Range of Experimental Dinosaur (Hypsilophodon foxii) Footprints Due to Variation in Sand Consistency: How Wet Was the Track?

The laboratory-controlled simulations of dinosaur footprints in this study revealed characteristic track features that could be used to identify the consistency of sand substrates and provide an insight into the paleoenvironment. A model foot of Hypsilophodon foxii was indented into three sands of four different moisture (= water) contents. The two intermediate moist states were characterized by shallow tridactyl impressions, in which only digits II-IV were impressed, showing details of padding and claws. Where the foot penetrated more deeply, in the dry and saturated states, the hallux and heel were also impressed; in these cases, the foot detail was not preserved accurately and track morphology deviated significantly from that of the foot. Dry sand tracks were characterized by the outward and upward movement of sediment and tracks in saturated sand by mainly downward displacement. The finer-grained saturated sand was also associated with liquefaction and closure of digit imprints. Tracks from the Middle Jurassic Cleveland Basin of Yorkshire showed features of the saturated state. The range of experimental track morphotypes formed by one foot highlighted the difficulties in assigning a print type to a particular trackmaker and the importance of excluding preservational variants from ichnotaxonomic studies. [ABSTRACT FROM AUTHOR]