The Postal Service issued four 32-cent Prehistoric Animals commemorative stamps, in a pane of 20, on June 8, 1996 in conjunction with the CAPEX '96 World Philatelic Exhibition in Toronto, Canada. These stamps were deferred from 1995 to 1996, due to technical problems in the printing process. The four stamps were designed by Davis Meltzer of Huntingdon Valley, Pennsylvania. The stamps feature four mysterious creatures from the past: the eohippus, woolly mammoth, mastodon, and the saber-toothed cat.
The eohippus, the earliest relative of the horse, roamed North America more than 50 million years ago. This small, horse-like creature was roughly the size of a whippet dog, with four toes on its front feet and three toes behind. The eohippus is the earliest known ancestor of the family tree of horses that evolved into many creatures we know today, including zebras.
First discovered in drawings on the walls of prehistoric cave dwellings in France and later recovered from the age-old Siberian permafrost, the woolly mammoth is thought to be the ancestor of the Asian elephant. At first glance, the woolly mammoth resembles the present-day elephant, but on closer inspection its differences become apparent. Distinguished by its thick coat of black wool and long drooping "guard-hairs," the woolly mammoth carried large fat deposits on its shoulders and head that scientists believe provided reserve energy for the extreme conditions in which it lived and roamed.
The American mastodon was the last of a long line of diverse elephants that roamed the Earth during the last Ice Age. About the size of current-day Asian elephants, this enormous, gentle species roamed the continent of North America from Alaska to Florida. Strict vegetarians, these great creatures fed on small shrubs and other bog vegetation. Like their counterpart the woolly mammoth, mastodons disappeared at the close of the last Ice Age, roughly 10,000 years ago.
The saber-toothed cat, boasting large, blade-like canine teeth as long as 6 inches, roamed throughout North and South America. These sleek yet ferocious saber-toothed cats are thought to have preyed on large-bodied mammals such as the offspring of woolly mammoths and mastodons. They, too, became extinct during the last Ice Age.
The Prehistoric Animals commemorative stamps went on sale nationwide on June 10, 1996. The stamps were produced by Ashton-Potter (USA) Ltd. in the offset process.
Reference: Postal Bulletin (May 9, 1996)