by Spaulding et al. as "the least inclusive clade that includes Bos taurus (cow) and Tragulus napu (mouse deer)". Ruminantiamorpha is a higher-level clade of artiodactyls, cladistically defined by Spaulding et al. as "Ruminantia plus all extinct taxa more closely related to extant members of Ruminantia than to any other living species." This is a stem-based definition for Ruminantiamorpha, and is more inclusive than the crown group Ruminantia. As a crown group, Ruminantia only includes the last common ancestor of all extant (living) ruminants and their descendants (living or extinct), whereas Ruminantiamorpha, as a stem group, also includes more basal extinct ruminant ancestors that are more closely related to living ruminants than to other members of Artiodactyla. When considering only living taxa (neontology), this makes Ruminantiamorpha and Ruminantia synonymous, and only Ruminantia is used. Thus, Ruminantiamorpha is only used in the context of paleontology. Accordingly, Spaulding grouped some genera of the extinct family Anthracotheriidae within Ruminantiamorpha (but not in Ruminantia), but placed others within Ruminantiamorpha's sister clade, Cetancodontamorpha. Ruminantia's placement within Artiodactyla can be represented in the following cladogram: Within Ruminantia, the Tragulidae (mouse deer) are considered the most basal family, with the remaining ruminants classified as belonging to the infraorder Pecora. Until the beginning of the 21st century it was understood that the family Moschidae (musk deer) was sister to Cervidae. However, a 2003 phylogenetic study by Alexandre Hassanin (of National Museum of Natural History, France) and colleagues, based on mitochondrial and nuclear analyses, revealed that Moschidae and Bovidae form a clade sister to Cervidae. According to the study, Cervidae diverged from the Bovidae-Moschidae clade 27 to 28 million years ago. The following cladogram is based on a large-scale genome ruminant genome sequence study from 2019: Classification ORDER ARTIODACTYLA Suborder Tylopoda: camels and llamas, 7 living species in 3 genera Suborder Suina: pigs and peccaries Suborder Cetruminantia: ruminants, whales and hippos unranked Ruminantia Infraorder Tragulina (paraphyletic) Family †Prodremotheriidae Family †Hypertragulidae Family †Praetragulidae Family †Protoceratidae Family Tragulidae: chevrotains, 6 living species in 4 genera Family †Archaeomerycidae Family †Lophiomerycidae Infraorder Pecora Family Cervidae: deer and moose, 49 living species in 16 genera Family †Gelocidae Family †Palaeomerycidae Family †Hoplitomerycidae Family †Climacoceratidae Family Giraffidae: giraffe and okapi, 2 living species in 2 genera Family Antilocapridae: pronghorn, one living species in one genus Family †Leptomerycidae Family Moschidae: musk deer, 4 living species in one genus Family Bovidae: cattle, goats, sheep, and antelope, 143 living