Plagiolophus is an extinct genus of perissodactyl mammals belonging to the family Palaeotheriidae. The genus lived in Europe from the middle Eocene (≈ 45 Ma) to the early Oligocene (≈ 27 Ma). Its name derives from the Ancient Greek πλάγιος (“oblique”) and λόφος (“crest”), referring to the characteristic shape of the animal’s skull.
Taxonomy and species
The type species, Plagiolophus minor, was first described by Georges Cuvier in 1804 on the basis of fossils from the Paris Basin. The genus was later elevated from a subgenus of Palaeotherium to full generic status by Auguste Pomel (1847). Over a dozen species have been assigned to the genus, including P. ovinus, P. annectens, P. javali, P. lugdunensis, P. major, and several others described throughout the 19th and 20th centuries. Some authors have recognized three subgenera—Plagiolophus, Paloplotherium, and Fraasiolophus—based on dental and cranial differences.
Morphology
Members of Plagiolophus were medium‑to‑large palaeotheriids, with body masses ranging from under 10 kg in the smallest species (P. minor) to more than 150 kg in the largest (P. javali). They possessed tridactyl (three‑toed) fore‑ and hind‑limbs, an elongated facial region, a deep nasal notch, and posteriorly positioned orbits. Their dentition was initially brachyodont (low‑crowned) but became increasingly hypsodont (high‑crowned) in later species, reflecting a dietary shift toward more abrasive vegetation as climates grew drier.
Ecology and behavior
Dental wear patterns suggest that early Plagiolophus species were browsers, consuming leaves, fruits, and soft plant parts, while later species showed adaptations for grazing tougher, more abrasive foliage. Variation in limb proportions indicates a range of locomotor strategies, from lightly built, cursorial forms (P. minor, P. ministri) to stockier, less cursorial taxa (P. annectens, P. javali).
Evolutionary significance
Plagiolophus is considered a derived member of the Palaeotheriinae, likely descending from the earlier Pachynolophinae subfamily during the middle Eocene. The genus persisted through the Grande Coupure—a major faunal turnover at the Eocene–Oligocene boundary—thanks in part to its dietary flexibility and cursorial adaptations. Its eventual disappearance in the early Oligocene marks the extinction of the Palaeotheriidae.
Fossil record
Fossils of Plagiolophus are found throughout Western Europe, particularly in the Paris Basin (France), the Germanic Basin, and the Iberian Peninsula. Notable specimens include a relatively complete skeleton of P. minor from the Baden‑Württemberg region, housed in the State Museum of Natural History Stuttgart.
Historical context
The genus was first recognized by Cuvier, who initially assigned the type species to Palaeotherium. Subsequent 19th‑century work by Owen, Pomel, and others refined its classification. Plagiolophus was among the extinct mammals represented in the Crystal Palace Dinosaurs sculptures (mid‑19th c.), where it was depicted as a small, tapir‑like animal—a reflection of early interpretations of its morphology.
Plagiolophus thus provides valuable insight into the diversification of early perissodactyls and the ecological transitions that occurred in Europe during the late Paleogene.