Nav: Home

New early Cretaceous mammal fossils bridge a transitional gap in ear's evolution

December 05, 2019

Fossils of a previously unknown species of Early Cretaceous mammal have caught in the act the final steps by which mammals' multi-boned middle ears evolved, according to a new study. The new species the study unearths - based on fossil specimens collected in China's Yixian Formation - provides a reference in the evolutionary tree of mammals, supporting the idea that the decoupling of mammals' hearing apparatuses from their jaw - here shown at the initial stages of this process - removed the physical constraints the hearing and chewing systems imposed on one another; this laid the phenotypic groundwork for improved hearing and chewing in future mammal species. While modern mammals like us 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. While the evolutionary event in which jaw bones were co-opted to form the tri-ossicular hearing apparatus of mammals is widely recognized, fossilized examples demonstrating the intermittent steps are elusive. In the fossil-rich Jehol Biota of northeastern China, Fang-Yuan Mao discovered the remains of a new genus and species of Early Cretaceous mammal - Origolestes lii - whose detached auditory bones likely represent an initial morphological state important final step in the evolution of the definitive mammalian middle ear, a step otherwise unrepresented by mammalian fossils. Here, after high-resolution CT scanning and other imaging efforts, Mao et al. describe the well-preserved specimens in detail, including structures of the creatures' auditory bones and cartilage, which lacked the bone-on-bone contact of earlier species. The decoupling of the jaw joint and hearing apparatus as described here ultimately led to the diversity in the masticatory and auditory systems seen in mammals today.

American Association for the Advancement of Science

Related Evolution Articles:

Artificial evolution of an industry
A research team has taken a deep dive into the newly emerging domain of 'forward-looking' business strategies that show firms have far more ability to actively influence the future of their markets than once thought.
Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.
A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.
Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?
Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.
Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
More Evolution News and Evolution Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at