A fossil that sat misidentified in scientific literature for nearly forty years has turned out to be one of the earliest known insects, and it is reshaping how scientists think insects made the leap from water to land.

The specimen, named Chosha praecursor, was collected in 1985 from a shale bed in the Tesnus Formation near Big Bend National Park in Texas. For decades it was classified as a juvenile of an aquatic crustacean called Tesnusocaris goldichi. A new re-examination, using cross-polarized light imaging to reveal anatomical details invisible to earlier researchers, has overturned that identification entirely.

A creature caught between two worlds

According to the study, published in Nature on 26 August 2026, Chosha praecursor lived around 324 million years ago, during the Late Mississippian part of the Carboniferous period. It had the three pairs of walking legs that define modern insects, along with an ovipositor for laying eggs, a tail-like filament and a single pair of unbranched antennae.

But it also retained something no living insect has: paddle-like, multisegmented limbs along its abdomen, structures more typical of aquatic arthropods. Some outlets covering the findings, including Science News, have described the animal as having 24 legs in total, six for walking and 18 additional paddle-like limbs.

That combination is the crux of the discovery. Rather than insects making an abrupt jump from swimming ancestors to fully terrestrial, six-legged bodies, the fossil suggests a long amphibious phase in which both traits coexisted.

Revisiting old collections

The study was led by Chenyang Cai of the Nanjing Institute of Geology and Palaeontology at the Chinese Academy of Sciences, together with Erik Tihelka, a joint-training PhD student at the University of Cambridge. Researchers from the United States, Spain and other countries also contributed.

The team did not stop at the Texas specimen. They also reexamined other puzzling stem-insect fossils, including material from the Early Devonian chert deposits of Britain and the Late Carboniferous Mazon Creek fossil beds in Illinois, material that had likewise resisted clear classification.

The species name itself nods to that history of misunderstanding. Chosha draws on a Navajo word linked to insect-like beings from creation stories, a departure from the purely Latin naming conventions usually used for such fossils.

The reclassification underscores how much can be learned by revisiting decades-old museum material with modern tools rather than relying solely on new excavations.

The finding adds to a broader picture of the Carboniferous period as a formative era for terrestrial life, when early ecosystems, including the coal-forming forests that gave the period its name, were taking shape alongside the arthropods that would eventually dominate land environments. For researchers working through old drawers of unidentified fossils, according to Nature and the reporting outlets covering the study, the case is a reminder that old evidence, seen with new eyes, can still upend settled assumptions.

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