History of invertebrate paleozoology and simpler sea-dwelling organisms. By far, invertebrate paleozoology is the easiest type of fossil collecting. "Unlike" the difficult-to-analyze and hard-to-interpret fossils of paleobotany (plants) and micropaleontology (microbes), and "unlike" the rarely found and poorly preserved skeletons of vertebrate paleontology, invertebrate fossils are usually both common and simple to identify. This is because many prehistoric invertebrates were hard-shelled mollusks, brachiopods, trilobites, bryozoans, crinoids or corals who were buried amid marine, sediment-preserving conditions; and therefore frequently fossilized. Stone-age people were without doubt the very first fossil collectors. Fossilized echinoderms have been found in Dunstable, Bedfordshire, central England, decorating a long-buried human skeleton;
Sea slug are within the informal taxonomic group Opisthobranchia: There is also one group of "sea slugs" within the informal group Pulmonata: Like many nudibranchs, "Glaucus atlanticus" can store and use stinging cells from its prey (Portuguese man o' war) in its finger-like cerata. Other species like the Pyjama slug "Chromodoris quadricolor" may use their striking colors to advertise their foul chemical taste. The Lettuce Sea Slug ("Elysia crispata") has lettuce-like ruffles that line its body. This slug, like other Sacoglossa uses kleptoplasty, a process in which the slug absorbs chloroplasts from the algae it eats, and uses "stolen" cells to photosynthesize