Several Species of Pseudo-Horses Lived in Spain 37 Million Years Ago

Thursday, July 8, 2021

Palaeotheriid mammal Leptolophus cuestai (left) and equoid perissodactyl Pachynolophus zambranen (center and right). Image credit: Ulises Martínez Cabrera.

Paleontologists have identified two new species of palaeotheriid mammals from fossils found at the Eocene site of Zambrana in Alava, Spain.

The two new species, named Leptolophus cuestai and Leptolophus franzeni, lived 37 million years ago in what is now Spain.

They belong to Palaeotheriidae (pseudo-horses), an extinct family of herbivorous that ranged across Europe and Asia from the Eocene through to the early Oligocene.

“Can one imagine animals similar to horses with three toes, the size of a fox terrier, a Great Dane and a donkey living in a subtropical landscape in Alava? Many of these pseudo-horses have been described at the Zambrana site,” said Dr. Ainara Badiola, a researcher at the Universidad del País Vasco/Euskal Herriko Unibertsitatea.

“Examples of them are Pachynolophus zambranensis and Iberolophus arabensis, which were first specified in this paleontological enclave.”

Leptolophus cuestai and Leptolophus franzeni not only expand the fossil record and the biodiversity of palaeotheriid fauna, but also display dental features atypical for Eocene horses.

“Their molars have a very high crown and are covered with a thick layer of cementum,” said Dr. Leire Perales-Gogenola, also from the Universidad del País Vasco/Euskal Herriko Unibertsitatea.

“This type of dentition, also present in other endemic Iberian palaeotheriids, could be indicative of a difference in environmental conditions between the Iberian and Central European areas, with more arid conditions or less dense or closed forests and the presence of more open areas in Iberia.”

Leptolophus cuestai also had molars with atypically high crowns, similar to those of some of the earliest horses in Europe.

“At the end of the Eocene in Europe, forests of an intertropical type gradually disappeared, giving way to plant communities of a more temperate type with more open areas,” the paleontologists said.

“Modern horses appeared in Europe later on during the Miocene (23-5.3 million years ago).”

“Their dentition, with very high crowns, was adapted for eating vegetation with high grit content (grasses).”

The findings were published in the Journal of Vertebrate Paleontology.


Leire Perales-Gogenola et al. New Leptolophus (Palaeotheriidae) species from the Iberian Peninsula and early evidence of hypsodonty in an Eocene perissodactyl. Journal of Vertebrate Paleontology, published online May 20, 2021; doi: 10.1080/02724634.2021.1912061