National Geographic News
A nocturnal mammal pads along a lake shore at night.

An illustration of Rugosodon eurasiaticus padding along a lake shore at night.

Illustration courtesy April Isch, University of Chicago

Ker Than

for National Geographic

Published August 15, 2013

The discovery of a 160-million-year-old fossil of a rodent-like creature is helping shed light on how one of the most evolutionarily successful mammalian groups to ever live gained dominance.

Dubbed Rugosodon eurasiaticus, the creature bore a superficial resemblance to a small rat or a chipmunk and was an early member of the group of mammals known as multituberculates.

Its nearly complete skeleton was found in the province of Liaoning in northeastern China—the same region that has gained fame for its fossils of feathered dinosaurs such as Anchiornis.

"This multituberculate belongs to the basal-most family, so its one of the first lineages that ever came into existence for the whole multituberculate group. That's why we're so hot about it," said study leader Zhe-Xi Luo, a paleontologist and early-mammal expert at the University of Chicago.

Multituberculates lived from about 165 million years ago to about 35 million years ago. They scurried alongside dinosaurs and even managed to outlive the fateful asteroid strike that ended the giant reptiles' reign.

The creatures not only survived, but thrived, creating niches for themselves on the ground, in the treetops, and even underground.

"Their lineage lasted 130 million years, and that's something," said Luo.

The research is detailed in this week's issue of the journal Science.

What's New?

One key to the multituberculates' success was a wide-ranging diet. They were omnivores, meaning they ate both meat and plants.

Based on a study of its teeth, scientists proved that Rugosodon, in particular, was also an omnivore. Its remains were found near the edge of an ancient lake, where the creature could have dined on plants such as ferns, as well as insects and a clam-like crustacean called Conchostraca, Luo said.

What surprised Luo and his team, however, were Rugosodon's ankles, which appear to have been capable of "hyper-back-rotation." Such highly mobile ankle joints are normally associated with the foot functions of animals that are exclusively tree-dwellers—those that navigate uneven surfaces.

"If your ankle gets twisted 90 degrees, you'd suffer pain," Luo said.

"[Rugosodon] could twist its ankle for the joy of its life."

Why Is It Important?

Scientists had known previously that some younger multituberculates living about 65 million years ago could hyper-rotate their ankles.

"Now, lo and behold, we now find that Rugosodon, which lived 100 million years earlier, has exactly the same joint!" Luo said.

What Does This Mean?

The discovery of hyper-back-rotation ankles in such an early multituberculate supports the idea that this was a key reason they were so successful, Luo said.

"Essentially, from the very beginning of their whole lineage, multituberculates were already well equipped to be capable of such a versatile locomotor adaptation," he added.

All of that versatility couldn't save the group from extinction, however. Multituberculates disappeared about 35 million years ago, their evolutionary niches taken over by another group that shared their omnivorous diet and talent for adaptability: rodents.

It's not entirely clear why multituberculates lost to rodents, but one idea is that they just couldn't reproduce fast enough.

"Rodents were more prolific, perhaps, than multituberculates," Luo said.

Moreover, multituberculates are such an ancient lineage of mammals that they had not evolved the placental reproduction that rodents had.

What's Next?

As exciting as the discovery of Rugosodon was for Luo and his team, he said they are already moving on to study other fossil discoveries.

"There are so many important fossil discoveries, and we are thrilled about it, but we feel like we drink water from a fire hose," Luo said.

"If you take one gulp, the rest just passes you by."

Follow Ker Than on Twitter.

Shiva Kumar
Shiva Kumar

Its nature which induces genetical modifications in every living being... we are just in course of mapping the path of evolution but not exactly finding what triggers evolution its best secret of nature....

Babu Ranganathan
Babu Ranganathan

NATURAL LIMITS TO EVOLUTION: Only micro-evolution, or evolution within biological "kinds," is genetically possible (such as the varieties of dogs, cats, horses, cows, etc.), but not macro-evolution, or evolution across biological "kinds," (such as from sea sponge to human). How could species have survived if their vital tissues, organs, reproductive systems, etc. were still evolving? A partially evolved trait or organ that is not complete and fully functioning from the start would be a liability to a species, not a survival asset. Plants and animals in the process of macro-evolution would be unfit for survival. For example, “if a leg of a reptile were to evolve (over supposedly millions of years) into a wing of a bird, it would become a bad leg long before it became a good wing” (Dr. Walt Brown, scientist and creationist). Survival of the fittest actually would have prevented evolution across biological kinds! Read my Internet article: WAR AMONG EVOLUTIONISTS! (2nd Edition).

What about natural selection? Natural selection doesn't produce biological traits or variations. It can only "select" from biological variations that are possible and which have survival value. The term "natural selection" is a figure of speech. Nature doesn't do any conscious selecting. If a variation occurs in a species (i.e. change in skin color) that helps the species survive then that survival is called being "selected." That's all it is. Natural selection is a passive process in nature, not a creative process.

The real issue is what biological variations are possible, not natural selection. Only limited evolution, variations of already existing genes and traits, is possible. Nature is mindless and has no ability to design and program entirely new genes for entirely new traits. Evolutionists believe and hope that over, supposedly millions of years, random genetic mutations caused by environmental radiation will generate entirely new genes. This is total blind and irrational faith on the part of evolutionists. Read my articles.

Visit my latest Internet site: THE SCIENCE SUPPORTING CREATION .

I discuss: Punctuated Equilibria, "Junk DNA," genetics, mutations, natural selection, fossils, dinosaur “feathers,” the genetic and biological similarities between various species, etc., etc.

Babu G. Ranganathan*
B.A. Bible/Biology
*I have given successful lectures (with question and answer period afterwards) defending creation before evolutionist science faculty and students at various colleges and universities. I've been privileged to be recognized in the 24th edition of Marquis "Who's Who in The East" for my writings on religion and science.

Richmond Acosta
Richmond Acosta

Oh my God, for the first time since I signed up to Nat Geo site, I can now post a comment!

Mason Hein
Mason Hein

@Shiva Kumar While most genetic modifications are harmful to an organism, I agree that there can be modifications which could cause a living organism to adapt to a given environment and even improve its function. However, these changes are very tiny and take a very long time to have a cumulative effect on a given species.

However, there is absolutely no way for these tiny long term changes to create a self-sustaining organism which is capable of replication or reproduction from inorganic material. 

That initial jump from inorganic to organic to organism is something that evolution is simply not capable of. 

Evolution is fine-tuning living organisms which were created by some intelligent force we cannot discern or define.

Shiva Kumar
Shiva Kumar

@Babu Ranganathan if nature cannot bring an evolution who does... we are living in nature so it has upper hand in designing us... how exactly nature modifies our DNA needs to be found. Dont under estimate nature it can destroy and build everything.  All powerful nature which is creating us and destroying us. So go out and get caught in thunderstorm you will get first lesson...

Frank Stein
Frank Stein

@Babu Ranganathan Hey Babu, I'll say basically the same to you that I said below. Evolution by natural selection is a fact. Deal with it. Just because you don't understand evolution doesn't mean it's not true and it also doesn't mean that it's somebodies job here in these comments to teach it to you. Don't like evolution because it disagrees with your supernatural beliefs? Too bad. Want to "disprove" evolution? Then learn about what scientific evidence would actually do so and have at it. Otherwise, shut your yap because you're making yourself look really stupid.

C. Dufour
C. Dufour

@Babu Ranganathan "How could species have survived if their vital tissues, organs, reproductive systems, etc. were still evolving?"

You do know organs do not evolve independent of their host right? They possess the same genetic information as their host and DO NOT CHANGE HROUGH THE ANIMALS LIFE, that is NOT HOW EVOLUTION WORKS. thats magic.

“if a leg of a reptile were to evolve (over supposedly millions of years) into a wing of a bird, it would become a bad leg long before it became a good wing”

Yes which is why in many cases the unformed limb can serve a secondary evolutionary purpose. In the cases of fish, several species such angler fish and frogfish have legs they use to stalk prey underwater. These legs allow the fish to move slower and pass undetected by their prey. In the case of a birds limb, wings probably served thermoregulatory, display of communication purposes long before flight.

Honestly this isn't rocket science, you just need to read up on some new material. 

Mason Hein
Mason Hein

Russell, Before you berate others for their lack of qualification to post on this topic, you might offer more than a vague opinion on your own behalf. 

Please describe how the process you describe generates a single celled organism from inorganic material through random natural processes.

A simple citation to any published peer-reviewed scientific study showing the mechanisms of how this process occurs will be perfectly sufficient.

I'd be most interested in reviewing such a document. Surely, a scientific viewpoint has the evidence to back it up, correct?

Russell Hatton
Russell Hatton

@Babu Ranganathan If you can grasp the concept that the gene pool is the organism and it is plastic over the generations then you will understand evolution and not made such a fool of yourself as you have in this comment. You have shown yourself to have a minimal grasp of the topic and are therefore unqualified to offer an opinion. A little more inciteful meditation is needed before you speak on this matter again.

Mason Hein
Mason Hein

@Frank Stein OK... here's the scientific evidence that would disprove "macro-evolution" (this is the idea that life can spring forth from inorganic matter).

Scientists have shown how amino acids can form though random natural action... however, we now know that even the simplest single celled creature has 2 billion base pairs of amino acids joined together in just the right pattern. 

If any part of that chain is wrong, the organism dies, or is sterile (it cannot reproduce, and pass along that change to future generations).

The process to form ANY single celled life through natural random action has NEVER been explained, documented, or proven in ANY peer-reviewed scientific study.

Your fanatical belief in the religion of evolution is blinding you to the simple scientific fact that evolution CANNOT form organic life from random natural action.

If I'm wrong, simply point me to the study where scientists have explained this... 

Proof... got some? any at all?

D Kennedy
D Kennedy

@Frank Stein @Babu Ranganathan Hey Frank.. how many tries did it take the stick bug until he mutated into a form that looks exactly like a stick on a tree?  Especially considering evolution has absolutely no idea what it's trying for?  Did it try millions of times? billion?  And next question - WHERE ARE ALL THE OTHER ONES?  All of those other insects .. the ones that were incrementally different.. did they just die off? And why?  It's not like simply because one is better at camouflage all the rest fade out of existence.  Same idea with every other species.. there would be millions of variations in every single step leading up to it's current form - most still living.

Frank Stein
Frank Stein

@Mason Hein No sir! it is not Russell Hattons job to teach you evolution (especially not in a comment section). If you REALLY want to know why the post he commented on is so misinformed, that is effort that YOU have to expend in actual honest study. YOU have to take responsibility for your own lack of knowledge. Evolution is a fact! (Micro, Macro, Mini, Maxi, and super-duper deluxe). Deal with it! I'm so tired of you morons trying to walk us back in to the dark ages!

Mason Hein
Mason Hein

@Frank Stein I didn't ask him to teach me anything... and I doubt he could if he wanted to. 

All I asked was that he provide a citation to any documented scientific evidence of his viewpoint.

So far he hasn't been able to.

I note with interest that you can't provide one either.


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