I sadly am having trouble finding the exact species but they were a type of amphipods (a diverse group of crustaceans)
I actually got to see some today at a beach in the form of sandhoppers, which are the little shrimps guys you will sometimes find in the sand that tend to hop (as the name implies)
A sand pendulum that creates a beautiful pattern only by its movement.
But why does the ellipse change shape?
The pattern gets smaller because energy is not conserved (and in fact decreases) in the system. The mass in the pendulum gets smaller and the center of mass lowers as a function of time. Easy as that, an amazing pattern arises through the laws of physics.
BettSplendens Tumblr Evac 