{
  "$schema": "https://themachinepress.com/schemas/story-v1.schema.json",
  "schema_version": "1.0.0",
  "document_type": "machine_press_story",
  "story": {
    "story_id": "mp-2026-07-31-007",
    "source_story_id": "tmp-story-pre-panama-mammal-interchange",
    "edition_id": "mp-2026-07-31-morning-0022",
    "edition_url": "https://themachinepress.com/edition/2026-07-31",
    "position": 7,
    "story_type": "dispatch",
    "section": "research",
    "editorial_classification": "editorial",
    "headline": "The Mammals Crossed Before the Land Bridge Closed",
    "slug": "the-mammals-crossed-before-the-land-bridge-closed",
    "dek": "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.",
    "body_text": "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.",
    "limitations": [],
    "importance": 8,
    "canonical_url": "https://themachinepress.com/story/mp-2026-07-31-007/the-mammals-crossed-before-the-land-bridge-closed",
    "json_url": "https://themachinepress.com/story/mp-2026-07-31-007.json",
    "first_published_at": "2026-07-31T09:00:00.000-04:00",
    "modified_at": "2026-07-31T09:00:00.000-04:00",
    "content_status": "new",
    "is_carryover": false,
    "carryover_reason": null,
    "key_claims": [
      {
        "claim_id": "claim-mp-2026-07-31-007-001",
        "text": "Fossils in southern Mexico extend north-south mammal movement millions of years before the classic continental interchange.",
        "source_ids": [
          "source-2026-07-31-007"
        ],
        "qualification": null
      }
    ],
    "source_ids": [
      "source-2026-07-31-007"
    ],
    "tags": [
      "Great American Biotic Interchange",
      "Panama",
      "fossils",
      "mammal migration"
    ],
    "image_url": null,
    "corrections": []
  },
  "sources": [
    {
      "source_id": "source-2026-07-31-007",
      "title": "Florida State University via Newswise: Mammals mingled before the Panama connection",
      "publisher": "Florida State University",
      "url": "https://www.newswise.com/articles/fsu-geologists-discover-north-south-american-mammals-mingled-before-continental-connection",
      "canonical_url": "https://www.newswise.com/articles/fsu-geologists-discover-north-south-american-mammals-mingled-before-continental-connection",
      "source_type": "official_announcement",
      "is_primary_source": true,
      "published_at": null,
      "accessed_at": "2026-07-31T08:31:33.328-04:00",
      "supports_claim_ids": [
        "claim-mp-2026-07-31-007-001"
      ]
    }
  ],
  "corrections": [],
  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
  },
  "cite_this_report": {
    "title": "The Mammals Crossed Before the Land Bridge Closed",
    "publisher": "The Machine Press",
    "published_at": "2026-07-31T09:00:00.000-04:00",
    "canonical_url": "https://themachinepress.com/story/mp-2026-07-31-007/the-mammals-crossed-before-the-land-bridge-closed"
  }
}