An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Hamamelidae of the class Magnoliopsida (dicotyledons). The order consists of a single family (Casuarinaceae) and genus (Casuarina), with about 50 species. Native to the southwestern Pacific region, especially Australia, they are sometimes called Australian pine. They are trees with much reduced flowers and green twigs that bear whorls of scalelike, much reduced leaves. Some species are grown as street trees in tropical and subtropical regions.