Extinct marine life discovered in Thai reserve. Ten newly discovered species of trilobites have been hidden in a little-studied area of Thailand for 490 million years, and they may be the missing piece in the complex puzzle of ancient world geography. Trilobites are extinct sea creatures with half-moon-shaped heads that breathe with their legs. A 100-page monograph published in a British magazine details the new species, including one named after Thai Princess Maha Chakri Sirindhorn.
Ten new trilobite species discovered in Thailand date back 490 million years, providing a unique insight into Earth's geological history and the ancient supercontinent of Gondwana. The picture above is a rendering of a trilobite drawn by an artist based on the preserved software parts. Image source: NobuTamura
Fossil Preservation and Dating Methods
The trilobite fossils were trapped between layers of petrified ash in the sandstone, the product of ancient volcanic eruptions that settled on the ocean floor to form a green layer called tuff. Unlike some other rocks or sediments, tuff contains zircon crystals -- a mineral formed during volcanic eruptions. As the name of the rock formation containing zircon crystals suggests, zircon crystals are extremely hard.
Zircon has stable chemical properties, heat and weather resistance. It's as hard as steel and remains when minerals in other types of rock are eroded away. In these ductile zircon crystals, individual uranium atoms gradually decay and transform into lead atoms.
"We can use radioisotope techniques to date the formation of zircons, and thus find the age of volcanic eruptions and the age of fossils," said co-author Nigel Hughes, a professor of geology at the University of California, Riverside.
This discovery is of great significance in the history of the earth. Tuffs from this special period were very rare during the late Cambrian period between 497 million and 485 million years ago. "Not many places in the world have tuff like this. It's one of the oldest periods in Earth's history," Hughes said.
"Not only will these tuffs allow us to date fossils found in Thailand, but they will also give us a better understanding of other parts of the world, such as China, Australia and even North America, where similar fossils have been found in these undated rocks," said Shelly Wernette, a former geologist at the Hughes Laboratory and first author on the monograph, now at Texas State University.
The fossils were discovered off the coast of an island called KoTarutao. The island is about a 40-minute high-speed boat ride southwest of the mainland and is part of a UNESCO Geopark.
Global Impact and Future Research
For Warnett, the most interesting finds were 12 species of trilobites that had been seen elsewhere in the world but never in Thailand. "We can now connect parts of Thailand and Australia, which is a really exciting discovery."
During the trilobite's lifetime, this region was located on the outer edge of Gondwana, an ancient supercontinent that included Africa, India, Australia, South America, and Antarctica.
"Because continents move over time, part of our job is to study how this region of Thailand relates to the rest of Gondwana," Hughes said. "We're trying to piece together a moving, ever-changing three-dimensional puzzle. This discovery will help us do that."
For example, the species named after Princess Sirindhorn. The species was named in honor of the princess' unwavering devotion to the advancement of science in Thailand. "I also think this species has a majestic air. It has a broad headdress and clean lines," Warnett said.
If researchers can get a date from the tuff containing her namesake species, Tsinaniasirindhornae, and determine when they lived, they will be able to say that closely related Tsinania species found in northern and southern China are of roughly the same age.
Ultimately, the researchers believe that the hidden picture of the ancient world contained in the fossils they discovered contains information that is very valuable to the present day.
"What we see here is a chronicle of evolutionary change that accompanied extinction. The Earth wrote this record for us, and we are lucky to have it," Hughes said. "The more we learn from them, the better equipped we will be to meet the challenges we design for ourselves on Earth today."