Lantern North Reveals an Early Pennsylvanian Ecosystem

During the Carboniferous period, carbon-rich swamps and forests spread across Earth’s rocky land surface. Atmospheric oxygen increased, while enormous amounts of carbon dioxide became locked away in deposits that would ultimately form Earth’s coal. Plant and animal life on land prospered under these shifting conditions.

Yet the opening part of this story has remained poorly understood. Much of what is known about this pivotal stage in Earth’s evolutionary history comes from coal-forming swamp layers dating to 315–307 million years ago, during the Middle Pennsylvanian.

Lantern North reveals an Early Pennsylvanian ecosystem

An international research team has now uncovered a complete ecosystem preserved in sedimentary rock from the Early Pennsylvanian, roughly 320–318 million years ago. The site contains more than a hundred distinct organisms.

Named Lantern North, the fossil locality was found in the Wamsutta Formation of eastern North America.

Unlike other sites from the Pennsylvanian, its geological setting consists of fragmented material from much older rocks. Lantern North preserves a drier upland landscape, recording the everyday existence of tetrapod, arthropod and seed-plant groups during a period when land environments - and the organisms that had only recently spread into them - were undergoing rapid change.

A basin was formed by coarse sedimentary layers alternating with fossil-rich, oxidised-red sheets of sandstone shale. These deposits were laid down before the period’s characteristic carbon-rich sediments filled a marshy central area.

"The exceptional preservation of delicate impressions and traces allows us to reconstruct behaviors and ecology in ways not usually possible with body fossils alone," says University of Tennessee palaeoecologist Jacob Benner, who led the study with Harvard University palaeobiologist Richard Knecht.

"We can see how these early terrestrial communities functioned as integrated ecosystems."

"The fossiliferous red shale facies may, therefore, represent deposition in shallow depressions near the base of a fan complex that hosted ephemeral or seasonal ponds and pools in which suspended sediment could settle after a flood," the authors write.

Plants and traces of ancient animal life

For millions of years, these layers preserved the bodies and impressions of ancient plants, vertebrates and invertebrates, like carefully pressed flowers between the pages of a book. The team recognised 131 plant taxa, including 83 distinct types of plant foliage.

The remarkable discovery also provides the earliest known evidence of insect oviposition, the process in which eggs are placed into or on a surface using an ovipositor.

The researchers identified lesions on a species of Cordaites, trees that reached about 30 metres in height and may represent the earliest conifers. Such marks are produced when insects lay eggs on a plant’s surface, and the newly found fossils indicate that insects may have begun using this method at least 14 million years earlier than previously believed.

They also found some of the earliest evidence for insect gall formation. In this process, an insect or its larvae burrows into a plant’s living tissue, creating both shelter and a food supply. The insect chemically alters the plant’s growth, producing the distinctive swellings and shapes on its surface known as galls.

According to the researchers, this represents one of the oldest recorded examples of gall damage caused by insects.

"We're seeing evidence of complex plant-insect interactions and some of the earliest appearances of major animal groups that went on to dominate terrestrial habitats," says Knecht.

"This site gives us an unprecedented look at a terrestrial ecosystem from a crucial time in the evolution of life on land."

A detailed Carboniferous fossil record

This unusually detailed record of a little-known interval should continue to uncover insights into the early Carboniferous through future research.

The research is published in Nature Communications.