Later thorough descriptive work by Sotnikova on material from the late Early Pleistocene site of Untermassfeld, Germany, provided a more solid basis for the diagnosis of C. mosbachensis.

[15] In 2022, Cajus Dietrich proposed the new subspecies Canis lupus bohemica for remains in the Bat Cave system located near Srbsko, Central Bohemia, Czech Republic dating to around 800,000 years ago.

Specimens of C. mosbachensis are smaller than the largest modern populations of C. lupus, exhibiting a lower range of size variability.

The only difference he noted was that C. variabilis had "nasal bones that terminate at or anterior to the most posterior position of the frontal-maxillary suture", and therefore he proposes these two taxa to represent a variation in the one geographically widespread mid-Pleistocene wolf.

The difference is that C. m. variabilis possesses a shorter nasal bone and a slight variation in the ridge of the first upper molar tooth.

in Latin means confer, uncertain) is thought to have been widespread in Eurasia until around 300,000 years before present YBP and does not appear to overlap with the earliest occurrence of the morphologically distinctive grey wolf.

[16] Fossils of C. variabilis were found at the Zhoukoudian (once spelt Choukoutien) cave system and archaeological site in 1934 and named by its discoverer, Pei Wenzhong.

At the site, the small wolf's remains were in close proximity to Homo erectus pekinensis or Peking Man, in layers dating back to 500,000-200,000 YBP.

Pei describes this small wolf as exhibiting variation in size and tooth adaptations, stating that its skull differs from the typical wolf in much smaller size (about 175.0 mm total length for a large C. variabilis specimen), with a more slender muzzle and noticeably reduced or absent sagittal crest.

A later researcher has confirmed Pei's measurements, and describes the wolf's skull as having "heavy, wolf-like proportions although smaller than any extant C.

The study concluded that "It is very likely that this species is the ancestor of the domestic dog Canis familiaris, a hypothesis that has been proposed by previous authors.

"[2][24][27][28] In 2015, a study looked at the mitochondrial control region sequences of 13 ancient canid remains and one modern wolf from five sites across Arctic north-east Siberia.

[16] The authors concluded that the structure of the modern dog gene pool was contributed to from ancient Siberian wolves and possibly from Canis c.f.