A farkon zamanin Eocene, sabbin kungiyoyin dabbobi masu shayarwa da yawa sun isa Arewacin Amurka. Wadannan dabbobi masu shayarwa na zamani, kamar artiodactyls, perissodactyls da primates, suna da fasali kamar dogaye, siriri ƙafafu, ƙafafu da hannaye masu iya kamawa, gami da bambance bambancen hakora da aka daidaita don tauna. Siffofin dwarf sun yi mulki. Duk membobin sabbin umarnin dabbobi masu shayarwa sun kasance ƙananan, ƙasa da 10 kg; dangane da kwatancen girman haƙori, dabbobi masu shayarwa na Eocene sun kasance kashi 60% ne kawai na girman dabbobi masu shayarwa na Palaeocene na farko da suka riga su. Sun kasance ƙananan dabbobi masu shayarwa da suka biyo baya.
dogon kafafu masu kauri