Tiny life-forms wiht luminous colors might point the way to big dinosaur bone discoveries.
In the badlands of western canada, two species of lichen prefer making their homes on dinosaur bones instead of on the surrounding desert rock, and their distinct orange color can be detected by drones, possibly aiding future dino discoveries, researchers report November 3 in Current Biology.
“Rather than finding new sites serendipitously, this approach can help paleontologists to locate new areas that are likely to have fossils at the surface and then go there to investigate,” says paleontologist Brian Pickles at the University of Reading in England.
Lichens are photosynthetic organisms built by a symbiotic relationship between fungi and algae or cyanobacteria. They come in many colors. Some are white or near-black; others appear green, yellow, orange or red. They often grow in challenging environments,such as deserts or polar regions.
Lichens tend to be quite picky about where they grow, says AJ Deneka, a lichenologist at Carleton University in Ottawa, Canada, who was not involved with the research. Species that grow on granite do not grow on sandstone or limestone and species that grow on wood don’t grow on rock.
Dinosaur bones covered in lichen have long been known to paleontologists working in desert fossil hotspots of western North America. In 1922, paleontologists found an Ankylosaurus fossil covered in orange lichen in the Canadian badlands. In 1979, a similarly colored lichen was reported growing over a Centrosaurus bonebed in the same area. the orange-colored symbiote is frequently enough the first thing researchers notice when working in these regions, with the discovery of bone coming second.
By scrutinizing vibrantly colored lichen and where it grows in Dinosaur Provincial Park in Alberta, Pickles and his colleagues found that two species of lichen, Rusavskia elegans and Xanthomendoza trachyphylla, had a strict preference for colonizing fossil bones and were almost entirely absent from surrounding ironstone rock.
“The porous texture of fossils probably plays a role in making them [a] suitable lichen habitat, perhaps by retaining moisture or providing tiny pockets where lichen [can] become trapped and established,” Deneka says.
Pickles and his colleagues next measured light frequencies reflected by the rock, bones and bone-inhabiting lichen and tested whether they could distinguish the lichen from these surroundings using drones. Spectral analyses found the lichen primarily reflected certain infrared light frequencies, which the researchers then used to develop drone sensors that could detect this light from above.
Using these drones, the researchers were able to identify fossil bonebeds from a height of 30 meters. “We could only locate the fossils thanks to the lichen association,” Pickles says.
The technique “has great potential for use in little-explored or difficult-to-access areas,” says Renato García, a paleontologist at Universidad Nacional de Avellaneda in Buenos Aires, who was not involved with the research. in 2020, García and his colleagues uncovered a similar predilection of certain lichen toward fossil penguin bones in antarctica, hinting at another region where this work may be fruitful.
Pickles and his team have their own plan: “other badlands are our next target.”
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