More than a 100 groups of mammals have been found in the early Miocene (37 – 20 mya) John Day Formation that underlies the Mascall near Kimberly, north central Oregon. I'm planning a field trip this August to collect in the fossiliferous strata along the beaches and those of the John Day that have yielded beautifully preserved speciments of many of the animals we see domesticated today.
Primative dogs, cats, swine and horses are common. Oreodonts, opposums, squirrels, rabbits, sabre-tooth cats, camels, rhinoceras and rodents have also been found in this ancient deciduous forested area. Look for modern metasequoia, Oregon's state fossil, once thought extinct but now flourishing in the temperate climate.
Oregon with its rugged coastline is always appealing, but adding in the fossils makes it simply irresistable and a wonderful trip for all ages. The photo below is of my young cousin holding a well-preserved oreodont skull from the Graham Beard Collection, beautifully prepped by 'Renaissance Man,' Rod Bartlett.