Ten previously undiscovered species of trilobites, concealed for approximately 490 million years within an under-explored area of Thailand, may represent crucial elements in unraveling the complex puzzle of ancient world geography.
Trilobites, ancient marine creatures characterized by half-moon-shaped heads and respiration through their legs, are the focus of a comprehensive 100-page monograph in a British journal, meticulously detailing these new species. Notably, one species is named in honor of Thai Royal Princess Maha Chakri Sirindhorn.
Preserved within layers of petrified ash in sandstone, these trilobite fossils were ensnared by aged volcanic eruptions that settled on the sea floor, forming a distinct green layer known as a tuff. Unlike other rock types, tuffs contain zircon crystals—a mineral formed during eruptions and known for its durability. Zircon remains chemically stable, heat-resistant, as hard as steel, and endures even as minerals in other rock types erode. Encapsulated within these resilient zircon crystals, individual uranium atoms gradually decay over time, transforming into lead atoms.
Nigel Hughes, a co-author of the monograph and a geology professor at UC Riverside, explained: “We can use radio isotope techniques to date when the zircon formed and thus find the age of the eruption, as well as the fossil.”
Discovering tuffs from the late Cambrian period (approximately 497 to 485 million years ago) is rare. Hughes remarked, “Not many places around the world have this. It is one of the worst-dated intervals of time in Earth’s history.”
Shelly Wernette, former geologist at Hughes’ lab (now at Texas State University) and the monograph’s first author, emphasized the significance of these findings, stating, “The tuffs will allow us to not only determine the age of the fossils we found in Thailand, but to better understand parts of the world like China, Australia, and even North America where similar fossils have been found in rocks that cannot be dated.”
Unearthed on the coast of Ko Tarutao island, this discovery has crucial implications. Wernette noted the revelation of 12 trilobite types previously observed elsewhere but never before in Thailand, connecting Thailand to parts of Australia.
During the trilobites’ era, this region resided on the periphery of Gondwanaland, an ancient supercontinent encompassing Africa, India, Australia, South America, and Antarctica. Hughes explained, “Continents shift over time, and part of our work involves locating this Thai region in relation to the rest of Gondwanaland. It’s akin to solving a dynamic, shape-shifting, three-dimensional jigsaw puzzle.”
The species named after Royal Princess Sirindhorn could potentially aid in determining the age of related species in China, showcasing the interconnectedness of these findings across regions.
“What we have here is a chronicle of evolutionary change accompanied by extinctions. The Earth has written this record for us, and we’re fortunate to have it,” Hughes said. “The more we learn from it the better prepared we are for the challenges we’re engineering on the planet for ourselves today.”
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