Now inspect the arrangement of the bones. Aside from the differences of scale, the body plans are roughly the same. And the animals' limbs are patterned similarly. Though specialized for different functions, it is clear they are embellishments of a single blueprint. Not so with echinoderms.
Echinoderms are an ancient phylum with a huge fossil record.
The sea urchin on his bench looks like a guava-sized Koosh Ball, one which, he explains, is likely equipped with venomous spines. A nearby fossilized sea lily, however, is a knee-high creature which looks most like a mop head mounted on a jointed bamboo pole. Loosely speaking, these organisms are phylogenetic kissing cousins. You'd just never know it looking at them. Unless you look very carefully, and in the right places.