Eurybacteria is a taxon created by Cavalier-Smith, which includes several groups of Gram-negative bacteria. Their Endospores are characterized by producing and presenting external flagella or mobility by bacterial displacement. Specifically, it includes:
⇒ Selenobacteria. For example, Sporomusa
  ⇒ Includes Heliobacteriales, for example, Heliobacterium
⇒ Fusobacteria. For example, Leptotrichia and Fusobacterium
⇒ Togobacteria (=Thermotogales). For example, Thermotoga.

In the standard classification, selenobacteria are usually included in the phylum firmicutes, whereas fusobacteria and togobacteria are classified as their own groups. The following graph shows Cavalier-Smith's version of the tree of life, indicating the status of eurybacteria.