The bizarre, bipedal, three-toed beasts that once roamed the islands of ancient Europe

Nature · Published 3 October 2026 Swipe more like this →

In short: Long before modern mammals dominated, a unique family of artiodactyls called Anoplotheriidae thrived across the subtropical archipelago of Eocene Europe. These creatures, which included the massive, potentially bipedal Anoplotherium, possessed such strange skeletal structures that scientists have struggled for two centuries to determine exactly how they lived and moved.

The Anoplotheriidae were a diverse group of endemic European artiodactyls that existed from the Middle Eocene to the Early Oligocene. Taxonomically, the family is split into two primary groups: the Anoplotheriinae and the Dacrytheriinae. While the former included larger, more robust animals like the genus Anoplotherium, the latter were generally smaller, with Dacrytherium weighing as little as 13.2 kg compared to the 266 kg estimated for its larger relatives. These animals were defined by their leaf-eating diets, evidenced by crescent-shaped ridges on their teeth, and a complete set of 44 teeth.

What truly sets these animals apart is their highly unusual anatomy. Unlike any other known artiodactyls, some species, such as Diplobune and Anoplotherium latipes, were three-toed, while others like Anoplotherium commune were two-toed. Their limb structures were so distinct that they lack modern biological analogues. Early researchers, including Georges Cuvier in 1812, initially speculated that these beasts were semi-aquatic swimmers. However, 21st-century consensus has shifted, with modern analysis suggesting they were terrestrial. Some experts hypothesize that Anoplotherium was capable of bipedalism, using its robust tail and pelvis to stand on its hind legs to browse, a behavior seen in other specialized mammals like ground sloths.

The evolutionary history of the family was marked by significant environmental shifts, particularly the Grande Coupure extinction event, which led to a drastic reduction in their diversity. By the late Early Oligocene, only one species, Diplobune minor, remained. Their phylogenetic placement remains a subject of intense debate; while some studies link them to ruminants or tylopods, recent analyses suggest they belong to a broader clade of endemic European artiodactyls. Despite their historical significance—having been featured in 19th-century reconstructions like the Crystal Palace Dinosaurs—the exact nature of their relationships and behaviors continues to challenge paleontologists today.

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