How Small Can Sea Urchins Be?
There are species that are very tiny, on the scale of the Martian urchins If you were to surf the web looking for the world’s smallest sea urchin, you would likely find the data on Echinocyamus scaber, which measures only 5.5 mm (or just over a fifth of an inch) in diameter. And, a good proportion of the Martian urchins (murchins) measure up to about 5 mm in diameter, making them small but not unduly so.
