ST. DAVID — There’s no telling how many times Milton Curtis stepped over those odd-looking rocks as he went about the day-to-day business of ranching. Back in 1921, life on Curtis Ranch in St. David was filled with cattle and horses and providing for a young family. Things like dinosaurs really weren’t the topic of discussion, nor did they get much attention. But in 1921, that changed. “What my father thought were rocks were actually the tips of tusks from a giant mastodon dinosaur,” chuckled 98-year-old Clea Brown, her eyes sparkling as she talked about a discovery that launched the...