Earliest record of rhinocerotoids (Mammalia: Perissodactyla) from Switzerland: systematics and biostratigraphy

Abstract

Earliest rhinocerotoids from Switzerland are reviewed on the basis of dental remains from the earliest Oligocene north-central Jura Molasse localities of Bressaucourt (MP21/22) and Kleinblauen (top MP22). The record in Bressaucourt is restricted to Ronzotherium and Cadurcotherium, representing Switzerland's oldest, well-dated post-"Grande Coupure" large mammal association, the only occurrence of Cadurcotherium, and the earliest occurrence of rhinocerotoids in Switzerland. The correlation with high-resolution stratigraphy of this locality permitted a dating of the fauna to ca. 32.6 Ma, less than a million years after the "Grande Coupure" event. The rhinocerotoids of Kleinblauen are represented by Epiaceratherium, Ronzotherium and Eggysodon. With the presence of Plagiolophus ministri, they are the only well-dated Swiss post-"Grande Coupure" large mammal assemblage with the persistence of an endemic pre-"Grande Coupure" taxon. Moreover, the coexistence of Epiaceratherium magnum and E. aff. magnum could indicate a new speciation within the Epiaceratherium lineage around the top of MP22. The rhinocerotoid associations of Bressaucourt with Ronzotherium -Cadurcotherium on the western side of the southernmost Rhine Graben area, and Kleinblauen with Epiaceratherium -Ronzotherium -Eggysodon on the eastern side, respectively, reveal a possible environmental barrier constituted by the Early Oligocene Rhenish sea and its eventual connection with the Perialpine sea. This one could have separated an arid area in central-eastern France from a humid area in Switzerland and Germany. These results, combined with the repartition of similar rhinocerotoid associations in Western Europe, also give new insights into an alternative earliest Oligocene dispersal route of rhinocerotoids from Asia towards Western Europe via North Italy.

Large mammals from Rickenbach (Switzerland, reference locality MP29, Late Oligocene): biostratigraphic and palaeoenvironmental implications

“…Additionally, the lower premolar series is short with respect to the molar series (mean Lp3-4/Lm1-3 = 0.45), the probable absence of p1/d1 in adults (no corresponding alveoli are attested on the referred mandible), the reduction of p2 (curved paralophid without constriction, reduced paraconid, and closed posterior valley), the strongly reduced lingual and labial cingulids, and the developed external groove of the lower cheek teeth, impede referring the large rhino from Rickenbach to R. filholi or R. velaunum. Most morphological features aforementioned are consistent with those of R. romani (e.g., Heissig 1969;Brunet 1979;Becker 2009; Ménouret and Guérin 2009), however, being even more similar to the latest representatives of the concerned species, known from the latest Oligocene, as suggested by Brunet (1979) and Brunet et al (1987 According to Heissig (1969), Brunet (1979), and Ménouret and Guérin (2009), the available specimens show some similarities with those attributed to Ronzotherium romani (KRETZOI 1940), such as a continuous lingual cingulum joined to the anterior and posterior ones, a reduced labial cingulum, a distinct crista, and a wide postfossette on upper premolars. On P2, the protocone is less developed than the hypocone, and the M2s bear a strong antecrochet, as well as a simple crochet, and a crista.…”

A new genus of Rhinocerotidae (Mammalia, Perissodactyla) from the Oligocene of Europe

“…On the other hand, most of these characters are also described on the upper cheek teeth specimens from Offenheim (Germany), Kleinblauen (Switzerland) and Monclar-de-Quercy (France) attributed to E. aff. magnum by Uhlig (1999) and Becker (2009), and partly on the specimens from Habach 5 (Germany) attributed to cf. Epiaceratherium sp.…”

“…The additional referred specimens of this study include dental remains from Offenheim (Germany), Kleinblauen (Switzerland) and Monclar-de-Quercy (France), attributed by Uhlig (1999) and Becker (2009) to Epiaceratherium aff. magnum, and also specimens from Habach 5, attributed by Göhlich (1992) to Epiaceratherium sp.…”

“…The general stratigraphical context of this Jura Molasse Formation (termed NW Swiss Molasse Basin) was described in previous works (Picot. et al 2008;Becker 2009). The succession consists of a lithofacies assemblage (tabular sandy beds with sigmoidal or planar crossstratifications, erosional sandy beds with low angle trough cross-stratifications or tough cross-stratifications, massive fines) typical of a coastal to alluvial floodplain controlled by a mouth complex of distributary channels, interdistributary bays and tidal bars, and by sandy channels and muddy floodplains.…”

Tapiridae (Perissodactyla, Mammalia) of the Swiss Molasse Basin during the Oligocene–Miocene transition

“…At the scale of the Western Swiss Molasse Basin, these late Oligocene to early Miocene climatic and environmental changes are also well developed in the sedimentological record (e.g., Berger, 1990;Schlunegger et al, 2001;Becker, 2003), accentuated by the Alpine orogenesis. Figure 8 illustrates the occurrences of early Oligocene to early Miocene European Tapiridae (according to Heissig, 1978Heissig, , 1999aCerdeño and Ginsburg, 1988; this study), Rhinocerotoidea (Heissig, 1999b;Uhlig, 1999;Antoine et al, 2000;Becker, 2003Becker, , 2009Becker et al, 2009;pers. observ.…”