Which of the following are considered "irregular" urchins?
A)Sea urchins that swim
B)Sand dollars and heart urchins
C)Sea cucumbers
D)Crinoids
E)Brittle stars

Question

Quizplus · Accepted Answer

Sand dollars and heart urchins are considered irregular urchins because they have a disk-shaped body rather than the typical spherical shape of regular sea urchins. They also have unique feeding structures and tube feet adapted for burrowing in sand. Sea urchins that swim are referred to as irregular echinoids, but not necessarily irregular urchins. Sea cucumbers, crinoids, and brittle stars are all different types of echinoderms but are not considered urchins.

Which of the Following Are Considered "Irregular" Urchins