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The Mammals Crossed Before the Land Bridge Closed
Fossils in southern Mexico extend north-south mammal movement millions of years before the classic continental interchange.
Summary
Fossils in southern Mexico extend north-south mammal movement millions of years before the classic continental interchange.
Florida State University researchers report fossil evidence that mammals from North and South America were mingling before the Isthmus of Panama fully connected the continents. Smaller species appear farther south about 7 million years ago, and the broader exchange began at least 4 million years before the conventional Great American Biotic Interchange date. The routes may have involved island hopping or rafting rather than a continuous land bridge.
Why it matters
Fossils in southern Mexico extend north-south mammal movement millions of years before the classic continental interchange.
Limits and context
No additional limitation was separately recorded.
Key claims
Fossils in southern Mexico extend north-south mammal movement millions of years before the classic continental interchange.
Evidence: source-2026-07-31-007
Sources
- Florida State University via Newswise: Mammals mingled before the Panama connectionFlorida State University · official announcement
Corrections
No corrections have been recorded for this story.