This ancient creature, Vilevolodon diplomylus
may have just solved a debate that puts the origin of mammals
millions of years earlier than previously thought,
and it did it with its ears.
So Vilevolodon actually means glider's tooth, and this animal was a glider
somewhat like a flying squirrel in terms of its size and lifestyle
and the specimen that we are reporting preserves some features
that the original specimen of Vilevolodon does not preserve very well.
Vilevolodon is a haramiyid, it lived during the mesozoic era, the age of the dinosaurs.
Until recently, haramiyids were only known from a few fossilised teeth and they remain enigmatic.
Where do the haramiyids fall on the family tree of life of mammals?
Or are they even mammals?
So some scientists believe that the haramiyids actually are inside of the group of mammals,
including us and living monotremes and marsupials.
But other scientists believe that they fall outside of that group,
that they would not be technically called mammals,
they would be near mammals,
and the controversy has really centered around how their ear is organized.
Ear bones are one of the defining traits used to identify mammals,
and they're one of the keys to understand mammalian evolution.
Modern mammals have a distinctive middle ear,
made up of three small bones or ossicles.
The malleus, incus, and stapes.
These allow us to hear a broad range of sound frequencies in great detail.
But this wasn't the case for our evolutionary precursors.
Ear bones originally formed part of the jaw.
Here you can see two of the middle ear bones; the malleus and incus,
plus another part of the ear: the tympanic annulus.
And as you go back in the fossil record you can see them changing.
Some early animals had bones that were used for both hearing and chewing
and before that there were creatures that heard the world entirely through their jaws.
Paleontologists can therefore use the structure of the middle ear
to tell them where along the evolutionary tree an animal sits.
The group of scientists that have them falling outside of mammal,
give them an ear that is a much more primitive type of ear,
and the scientists that have the haramiyids falling inside of mammals
has the ear as being more advanced.
When you look at our fossil under a microscope
the lower jaw jumps out at you as a very identifiable structure,
and situated behind the lower jaw
were some funny shaped little elements that we were not a hundred percent sure what they were.
So when we first saw them you know they were of the size and general shape
that we thought they might be two of the three middle ear ossicles
but it wasn't until we actually looked at the CT scans of the specimen
that we were really able to say "yes those are two of the three middle ear ossicles".
And on looking at them it was clear that they were very similar
to the malleus and incus that occur in living monotremes,
the egg laying mammals which today are represented by the duck-billed platypus
and the spiny anteater or echidna.
Because haramiyids are so ancient placing them within mammals pushes the origin of mammals as a group
back to the late Triassic, about 200 million years ago.
But this might not be the end of the story.
You know I think the debate has an answer today,
but tomorrow when somebody finds another haramiyid,
or another fossil that has impact on the position of haramiyids,
that debate will start up again and we'll cycle through this again.