Plate Nº 40 · recorded November 5, 2026
Biology & EvolutionReported finding
Amber Fossils Show Australia Fragment Seeded Asia's Rainforests
Plant fossils in 100-million-year-old Myanmar amber show a crustal fragment from Australia carried hundreds of plant lineages across the Tethys Ocean to seed Southeast Asia's rainforests.
By Marcus Bennett3 min read688 words
In brief
- Study published Oct. 27 in Nature Ecology & Evolution analyzed 3,000+ plant fossils in ~100-million-year-old Myanmar amber
- The West Burma Block split from northwestern Australia ~150 million years ago and collided with Southeast Asia starting ~50 million years ago
- Fossils include at least 392 types of flowering plants plus conifers, ferns, mosses, cycads and liverworts
- The Indian Plate, moving 4 inches (10 cm) per year, struck the block ~80 million years ago before both hit Asia
Roughly 50 million years ago, a fragment of crust that broke away from Australia collided with Southeast Asia and seeded the tropical forests that define the region today — that is the central finding of a study published Oct. 27 in the journal Nature Ecology & Evolution, based on more than 3,000 plant fossils preserved in Myanmar amber.
The fragment, called the West Burma Block (or Burma terrane), split from what is now northwestern Australia about 150 million years ago. It carried hundreds of flowering plant species and a wide collection of other ancient plants north across the prehistoric Tethys Ocean, eventually building the lush ecosystems of modern Southeast Asia.
The finding overturns two earlier assumptions: that the fragment originated closer to present-day Southeast Asia, and that the region's tropical forests evolved only after the non-avian dinosaurs went extinct around 66 million years ago.
What did the researchers actually examine?
The team analyzed plant fossils trapped in amber roughly 100 million years old, mined from the north end of a valley in western Myanmar. Amber — tree resin that hardened into a translucent time capsule — preserved flowers, leaves, fruits and seeds in three dimensions.
The assemblage includes:
- at least 392 types of flowering plants;
- conifers, ferns, mosses, cycads and liverworts.
All of these lineages, the researchers argue, reached Southeast Asia by riding the West Burma Block across the ocean.
"The rich tropical rainforest flora of [Southeast Asia] is not endemic but owes much of its biota to the great southern land, Gondwana," study co-author Byron Lamont, distinguished professor emeritus at Curtin University's School of Molecular and Life Sciences in Australia, told Live Science in an email. At the time the block broke free, Australia sat joined to Antarctica and India within the supercontinent Gondwana, which the Tethys Ocean separated from the northern supercontinent Laurasia.
How did a drifting island become a biodiversity cradle?
The answer lies in geography plus climate. After drifting northward for 100 million years, the microplate spent tens of millions of years hovering near the equator, where conditions were hot and humid much as they are now. That climate, combined with the block's isolation, created a refuge where ancient plant lineages could survive and diversify, Lamont said.
The journey's final leg was violent. Around 100 million years ago the Indian subcontinent was also crossing the Tethys Ocean, moving at a brisk 4 inches (10 centimeters) per year. About 80 million years ago the Indian Plate bumped into the West Burma Block, altering its orientation, then shoved it along until both collided with Asia. The Indian Plate slid beneath the Eurasian Plate to build the Himalayas, while the West Burma Block ground to a halt west of present-day Myanmar, forming a deep valley between mountain ranges about 35 million years ago.
Both the Indian Plate and the block "took some time to stop," Lamont said.
What are the study's limits?
The fossil record here has a built-in bias: only creatures small enough to be trapped in resin appear in it. The animals found in the amber are small insects such as ants and mosquitoes. Iconic Australian vertebrates — marsupials, emus, nectar-feeding birds — reached Australia from South America more than 100 million years after the block split off, and would never have been caught in resin anyway, Lamont noted.
The findings do not mean Australia lost its ancient flora. Descendants of many plants found in the 100 million-year-old amber still grow in Australia's hot, humid Northeast today.
How did the amber reach scientists?
The amber has been mined from the valley's north end for at least a century, and its three-dimensional fossils have long drawn interest for their novelty alone — including commercial interest, especially from Chinese traders, Lamont said. Some co-authors bought amber chunks from traders at least a decade ago and have studied them since, drawing on advice from experts at institutions worldwide; that is how Lamont joined the project.
In short: a piece of Gondwana ferried an entire flora across an ocean, and Southeast Asia's rainforests still carry the receipt.
via doi.org (Original)
More from Marcus Bennett
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News editor covering regulation, policy and their impact on general science news at SciBeat.
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