Life reconstruction of Origolestes lii. Image credit: Chuang Zhao.
Sci-News has a story about a new mammal that lived along side the dinosaurs during the Mesozoic Era. The animal, named Origolestes lii, is part of the famous Jehol Biota, which dates to the Cretaceous Period 133 to 120 million years ago. This biota was a terrestrial and freshwater ecosystem found across the Chinese provinces of Liaoning, Hebei, and Inner Mongolia. Origolestes is important as it shed lights on the final step in the evolution of the mammalian middle ear. Detail can be found in a paper published in the journal Science.
“While modern mammals owe their keen sense of hearing to the three tiny bones that form the complex architecture of the middle ear, these tiny ossicles were once instead part of the jaw, which served a dual function for both chewing and hearing in our earliest ancestors,” said Dr. Fangyuan Mao, a researcher in the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, the CAS Center for Excellence in Life and Paleoenvironment, and the American Museum of Natural History, and her colleagues.
“The evolutionary event in which jaw bones were co-opted to form the tri-ossicular hearing apparatus of mammals is widely recognized. However, fossilized examples demonstrating the intermittent steps are elusive.”
“The detached auditory bones of the newly-discovered Cretaceous mammal represent an important final step in the evolution of the definitive mammalian middle ear.”
The ancient mammal belongs to Symmetrodonta, a group of Mesozoic mammals and mammal-like synapsids.
