Trailside tracks on Bright Angel Trail

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This block of rock on the Bright Angel Trail in Grand Canyon National Park is a boulder from the Manakacha Formation which is associtated with the Atokan/Moscovian Age of the Pennsylvanian Epoch. The side of the boulder shows basal reptiles or basal synapsids fossil tracks on the bedding surface of deposits from ancient dunes. Recent research on this this rockfall boulder, indicates that these are among the earliest known tracks of a early land-dwelling animal to inhabit desert like conditions. Two trackways can be seen on the suface, and may represent when different animals passed over the location at different times, possibly within days of each other. Model is by NPS; photos taken 4/3/2019 Rowland SM, Caputo MV, Jensen ZA (2020) Early adaptation to eolian sand dunes by basal amniotes is documented in two Pennsylvanian Grand Canyon trackways. PLoS ONE 15(8): e0237636. https://doi.org/10.1371/journal.pone.0237636