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The Halanaerobiales are an order of bacteria placed within the class Clostridia, and encompassing two families, the Halanaerobiaceae and the Halobacteroidaceae. Originally placed within the highly polyphyletic class Clostridia, according to the NCBI and LPSN, it is now thought to lie outside of the Firmicutes. Halanaerobiales are halophilic obligate anaerobes with a fermentative or homoacetogenic metabolism.
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)  and National Center for Biotechnology Information (NCBI) and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project 
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN).