The earliest species of "Smilodon" is "S. gracilis", which existed from 2.5 million to 500,000 years ago (early Blancan to Irvingtonian ages) and was the successor in North America of "Megantereon", from which it probably evolved.
"Smilodon gracilis" (or "S. fragilis") was the ancestral, smaller, species (2.5 to 0.5 million years ago).
"Smilodon gracilis" (or "S. fragilis") was the ancestral, smaller, species (2.5 to 0.5 million years ago).
Simplification: The earliest species of "Smilodon" is "S. gracilis", which existed from 2.5 million to 500,000 years ago (early Blancan to Irvingtonian ages) and was the successor in North America of "Megantereon", from which it probably evolved. Output: