Horse
The horse adapted to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not. Horses and other equids are odd-toed ungulates of the order Perissodactyla, a group of mammals that was dominant during the Tertiary period. In the past, this order contained 14 families, but only three—Equidae (the horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)—have survived to the present day.
Equisetaceae
All living horsetails are placed in the genus "Equisetum". But there are some fossil species that are not assignable to the modern genus. "Equisetites" is a "wastebin taxon" uniting all sorts of large horsetails from the Mesozoic; it is almost certainly paraphyletic and would probably warrant being subsumed in "Equisetum". But while some of the species placed there are likely to be ancestral to the modern horsetails, there have been reports of secondary growth in other "Equisetites", and these probably represent a distinct and now-extinct horsetail lineage. "Equicalastrobus" is the name given to fossil horsetail strobili, which probably mostly or completely belong to the (sterile) plants placed in "Equisetites".