Some
ancient echinoids, ophiuroids, and asteroids had slipped the bottleneck and coexisted with the ancestors of modern - day sea urchins, brittle stars, sand dollars, and relatives, for many millions of years.
Smaller holes in the surface of the reef are the result of boring organisms such as the
spiny echinoids (sea urchins) and the boring mollusks.
Recent quantitative genetics and genomic studies
with echinoids indicate the presence of traits to facilitate resilience and adaptation (genetic) to ocean acidification [31,32,54,109], ocean warming and both stressors [110].
The ichthyosaurs, plesiosaurs, and marine crocodiles flourished, as did bivalves, belemnites, brachiopods,
echinoids, starfish, sponges and ammonites among the invertebrates.
Thalassia residents include starfish,
echinoids (sea urchins), worms, young lobsters, sea anemones and many varieties of gastropods (snails).