Tutellix circumferus
Extinct (April 19th, 2020): Outcompeted by Tendocirculix interretus
Descended from H. quattuorus, this species has a round shell and wider feet, with tough cartilage plates on top.
Young H. quattuorus were preyed upon by p. filterarious, so naturally the greatest concentration occurred in parts of the water away from the shoreline. Still mostly feeding on plant matter dropped into the water, food is less plentiful there.
The rounded shell is more space efficient and provides a bit more space to store additional mass for when food is scarce. The wider feet provide them with a stronger grip, so even young specimens are less likely to be preyed upon. When in danger, they curl their feet underneath of them with their cartilage plates facing outward.
