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The Thermoanaerobacteriales are a polyphyletic order of bacteria placed within the polyphyletic class Clostridia, and encompassing three families: the Thermoanaerobacteraceae, the Thermodesulfobiaceae, Thermoanaerobacterales Family III. Incertae Sedis and various unplaced genera. This order is noted for the species abilities to survive in environments of extreme elevated temperature. An example organism in this order is Thermoanaerobacterium autearoensis.
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 111 by The All-Species Living Tree Project 
The Thermoanaerobacteriales as previously mentioned are polyphyletic, and consist of over six morphologically and physiologically similar clades:
♣ International Journal of Systematic Bacteriology or International Journal of Systematic and Evolutionary Microbiology (IJSB/IJSEM) published species that are in press.
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LPSN).