The genesis of eucalyptus trees was Argentina. Now they are extinct there. They thrive in Australia. How did this happen? (Photo Credit: Dave Burbank)

Secrets of an Extinct Landscape

Cornell Research
Jul 22, 2019 · 6 min read

by Colton Poore

Standing on the edge of a quarry in Patagonia, Argentina, one can easily take in the beauty of the landscape. Hills covered delicately with grasses stream into the horizon. The sky is big and blue and grand. Yet there is a secret history to this world, bordering on the unbelievable.

From this rocky outcrop with arid land stretching in every direction, it is hard to imagine that this land could ever have been a rainforest profuse with trees and greenery or that parts of it were submerged with aquatic plants dotting the water’s surface. It is hard to imagine that a landscape, which seems so unchangeable, so permanent, could have once been so radically different from itself. That is the land’s secret, and it is only accessible to those who know where and how to look.

That is precisely what María Alejandra Gandolfo-Nixon, a plant biology professor at Cornell University, is doing while standing in the quarry — looking. She and the paleontologists with her on the expedition are sorting through rocks and splitting them apart, uncovering a world of antiquity. They are piecing together a hidden landscape with the fossils they discover — clues that history has left behind for the curious. In paleontology, fieldwork is like some sort of magic.

“The minute we leave the field, we want to go back. There are so many things there — fossils that are 55 million years old or 80 million years old or 120 million years old. And I’m the first person in the world that gets to see it. That’s a feeling that never goes away,” Gandolfo-Nixon says.

Eucalyptus Trees — Vanished from Argentina But Growing in Australia

The Gandolfo-Nixon lab studies the origin of Southern Hemisphere floras. “I initially became interested in the biogeographical patterns of extant plants — how these plants are distributed and how they have dispersed until they get to where we find them alive today. But I realized that I needed the fossil record in order to do that,” explains Gandolfo-Nixon.

Gandolfo-Nixon’s work has raised major discussions about where certain families of plants originated and how changing climate patterns have facilitated their dispersal.

Gandolfo-Nixon documented the oldest known record of the Eucalyptus genus on a fieldwork expedition to Patagonia. What’s intriguing is that Eucalyptus currently grows only in Australia and some nearby islands in Oceania. It is completely absent in South America. So how did Eucalyptus fossils end up in Argentina?

Millions of years ago, the continents South America, Australia, Africa, and Antarctica were all connected in one landmass known as Gondwana. Plants and animals could disperse freely throughout this region until the continent broke up about 180 million years ago. The Eucalyptus fossils that Gandolfo-Nixon and her colleagues discovered date back to the early Eocene — roughly 52 million years ago. By this time, Gondwana had separated.

What Gandolfo-Nixon’s fossil shows is that there was a line of the Eucalyptus genus that was ultimately extirpated from South America, while it persists in modern day Australia. The fossils they found are also the oldest known record of the entire Eucalyptus genus, suggesting that the family itself had originated and diversified much earlier than was previously believed.

Piecing Together the History of the Natural World

At the center of Gandolfo-Nixon’s work is also the flora surrounding the K-Pg (Cretaceous-Paleogene) Boundary. This was the mass extinction event famously responsible for the elimination of all dinosaurs, excluding birds. Yet many plant taxa seem to have survived and crossed the boundary. “We have found many fossil aquatic ferns from the early Danian, which is the time period directly following the K-Pg Boundary, that are so well preserved that they simply wouldn’t have had the time to originate and diversify that quickly. They had to have already existed well before the boundary,” says Gandolfo-Nixon.

In her research, Gandolfo-Nixon is piecing together the history of the natural world. “It’s really exciting to think about,” she says. “Because once you have characterized all the types of plants that were living in the area, you can start to reconstruct what that environment must have resembled. And then you can start to draw conclusions about the type of climate that existed in that part of the world five, ten, or 100 million years ago.”

Antarctica was once full of beautiful temperate forests. The arid sites of Patagonia were once like the temperate forests found in some areas of present-day Australia and New Zealand.

Carrying the Water, Pitching the Tents: The Rigor of Paleobotany Fieldwork

Gandolfo-Nixon conducts fieldwork in Patagonia several times each year, collecting the fossils that she will be working with once she returns to Cornell. “It’s definitely hard work. We’re out there for two to three weeks at a time, camping in tents. Sometimes we even have to carry in all of the water we will need, because there is no source of water nearby,” she says.

“Two things really move me: one is fieldwork — seeing the excitement in a student’s eyes when they pick up a fossil that no one has ever seen before — and the other is teaching.”

Gandolfo-Nixon continues, “But fieldwork is fundamental to any paleobotanist. If you’re not comfortable with it, it’s very hard to become one. And ever since I was young, I’ve always enjoyed being outside. I never wanted to work in an office all day long. I went on a fieldwork expedition as an undergraduate, and I immediately fell in love with the type of work that you do in paleobotany.”

Despite her passion for fieldwork, Gandolfo-Nixon also values the opportunity she has as a professor to teach and inspire others. “Two things really move me: one is fieldwork — seeing the excitement in a student’s eyes when they pick up a fossil that no one has ever seen before — and the other is teaching. Teaching is probably one of the best things for a researcher. It opens your mind to what your students are interested in doing,” she says.

Teaching the Beauty of the Natural World

Teaching allows Gandolfo-Nixon to showcase to others what she loves about the world and to pass it on to the next generation. “What motivates me more than anything is to show the beauty of the world to the students — to teach them about all the things they don’t know yet and to show them that there are things that still need to be discovered and things that still need to be worked on,” she says.

It is believed that scientists only know about five percent of the entire fossil record. As paleontologists conduct fieldwork at sites that haven’t been explored before, they gain new insights into the natural history of the world: what it looked like, what life existed on it, and how it changed.

As more fossils from the underexplored Southern Hemisphere are discovered, new species and lineages are described, and pre-existing species are redefined, scientists begin to understand more completely the evolutionary processes registered in the fossil record. Gandolfo-Nixon says, “There are always a lot of new techniques that we use, not only to preserve and classify the fossils we find in the field, but also to improve upon the fossil descriptions that scientists have already discovered. Paleobotany is exciting because it is always growing.”

Photo Credit: Dave Burbank

Originally published on the Cornell Research website. All rights are reserved in the images. If you’d like to reproduce the text for noncommercial purposes, please contact us.

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