Horse
Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus".
Equisetales
In the molecular phylogenetic classification of Smith et al. in 2006, Equisetales, in its present circumscription, was held to be the sole member of class Equisetopsida. The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009) which placed all land plants in Equisetopsida, made it the sole member of subclass Equisetidae, equivalent to Smith's Equisetopsida. The placement of Equisetales in subclass Equisetidae has subsequently been followed in the classifications of Christenhusz and Chase (2014) and PPG I (2016).