These fungi are all biotrophic mutualists. Most employ the arbuscular mycorrhizal method of nutrient exchange with plants. They produce large (.1-.5mm) spores (azygospores and chlamydospores) with thousands of nuclei.
All members of their phylum were once thought to be related to the Endogonaceae, but have been found through molecular sequencing data, to be a closer relation to the Dikarya. Their fossil record extends back to the Ordovician period (460 million years ago).
The family name Glomeraceae upon which this order level name is based, was incorrectly spelled 'Glomaceae', hence the order name was incorrectly spelled 'Glomales'. Both are correctable errors, to Glomeraceae and Glomerales, as governed by the International Code of Botanical Nomenclature. The incorrect spellings are commonplace in the literature, unfortunately.