FIGURE 1. Geographical and geological setting of the Rusce locality. 1. Location of the Pčinja basin (black square) in Serbia; 2. Simplified lithologic section of the Pčinja basin with the approximate stratigraphic position of the Rusce Eocene ruminant (red star); 3. Simplified geological map of the Pčinja basin with the location of Rusce (red star: Rusce Eocene ruminant locality; red square: Buštranje Eocene mammal locality).

FIGURE 2. Original pictures and drawing of the Eocene ruminant from Rusce in lingual (1) and occlusal (2) views with associated measurements (3) (from Laskarev, 1939), and occlusal view interpretation (4). Dental nomenclature: 1, protoconid; 2, preprotocristid; 3, internal postprotocristid; 4, hypoconid; 5, prehypocristid; 6, posthypocristid; 7, metaconid; 8, premetacristid; 9, postmetacristid; 10, entonconid; 11, preentocristid; 12, postentocristid; 13, external postprotocristid; 14, ectostylid; 15, anterior cingulid; 16, posterior cingulid. The outline in grey (d2 and d3) is interpretative.

FIGURE 3. Paleobiogeography of the ruminant Bachitherium and associated Balkanic rodents absent from Western Europe during the late Eocene (mostly Priabonian) and earliest Oligocene (MP21-22) (1) and dispersing through Western Europe from ca. 31 Mya (MP23-24; 2). The purple arrow represents the Grande-Coupure dispersal event (MP21). The red arrow represents the Bachitherium dispersal event (MP23). Circle, Bachitherium spp.; square, Pseudocricetodon spp.; hexagon, Paracricetodon spp.; diamond, Melissiodontinae. The map has been modified from Mennecart et al. (2018) based on Popov et al. (2004). Biogeographical and biostratigraphical data are from Alvarez Sierra et al. (1999), Baciu and Hartenberger (2001), Martín-González et al. (2014), and de Bruijn et al. (2018).