Author: Carolyn Gramling / Source: Science News
ALBUQUERQUE — Fossilized lungs found preserved along with an ancient bird may breathe new life into studies of early avian respiration.
If confirmed as lungs, the find marks the first time that researchers have spotted the respiratory organs in a bird fossil.Scientists have previously described four fossils of Archaeorhynchus spathula, an early beaked and feathered bird that lived about 120 million years ago. But unlike those discoveries, a newly described fifth specimen contains significant traces of plumage, and, even more startling, the probable remnants of a pair of lungs, researchers say.
Vertebrate paleontologist Jingmai O’Connor and colleagues reported the findings October 18 at the Society for Vertebrate Paleontology’s annual meeting. The results were also published online October 18 in the Proceedings of the National Academy of Sciences.
About the size of a thrush, Archaeorhynchus was among the earliest ornithuromorphs, the lineage that led to modern birds. It was probably an herbivore, as all known fossils of the creature contain preserved gastroliths, or gizzard stones which some animals use to help grind food, in the belly. The new fossil was found in northeastern China and is part of the Jehol Biota. That wealth of well-preserved fossils dates to between 133 million and 120 million years ago and includes numerous feathered dinosaurs as well as birds.
It’s rare for soft tissues to survive the pressure, heat and chemical transformation of fossilization. But scientists are increasingly reporting finding fossilized feathers, skin and even bits of brain preserved along with bones (SN: 4/1/17, p. 32; SN: 11/26/16, p. 9). Fossilized lungs are also not completely unheard of: The petrified organs have been observed preserved with a 125-million-year-old mammal fossil (SN Online: 10/21/15) and with a 35-million-year-old salamander fossil.
“But we’re arguing that this is the first lung tissue preservation that is anatomically informative,” said O’Connor, of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.
That’s because modern birds have a highly specialized and efficient respiratory system that allows them to absorb enough oxygen to meet the demands of powered flight. Unlike mammalian lungs that are elastic and pump air in and out, bird lungs don’t change size when the bird breathes. Instead, several air sacs connected to the lungs act like a bellows to draw the air in through the lungs….
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