Urocystidales
The Urocystidales are an order of fungi within the class Ustilaginomycetes. The order contains 6 families and about 400 genera. They are a sister order to Ustilaginales. Urocystidales is also known and classified as the smut fungi. They are serious plant pathogens, Urocystis, is one of the representative genera of the order, it is an example of a smut genus that has a wide host range. The type species Urocystis occulta , was described as a pathogen on rye (Secale cereale). They are found in marine and terrestrial environments. The aquatic members of the Doassansiopsis genera are found in the tropics or subtropics. Morphology
They are distinguished from other fungi by the existence of haustoria (root-like structure) and pores in the septa of soral hyphae. Families
It was formed in 1997, and consisted (then) of 4 families, (Doassansiopsidaceae, Glomosporiaceae, Melanotaeniaceae and Urocystidaceae with 1 genus. Later, Melanotaeniaceae was moved to the Ustilaginales order by Begerow et al. in 2006, and others were added such as Fereydouniaceae and Floromycetaceae in 2014 , and Mycosyringaceae in 2008. As accepted by GBIF and others;
 Doassansiopsidaceae (19) - only includes Doassansiopsis 
 Fereydouniaceae (3) - includes Fereydounia
 Floromycetaceae (21) - includes Antherospora and Floromyces
 Glomosporiaceae (117) - includes Thecaphora (incl. Glomosporium Sorosporium)
 Mycosyringaceae (5) - includes Mycosyrinx
 Urocystidaceae (228) - includes Flamingomyces, Melanoxa, Melanustilospora, Mundkurella, Tuburcinia, Urocystis, Ustacystis and Vankya

Figures in brackets are approx. how many species per family. Note the DNA of family Doassansiopsidaceae has been studied. Ecology
The leaves of the water-lily (Nymphaea nouchali) can be affected by the water-born fungi, Doassansiopsis nymphaea. The leaves of Caldesia parnassifolia (Alisma reniforme) can be affected by the water-born fungi, Doassansiopsis hydrophila  (syn Doassansiopsis martianoffiana). References

Other sources
C.J. Alexopolous, Charles W. Mims, M. Blackwell  et al., Introductory Mycology, 4th ed. (John Wiley and Sons, Hoboken NJ, 2004)  

Ustilaginomycotina
Fungal plant pathogens and diseases
Basidiomycota orders
Taxa named by Franz Oberwinkler
Taxa described in 1997