Node Calibrated. Common ancestor of Caniformia (dogs, bears, raccoons, seals) and Feliformia (cats, mongooses, hyaenas), excluding stem carnivoramorphans sensu Wesley Hunt and Flynn (2005).

Fossil Taxon and Specimen. Hesperocyon gregarius (SMNH P1899.6; Bryant, 1992) from the Cypress Hills Formation, Duchesnian NALMA, Lac Pelletier local fauna, Saskatchewan.

Phylogenetic Justification. Phylogenetic analysis shows that Hesperocyon is closely related to Canidae, based on its possession of a fully ossified auditory bulla composed mainly of the caudal entotympanic, with contributions from the ecotympanic and rostral entotympanic, and the caudla entotympanic forms a partial septum within the middle-ear cavity (Wesley-Hunt and Flynn, 2005).

Minimum Age. 37.3 Ma

Soft Maximum Age. 66 Ma

Age Justification. The oldest caniforms are amphicyonids such as Daphoenus and canids such as Hesperocyon, known from the earliest Duchesnean NALMA, which corresponds to magnetochron 18N and is dated as 39.74 Ma ± 0.07 Myr, based on radiometric dating of the LaPoint Tuff (Robinson et al., 2004). This correlates to the Bartonian stage with a minimum limit of 37.8 ± 0.5 Ma (Gradstein et al., 2012), thus providing a minimum constraint of 37.3 Ma.

The soft maximum constraint is based on the occurrence of the oldest stem-carnivorans (miacids, viverravids) in the early Paleocene (Fox et al., 2010), so 66.04 Ma ± 0.4 Myr = 66 Ma.

Discussion. Daphoenus is also known from the Duchesnian (Bryant, 1992); both genera are reconstructed by Wesley Hunt and Flynn (2005) as basal caniformes. The oldest stem carnivorans are viverravids (not to be confused with extant, feliform viverrids) and paraphyletic "miacids", known from the early Paleocene onwards. Both groups have been reconstructed outside crown Carnivora (Wesley-Hunt and Flynn, 2005) and cannot provide a minimum date for the dog-cat split. Tapocyon may be an even older caniform; it comes from the Middle Eocene, Uintan, dated as 46-43 Ma, although Wesley-Hunt and Flynn (2005) place this taxon outside crown Carnivora. The oldest feliforms may be the nimravids, also known first from the White River carnivore fauna of the Chadronian NALMA, with uncertain records extending to the base of that unit (Hunt, 2004).