Mayflies, present in many modern freshwater streams, are often known by their mass hatches in which large numbers gain wings and fly in the air for as little as one day to procreate before dying. This natural event results in fish feasting on the remains, which spawned fly-fishing, where anglers try to mimic the bodies of these insects floating along the water’s surface to catch fish.

While the mayfly’s flight is probably the most notable to us because we see the mass of insects for a short period of time, mayflies spend most of their time living underwater. Mayflies have the ability to live underwater for several years before they emerge in flight. While living underwater, some live freely in the water using objects such as rocks, sticks, and leaves for protection from strong water current and predators. Others construct homes (burrows) in the muddy river banks for protection.

Many organisms in multiple environments create these u-shaped homes for the purpose of both living and feeding. Organisms living in these types of homes use their bodies (typically gills) to create a current that brings food into one side of their home and waste out the other side of their home.

When a paleontologist is trying to figure out what organism made this home (burrow) in the rock record, the question is how to differentiate the creator of one of these burrow fossils from another if they have roughly the same u-shape?

In a new study published in the Journal of Paleontology, paleontologists from Western Colorado University, University of Waikato, and NC State have named a new species of Late Cretaceous fossilized burrow, Glossifungites gingrasi, that have dig markings that are transverse to these roughly u-shaped structures which is similar and appear unique to modern underwater insect burrows, such as mayflies.

Burrow size in these structures are often dictated by the size and shape of the organism constructing them. These ninety million year old burrows at times obtain maximum widths larger than the observed modern examples, which may indicate that ancient mayflies obtained larger sizes. Although, several reasons may alter this: anthropogenic stresses may play a role in modern mayfly size, modern burrows are under described, or that the shape of the body was slightly different.

More importantly, this newly described burrow provides a tool for ancient environmental interpretation in being able to differentiate ancient freshwater mayfly burrows from similar structures created in higher salinity environments by crustaceans that have a different orientation of digging marks.

By being able to more precisely interpret the salinity of channel deposits, we can better interpret the long-term effects of sea level rise on coastal systems in the rock record. Furthermore, the indication that subaqueous insects such as mayflies occupied these burrows suggests that mayflies were utilizing the same niches and feeding behavior ninety million years ago as they do today.

“Glossifungites gingrasi n. isp., a probable subaqueous insect domicile from the Cretaceous Ferron Sandstone, Utah” by M. Ryan King, Andrew D. La Croix, Terry A. Gates, Paul B. Anderson and Lindsay E. Zanno has been published in Journal of Paleontology, published by Cambridge University Press on behalf of the Paleontological Society. The article has been made freely available for a limited time.

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