloph is shorter and joins the elongated anterior arm of the protocone with a right angle. The sinus is wider and reaches the middle of the occlusal surface and the synclines are shorter, synclines II and IV being the longest;
– A damaged and worn right tooth possibly a P4 (or M1/2) shows a disorganized pattern. The protoloph is transverse but the metaloph is interrupted, its labial part bending to the posteroloph. The mesoloph is not obvious but seems interrupted, partly parallel to the protoloph and fused with the paracone. Th e entoloph is interrupted behind the mesoloph.
DISCUSSION
The two teeth found in Möhren 20 display a mixture of morphological features known in Eomys from
Early Oligocene with features that were previously known only since the late Oligocene.
Some features are close to Eomys such as: the brachyodont and bunodont teeth with the rounded lingual tubercles and transverse crests joining the anterior part of the protocone and hypocone. Long mesolophs are known only in more recent Eomys .
Other features are observed for the first time in the Early Oligocene, the buno-lophodont pattern with elongated paracone and metacone more or less fused within the transverse crests, the long synclines resemble Pseudotheridomys Schlosser, 1926 . However the connection of the protoloph with the anterior part of the protocone indicates without doubt that the teeth do not belong to Pseudotheridomys where the protoloph always joins the posterior part of the protocone; it is also generally the case for Eomyodon Engesser, 1987 where the protocone is compressed and obliquely directed antero-labially and where the interruption of the entoloph takes place before the mesoloph. Th e greater similarity is with the genus Asianeomys Wu, Meng, Ye & Ni, 2006 from the late Oligocene/Early Miocene of China ( Wu et al. 2006) and especially with A. fahlbuschi Wu, Meng, Ye & Ni, 2006 , with its long mesolophs fused with the paracone. Asianeomys fahlbuschi is however smaller, also some clear difference can also be observed as the mesoloph connects directly to the protocone.
It is noteworthy that, unfortunately, no lower molars with correspondant morphology are associated with the upper ones in Möhren 20. However, we know from Asianeomys that the upper and lower molars of eomyids can present a completely different pattern. Consequently we can hypothesize that the lower molars of this taxon could present a pattern more similar to Eomys , making it difficult to differentiate from the previously described Eomys sp.
Considering the little material known from Möhren 20 and the clear differences of upper molars with all the eomyids genera known up to now, we propose here that this taxon is a new genus of Eomyidae and we let the nomenclature open until the discovery of new material in this locality or another.
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Mohonk Preserve, Inc. |
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