Largest organisms photosynthetic unicellular and multicellular protists that are related to land plants. The thallus of the unicellular mermaid's wineglass, "Acetabularia", can grow to several inches (perhaps 0.1 to 0.2 m) in length. The fronds of the similarly unicellular, and invasive "Caulerpa taxifolia" can grow up to a foot (0.3 m) long. A member of the order Cetacea, the blue whale ("Balaenoptera musculus"), is thought to be the largest animal ever to have lived. The maximum recorded weight was 190 metric tonnes for a specimen measuring , whereas longer ones, up to , have been recorded but not weighed. The African bush
Animal measuring up to long. The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as "Argentinosaurus", which may have weighed as much as 73 tonnes. Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 µm, and one of the smallest species ("Myxobolus shekel") is no more than 8.5 µm when fully grown. The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates