El Frontal, Regumiel de la Sierra (Burgos)


In the El Frontal site there are 86 listed ichnites gathered in 8 trackways and isolated marks.  Most of the footprints are from iguanodontids, maybe belonging to individuals of the same species.  One of the trackways are identified as a small sized theropod, of bipedal walking and with narrow and long footprints, slender toes and sharp ends (claws). Among the iguanodontid tracks there are 2 wide quadruped tridactyl “foot” trackways that standout, with short blunt toes; the “hand” prints are oval shaped.  Some studies have deducted from these tracks that the dinosaur had two of its “hands’” middle fingers joined together, the other finger being separate from these two.  The typical iguanodontid “thumb” or spur would not touch the ground.


The site’s sandstone rocks abound in this region; they come from sand deposited about 125 million years ago in the channels and flood plains of large rivers.  Here the dinosaurs would have water and vegetation available in a subtropical climate.  They left their tracks to posterity in the sandy mud of these fluvial lands.