The skull was unearthed in the 1990s during one of the excavation campaigns at Els Casots, the site in the municipality of Subirats (Alt Penedès) that over time has become one of the key Miocene locations in Europe.
At the time, researchers assumed it belonged to an already known specimen of the genus Paludocyon, of which fragmentary remains had been found in the area and in other countries. With nothing new to investigate, the piece was put into storage.
It was not until 2014, in the course of a doctoral thesis, that someone took another look at that skull and realised something did not quite add up. The species it had been compared with was much more robust, roughly the size of a lion or tiger and with a weight close to 200 kilograms.
What they actually had in front of them seemed smaller and probably less muscular. The team at the Institut Català de Paleontologia Miquel Crusafont spent the last two years confirming their suspicion: it was not a known Paludocyon, but a species that no one had described before.
The newly identified species has been named Paludocyon moyasolai, in honour of the palaeontologist Salvador Moyà-Solà, and makes Els Casots the global reference site for this species.
Alongside the ICP, the study involved the National Museum of Natural Sciences (CSIC), the University of Valencia, the Autonomous University of Barcelona, Complutense University of Madrid, Ecuador’s National Institute of Biodiversity and the Iziko museum in South Africa.
A medium-sized predator in a tropical lagoon
According to the researchers’ calculations, this amphicyonid, a member of an extinct group of carnivores that combined dog-like and bear-like traits without truly belonging to either, was about the size of a large dog and weighed between 50 and 70 kilograms.
The remains recovered include the skull, much of the dentition and a single isolated lower molar, enough material to reveal something that caught the team’s attention: the unusual development of the posterior molars, with a second upper molar that is especially broad and a third that is larger than usual for the genus.
That dentition points to a varied diet, consistent with a mesocarnivorous hunter capable of chasing small and medium-sized prey – primitive deer, bovids, ancestral pigs – without being the most powerful animal in its environment. In fact, the same site yielded a second, considerably larger amphicyonid species, roughly the size of a leopard, which has not yet been formally described.
The setting in which it lived around 15.9 million years ago was very different from today: a shallow lagoon surrounded by tropical forest, with crocodiles, snakes, fish and a striking diversity of mammals sharing the same space.
That aquatic environment, the excavation leaders point out, is precisely what allowed such good preservation of the fossils: after death, the bodies became trapped in the mud, which protected them from decomposition.
Another piece in the map of Miocene carnivores
The find adds to a broader body of research on how communities of large carnivores were organised during the Miocene on the Iberian Peninsula. A previous study, involving Complutense University of Madrid, had already examined slightly more recent sites, Los Valles de Fuentidueña in Segovia and Cerro de los Batallones in Madrid, where an unusually high number of carnivore species lived side by side: bear-dogs, felids, hyenas and bears.
Using stable isotope analysis on more than 200 samples of tooth enamel, that study, published in Palaeontology, showed that competition between them was intense, except in cases such as the amphicyonid itself or the primitive hyena, which hunted different prey in more open habitats.
This kind of work with isotopes makes it possible to reconstruct with considerable precision what each animal ate while barely damaging the fossil: just a few milligrams of enamel need to be extracted with a dentist’s drill and analysed by mass spectrometry.
Applied to different sites and different moments of the Miocene, this approach is gradually building an increasingly detailed picture of how fauna responded to the environmental changes of the time – the shift from dense forests to more open, arid landscapes – and of the strategies that allowed some species to coexist despite such fierce competition for the same territory.
Paludocyon moyasolai fits into that story as one more piece of the puzzle, slightly earlier in time than the episodes studied at Fuentidueña or Batallones but belonging to the same amphicyonid family that dominated much of Eurasia and North America during the Cenozoic. Every new specimen described, researchers agree, helps to refine the group’s evolutionary tree and to better understand how it became completely extinct a few million years ago.
