This is a moderately small group of algae with about 100 genera and 600 species. They are primarily freshwater or soil algae; a few are marine. Typically they are rare algae and found in low abundance, although a few genera, including [Tribonema] and [Vaucheria] are reasonably common.
The taxonomy is unclear with different treatments according to author. Some place the class Xanthophyta in the Heterokontophyta and others in Phytophyta (the larger grouping of algae).