Geologists discovered fossil evidence of mesohippus, an ancestor of the modern horse. mesohippus lived in north america about 40 million years ago. mesohippus was about two feet tall, ran on hooves with three toes, and had large, grinding teeth. what statement is best supported by the fossil evidence? a) ancient horses were once carnivores. b) horses have evolved over the last 40 million years. c) horses migrated from south america into north america. d) modern-day horses share a common ancestor with all mammals.