The freshwater and terrestrial turtles from Monte Pila and Fuenmayor (La Rioja, northern Spain): new data on the lower Miocene turtle diversity of the Ebro Basin

Abundant turtle fossils from two lower Miocene localities in which this lineage had not previously been studied are described herein. The localities are Monte Pila and Fuenmayor, which are 10 km apart, both located in the Autonomous Community of La Rioja (northern Spain), in the Ebro Basin. Information about the turtles from the lower Miocene levels in this basin was until now restricted to the finds made in the MN3 biozone of the Bardenas Reales of Navarre. Several turtle taxa had been recognized there. However, the material attributed to each of them was scarce. Monte Pila and Fuenmayor are located in biozone MN2. The remains of turtles are abundant in both sites. A terrestrial lineage, recognized at Monte Pila, is not represented in the Bardenas Reales fauna of Navarre. It represents the first record of Titanochelon Pérez-García & Vlachos, 2014 in La Rioja and is one of the oldest member of this genus, being assigned to Titanochelon cf. bolivari (Hernández-Pacheco, 1917). The only lineage of turtles identified in Fuenmayor, and the most abundant in Monte Pila, is Ptychogasterinae. All material of this clade of freshwater turtles identified there is compatible with a single form, for which a high range of intraspecific variability is recognized. It is attributed to Ptychogaster (Temnoclemmys) cf. bardenensis Murelaga, Lapparent de Broin, Pereda Suberbiola & Astibia, 1999, this species having been recognized, until now, as exclusive to the Bardenas Reales of Navarre.