are found only throughout former Laurasia. This suggests that much of the potential habitat in this supercontinent, now occupied by Anostraca, to have been unoccupied by ecologically similar species, or to have been inhabited by species with less adaptive ability. Studies have found Anostraca capable of rapid colonization and speciation. Diversity Anostraca is the most diverse of the four orders of Branchiopoda. It comprises around 313 species, grouped into 26 genera in eight families: Artemiidae – 1 genus, 8 species Branchinectidae – 1 genus, 45 species Branchipodidae – 5 genera, 35 species Chirocephalidae – 9 genera, 81 species Parartemiidae – 1 genus, 18 species Streptocephalidae – 1 genus, 56 species Tanymastigidae – 2 genera, 8 species Thamnocephalidae – 6 genera, 62 species References External links Crustacean orders Freshwater crustaceans Extant Ordovician first appearances