[1] It has a nearly cosmopolitan distribution, but is concentrated in two centers of diversity, one in Australia, the other in western North America.

[2] Members of this family occur in diverse habitats, including deserts, river banks and mountains.

Phrymaceae is a family of mostly herbs and a few subshrubs, bearing tubular, bilaterally symmetric flowers.

One of these, Glossostigma, is among the smallest of flowering plants, larger than the aquatic Lemna but similar in size to the terrestrial Lepuropetalon.

The smallest members of Phrymaceae are only a few centimeters long, while the largest are woody shrubs to 4 m tall.

[5] This clade has the topology of a phylogenetic grade and can therefore be represented as {Mazaceae [Phrymaceae (Paulowniaceae )]}.

[8] The composition of Phrymaceae and the delimitation of genera changed radically from 2002 to 2012 as a result of molecular phylogenetic studies.

Research on phylogenetic relationships revealed that several genera, traditionally included in Scrophulariaceae, were actually more closely related to Phryma than to Scrophularia.

Mazus and Lancea were included in Phrymaceae for a short time before further studies indicated that they, along with Dodartia should be segregated as a new family, Mazaceae.

Phrymaceae consists of four clades, all of which have strong statistical support in cladistic analyses of DNA sequences.

[20] In 2002, a molecular phylogenetic study showed that Phryma formed a strongly supported clade with Mimulus and its various relatives.

Chloroplast DNA showed Phryma to be embedded within a broadly defined Mimulus, but this result was not strongly supported, and was contradicted by data from the ITS and ETS regions of the nuclear genome.

[9] In 2004, in the most recent comprehensive treatment of families and genera in Lamiales, Phrymaceae consisted of Phryma only.

The 11 "additional genera" were Dodartia, Mazus, Lancea, Bythophyton, Encopella, Hemianthus, Micranthemum, Bryodes, Dintera, Psammetes, and Mimulicalyx.

[8] The monotypic genera Bythophyton and Encopella might properly belong to Plantaginaceae tribe Gratioliae.

Thus Bythophyton, Encopella, Dintera, Psammetes, and Mimulicalyx might be considered as possible members of Phrymaceae since they have not been unequivocally placed elsewhere.

Instead of recognizing Phrymaceae and several of the other Lamiales families of APG III, some authors have chosen to maintain a large polyphyletic Scrophulariaceae until there is a clear understanding of how it should be "disintegrated".