Paleontologists have identified two new types of fossil flowers — one identical to those of the living genus Phylica and the other a sister to Phylica — in Cretaceous amber from the Hkamti and Tanaing mines, northern Myanmar, dated to at least 99 million years ago.
The diversification of flowering plants (angiosperms) was one of the major episodes in the history of life that transformed global ecosystems, bringing about the diversification of insects, amphibians, mammals, early birds and other clades, ultimately marking the first time in geological history when life on land became more diverse than life in the sea.
Their rapid radiation between 135 million years ago and 65 million years ago that led the angiosperms to dominate many land environments by the end of the Cretaceous period and replace the incumbent gymnosperms, has fascinated evolutionary biologists starting with Charles Darwin who famously referred to the angiosperm radiation as an ‘abominable mystery.’
However, our knowledge of the early evolution of angiosperm’s most distinctive feature, the flower, is scarce owing to its delicate construction and thus low fossilization potential.
Much of what is known about early angiosperm floral diversity comes from flowers that were rendered biologically inert through burning and conversion to charcoal.
“These exquisitely preserved flowers, fruits, leaves and pollen from 100 million years ago provide a snapshot of an important time in the evolution of flowering plants, showing that early flowers were not primitive as many people suppose, but were already superbly adapted to survive the frequent wildfires that ravaged the warm ‘greenhouse’ world of the Cretaceous,” said Professor Robert Spicer, a researcher in the School of Environment, Earth and Ecosystem Sciences at The Open University and the Key Laboratory of Tropical Forest Ecology at Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences.
“If Darwin had had access to such fossils his ‘abominable mystery,’ as he called the origin of flowering plants, may have been less perplexing as fire was a key component in shaping the evolution of flowers.”
One of the two new species, named Phylica piloburmensis, belongs to the genus Phylica of the family Rhamnaceae, an endangered plant group typical of the unique Cape Fynbos flower, that survives despite frequent wildfires.
The other species, Eophylica priscastellata, represents a sister group to the Phylica genus.
The fossils show that their flowers, fruits, leaves and pollen have not changed despite 100 million years of evolution during which dinosaurs disappeared, mammals diversified, and climate underwent dramatic changes.
Their special structure and ability to survive almost unchanged shows their special adaptations, particularly those that allow them to survive the ravages of fire, have been particularly successful.
The exquisite preservation of the fossil flowers shows they were also fire-adapted due to being found alongside amber, containing partially burned plants.
“On the sustainability front it is worth remembering that as fires become more frequent in our warming world, we may be able to learn a lot from looking back to a time when wildfires were so frequent that they shaped the evolution of the group of plants that dominate much of today’s world vegetation,” Professor Spicer said.
The team’s paper was published in the journal Nature Plants.
C. Shi et al. Fire-prone Rhamnaceae with South African affinities in Cretaceous Myanmar amber. Nat. Plants, published online January 31, 2022; doi: 10.1038/s41477-021-01091-w
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