Eucricetodon, Thaler, 1966

Maridet, Olivier, Codrea, Vlad A., Fărcaș, Cristina, Solomon, Alexandru A., Venczel, Márton & Tissier, Jérémy, 2025, The record of cricetid rodents across the Eocene-Oligocene transition in Transylvania, Romania: implications for the “ Grande Coupure ” at European scale, Acta Palaeontologica Polonica 70 (2), pp. 291-327 : 303-306

Eucricetodon aff. Eu. huerzeleri Vianey-Liaud, 1972

Fig. 9A–D.

Material. —Two upper molars and three lower molars from Cetățuie, Rupelian, lower Oligocene, Dâncu Formation, Gilău sedimentary area, Transylvanian Basin, Romania.

Measurements.—See Table 5. Description.—The molars are characterized by large cusp(id)s with a rounded shape in lateral view due to the wear.

For the M2 ( Fig. 9A), the labial and lingual anterolophs are both long and respectively closing the anterosinus and the protosinus; however, the lingual anteroloph is noticeably lower and thinner than the labial one. A small paracone spur, close to the labial border, merges with the mesostyle, itself connected to the base of the metacone, so the mesosinus is labially closed. Both the mesial protolophule and the metalophule are slightly transverse, connected mesially to respectively the protocone and the hypocone. The distal protolophule is incomplete and ends in the middle of the mesosinus, like the mesoloph. Additionally, a small spur starts from the extremity of the mesoloph, oriented toward the metalophule. The posterosinus is narrow whereas the posteroloph is thick and connectes to the metacone so the posterosinus is closed labially. The M2 has three roots.

The M3 ( Fig. 9B) displays a rounded shape due to the reduced hypocone and metacone. It has long labial and lingual anterolophs respectively closing the anterosinus and the protosinus. The protolophule, the mesoloph and the metalophule are slightly oblique. The mesolophe starts from a point between the protocone and the metalophule and reaches the mesostyle. A well-developed paraconule is present in the mesosinus between the protolophule and the mesoloph, it is connected to the protolophule. The mesosinus is closed labially by a long cingulum connecting the paracone to the metacone. The metacone is strongly reduced so it is not larger than the mesostyle. The posteroloph is long and closes the posterosinus labially. The roots are not preserved.

The m2s have a long and well-developed lingual anterolophid reaching the base of the metaconid whereas the labial anterolophid is short and poorly developed; as a result, the protosinusid remains opened labially. The protoconid hind arm is long and reaches the metaconid. The mesolophid is either short and ends in the middle of mesosinusid (2/3; with a little stylid at its extremity for one m2, Fig. 9C), or long. The metaconid ridge is well developed and long, it reaches the base of the entoconid lingually and closes the mesosinusid. An entoconid ridge is also present, merging with the posterolophid. The sinusid is also closed labially by a low cingulid. There are no hypoconid hind arm or ectomesolophid. The posterosinusid is large, closed lingually, and delimited by a thick posterolophid. The m2s have two roots

Remarks.— The five teeth described above from Cetățuie differ by their large size, slightly higher crown and more robust cusp(id)s when compared to Tenuicricetodon arcemis gen. et sp. nov. (see below). The robust but lower cusp(id)s, the absence of hypoconid hind arm in m2s and the reduced distal part of M3 (but more developed than in Tenuicricetodon arcemis gen. et sp. nov.) indicate that they belong to the Eucricetodontinae subfamily. They are much larger than most species referred to Eucricetodon (or Atavocricetodon ): Eu. ( A.) atavoides Freudenthal, 1996 ; Eu. ( A.) atavus Misonne, 1957 ; Eu. ( A.) minusculus Freudenthal, 1996 ; Eu. ( A.) nanoides Freudenthal, 1996 ; Eu. ( A.) nanus Peláez-Campomanes, 1995 ; Eu. ( A.) hugueneyae Freudenthal, 1996 ; Eu. caducus (Shevyreva, 1967) ; Eu. huberi ( Schaub, 1925) ; Eu. asiaticus (Matthew & Granger, 1923) ; Eu. occasionalis Lopatin, 1996 ; Eu. ( A.) paaliensis Marivaux, Vianey-Liaud, & Welcomme, 1999 ; Eu. murinus (Schlosser, 1884) ; Eu. praecursor ( Schaub, 1925) ; Eu. leptaleos ( Wang & Meng, 1986) (see Freudenthal 1996; Lopatin 1996; Maridet et al. 2009, 2013; Vianey-Liaud 1972; Wang and Meng 1986 for size comparisons). However, these teeth from Cetățuie fit in the size range of Eu. huerzeleri Vianey-Liaud, 1972 , with the exception of the M3 which is noticeably wider. Their morphology also mostly fit the description of Eu. gergovianum (Gervais, 1848–1852) by Schaub (1925) later emended into a diagnosis for Eu. huerzeleri by Vianey-Liaud (1972): the generally thick and short mesoloph(id)s and the low cingulums and cingulids compared to cusp(id)s, the rounded M3 without complete entoloph and with poorly-developed hypocone and metacone, and the elongated m2 with an oblique ectolophid. The m2s also possess a well-developed mesoconid as described by Schaub (1925) whereas the only M2 from Cetățuie does not show a distinct mesocone as opposed to the emended diagnosis from Vianey-Liaud (1972). There are also some significant differences in the teeth from Cetățuie such as the well-developed distal protolophule in M2 and protoconid hind arm in m2s, and the better developed lingual anteroloph in M2. This material is consequently referred to an affine form of Eu. huerzeleri , waiting for more material to confirm the occurrence of a new species in the lower Oligocene of Transylvania.

Genus Tenuicricetodon nov.

Zoobank LSID: urn:lsid:zoobank.org:act:.

Etymology: From Latin tenuis, thin or fine, and the genus Cricetodon Lartet, 1851 .

Type species: Tenuicricetodon arcemis gen. et sp. nov.

Diagnosis.—Medium-sized cricetid with thin and narrow cusp(id)s and loph(ids). M1 with a long anterolophule reaching the anterocone or not. Thick posteroloph forming a bulge in M1, with possibility of a posterostyle extending from the posteroloph lingually in the posterosinus. M1 and M2 with long and straight mesoloph often reaching the labial mesostyle. A continuous lingual cingulid extends from the metaconid to the entoconid in both m1 and m2. Both m1 and m2 have two hypoconid hind arms, one being smaller than the other is.

Differential diagnosis.—Differs from:

– Raricricetodon Tong, 1997 , Palasiomys Tong, 1997 , Pappocricetodon Tong, 1992 , in having a well-developed mesial lobe in upper and lower first molars, and missing the protocone distal arm (sensu Maridet and Ni 2013) in upper molars.

– Eucricetodon Thaler, 1966 (including Atavocricetodon Freudenthal, 1996 ) in having thinner and narrower cusp(id)s and loph(ids) giving a more lophodont aspect. Also differs in having a long mesial arm of the protocone (more developed than the distal one) which can reach the anterocone (possible but very rare in Eucricetodon see Freudenthal 1996) and a concave labial border in M1, and a divided anteroconid in m1.

– Eocricetodon Wang, 2007 , in being larger, having a shorter mesial lobe in M1; also, in having a more elongated m1 with longer mesolophid and ectomesolophid, well-developed anterolophids and a divided anteroconid.

– Oxynocricetodon Wang, 2007 , in having a smaller mesial lobe in M1, having mesolophs and distal protolophule in upper molars, also in having long mesolophids and a continuous lingual cingulid extends from the metaconid to the entoconid in both m1 and m2.

– Pseudocricetodon Thaler, 1969 (including Allocricetodon Freudenthal, 1994 ) in having a short and narrow mesial lobe and a mesial protolophule more developed than the distal one in M1. It also differs in missing the anterolophulid but having a long and oblique mesolophid in m1. Another striking difference is the presence of one, or even two, hypoconid hind arms in m1 and m2.

– Witenia de Bruijn, Ünay, Saraç, & Yïlmaz, 2003 , in being smaller with more gracile cusp(id)s and loph(id)s (more lophodont occlusal pattern), in having also much less developed distal part of 3rd molars (upper and lower), and a broader mesial lobe of M1.

– Heterocricetodon Schaub, 1925 , in having a lower crown and less elongated molars, especially much-reduced third molars, and in having hypoconid hind arms in m1 and m2.

– Adelomyarion Hugueney, 1969 , in having longitudinal and complete entoloph(id)s (as opposed to the often strongly oblique and interrupted entoloph(id)s in Adelomyarion ) and having hypoconid hind arms in m1 and m2.

– Bustrania de Bruijn, Marković, Wessels, & van de Weerd, 2019 , in being much larger, missing the irregular array of low ridges and cuspules present on all molars of Bustrania , in having a sinus of M1 and M2 directed mesially (as opposed to the distally for Bustrania ) and in having a well-developed anteroconid on m1.

– Kerosinia Ünay-Bayraktar, 1989 , in missing the direct connection between the anterocone and paracone in M1, in having a more developed distal part of the M3 including a long mesoloph, also in missing the complete anterolophulid linking the anteroconid to the protoconid in m1 and in missing the distal arm of the hypoconid in m1 and m2.

– Ulaancricetodon Daxner-Höck, 2000 , in being much larger, in missing the trapezoidal shape and the weakly developed mesial lobe and anterocone in M1, also in having the entoconid on m1 located mesially to the protoconid (the opposite for Ulaancricetodon ).

Stratigraphic and geographic range.—Dâncu Formation Rupelian), Transylvania ( Romania).