Haplomitriopsida

Haplomitriopsida is a class of liverworts comprising fifteen species in three genera. Recent cladistic analyses of nuclear, mitochondrial, and plastid gene sequences place this monophyletic group as the basal sister group to all other liverworts. The group thus provides a unique insight into the early evolution of liverworts in particular and of land plants in general.

== Description == Plants of Treubia grow as a prostrate leafy thallus. The bifid leaves extend like wings on either side of the midrib, or may be folded upwards and pressed close together, giving the plants a ruffled appearance. By contrast, Haplomitrium grows as a subterranean rhizome with erect leafy stems. The thin, rounded leaves are arranged around the upright stems, giving the appearance of a soft moss. The species Haplomitrium ovalifolium of Australia often has bifid leaves that are asymmetrical, somewhat like those in Treubia.