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Professor uses fossils to answer questions about ancient land mass

Wednesday, February 21, 2024

The study of the fossils of ancient, extinct creatures can not only inform our understanding of species from millions of years ago, but can teach us about the impacts of the earth on biodiversity as well as inform us on the location of different terranes and their proximity to one another at that time, according to Shelly Wernette, a Texas State University Department of Geography and Environmental Studies senior lecturer. She went on TXST’s Big Ideas podcast to discuss her studies of stratigraphy and invertebrate paleontology with special attention to the lower Paleozoic of Gondwana and Trilobites, according to a press release. Through her research, she’s investigating the impacts of the physical earth on biodiversity using paleogeography and geochronology.

“First and foremost I consider myself a geologist, and then I use the fossil record to answer geological questions,” Wernette said. “We know that animals are located in different areas, and the more specialized [and] the more isolated the group of animals is, the more it tells you that that area was restricted and cut off from the previously known areas — typically islands.”

Wernette said her research team was responsible for finding ten previously unknown species of Trilobites, an ocean dwelling creature with no modern descendants, in a little studied part of Vietnam that were alive approximately 540 million to 250 million years ago.

“If you know about isopods — and Rollie Pollies are a type of isopod — they’ve got these bands that allow them to take their shell and roll up into a little ball. And Trilobites are like that as well, but they are not related to isopods,” Wernette said. “All the way to their tail there’s a central ovalshaped bulge down the middle then the two sides of the head, two sides of the middle [and] two sides of the tail. Those two sides plus the middle lobe make up the tri-lobe-ite … Trilobites have two sets of legs that go under all of their segments. They have a whole bunch of legs just like Rollie Pollies, and one of those sets of legs has gills on it. And the other sets of legs have these little bulges that have spikes on them that they use to move and process their food.”

Wernette said the research team would collect rocks with visible fossils in Vietnam and ship them back.

“The nice thing about invertebrates [creatures without a backbone] is that they really are just sitting in the rock at the surface. If you go hiking anywhere in this area, you are likely to come across an image of a shell in the rock. That’s a fossil,” Wernette said. “Depending on where you are, there are hundreds of these things [or] thousands of these things. I lost track of how many fossils I processed. I think by the time it was all said and done it was over 600-something fossils.”

Once Wernette gets the fossils into the lab, they must be cleaned up using small tools and drills, and then many photographs are taken of the specimen in order to compare and identify the species.

“When I break open rock and see it for the first time … you make eye contact with these remains that literally haven’t seen daylight in 498 million years,” Wernette said, adding that she takes the photographs and compares them to the literature. “And I go through what fossils other people have found, and I look at the definition of how they define different species or different groupings. And one by one I try to connect the fossils to those pictures.”

Wernette said that isotopes are used to identify the age of the specimen, but those isotopes come from the ash bed layer — old volcanic ashes — that is in between the fossils. According to the International Atomic Energy Agency isotopes are a type of atom — the smallest unit of matter that retains all the chemical properties of an element — that have the same number of protons but different numbers of neutrons.

“What we’re looking for are those volcanic rocks, the rocks that actually form the crystals as they erupted and they dropped straight onto that … shallow marine water,” Wernette said. “So I have a colleague out of Princeton, he’s doing the dating of the ashbeds. … and then we’ll take the ash beds and apply those dates to the fossils. Then we’ll take the fossils and correlate the dates from the ash bed to other locations that have similar fossils.”

Wernette said the mapping portion of her research is paleogeography, also known as ancient geography, which is identified from comparing fossils from different locations. She said she created a spreadsheet of different fossils, genus and species as well as the location in which they were found.

“I take all of these different terranes, I make a big spreadsheet about where the same thing occurs in each one. And then I use those common occurrences to look at what most likely was … geographically related,” Wernette said, meaning that this can be used to identify where the different land masses were located at that time and their proximity to one another. “Most of the world, we already had a pretty good picture [of where the different land masses were in proximity to one another]. The Sibumasu Terrane, which is the name of the terrane that contains Myanmar and Thailand. Sibumasu was kind of on the outskirts of the big continent called Gondwana, and Gondwana has most of Africa [and] parts of Europe, Australia, Antarctica, India, South America and all of those relative positions were already pretty well known. We’re looking at these smaller continental blocks that were floating around the edges, so North and South China and Sibumasu.”

Wernette said this research is valuable in identifying where certain minerals will be located.

“So if you know that there is a Zinc deposit right in the mountains of Thailand, and you know that it formed 500 million years ago. Well, that Zinc deposit might be continuous with another continent that it was pressed up against at that time. So, we see this especially from the breakup of Pangea,” Wernette said. “[Pangea is] not the only supercontinent we’ve ever had, it’s just the most well known one. When we go up to Maine and up to the region that gets called Abalonia in paleogeography, a lot of those rocks correspond with rocks in Europe. And you can follow some of these mountain areas [and] some volcanic areas right across the Atlantic Ocean. So it really helps open up possibilities for mineral explorations. It also helps us better understand biogeographic trends. … So we can look at the trends in different animals over time and see where the continents have moved around.”

Listen to this episode of the Big Ideas podcast at this link news.txst. edu/inside-txst/big-ideaspodcast/ episode-48 or on Spotify, Anchor or Apple Podcasts.

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