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Ancient Complex Mammal: ~164 Million Years

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Mesozoic mammals have been thought to have been small, nocturnal, and confined to a few niches on land until the demise of the dinosaurs 65 million years ago. Most are recorded by isolated jaw fragments or teeth. Ji et al. (p. 1123; see the cover and the Perspective by Martin) now describe a Jurassic mammal from China that breaks this mold. The fossil is well preserved, and impressions of fur can be seen on its body and scales on a broad tail (similar to a beaver overall). The animal was fairly large, approaching not quite half a meter in length, and the shape of its limbs suggest that it was adapted for swimming and burrowing. The combination of both primitive and derived features in this early mammal, and the demonstration that mammals had occupied aquatic habitats by this time, expands the evolutionary innovations of early mammals.


WASHINGTON (AP) — For years the mammals living in the era of dinosaurs have been thought of as tiny shrew-like creatures scurrying through the underbrush. Now the discovery of a furry aquatic creature with seal-like teeth and a flat tail like a beaver has demolished that image.

Some 164 million years ago the newly discovered mammal was swimming in lakes in what is now northern China, eating fish and living with dinosaurs.

“Its lifestyle was probably very similar to the modern day platypus,” Zhe-Xi Luo, curator of vertebrate paleontology at Carnegie Museum of Natural History in Pittsburgh, said in a statement. “It probably lived along river or lake banks. It doggy-paddled around, ate aquatic animals and insects, and burrowed tunnels for its nest.”

Luo was part of a team led by Qiang Ji of the Chinese Academy of Geological Sciences in Beijing that discovered the remains in the Inner Mongolia region of China. They report their findings in Friday’s issue of the journal Science.

Thomas Martin of the Research Institute Senckenberg in Frankfurt, Germany, said the discovery pushes back the mammal conquest of the waters by more than 100 million years.

“This exciting fossil is a further jigsaw puzzle piece in a series of recent discoveries,” commented Martin, who was not part of Luo’s team.

Matthew Carrano, curator of dinosaurs at the Smithsonian’s National Museum of Natural History, called the find “a big deal.”

An important factor is how specialized the creature was, said Carrano, who was not part of the research group.

“It gives a hint that early mammals were not just these shadowy creatures at the time of dinosaurs” but were having their own evolution. There have been hints of such animals in the past but nothing equal to the remains found by Luo and colleagues, he said.

It’s the first evidence that some ancient mammals were semi-aquatic, indicating a greater diversification than previously thought, according to the researchers.

Modern semi-aquatic mammals such as beavers and otters and aquatic mammals like whales did not appear until between 55 million years ago and 25 million years ago, according to the researchers.

The animal is not related to modern beavers or otters but has features similar to them. Thus the researchers named it Castorocauda lutrasimilis. Castoro from the Latin for beaver, cauda for tail, lutra for river otter and similis meaning similar.

The animal had fur, a broad scaly tail with vertebra similar to those in a beaver or otter, swimmer’s limbs and seal-like teeth for eating fish, they said.

The researchers found imprints of the fur, both guard hairs and short, dense under fur that would have kept water from the skin. Scales were also apparent on the tail as well as a suggestion of soft tissues. There was also the skeleton including teeth.

Weighing in at between 1.1 and 1.7 pounds, about the size of a small female platypus, Castorocauda is also the largest known Jurassic early mammal.

The research was funded by the U.S. National Science Foundation, National Natural Science Foundation of China, Ministry of Science and Technology of China, Chinese Ministry of Land Resources, National Geographic Society and Carnegie Museum.


Newfound remains of a beaver-like creature suggest that mammals swam with dinosaurs.

This critter was a “giant among midgets,” researchers said, dwarfing the other pint-sized mammals scurrying around during the Jurassic period.

It also holds the title of the first-known aquatic mammal, arriving on the scene nearly 100 million years before the previous record holder.

Swimming phenom

The animal, called Castorocauda lutrasimilis, was discovered in dried-up lake bed within the Inner Mongolia Region in China and has been dated to the Middle Jurassic period, about 164 million years ago.

Preservation of specialized, bi-layer fur—one to keep them warm and dry, the other for protection—is the first of its kind in mammals. Beavers and otters, which also have this type of fur, didn’t show up until about 55 million and 25 million years ago. Full-time aquatic mammals such as whales and manatees first appear during that period as well.

Like a beaver or platypus, the newfound creature’s hind feet were webbed for easy paddling while its front feet were better suited for digging and burrowing. It had a flattened, scaly tail like a beaver, and it sported sharp teeth, like an otter.

“We discovered the world’s first mammalian swimmer,” said study author Zhe-Xi Luo of the Carnegie Museum of Natural History. “This mode of life of fish eating, swimming, and digging combined is very different than the traditional stereotype that Jurassic mammals were very small, limited to eating insects, and lived mainly on the ground.”

The finding is detailed in the Feb. 24 issue of the journal Science.

Big mammal on the block

From snout to tail, Castorocauda, measures about 17 inches, roughly the same size as a modern-day female platypus. Indeed, at a time when most mammals weighed in just around one tenth of a pound, Castorocauda was a relative behemoth.

“This thing is close to 800 grams (1.75 pounds), so it’s a giant among the midgets,” Luo told LiveScience. “It got so much larger because it was capable of doing different things than the small-body mammals.”

As Castorocauda evolved larger and larger, Luo said, one of those different things was to make the move to the water, where its fish-snaring teeth likely helped it grow even more.

Dead end

Although Castorocauda bears many similarities to beavers, otters, and platypuses, it’s not an ancestor of any of them. It is what scientists sometimes call a “dead-end species.”

Modern mammals fall into three categories—the live-birthing placentals, the egg-laying monotremes, and the pouch-rearing marsupials. After comparing telltale jaw and skull characteristics of each of these groups to Castorocauda, researchers determined that it was something else entirely.

“This creature falls outside the common ancestor of both monotremes and beavers, although it is a near relative,” Luo said.

That means that mammalian adaptations for swimming must have evolved a second time. This is an example of convergent evolution, in which different species in similar environments adaptively evolve structures that look and function similarly, such as the wings of both birds and insects.

Castorocauda was most likely an egg layer, like platypuses, Luo said. Live birthing is a more recent adaptation, and this animal most likely went the primitive route.

Abruptly the origin of aquatic mammals is pushed back 100 million years. It’s interesting that the story-telling has already begun:

“As Castorocauda evolved larger and larger, Luo said, one of those different things was to make the move to the water, where its fish-snaring teeth likely helped it grow even more.”

It’s also interesting that soft-tissue features, including webbing between toes, carbonized underfur and fur impressions have conserved for 164 million years. See here for a hypothesis on how this preservation could occur:


Then to top it off the historical narrative isn’t adjusted but instead it’s yet another case of convergent evolution. Amazing how often this occurs.

"Is that simply someone who accepts Darwin’s theories?" Well, the common use of the term apparently has gone beyond just that since this is what Lynn Margulis had to say after declaring Neo-Darwinism is dead: "'It was like confessing a murder when I discovered I was not a neo-Darwinist.' But, she quickly added, 'I am definitely a Darwinist though.'" Since Darwinists themselves are using the term to imply a belief beyond just a simple acceptance of Darwin's theory I'd say it now has metaphysical connotations. Then of course there are Social Darwinists: http://en.wikipedia.org/wiki/Social_Darwinist Now if I'm referring to someone like Dave described I'd use the word "materialist". Patrick

What does "Darwinist" mean? I've seen that term used A LOT here. (i think a post of mine got moderated out of existence because I poked fun at it) Is that simply someone who accepts Darwin's theories? Or is there more of a definition behind that word? For instance, someone who extends Darwins theories to support non scientific issues like social Darwinism, atheism, materialism, etc?

Implies evolutionary dogmatism. Chance worshipper. Member of the Church of St. Charles. NeoDarwinian apologist. Teller of fairy tales. Sucker for the biggest hoax in the history of science. -ds


"Sexual selection?"


"Since its proposal, problems with this narrative have continued to accumulate, and it is our view that sexual selection theory needs to be replaced.”

-John/Joan/Whatever Roughgarden

More on the subject:


"Genetic drift?"

See Dave.

"Convergent evolution?"

How is that a new mechanism?


Despite what Lynn Margulis thinks, other than the two proposed examples of mitochondria and chloroplasts there is no clear evidence of other major traits or transitions that can be attributed to symbiogenesis. But I don't mind her going up in front of a crowd of Darwinists and pronouncing that Neo-Darwinism is dead like she did a little over a year ago. :)


If they want to propose a new mechanism in addition to RM+NS that can produce CSI/IC that’s fine.

They have and they do. RM+NS is not the complete story. What about sexual selection? Genetic drift? Convergent evolution? Symbiogenesis?

And just out of curiosity, I've seen a lot of explanations (evidence) by ID about things like the blood-clotting cascade and the bacterial flagellum; but what "readily available" evidence provided by ID addresses the appearance of furry animals?

Random mutation is still the purported source of all variation if one rules out intelligent agency a priori and selection is still bound to natural means. For example in genetic drift mutation is random and selection will eventually play a role if the mutated element ever becomes non-neutral. I'm not sure what you're asking about in the furry animals question. -ds aldo30127
"Out of curiosity, do IDists accept the new time line for mammals based on this find and just disagree with the evolutionary description of it?" That question is outside the scope of ID theory itself and since ID is a big tent you'll get a wide range of answers. "On broader note, do IDists generally accept the geological record of extinction events?" Last time I checked there was still a large amount of disagreement over these extinction events even among Darwinists. Patrick
I won't make a stab at "what", but where -> China, the new frontier. Wrasqally wrabbits might be wrlurking. "Evolutionary Story-telling as Historical Narrative and Artistic License of Broad Speculation" should be a required class for all students going into natural sciences. Ooops, forgot, its covered in textbooks in every school in the nation. Back to new frontiers. Joseph all the best to you and volunteers at the new ResearchID wiki! Love the Net - what a powerful equalizer! Thanks to IDEA for sponsorship! Students and Scholars at all levels will have a wonderful place to interact, build new tools, track new research, tap into creative minds and spur good communication. Hopefully it will inspire spirited exchange of IDEAs across old boundry lines of demarcation. In fact what leading engineers are doing now for example transferring fish aerodynamics design to auto design. It looks to be an exciting beginning in new frontier of IDCOM3. First there was Da Wedge(In the Beginning), den dere was Da Blog(IDtheFuture), now dere is Da ID Wiki(Sum of all Parts)! Music fades in - 2001 Space Odyssey. Or for Macro-Evolution - Jaws. Or a composition on HandBells, "Chaos into Order". Unsure of title or Composer, but most appropriate for the season. It reminds me of the strikingly beautiful tapestry of Chaotic Order applied by computer simulations. How astonished I was that what once seemed random, was beautiful order. One just needed to be able to step outside - the Computer simulations allowed this. And suddenly beautiful majestic patterns of precise mathematical equations came to life for the eye to see. And the recognition in spirals of shells to galaxies and rugs woven by tribes around the world. I could never look at another paisley print the same after that discovery. I'm convinced there's more patterns to find in the seeming chaos of life. There's order in them bones, the cells, the pathways, the communications, the double-helix. Yes.... God Speed Joseph, IDEA. "Faster Please". Bookmarked, for daily apertifs in the future of ID! And so.... Tom Bombadil del dillo, dol dally, dal dolly, dil dello. he danced, he sang, a funny fine fellow Michaels7

The first question I asked myself when reading the headline was "ok, how beaver like was it?" Was it placental? Marsupial? Monotreme? It was actually something that didn't fit into any of those groups. I'm always amazed by the amount of diversity in the life forms that once existed on earth. I especially love odd finds like this that challenge the older and more boring views. (now I can imagine a plethora of early mammals running around tripping up the dinosaurs, instead of those boring furry mice like things).

Out of curiosity, do IDists accept the new time line for mammals based on this find and just disagree with the evolutionary description of it? On broader note, do IDists generally accept the geological record of extinction events? I'm just curious if I.D. peeps have a historical type narrative of life that differs from an evolutionary narrative. (for instance, the KT boundary shows an extinction event with signs of interspersed "design" events above the KT boundary.


Do Darwinists generally have tea or coffee with breakfast? Why are you asking personal questions about beliefs that have nothing to do with ID theory? -ds Fross
Haldane's "rabbit in the pre-Cambrian" (http://www.talkorigins.org/origins/feedback/jan06.html#r33) isn't likely to happen, but perhaps this "beaver in the Jurassic" will help us see that neo-Darwinian mechanisms are insufficient to account for the truly robust nature of biological organisms. Anyone wanna' have a stab at what the next evolutionary surprise might be? Joseph C. Campana Founder and Webmaster, ResearchID.org jccampana at gmail dot com http://www.researchid.org/ JosephCCampana

From an ID critic on this blog:


"You can bet that two things will happen because of this new find. Young earth creationists will point to it as proof that the fossil record doesn’t show evolution, while intelligent design advocates will use the flawed logic of “if biologists can’t even get the evolution of beaver-like mammals right, how do we know they’re right about anything…” Both are regrettable and dishonest."

Actually, it's claimed this creature is a different species with similar features that came about by convergent evolution.

"When Einstien realized there were problems with our theories of gravity, he worked to provide new understandings. He didn’t suggest the apple doesn’t fall from the tree. In the same way, Jurassic beaver like mammals don’t overthrow our theory of evolution, rather they overthrow our theory that mammals remained small and “undiverse” until the extinction of the dinosaurs. And while we evolutionary biologists can be a persnickety group, we also build our theories on the evidence around us. Sometimes that evidence causes us to change our understanding. This is a good and healthy thing, not to mention the very essence of science."

Whether new data calls for a revised understanding of a hypothesis or model depends on a number of things, including: does the data represent a significant trend, or an exceptional situation? Is the new understanding consistent with the prior hypothesis? Was the previous understanding so central to the hypothesis as a whole that the hypothesis should be considered falsified?

Obviously this new evidence is primarily within the scope of a select area of the historical narrative. But the problem with evolutionary biologists is that evidence provided by ID is readily available. ID strikes at the core of Neo-Darwinism and yet people dogmatically cling to their ideas. If they want to propose a new mechanism in addition to RM+NS that can produce CSI/IC that's fine. But how is the current reaction a "good and healthy thing"?

Aren't facts what change theories? http://en.wikipedia.org/wiki/Theories "...a theory is a logically self-consistent model or framework for describing the behavior of a certain natural or social phenomenon, thus either originating from or supported by experimental evidence (see scientific method). In this sense, a theory is a systematic and formalized expression of all previous observations made that is predictive, logical, testable, and has never been falsified." Wikipedia What is the consequence of the Beaver fossil found in respect to Evolution? Less time to bring about more complex lifeforms through natural selection, correct? It seems the "experts" sources claim different time spans. My link quotes 40 million year pushback whereas Patricks caims even 100 Million years. Can anybody try to explain what impact a 40 million year mamaliean pushback has on the Evo? tb
Hadn't noticed your comment on this before. I ran into this news on a blog where an ID critic was defending Darwinism and quoting Ken Miller: "very often facts in science change and theories don't." Patrick
Thanks Patrick :) I already put this comment on "Darwin knocked off pedestal in high school textbook" yesterday since I found it rather interesting. "How much does 40 million years weigh in terms of evolution? Check out the newest Fossil found in China: http://news.nationalgeographic.com/news/2006/02/0223_060223_beaver.html “This discovery has pushed fur-bearing nearly 40 million years further into the past,” Maybe someone wants to open a new thread about it." Cheers tb

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