Seorsumuscardinus

''Seorsumuscardinus'' is a genus of fossil dormice from the early Miocene of Europe. It is known from zone MN 4 (see MN zonation) in Oberdorf, Austria; Karydia, Greece; and Tägernaustrasse-Jona, Switzerland, and from zone MN 5 in a single site at Affalterbach, Germany. The MN 4 records are placed in the species ''S. alpinus'' and the sole MN 5 record is classified as the species ''S. bolligeri''. The latter was placed in a separate genus, ''Heissigia'', when it was first described in 2007, but it was reclassified as a second species of ''Seorsumuscardinus'' in 2009.

The two species of ''Seorsumuscardinus'' are known from isolated teeth, which show that they were medium-sized dormice with flat teeth. The teeth are all characterized by long transverse crests coupled with shorter ones. One of these crests, the anterotropid, distinguishes the two species, as it is present in the lower molars of ''S. alpinus'', but not in those of ''S. bolligeri''. Another crest, the centroloph, reaches the outer margin of the first upper molar in ''S. bolligeri'', but not in ''S. alpinus''. ''Seorsumuscardinus'' may be related to '' Muscardinus'', the genus of the living hazel dormouse, which appears at about the same time, and the older '' Glirudinus''.

Taxonomy

In 1992, Thomas Bolliger described some teeth of ''Seorsumuscardinus'' from the Swiss locality of Tägernaustrasse ( MN 4; early Miocene, see MN zonation) as an indeterminate dormouse (family Gliridae) perhaps related to ''Eomuscardinus''.Bolliger, 1992, p. 129 Six years later, Hans de Bruijn named the new genus and species ''Seorsumuscardinus alpinus'' on the basis of material from Oberdorf in Austria (also MN 4) and included fossils from Tägernaustrasse and from Karydia in Greece (MN 4) in ''Seorsumuscardinus''. In 2007, Jerome Prieto and Madeleine Böhme named ''Heissigia bolligeri'' as a new genus and species from Affalterbach in Bavaria (MN 5, younger than MN 4), and referred the Tägernaustrasse material to it, but failed to compare their new genus to ''Seorsumuscardinus''. Two years later, Prieto published a note to compare the two and concluded that they were referable to the same genus, but different species. Thus, the genus ''Seorsumuscardinus'' now includes the species ''Seorsumuscardinus alpinus'' from MN 4 and ''S. bolligeri'' from MN 5. Prieto provisionally placed the Tägernaustrasse material with ''S. alpinus''.Prieto, 2009, p. 378 He also mentioned '' Pentaglis földváry'', a name given to a single upper molar from the middle Miocene of Hungary, which is now lost. Although the specimen shows some similarities with ''Seorsumuscardinus'', published illustrations are too poor to confirm the identity of ''Pentaglis'', and Prieto considered the latter name to be an unidentifiable ''nomen dubium''.Prieto, 2009, p. 379

Because of its derived and specialized morphology, the relationships of ''Seorsumuscardinus'' are obscure. However, it shows some similarities with '' Muscardinus'', a genus which includes the living hazel dormouse, and may share a common ancestor with it, such as the earlier fossil genus '' Glirudinus''. All three are part of the dormouse family, which includes many extinct forms dating back to the early Eocene (around 50 million years ago), as well as a smaller array of living species. The generic name ''Seorsumuscardinus'' combines the Latin ''seorsum'', which means "different", with ''Muscardinus'' and the specific name ''alpinus'' refers to the occurrence of ''S. alpinus'' close to the Alps. ''Heissigia'' honored paleontologist Kurt Heissig for his work in Bavaria on the occasion of his 65th birthdayPrieto and Böhme, 2007, p. 302 and ''bolligeri'' honors Thomas Bolliger for his early description of material of this dormouse.Prieto and Böhme, 2007, p. 303

Description

Only the cheek teeth of ''Seorsumuscardinus'' are known; these include the fourth premolar and three molars in the upper ( maxilla) and lower jaws ( mandible). The teeth are medium-sized for a dormouse and have a flat occlusal (chewing) surface. ''S. bolligeri'' is slightly larger than ''S. alpinus''.

Upper dentition

The fourth upper premolar (P4) has four main, transversely placed crests;De Bruijn, 1998, p. 112; Prieto and Böhme, 2007, p. 303 the description of ''S. bolligeri'' mentions an additional, centrally placed small crest. De Bruijn interpreted the four main crests as the anteroloph, protoloph, metaloph, and posteroloph from front to back and wrote that these crests are not connected on the sides of the tooth. Prieto and Böhme note that the posteroloph is convex on the back margin of the tooth. In ''Muscardinus'', the number of ridges on P4 ranges from five in '' Muscardinus sansaniensis'' to two in '' M. pliocaenicus'' and the living hazel dormouse, but the protoloph and metaloph are always connected on the lingual (inner) side of the tooth. P4 is two-rooted in ''S. alpinus''De Bruijn, 1998, p. 112 and three-rooted in ''S. bolligeri''.

The first upper molar (M1) was described as square by De BruijnDe Bruijn, 1998, p. 111 and as rounded by Prieto and Böhme. There are five main transverse crests, which are mostly isolated, but some may be connected on the borders of the teeth. The middle crest, the centroloph, reaches to the labial (outer) margin in the single known M1 of ''S. bolligeri'', but does not in any of the five M1 of ''S. alpinus''.Prieto, 2009, p. 377 The front crest, the anteroloph, is less distinct in ''S. bolligeri'' than most ''S. alpinus'', but one M1 of ''S. alpinus'' is similar to that of ''S. bolligeri''. M1 has three roots in ''S. alpinus'', but the number of roots in ''S. bolligeri'' is not known.Prieto and Böhme, 2007, p. 304

Prieto and Böhme describe M2 as less rounded than M1 and De Bruijn notes that the crests are more parallel.De Bruijn, 1998, p. 113 In addition to the five main crests, small crests are present in front of and behind the centroloph that do not cover the full width of the tooth.De Bruijn, 1998, p. 113; Prieto and Böhme, 2007, p. 304 In one ''S. bolligeri'' M2, there is a small crest on the lingual side in front of the centroloph, but such a crest does not occur in any ''S. alpinus''. Another M2 of ''S. bolligeri'' has this crest on the labial side. On the other hand, all five M2 of ''S. alpinus'' have a minor crest on the labial side behind the centroloph. In two M2 of ''S. alpinus'', the centroloph and the metaloph are connected by a longitudinal crest, which is never present in ''S. bolligeri''. There are three roots.De Bruijn, 1998, p. 112; Prieto and Böhme, 2007, p. 304

M3 is known from a single specimen each from Oberdorf, Affalterbach, and Tägernaustrasse. In addition to the main crests, there are two or three additional smaller crests. The roots are unknown.

Lower dentition

The fourth lower premolar (p4) is known from a poorly preserved specimen from Oberdorf and a less worn specimen from Tägernaustrasse. There are four ridges, of which the front and back pair are connected at the lingual side and in the Oberdorf specimen also at the labial side. This tooth is similar to that of ''Muscardinus hispanicus'', but the front pair is better developed. There is one root.

The first lower molar (m1) bears four main crests and a smaller one between the two crests at the back. An additional crest (the anterotropid) is present between the two front crests, the anterolophid and the metalophid, in ''S. alpinus'', but not in ''S. bolligeri''. The occlusal pattern of m2 resembles that of m1.De Bruijn, 1998, p. 113; Prieto and Böhme, 2007, p. 303 ''S. bolligeri'' also lacks an anterotropid on m2, but the tooth is not known from Oberdorf. In a worn m2 from Tägernaustrasse, there is a thickened portion in the labial part of the anterolophid, which Prieto interpreted as a remnant of the anterotropid; this led him to identify the Tägernaustrasse population as ''S.'' cf. ''alpinus''. Only Oberdorf has yielded the m3 of ''Seorsumuscardinus''. It resembles the m1 and has a short anterotropid, but has more oblique crests. In ''S. alpinus'', the lower molars have two and occasionally three roots. The roots of the m1 of ''S. bolligeri'' are not preserved and the m2 has two roots.

Range

In MN 4, ''Seorsumuscardinus'' has been recorded from Oberdorf, Austria (sites 3 and 4, which yielded 6 and 17 ''Seorsumuscardinus alpinus'' teeth, respectively); Karydia, Greece (''S. alpinus''); and Tägernaustrasse, Switzerland (5 teeth; ''S.'' cf. ''alpinus''). Affalterbach, Germany, where 10 teeth of ''S. bolligeri'' were found, is the only known MN 5 locality. In all these localities, it is part of a diverse dormouse fauna. Because the distributions of the two known species are temporally distinct, Prieto suggested that the genus may be useful for biostratigraphy (the use of fossils to determine the age of deposits). ''Seorsumuscardinus'' occurred at the same time as the oldest known ''Muscardinus''.Prieto and Böhme, 2007, pp. 305–306

References

Literature cited

*Bolliger, T. 1992. Kleinsäuger aus der Miozänmolasse der Ostschweiz. Documenta Naturae 75:1–296.
*Bruijn, H. de. 1998. Vertebrates from the Early Miocene lignite deposits of the opencast mine Oberdorf (Western Styrian Basin, Austria): 6. Rodentia I (Mammalia). Annalen des Naturhistorischen Museums in Wien 99A:99–137.
*Doukas, C.S. 2003
Las faunas de la MN 4 de Aliveri y Karydia (Grecia)
Coloquios de Paleontología, Volúmen Extraordinario 1:127–132.
*McKenna, M.C. and Bell, S.K. 1997. Classification of Mammals: Above the species level. New York: Columbia University Press, 631 pp.
*Prieto, J. 2009
Comparison of the dormice (Gliridae, Mammalia) ''Seorsumuscardinus alpinus'' De Bruijn, 1998 and ''Heissigia bolligeri'' Prieto & Böhme, 2007
(subscription required). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 252(3):377–379.
*Prieto, J. and Böhme, M. 2007
''Heissigia bolligeri'' gen. et sp. nov.: a new enigmatic dormouse (Gliridae, Rodentia) from the Miocene of the Northern Alpine Foreland Basin
(subscription required). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 245(3):301–307.

{{Taxonbar, from=Q7451624

Dormice
Fossil taxa described in 1998
Miocene rodents
Prehistoric mammals of Europe