Carnegie Scientist: Fossil Shows How Mammals Developed Sensitive Hearing
Cronin, Mike, Tribune-Review/Pittsburgh Tribune-Review
Though it weighed 2 ounces and was 5 inches long, the chipmunk- like mammal that lived 123 million years ago had something its dinosaur predators didn't: middle ear bones partially independent of its jaw bone.
That evolutionary development helped Maotherium asiaticus have more sensitive hearing.
"This made it possible for mammals to be active in the night," said Dr. Zhe-Xi Luo, the Carnegie Museum of Natural History associate director of science and curator of vertebrate paleontology, in an e-mail from Germany.
"In the Mesozoic (Era), when dinosaurs dominated the world, this is a key adaptation for the survival of mammals," he said.
Luo and a team of paleontologists discovered the existence of the previously unknown mammal when it recovered a three-dimensionally preserved fossil in Liaoning Province in northeastern China among the famous beds of the Yixian Formation.
Finding a fossil preserved in three dimensions and not flattened "like prehistoric roadkill" is unusual, Luo said.
Luo and team members report the discovery in today's issue of the journal Science. The article's primary authors are Luo, Qiang Ji of the Chinese Academy of Geological Sciences in Beijing and Xinliang Zhang of the Henan Provincial Geological Museum.
The find is significant because it provides clues to how mammals' ears evolved from reptiles' ears, Luo said.
Professor Guillermo Rougier, a paleontologist at the University of Louisville not involved in the research, explained why the work by Luo and his team is critical to science.
"For mammalian evolution, the ear is crucial, really," Rougier said. "It's one of the key features that distinguish mammals from other animals today. …