The Burgess fossils show the first large-scale
evolution of a mineralized, or chitinous,
exoskeleton - a hard outer casing, usually found
over the top of the body and used for protection
as well as muscle anchorage Hurdla has been
included in the group known as anomalocarids.
Its mouthparts may have had an extra set of
teeth within, forming a so-called 'pharyngeal
mill' that would be able to grind up other
harder-bodied victims - showing that predators
were already adapting to well-protected prey.