A groundbreaking study led by researchers at The University of Texas at Austin has revealed that a 20-centimeter fossil discovered in Scotland in 1984 is 14 million years older than previously thought. The fossil, Westlothiana lizziae, dates back 346 million years and provides critical insights into the transition of vertebrates from water to land. Published in PLOS One, the research fills a gap in the fossil record known as Romer’s Gap, shedding light on one of evolution’s most pivotal milestones.
The fossil, initially found by an amateur paleontologist, belongs to Westlothiana lizziae, one of the earliest four-legged animals to inhabit land. These creatures, known as stem tetrapods, are ancestors to modern amphibians, reptiles, birds, and mammals. Despite their significance, their exact age remained uncertain until Hector Garza, a recent doctoral graduate, employed radiometric dating to analyze zircon crystals embedded in the surrounding rock.
Garza’s work was risky because the fossils were located near ancient volcanic basalt, where zircons are rare. However, his persistence paid off when he extracted zircons from six fossil samples, using uranium-lead dating to determine their age. The results placed the fossils at 346 million years old, squarely within Romer’s Gap—a mysterious period with few fossil records but critical to understanding vertebrate evolution.
“I can’t overstate the importance of the iconic East Kirkland tetrapods,” said Julia Clarke, a co-author of the study. “Better constraining the age of these fossils is key to understanding the timing of vertebrates’ emergence onto land and the environmental factors driving this transition.”
The revised age of Westlothiana lizziae not only highlights the fossil’s significance but also advances our understanding of early land animals. The East Kirkton Quarry, where the fossil was found, continues to be a vital site for uncovering clues about Earth’s evolutionary history. Future research may explore the environmental conditions that facilitated this monumental leap in evolution.
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