Located in the Fleming Fjord Formation of eastern Greenland, recently identified 210-million-year-old lungfish burrows provide valuable information about the fluctuating nature of the Late Triassic climate in ancient Greenland. Fossil burrows indicate that lungfish had a strategy of surviving seasonal drought in Late Triassic Greenland by digging into the soil through a biological process called ‘aestivation’, waiting for the environment to become hospitable again.This research, published on ResearchGate, expands our understanding (or lack thereof) of the Norian-Rhaetian transitional periods, revealing that environmental stress – not lush ecosystems – defined these ecosystems during the Late Triassic period. Geologists and paleontologists are reconstructing the ancient world from these ‘holes’ in the rock, where animals retreated to survive beneath the Earth’s surface.

Greenland burrows reveal survival of lungfish 210 million years ago

Researchers discovered ‘trace fossils’ created by lungfish (cylindrical structures) in sedimentary layers deposited in ancient lake valleys as a result of the geological processes of the Fleming Fjord Formation. Unlike body fossils, which record an organism’s form and appearance, these burrows document an organism’s actual behavior, specifically the behavior of burrowing into the substrate to avoid dehydration about 210 million years ago.

210 million year old mystery of Greenland’s fish

The discovery of these burrows provides evidence that Triassic period lungfish were able to enter a stage of dormancy (known as aestivation) as a method of coping with the conditions of their environment. This physiological response enabled the lungfish to survive in the intermittent lake; That is, these fish could survive in a lake that was subject to the drying up of water sources as a result of the Pangean megamonsoonal cycles.

What mudstone burrows tell us about Greenland’s continental drift

According to the book ‘Geological Survey of Denmark and Greenland (GEUS) Bulletin’, the layers in which these burrow holes occur are composed of mudstone and siltstone; They maintained the shape of the cavities from the time the soil was deposited until it hardened. These types of structures are important for researchers to understand how Pangea moved from one place to another and where Greenland was on Earth during this time period.

How Greenland’s tiny holes reshaped Triassic climate models

Furthermore, these ‘small holes’ act as climate proxies to indicate precipitation fluctuations at higher amplitudes. Data published in research at NCBI shows that Triassic high-latitude regions were significantly more thermally elevated than previous estimates. Also, they were drier than current models. This suggests that the high-latitude region was quite different from what current models suggest with respect to past atmospheric and climate conditions.