Crustaceans are large group of anthropods that are typically free-living in freshwater or marine environments. However, there are some land-dwelling crustaceans, such as woodlice, and non-mobile creatures, such as barnacles. Crustaceans have a segmented body with three distinct parts: the head, thorax, and abdomen and symmetrical legs. They also usually have eyes on stalks, antennae, and an exoskeleton that they molt in order to grow. The fossil record of crustaceans dates back to 540 million years ago, during the Cambrian period, with some species of crustaceans appearing evolutionarily unchanged since the Jurassic period.
'Popularity' is determined by the average monthly online search statistics for each category or element