Dr David Christophel with part of the Anglesea collection.
Image: Nicole Alley
Source: Museum Victoria
Dr David Christophel has transferred his collection of ancient Anglesea leaves to the museum’s Palaeobotany Collection. Around 250 types of rainforest plants are represented in the collection, which was discovered in the Alcoa coal mine in the 1970s.
Trapped in layers of damp compressed mud, the leaves remained soft and pliable for 40 million years. Preservation in this way allows survival of the more durable structures – such as the waxy cuticle and tough veins – to perfectly record the anatomy of the leaf.
Dr Christophel has spent much of his career at the University of Adelaide studying these leaves. His work tells a story about Victoria’s coastline during the Eocene period, when a very different climate allowed dense tropical rainforest to flourish. “It’s basically fossilised leaf litter,” he said during a visit to the museum to oversee the collection transfer. The Anglesea collection has been moved to Victoria since he believes that important specimens “should be held where they came from.”
Between 5,000 and 10,000 specimens were removed from the mine as excavation work uncovered the mudstone deposit. “As the rock dried out, the leaves would curl up, fall to bits and blow away,” described Dr Christophel. Through trial and error, he developed a technique to remove the leaves from the rock unharmed: submerging the rock in peroxide solution creates microbubbles of oxygen that gently prise the leaf loose.
The leaves are now preserved between glass plates and are quite beautiful. At first glance, they might be leaves freshly collected from the forest floor. However examination of their vein structure and microscopic characters shows that some of the plants have relatives living in Queensland rainforests, while over 200 varieties have not been linked to any extant plant families. Certainly, no plants like this survive in Anglesea.
Paleobotanists like Dr Christophel use clues from living plants to study how plants evolved. Many plants are identified from their fruit and flowers, rather than their leaves, which makes his work especially challenging. One of the most common leaves looks much like a eucalypt but is unrelated. “There is no family of living Queensland rainforest plants that it belongs to. So it’s either a completely extinct family or else it’s something which now only exists in an obscure rainforest somewhere else and we haven’t discovered it.”
Other specimens have revealed their secrets more readily. One type of leaf was placed in the ebony family, the Ebenaceae, after Dr Christophel identified a microscopic five-pointed structure unique to this family. Evidence of the Ebenaceae in Australia so early has completely reversed theories about the evolution of this family, suggesting that it arose in Australia and dispersed across a land bridge to the Indomalayan tropics where several hundred members of this family persist today.
With around 3,600 living Queensland species to compare the specimens against, identifying the leaves is a slow process. “The lifetime of me and several of my students haven’t been enough to conquer Anglesea, but we’ve preserved them for posterity.” Dr Christophel hopes to visit the museum and continue work on the specimens in his spare time. “It’s still my passion.”