A novel, strictly anaerobic, slightly alkaliphilic, halotolerant, peptide- and amino acid-utilizing bacterial strain, SD1T, was isolated from a hypersaline lake in Western Australia. The strain stained Gram-negative and was a motile, spore-forming rod. The strain grew between 15 and 50 °C (optimum 40 °C), 1–15% w/v sodium chloride (optimum 5%) and pH 6.0–10.0 (optimum 9.0). Major fatty acids included anteiso-C15 : 0 (24.9%), C14 : 0 dimethyl acetyl (13.2%), anteiso-C15 : 0 dimethyl acetyl (11.5%) and iso-C15 : 0 (10.4%). The DNA G+C content was 30.3 mol%. The isolate did not grow using any tested sugars but grew well on arginine and glycine. It is capable of using elemental sulfur and thiosulfate as alternate electron acceptors, but not sulfide, sulfate, nitrate or nitrite. 16S rRNA gene similarity indicates that the isolate is related to Sporosalibacterium tautonense MRo-4T (94.33% identity). SD1T showed 76.18%–76.31% average nucleotide identity with other strains within the family Thermohalobacteraceae. Phylogenetics, based on the 16S rRNA gene and whole-genome sequence, as well as phenotypic analysis, differentiates the isolate from close neighbors. We propose that SD1T represents a novel species in a new genus, which we have named Dethiothermospora halolimnae gen. nov., sp. nov., type strain SD1T (DSM 117405T = TSD-443T). From this work, we also propose repositioning of the genus Anaeromonas to the family Thermohalobacteraceae.