Feathers from a Montana coprolite may explain why the lineage of modern birds survived
In Montana, United States, scientists studied feathers preserved in a 66-million-year-old coprolite — the fossilized excrement of a large dinosaur. Along with scales of a gar and leg bones of a hesperornithiform water bird, the researchers found well-preserved feather remains. As ScienceDaily reports, their structure may offer a clue as to why Neornithes — the branch from which all modern birds descend — survived the mass extinction at the end of the Cretaceous period.
The study results were published in the journal Current Biology. The specimen was found in 2016 by researcher David DeMar Jr. during fieldwork in northeastern Montana. After analyzing its mineral composition, specialists scanned it using computed tomography, which made it possible to see the fossil's internal structure without destroying it.
Remains of a water bird
According to the researchers, the feathers and bones most likely belonged to a single hesperornithiform. These birds were ecologically similar to modern loons: most of them could not fly and dived into the water for fish. They were close evolutionary relatives of Neornithes, but belonged to a separate lineage that became extinct along with most other birds of that time.
The discovered feathers became the first known example of plumage from hesperornithiforms. Some of the feathers showed features of modern water-resistant plumage, but the bird also had small fluffy body feathers of a more primitive type associated with dinosaurs and enantiornithine birds.
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Hypothesis about thermal insulation
Scientists note that life near bodies of water could not have been the only reason Neornithes survived after the asteroid impact: hesperornithiforms also lived in aquatic environments but did not survive the extinction. One possible factor, according to the study's authors, lies in the properties of feathers and the way they molted.
Body feathers help birds retain heat. After the asteroid impact, dust and debris in the atmosphere reduced the amount of sunlight and contributed to cooling described as an impact winter. If the primitive plumage of hesperornithiforms and enantiornithine birds provided weaker thermal insulation than the feathers of Neornithes, this could have affected their ability to survive such conditions.
The researchers also believe that computed tomography of other coprolites may help find previously unnoticed remains of feathers, bones, and other evidence of ancient ecosystems, including data on the diets of prehistoric predators.
