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. Until the beginning of the 21st century it was understood that the family Moschidae (musk deer) was sister to Cervidae. Within Ruminantia, the Tragulidae (mouse deer) are considered the most basal family, with the remaining ruminants classified as belonging to the infraorder Pecora. Ruminantia's placement within Artiodactyla can be represented in the following cladogram: Artiodactyla 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. ![]() Thus, Ruminantiamorpha is only used in the context of paleontology. When considering only living taxa ( neontology), this makes Ruminantiamorpha and Ruminantia synonymous, and only Ruminantia is used. 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. 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. Ruminantiamorpha is a higher-level clade of artiodactyls, cladistically defined by Spaulding et al. as "the least inclusive clade that includes Bos taurus (cow) and Tragulus napu (mouse deer)". Ruminantia is a crown group of ruminants within the order Artiodactyla, cladistically defined by Spaulding et al. In smaller hindgut fermenters of the order Lagomorpha (rabbits, hares, and pikas), and Caviomorph rodents ( Guinea pigs, capybaras, etc), cecotropes formed in the cecum are passed through the large intestine and subsequently reingested to allow another opportunity to absorb nutrients. These hindgut fermenters digest cellulose in an enlarged cecum. Monogastric herbivores, such as rhinoceroses, horses, guinea pigs, and rabbits, are not ruminants, as they have a simple single-chambered stomach. However, their anatomy and method of digestion differs significantly from that of a four-chambered ruminant. Pseudoruminants, like traditional ruminants, are foregut fermentors and most ruminate or chew cud. The Hippopotamidae (comprising hippopotamuses) are well-known examples. Īlso, some mammals are pseudoruminants, which have a three-compartment stomach instead of four like ruminants. However, Woodall found that there is little correlation between the fiber content of a ruminant's diet and morphological characteristics, meaning that the categorical divisions of ruminants by Hofmann and Stewart warrant further research. Hofmann and Stewart divided ruminants into three major categories based on their feed type and feeding habits: concentrate selectors, intermediate types, and grass/roughage eaters, with the assumption that feeding habits in ruminants cause morphological differences in their digestive systems, including salivary glands, rumen size, and rumen papillae. Taxonomy and evolution An impala swallowing and then regurgitating food – a behaviour known as "chewing the cud" The suborder Ruminantia includes six different families: Tragulidae, Giraffidae, Antilocapridae, Cervidae, Moschidae, and Bovidae. Taxonomically, the suborder Ruminantia is a lineage of herbivorous artiodactyls that includes the most advanced and widespread of the world's ungulates. It has also been suggested that notoungulates also relied on rumination, as opposed to other atlantogenates that rely on the more typical hindgut fermentation, though this is not entirely certain. Ruminating mammals include cattle, all domesticated and wild bovines, goats, sheep, giraffes, deer, gazelles, and antelopes. The roughly 200 species of ruminants include both domestic and wild species. The word "ruminant" comes from the Latin ruminare, which means "to chew over again". ![]() The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The process, which takes place in the front part of the digestive system and therefore is called foregut fermentation, typically requires the fermented ingesta (known as cud) to be regurgitated and chewed again. Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions.
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