Scales found in 236-million-year-old dung heap push back existence of butterflies

New finding dating back 236 million years are pushing the known existence of butterflies and moths further into the past. A team of archaeologists and paleontologists from several Argentine institutes, in collaboration with a colleague from Great Britain, ancient Lepidoptera scales in dung samples excavated from Talampaya National Park.

The find may fill a crucial gap in the fossil record of Lepidoptera. Prior physical evidence of these insects only extended back to 201 million years ago, leaving a 40-million-year gap in understanding their early evolution. This new discovery not only bridges that gap but also suggests that lepidopterans were thriving much earlier than previously believed.

Excavations at the Talampaya site began in 2011. As the work progressed, researchers realized that the area once served as an ancient communal latrine. Numerous animals, including large herbivores, repeatedly used the same place for urinating or defecating. Dung samples collected from this site were sent to various institutions for study.

One particular dung sample found its way to the Argentine Regional Center for Scientific Research and Technology Transfer in La Rioja. It was here that scientists involved in this research discovered the lepidopteran scales. Taking the sample back to their laboratory, they conducted extensive analyses to determine its age and contents.

Using a variety of dating techniques, the team established that the dung sample is approximately 236 million years old, placing it squarely in the middle of the Triassic period. This era is noteworthy as it occurred just 16 million years after the Permian extinction, a catastrophic event that wiped out about 90% of all animal species on Earth.

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Under microscopic examination, the researchers found miniature scales, each measuring around 200 microns in length. These scales were identified as belonging to lepidopterans, specifically moths or butterflies. The morphology of the scales suggested they were from a subgroup known as Glossata.

Glossata are characterized by a specialized feeding apparatus—a proboscis—that modern moths and butterflies use to extract nectar from flowers. However, during the Triassic period, flowers as we know them did not yet exist. This means that these ancient moths and butterflies must have fed on alternative sources.

The scientists concluded that Ampatiri eloisae, the name they have proposed for this newly discovered species, likely sustained itself by feeding on sugary droplets produced by coniferous trees and sago palms. This adaptation shows the resourcefulness of early lepidopterans in exploiting food sources in their environment.

Publishing their findings in the Journal of South American Earth Sciences, the team opened avenues for understanding the evolution of Lepidoptera. The discovery challenges previous assumptions about when these insects first appeared and how they survived in prehistoric ecosystems.

This dung, preserved through the eons, provided a window into a world few could have imagined. The presence of lepidopteran scales in such ancient samples suggests that the diversification of insects after the Permian extinction happened more rapidly than previously thought. It also underscores the importance of coprolites—fossilized dung—as resources for paleontological research.

The research underscores the interconnectedness of ancient ecosystems. Large herbivores contributed to the preservation of microscopic organisms through their dung, which in turn has become a treasure trove for modern scientists. The communal latrine site at Talampaya National Park proved to be an archive of biological information from the distant past.

In light of the discovery, paleontologists are optimistic about uncovering more evidence that could further reshape our understanding of insect evolution. The team hopes that continued excavation and analysis will reveal additional specimens, offering deeper insights into how these early moths and butterflies adapted to their environments and how they may have influenced the ecosystems of their time.