Early Eocene hippomorph perissodactyls (Mammalia) from the Paris Basin Author Bronnert, Constance Muséum national d’Histoire naturelle, Centre de Recherche en Paléontologie – Paris (CR 2 P, UMR 7207), CNRS / MNHN / Sorbonne Université, case postale 38, 57 rue Cuvier, F- 75231 Paris cedex 05 (France) constance.bronnert@mnhn.fr Author Métais, Grégoire Muséum national d’Histoire naturelle, Centre de Recherche en Paléontologie – Paris (CR 2 P, UMR 7207), CNRS / MNHN / Sorbonne Université, case postale 38, 57 rue Cuvier, F- 75231 Paris cedex 05 (France) gregoire.metais@mnhn.fr text Geodiversitas 2023 2023-06-08 45 9 277 326 journal article 10.5252/geodiversitas2023v45a9 1638-9395 8037926 urn:lsid:zoobank.org:pub:1C430978-5EE6-49AE-AF7C-23C710161CB7 Genre Hallensia Franzen & Haubold, 1986 Hallensia Franzen & Haubold, 1986: 37 . TYPE SPECIES . — Hallensia matthesi Franzen & Haubold, 1986 by original designation. INCLUDED SPECIES . — Hallensia parisiensis , Franzen, 1990 ; Hallensia louisi , Hooker, 1994 . EMENDED DIAGNOSIS . — Perissodactyl of medium size (basicranium length: 175 mm ) with brachyodont and bunolophodont dentition. Dental formula 3.1.4.3/3.1.4.3. Nasal incisure extending at the posterior border of the I3 alveolus. Upper molars with or without mesostyle and without postprotocrista. Strong cingula on upper molars. M3 with strong hypocone. Upper and lower M3 larger than M2. Lower molars without paraconid. Hypoconulid of m3 relatively large. COMMENT Hallensia is a perissodactyl with a very characteristic morphology. This primitive morphology pushed Franzen & Haubold (1986) to classify it within the phenacodontid condylarths. The discovery of a complete skeleton of H. matthesi in Messel ( Germany ) indicates that it is a perissodactyl ( Franzen 1990 ), mostly because of the saddle-shaped navicular facet of its astragalus, a synapomorphic feature of perissodactyls ( Radinsky 1966 ).