Toxopneustes pileolus, commonly known as the flower urchin, is a widespread and commonly encountered species of sea urchin from the Indo-West Pacific. It is considered highly dangerous, as it is capable of delivering extremely painful and medically significant stings when touched. It inhabits coral reefs, seagrass beds, and rocky or sandy environments at depths of up to . It feeds on algae, bryozoans, and organic detritus. Its common name is derived from its numerous and distinctively flower-like pedicellariae, which are usually pinkish-white to yellowish-white in color with a central purple dot. It possesses short and blunt spines, though these are commonly hidden beneath the pedicellariae. The rigid "shell" (test) is a variegated deep red and gray in color, though in rare cases it may be greenish to light purple. Taxonomy Toxopneustes pileolus is one of four species belonging to the genus Toxopneustes. It belongs to the family Toxopneustidae in the order Camarodonta. It was originally described as Echinus pileolus by the French naturalist Jean-Baptiste Lamarck in 1816, in the second book of his Histoire naturelle des animaux sans vertèbres series. It was later used as the type species for the newly created genus Toxopneustes by the Swiss American biologist Louis Agassiz. The generic name Toxopneustes literally means "poison breath", derived from Greek τοξικόν [φάρμακον] (toksikón [phármakon], "arrow [poison]") and πνευστος (pneustos, "breath"). The specific name pileolus means "little cap" or "skullcap", from Latin pileus, a kind of brimless conical felt cap. In English, Toxopneustes pileolus is most widely known as the "flower urchin". It is also sometimes known under various other common names, including "trumpet sea urchin", "flower tip urchin", "felt cap sea urchin", and "poison claw sea urchin". In the seashell collecting trade, Toxopneustes pileolus is known as the "mushroom urchin", due to their spineless empty shells (tests) resembling the caps of mushrooms. It is also known as tapumiti in Samoan; tehe-tehe batu in Sinama and Tausug; rappa-uni (ラッパウニ) or dokugaze (毒ガゼ) in Japanese; and lǎbā dú jí hǎi dǎn (喇叭毒棘海膽) in Chinese. Description Flower urchins are relatively large sea urchins. They can reach a maximum diameter of around . Like most echinoderms, the body of adult flower urchins is equally divided into identical segments around a central axis in multiples of five (pentaradial symmetry). The rigid "shell" (test) has five interambulacral segments separated from each other by five ambulacral segments, each of them are composed of smaller regularly