Slabs at the excavation site in western Utah with circles indicating the locations of Elrathia kingii fossils, some of which can be as small as half a millimeter long. Credit: M. Hopkins/AMNH
Phys.org has an article about probably the most common trilobites, Elrathia kingii. The article is about new research that used this trilobite to understand the ontogeny of this iconic species. The research can be found in a paper in the journal Papers in Palaeontology.
If you've ever held a trilobite fossil, seen one in a classroom, or walked by one in a store, chances are it was Elrathia kingii, one of the most common and well-recognized trilobites, and collected by the hundreds of thousands in western Utah. But despite the popularity of this species, scientists had not determined how it grew—from hatchling to juvenile to adult—until now. New work from the American Museum of Natural History published today in the journal Papers in Palaeontology describes the development and growth rate of Elrathia kingii—only the second such dataset to be compiled for a trilobite—allowing for the first comparison among trilobite species.
"There's quite a big size range among trilobites. Some never got bigger than about a centimeter, while the largest on record is 72 centimeters (28 inches)," said Melanie Hopkins, an associate curator in the Museum's Division of Paleontology and the study's author. "Growth-rate studies like this one can help us tackle some of the big-picture questions: How did some trilobites get so big? What was the environmental context for that? And how did body size evolve over the evolutionary history of the clade?"
Trilobites are a group of extinct marine arthropods—distantly related to the horseshoe crab—that lived for almost 300 million years. They were incredibly diverse, with more than 20,000 described species. Their fossilized exoskeletons are preserved in sites all over the world, from the United States to China. Like insects, they molted throughout their lifetimes, leaving clues to how they changed during development. But to calculate the species' growth rate, scientists need fossils representing all stages of the animal's life—and lots of them.
