Paleo Gondwanaland Was Full of Lystrosaurs (Cont.)
Page 2/2 - Posted May 3, 2018
“Right at the end of the Permian, you have a lot of fossil forests with stumps in place and lots of Glossopteris leaves. Then you get the boundary event and you get a real sort of gap in the plant fossil record, but you have these early vertebrates showing up,” Makovicky said. “It’s quite a stratigraphic distance up section before you start picking up good abundant amounts of fossil wood and coal and indications that you’re back to a highly productive forested ecosystem again.”
Photo Credit: Mike Lucibella
Paleontologist Roger smith uses his rock hammer to pry away rocks to get at a fossil embedded in a cliff face.
By looking at which species first started appearing, the team can garner insights into how ecosystems as a whole tend to recover after a calamitous extinction event.
“We’ll also go into more nuanced questions about the biology of the animals themselves by doing histological studies to study patterns of growth or physiology from the animals… to try and understand if there are any traits or characteristics that are different in these animals that are living under a polar light regime than there are in their close relatives in other parts of the world like South Africa,” Smith said.
It’s a part of the project that Meg Whitney, graduate student at the University of Washington, is focused on, studying the biology of Lystrosaurus, a four-legged tusked creature about the size of a small pig that was a relative of mammals.
“They’re our close relatives,” Whitney said. “They’re more closely related to us than dinosaurs.”
They were by all measures a widely successful species, and ultimately became the most abundant terrestrial vertebrate in the Early Triassic. They were hardy generalists that have been found all over the world and were one of the few species to survive through the Permian-Triassic boundary.
“They were these really abundant animals,” Whitney said. “They were kind of these super survivors. They lived across the globe and they survived the largest mass extinction that the earth has seen to date.”
"They’re our close relatives," Whitney said. "They're more closely related to us than dinosaurs."
It’s these traits that make them so fascinating to researchers. While more than 90 percent of the species on Earth went extinct at the end of the Permian, Lystrosaurus survived well into the Triassic era.
“It’s an important animal to understand its biology because it’s an animal that made it through the largest mass extinction.” Whitney said. “We’re always thinking about that with our work because we’re in the middle of one right now… We want to know if there are things about this animal that made it more likely to make it through this mass extinction, and if there is something we can then apply to understanding conservation efforts today. But that’s first going to have to come from a basic understanding of their biology.”
The fossils discovered in Antarctica offer a unique insight into that biology. Whitney’s project delving into the predicted biological differences between Lystrosaurus living in the polar regions and their mid-latitude relatives.
Even 250 million years ago, Antarctica was already located near Earth’s geographic south pole and subject to months of perpetual darkness and sunlight. Animals that live in similar conditions today usually show various signs that during the cold dark winter months, they’re under a lot of stress and don’t grow nearly as much as they do during the bright, fertile summer.
Whitney is looking for evidence of this embedded in their teeth.
“We expect to see these longer durations of stress inside their tusks and we expect to see this kind of pulse of growth that’s super rapid,” Whitney said. “That’s just based off of modern ecosystems today, thinking about how animals adapt to living in that kind of environment. We expect Lystrosaurus to be doing something similar.”
Photo Credit: Mike Lucibella
The team operated out of the Shackleton Glacier camp, located in the Transantarctic mountains, about 400 miles away from McMurdo Station.
The cross-section of a Lystrosaurus tusk resembles the trunk of a tree with growth rings reflecting periods of growth and no growth. The team found about half a dozen marker-sized tusks this season that Whitney plans to analyze under a microscope. By comparing these Antarctic specimens with ones from India, China and South Africa, she hopes to be able to see a different pattern in the polar dwellers.
“There’s a lot of things that can influence these growth patterns, and so when you study them, you want to control for as many of these variables as you can. That includes using the same species, trying to get the same, more or less, snapshot of time across different places on Earth,” Whitney said. “We are trying to look at the same animal at the same time period, more or less on a geological timescale, and that way any differences we see is likely a result of where they live and not any of these other influences.”
Though the teams have returned from Antarctica and their samples have been brought to the United States, in many ways the project is only just beginning.
“For every hour or so in the field, there’s probably 100 or 200 hours of preparation time to actually remove the fossil form the rock even before you start studying it,” Smith said.
It’s a labor and time-intensive process. They and other preparators have to use delicate tools akin to dental picks and drills to carefully chip away the surrounding rock to remove the delicate fossils within. In addition they’ll put a number of the larger specimens through a CT-scanner to get a clearer view of what’s embedded within the rock.
The team has many months of work ahead of themselves, but they’re looking forward to learning more about this sparsely-studied continent.
“The amount of fieldwork that’s been done in Antarctica by paleontology teams is just scratching the surface,” Sidor said. “Every year you have an opportunity to find something that’s be never seen before.”
NSF-funded research in this story: Christian Sidor of the University of Washington, Award No. 1341304; Peter Makovicky of the Field Museum of Natural History, Award No. 1341645; Nathan Smith of the Natural History Museum of Los Angeles County, Award No. 1341475; Neil Tabor of Southern Methodist University, Award No. 1341376.