The species is based on dental remains from several localities, including La Dehesilla (Burgos) and La Dehesilla (Burgos), with additional material from La Dehesilla (Burgos). The holotype is a right M1 from La Dehesilla (Burgos).

Debrillina juliverte is characterised by its small size, the presence of a longitudinal crest on the M1, and the absence of a longitudinal crest on the M2. It differs from the slightly older Debrillina juliverte from the latest Miocene of Spain in its smaller size and simpler dental morphology.

The discovery supports the idea that Taterillinae gerbils entered the Iberian Peninsula in two waves: an earlier wave during the latest Miocene, represented by Debrillina juliverte, and a later wave during the earliest Pliocene, represented by Debrillina juliverte. The two waves likely correspond to two separate dispersal corridors through the Rifian corridor.

The new species also provides evidence for the persistence of Taterillinae gerbils in the Iberian Peninsula into the earliest Pliocene, suggesting that the group survived the Messinian Salinity Crisis.

The newly described gerbil, formally named Debruijnimys primaevus sp. nov., comes from the karstic site of La Piquera in the Duero Basin of central Spain, a locality that has produced a rich assemblage of Early Pliocene vertebrates including amphibians, squamate reptiles and mammals, dated to roughly 5.3 to 4.6 million years ago. The species name derives from the Latin primaevus, meaning early, in reference to the primitive morphological features that distinguish it from its later relatives.

The fossil material recovered from La Piquera during the 2021 and 2024 sampling campaigns consists of 38 isolated teeth, collected from six lithostratigraphic levels as well as from surface debris. All sediment was water-screened through superimposed sieves of 4, 1 and 0.5 millimetre mesh, a standard technique in micromammal palaeontology that allows even the smallest dental elements to be recovered. The holotype, an isolated right lower first molar, was found in level 5, while the paratypes, comprising upper and lower molars from several levels, document a consistent morphology across the sampled sequence. The specimens are currently housed at the Catalan Institute of Human Palaeoecology and Social Evolution, with their final repository designated as the Department of Geodynamics, Stratigraphy and Palaeontology at the Complutense University of Madrid.

Measurements were taken in millimetres using digital microscope imaging software, and the teeth were illustrated with an Environmental Scanning Electron Microscope, permitting detailed study of the enamel surfaces and occlusal morphology. The dental terminology follows classical rodent nomenclature established in the mid-twentieth century, allowing direct comparison with previously described material from other Iberian sites.

Debruijnimys primaevus differs from the type species Debruijnimys julii in its smaller dimensions and in the less developed longitudinal ridges on its lower molars. The genus itself was erected in 1996 on the basis of material from the Early Pliocene site of Asta Regia 3 in the Jerez Basin of south-western Spain, and is characterised by the development of a longitudinal ridge in the lower molars, a feature that places it within the subfamily Taterillinae. While the gerbils from Gorafe 4 and Baza 1 in the Guadix-Baza Basin can be confidently assigned to Debruijnimys julii, the older representatives of the genus found at other sites had long remained enigmatic, identified only at the genus level as Debruijnimys sp. because the available material was too scarce for a formal species-level diagnosis.

The new description resolves this long-standing taxonomic uncertainty. Teeth previously reported under open nomenclature from sites such as La Gloria 4 in the Teruel Basin, La Bullana 2B in the Cabriel Basin, Alcoy 4B in the Alcoi Basin, Botardo C and D in the Guadix-Baza Basin, Sifón de Librilla 413 and Puerto de la Cadena in the Fortuna Basin, and Asta Regia 3 itself, can now be attributed to Debruijnimys primaevus. This considerably extends the known geographic range of the species across the Iberian Peninsula, from the north-eastern Teruel corridor to the south-western Jerez Basin, and demonstrates that the archaic gerbil lineage was widespread during the Early Pliocene.

The phylogenetic affinities of the new species are particularly informative. The authors propose that Debruijnimys primaevus can be derived from the Moroccan species Debruijnimys davidi through an increase in size and modification of the shape of the lower molars. This derivation points to a North African origin for the Iberian lineage and implies a dispersal event across the western Mediterranean at the end of the Miocene. Importantly, the new species cannot be related to Protatera almenarensis, another African gerbil previously described from Late Miocene sites in eastern Spain, which suggests that the two gerbil lineages entered the Iberian Peninsula independently.

This conclusion underpins a two-phase model of gerbil immigration tied to the Messinian Salinity Crisis, the geologically brief interval when the Mediterranean basin was largely desiccated and re-flooded. During the first substage of the Lago Mare phase, between approximately 5.546 and 5.352 million years ago, Protatera almenarensis and other African and Asian faunal elements entered the Iberian Peninsula. A second dispersal, involving the ancestor of Debruijnimys primaevus, took place during the late stage of the Lago Mare phase, between roughly 5.338 and 5.333 million years ago. The Lago Mare phase refers to a period when brackish water conditions, the so-called lago mare or lake-sea environment, characterised the desiccated Mediterranean basins before the catastrophic Zanclean flood re-established normal marine conditions at the Miocene-Pliocene boundary.

The two-phase model is significant because it implies that land connections or dispersal corridors between Africa and Iberia were available at more than one moment during the crisis, rather than as a single window. The presence of African-origin rodents such as Myocricetodon and Protatera in latest Miocene Iberian faunas from sites including Almenara-Casablanca in Castellón, Salobreña in Granada and Negratín 1 in the Guadix-Baza Basin had already signalled such exchanges, but the precise timing and number of dispersal events remained debated. The stratigraphic distinction between the two gerbil waves now offers a finer resolution of these biogeographic dynamics.

Living gerbils of the family Gerbillidae occupy a vast corridor stretching across Africa, the Middle East, northern India and China, adapted to arid and sub-desert environments ranging from the African savannahs north and south of the Tropic of Cancer to the desert belt extending from northern Africa to China and the Asian steppes. This ecological tolerance for dry conditions is consistent with the palaeoenvironmental reconstructions of the late Messinian Iberian interior, which suggest increasingly arid settings as the crisis progressed. The ability of gerbils to exploit such habitats would have facilitated their rapid spread once dispersal routes opened.

After the Zanclean flood, the marine inundation that ended the Messinian Salinity Crisis and restored the Mediterranean Sea, members of the genus Debruijnimys persisted in several Pliocene sites of the Iberian Peninsula. Both Debruijnimys primaevus and Debruijnimys julii are recorded from these early Pliocene assemblages, indicating that the lineage survived the dramatic environmental upheaval of the crisis and its aftermath. The persistence of these rodents into the Pliocene, alongside other elements of African origin, illustrates how the Messinian Salinity Crisis acted not merely as a barrier but as a catalyst for biotic interchange, reshaping the composition of terrestrial faunas on both sides of the Mediterranean for millions of years afterwards.

The description of Debruijnimys primaevus also highlights the value of karstic fissure fillings as archives of small vertebrate evolution. Such sites, which accumulate the remains of owls and other predators’ prey over extended periods, often preserve dense concentrations of isolated teeth that permit fine-scale biostratigraphic and evolutionary studies. The large sample from La Piquera, distributed across six stratigraphic levels, provides an unusually complete picture of a single gerbil population through time, allowing morphological variation to be assessed within a well-constrained chronological framework.

More broadly, the study contributes to a growing body of evidence that the Messinian Salinity Crisis, far from being solely a marine event, had profound consequences for continental biogeography. The opening and closing of corridors around the Mediterranean, driven by dramatic changes in sea level and basin geometry, created episodic opportunities for mammalian dispersals that otherwise would have been impossible. Rodents, with their rapid evolutionary rates and fine fossil records, serve as particularly sensitive indicators of these dynamics, and the two-phase gerbil immigration documented here offers a model for how other faunal exchanges between Africa, Asia and Europe during the latest Miocene may have unfolded in discrete pulses rather than as continuous flows.

Subject of Research: A new species of gerbil ( Gerbillidae , Rodentia , Mammalia ) from the Early Pliocene of the Iberian Peninsula and its bearing on faunal dispersals during the Messinian (Late Miocene)

Article Title: A new species of gerbil ( Gerbillidae , Rodentia , Mammalia ) from the Early Pliocene of the Iberian Peninsula and its bearing on faunal dispersals during the Messinian (Late Miocene)

Article References: Agustí, J., Piñero, P., Blain, H.-A., Martín-Perea, D. M., Sevilla, P., & Laplana, C. (2026). A new species of gerbil (Gerbillidae, Rodentia, Mammalia) from the Early Pliocene of the Iberian Peninsula and its bearing on faunal dispersals during the Messinian (Late Miocene). Fossil Record, 29(1), 317-332. https://doi.org/10.3897/fr.29.190187

Image Credits: AI Generated

DOI: 10.3897/fr.29.190187

Keywords: species, gerbil, Gerbillidae, Rodentia, Mammalia, Early, Pliocene, Iberian, Peninsula, bearing, faunal, dispersals