What is Equidae?
Equidae is the taxonomic family of horses and related animals, including asses, zebras, and many extinct species known only from fossils. All living species belong to the single genus Equus.
Questions about Equidae
Short answers, pulled from the story.
When did Equidae evolve?
Equidae evolved more than 50 million years ago in the Eocene epoch. The oldest known fossils assigned to the family were found in North America and date from the early Eocene, 54 million years ago.
How did Equidae change from its early ancestors to modern horses?
Early equids were fox-sized browsers with three toes on the hind feet and four on the front feet, feeding on relatively soft plants. Over time they reduced the number of toes, developed grinding teeth for tough plant food, and shifted to bearing weight on the central third toe.
What order and superfamily does Equidae belong to?
Equidae belongs to the order Perissodactyla, which also includes the tapirs and rhinoceros. Within that order it sits in the superfamily Equoidea, whose only other family is the extinct Palaeotheriidae.
Why are Equidae called hindgut fermenters?
Equidae are hindgut fermenters, like other perissodactyls, and have evolved specialized teeth that cut and shear tough plant matter for a fibrous diet. This digestion strategy reflects their relatively large body size at the time it evolved.
What is the genus Equus and how many species does it have?
Equus is the sole surviving genus of Equidae and originated in North America. The record holds 22 species in the genus, of which 7 are extant, and it had evolved by the early Pleistocene before spreading rapidly through the world.