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.The work has documented seven new localities from the Lower Miocene, about 20 million years ago, and two from the Middle Miocene, about 16 million years ago. All these deposits configure a continuous stratigraphic context during an important part of the Miocene in the Tudela Formation, allowing a more precise dating of the vertebrate fossil findings in the area and the development of detailed comparative studies with other areas of the Spain.
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.
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.+ info Ruiz-Sánchez, F.J., Murelaga, X., Freudenthal, M., Larrasoaña, J.C., Furió, M., Garcés, M., González-Pardos, M. & Suárez-Hernando, O. (2012). Rodents and insectivores from the Lower Miocene (Agenian and Ramblian) of the Tudela Formation (Ebro Basin, Spain). Journal of Iberian Geology 38(2): 349-372.