Answer Monday!

Last week on Fossil Friday, I gave you a fickle footprint fossil to figure out. What could have left those tiny impressions?

Turns out it was a prehistoric spider!

Wired magazine has the scoop:

"These are footprints left behind when a tarantula-size arachnid crawled over the sand of what’s now northern Arizona, 260 million years ago. We don’t know where it was going or what it was doing, but each time the critter pressed one of its eight feet into the ground, it left a tiny, cup-shaped imprint in the dewy grains.

The sand’s moisture helped preserve the imprints of the creature’s journey: As the sand dried out, the delicate prints solidified. Over millennia, layers of sand covered the arachnid’s footwork and hardened into rock. Then, in 1968, the rock and its footprints were pulled from the Arizona desert; it now lives in The Raymond M. Alf Museum of Paleontology, where visitors can stop by and see the footsteps of an ancient spider."

The only person to identify this critter? Gerald Wilgus, who not only gets bragging rights for the week but gets to request the fossil in this week's Fossil Friday.

Special thanks for Andrew Farke and the Raymond M. Alf Museum of Paleontology in Calremont, CA, for letting us run this fossil. You can follow the museum on Facebook and Twitter @alfmuseum.

Photo Credit: josef.stuefer via Compfight cc