Geologists have discovered 10 new species of trilobite in a relatively unstudied area of Thailand. These extinct sea creatures were hidden for 490 million years and are helping scientists create a new map of the animal life during the late Cambrian period. They are described in a monograph that was published in October in the journal Papers in Palaeontology.
[Related: These ancient trilobites are forever frozen in a conga line.]
Trilobites were marine arthropods similar to today’s spiders and crustaceans and are known for a wide variety of body designs. A species called Walliserops may have jousted with ‘tridents’ on their heads to win mates and recent trilobite specimens have been found with full stomachs. More than 20,000 species lived in Earth’s seas before they went extinct about 250 million years ago.
The trilobite fossils described in the new paper were trapped between layers of petrified ash in sandstone and were the product of old volcanic eruptions. The sediment from the eruptions settled on the bottom of the sea and formed a green layer called a tuff. This important layer contains crystals of a critical mineral that formed during the eruption called zircon. Aside from being as tough as steel, zircon is chemically stable and heat and weather resistant. Zircon also persists while the minerals in other kinds of rocks erode over time. Individual atoms of uranium that transform into lead live inside these resilient zircon crystals and give paleontologists a benchmark for dating the fossils.
“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,” study co-author and University of California, Riverside geologist Nigel Hughes said in a statement.
Finding tuffs from the late Cambrian period (between 497 and 485 million years ago) is also rather rare. According to the team, it is one of the “worst dated” intervals of time in Earth’s…
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