Image of a landscape in the Bardenas Reales, Tudela Formation. http://www.fotopedia.com/items/flickr-3226772070

Although the presence of Miocene fossils are known in the Ebro Basin since the mid-nineteenth century, there are still few published studies. Sabadell paleontologist Miquel Crusafont unveiled two new sites, Tudela I and Tudela II, during the 60s of last century and in the early 90s more localities were discovered near Tudela and in other areas of the Bardenas Reales of Navarra. Since then, the number of excavations and prospections has been increasing, and in recent years numerous remains of vertebrates such as fish, amphibians, reptiles, birds and mammals have been found.

During the decades of 1990 and 2000, a multidisciplinary team of paleontologists and geologists from different Spanish centers began an extensive research in the area of ​​the Bardenas Reales, in the Tudela Formation, in order to make a detailed biostratigraphic study. The latest results of this study were recently published in two papers, one in the Journal of Iberian Geology and the other in the Bulletin of Geosciences. Marc Furió, one of the few Europpean experts in fossil insectivores, is the ICP researcher that participates in this research.

Insectivores fossil remains from the locality Pico de Fraile 2 (Ebro Basin)

The Lower Miocene deposits reflect the richness and diversity of the glirid faunas, one of the rodent families – dormice are the extant representatives- of those more ancient fossil remains are known. It is also worth to note the absence of Cricetidae, the rodent family that includes extant hamsters, and that is indicative of a time during the early Miocene when these small mammals mysteriously disappeared during a couple of million years throughout Europe.

Despite having one of the best continental Neogene fossil records worldwide, deposits of early Miocene (Agenian and Ramblian) are rather scarce in the Iberian Peninsula. This gives even more value to this fossiliferous sequence. As the ICP paleontologist Marc Furió comments

This moment is perhaps the darkest of the Miocene in the Iberian Peninsula. For this reason, any information about what happened between 22 and 17 million years ago, the initial period,  is of great importance. The further we go back in time, the more diluted are the fossil faunas of the Lower Miocene. With these new studies that combine paleontology, geology and paleomagnetism, we have just started to establish the pillars that will allow a better dating of the geological levels of this time period based on their faunal content.

+ info Ruiz-Sánchez, F.J., Murelaga, X., Freudenthal, M., Larrasoana, J.C,, Furió, M., Garcés, M., González-Pardos M., Suárez-Hernando, O. (2013). Micromammalian faunas from the Middle Miocene (Middle Aragonian) of the Tudela Formation (Ebro Basin, Spain)   Bulletin of Geosciences 88(1): 131-152.