324-million-year-old fossil reveals how insects conquered land

The discovery of a 324-million-year-old fossil has shed new light on how insects conquered land. This fossil, named Chosha praecursor, was found in Texas and belongs to a stem group insect from the Late Mississippian period. Researchers from various countries, led by Prof. Chenyang Cai and Erik Tihelka, analyzed this fossil alongside others from earlier and later periods to reconstruct a critical stage in early insect evolution.

They discovered that insects did not become fully terrestrial immediately after colonizing land. Instead, early forms retained and modified features inherited from aquatic ancestors, spending an extended period as semi-aquatic, amphibious beings. The fossil, preserved in fine detail, revealed distinctive features that initially led to misclassification.

However, a closer examination confirmed it was an adult female insect, measuring about 32 millimeters long. Its body had both hexapod and insect characteristics, with abdominal appendages that were unusual for modern crown group insects. The fossil suggests C. praecursor lived in near-shore, shallow-water delta coastal environments, spending much of its time in humid habitats along the boundary between water and land.

The researchers also examined three other enigmatic Paleozoic hexapods, concluding they belonged to a primitive stem lineage of insects, representing the oldest documented assemblage of insects known so far. This discovery helps fill a major gap in the group's evolutionary history and could significantly change how scientists understand the rise of terrestrial insects.