The use of gnotobiotics has gained large interest in recent years due to technological advances that have revealed the importance of host-associated microbiomes for host physiology and health. One of the oldest and most important gnotobiotics mouse model, the Altered Schaedler Flora (ASF) has been used for several decades. ASF comprises eight different bacterial species, which have been characterized to different extent, but only few are available through public strain collections. Here, the isolation of a close relative to one of the less studied ASF strains, Clostridium sp. ASF 502, is reported. Isolate TLL-A1, which shares 99.6% 16S rRNA gene sequence identity with Clostridium sp. ASF 502, was obtained from feces of C57BL/6J mice where is was detectable at a relative abundance of less than one percent. D-arabinose was used as sole carbon source in the anaerobic cultivation medium. Growth experiments with TLL-A1 on different carbon sources and analysis of its ~6.5 gigabase genome indicate that TLL-A1 harbors a large gene repertoire to utilize different carbohydrates for growth. Comparative genome analyses of TLL-A1 and Clostridium sp. ASF 502 reveal differences in genome content between the two strains, in particular with regards to carbohydrate activating enzymes. Based on physiology and genomic analysis it is proposed to name TLL-A1 to gen. nov. sp. nov Schaedlerella arabinophila TLL-A1 (DSMZ 106076T; KCTC 15657T). The closely related Clostridium sp. ASF 502 is proposed to be renamed to Schaedlerella arabinophila to reflect its taxonomic standing and to keep textquoterightASF 502textquoteright as strain designation.