17. CARNIVORES: THE AILURIDS

Currently, only one living species of this carnivore family is known: the red panda.

Ailurids are a family of carnivores that currently has a single living species: the red panda. However, their fossil record shows up to 26 species distributed in 9 genera.

In the Middle Miocene (16-11 million years ago), the main ailurid in the Madrid fauna was Magerictis imperialensis. In Cerro de los Batallones, the remains of Simocyon batalleri were found, a very large ailurid (65 kg) compared to the extant species. However, fossil remains of this family are generally very scarce, because their evolution was linked to forested environments, where fossilisation is more difficult than in other environments.

They would have inhabited forested and scrubland areas, feeding on all kinds of small vertebrates, eggs, carrion, fruits, and seeds. They had the so-called “false thumb”, a hyperdeveloped carpal bone that could flex over the other fingers, creating a claw that, in modern pandas, allows them to grasp bamboo branches while feeding on its leaves.
Red panda (Ailurus fulgens). Illustration: M. Antón

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Simocyon batalleri

Skull and left hemimandible

Cerro de los Batallones 1 (Torrejón de Velasco)
Upper Miocene (10-8 Ma)

Skull and left hemimandible of the giant red panda from the Miocene.
To date, this species has only been found at the Cerro de los Batallones site.

Simocyon batalleri

Anatomical assemblage

Cerro de los Batallones 1 (Torrejón de Velasco)
Upper Miocene (10-8 Ma)

Anatomical assemblage of a partial right hand (without phalanges).
This includes a palmar view of the giant panda Ailuropoda melanoleuca (A) and Simocyon batalleri (B), showing the “false thumb”: when the fingers are flexed, it acts as a pincer, allowing the panda to grasp bamboo leaves.

Palmar view of the articulated right carpus and metacarpus of the giant panda, Ailuropoda melanoleuca (A), and Simocyon batalleri (B), showing the position of the “false thumb” or radial sesamoid (RS). The drawings are not to scale, but they are identical in size for ease of comparison.
It is a structure that protrudes from the carpus, and when the fingers are flexed they form a kind of clamp that allows pandas to hold bamboo leaves while feeding on them.
Illustration: M. Antón