Eubrontes, a footprint of a theropod dinosaur, preserved in reddish sandstones of the Moenave Formation (Lower Jurassic), near Tuba City, north of Flagstaff, Arizona.[1] Scale: The coin is a US quarter dollar (25¢, diameter: 24.26 mm, 0.955 in) comparable in size to a 50 euro cent coin. Hence, the maximum width of the footprint is about 30 cm (1 ft).
↑see pictures at dinodomain.com at the Wayback Machine; Note: The whole domain is for sale now and there was only one picture of the original webpage archived, but it clearly shows the imprint in question, inferrable from the adjacent surface features of the rock.
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This is propably Tyrannosaurus rex tracks. The picture was taken from: http://pdphoto.org/PictureDetail.php?mat=pdef&pg=5493 I don't know which licence I should check.