Pharyngula

i-67934b626267982273568f6a5d7249a9-kha-nyou.jpg

Last year, a new and unusual species of rodent was discovered in Laos, called Laonastes aenigmamus, or kha-nyou. Here’s the skull:

i-feb91bc0c8b6c1d907419f9810c8bc6e-laonastes.jpg

It’s notable mainly because of that unusual jaw. It’s hystricomorphous—an obscure term that refers to how the jaw is muscled, in this case with a large masseter muscle (the big chewing muscle you can feel towards the back of your cheek), which inserts into a large hollow or fossa in the jaw—and has a reduced coronoid process (one of the two ‘prongs’ of the jaw), and it’s teeth are bilophodont, referring to a pattern of paired bumps on their surfaces (there are many amazing details about bumps on teeth). Trust the anatomists, it’s a distinctive arrangement.

In the 1970s, an extinct species of rodent, Diatomys shantungensis, was identified from some Chinese fossil remains. A better specimen was found in 2005, and here’s what its skull looks like.

i-daab68c4c0fe5735c7697fbdbc5272e2-diatomys.jpg

That specimen is about 11 million years old, and it is hystricomorphous, with a reduced coronal process, and bilophodont teeth. It lines up with Laonastes in other anatomical details, too—so what we have here is a rat-squirrel thought to be extinct, back from the dead.

Of course, it wasn’t really extinct, just rare and isolated. This phenomenon is unfortunately called the “Lazarus effect”, but when you get right down to it, it’s not a property of the organism at all, but merely a consequence of our own incomplete knowledge.

The “Lazarus effect” refers to the reappearance of taxa after a lengthy hiatus in the fossil record. The discovery of living examples of taxa that were previously thought to be extinct is a very special case of the Lazarus effect, one that has only rarely been documented among mammals and other vertebrates. With the exception of microbiotheriid marsupials, all fossil mammal taxa that were subsequently found to be alive have been Pleistocene in age and congeneric with their modern counterparts. Uniquely among placental mammals, Laonastes pertains to a clade (Diatomyidae) that was formerly believed to have been extinct for more than 11 million years. Diatomyids join tree shrews, flying lemurs, and tarsiers as examples of ancient and formerly wider-ranging mammalian taxa that are currently living with relictual distributions in southeast Asia.

From a paleontological and phylogenetic perspective, efforts to conserve Laonastes, the sole survivor of a morphologically distinctive family of rodents with deep evolutionary roots in Asia, should be given the highest priority. If it can be preserved, the Paleogene zoo that survives today in southeast Asia can offer invaluable insights regarding past and present biodiversity.


Dawson MR, Marivaux L, Li C-k, Beard KC, Métais (2006) Laonastes and the “Lazarus Effect” in Recent Mammals. Science 311(5766):1456-1458.

Comments

  1. #1 lt.kizhe
    March 10, 2006

    Unfortunately, the media in their usual…OK let’s not go there….are reporting it as the same species, which would be a bit unlikely. Anyone care to make book on when the first “Living Fossil Rodent Proves Earth Is Young” pronouncement will appear on YEC websites?
    (Just checked AiG: not there as of this posting).

  2. #2 Rolf Manne
    March 10, 2006

    Are there any theories why there are so many of these relict Pleistocene mammals just in southeast Asia?

  3. #3 wamba
    March 10, 2006

    Are there any theories why there are so many of these relict Pleistocene mammals just in southeast Asia?

    I think its because if they were hanging out in London, modern western science would have found them by now.

    Or maybe they have something there like Wisconsin’s Driftless Area.

    Or maybe it’s near the entrance to Hell, and there are always a few escapees.

  4. #4 MJ Memphis
    March 10, 2006

    I find it amusing that, like the coelecanth, this species was brought to the attention of scientists when some specimens were found for sale in a food market.

    I bet it tastes good in a nice red curry.

  5. #5 Myrmecos
    March 10, 2006

    Not to interject a note of bitter cynicism, but this is really only news because it’s a verterbrate. We published a paper earlier this week about the rediscovery of a 15-20 million year-old ant:

    Rediscovery of an extinct ant

    I won’t hold my breath for the front page of cnn, though…

  6. #6 windy
    March 10, 2006

    Yep, “Lazarus effect” is confusing. Especially when “Elvis taxon” means one that is really dead but looks like it has been “resurrected” by convergent evolution. But you start thinking about the mythical fates of Lazarus or Elvis and not “well, Lazarus was probably just faking, and Elvis is really dead!”

    Can’t we come up with better nicknames? The rodent was not really gone, so could it be the “Coelacanth effect”, or is that too boring, or living-fossily? Actually what happened was that it made a comeback. So it should be called a “Sinatra taxon”, or something like that :) (Not a Mariah Carey taxon, though, please..)

  7. #7 Sifu Tweety
    March 10, 2006

    Wow, a whole clade rediscovered!

    Not that I particularly know what that means.

    Is there any other modern mammal that these dealies are close to?

  8. #8 Ronald Brak
    March 10, 2006

    So I guess the discovery of an ant species that was thought to be extinct would be the Reverse Pink Panther effect. You know – Dead ant, dead ant, deadant deadant deadant deadant dead aaaaannnnt…

  9. #9 NatureSelectedMe
    March 11, 2006

    Myrmecos, I don’t see what the big deal is either. Wasn’t it just the other day that a dinosaur was spotted on these pages. ;)

  10. #10 Dan
    March 12, 2006

    I say, “Who cares about the stupid rat-squirrels?” The ecosystem will get along just fine without them. If they do become extinct, another species will simply evolve to fill the gap, right?

    Besides, if these rat-squirrel-thingies can’t compete with all the rest of us animals, who are we to try change the path of Evolution? Aren’t we an equal part of the Evolutionary Ecosystem? If we make them extinct, isn’t that, “natural selection” and “survival of the fittest”? Don’t we have just as much right to win as other species?

    We have to look out for ourselves. No one else will do it for us. I certainly don’t recall any other species building the Navajo Indian code-talkers, for instance, a preserve, a sanctuary or even including them on a single stinking endangered species list! Given a chance, any bear, lion, schnauzer or rat-squirrel would kill and eat us all. That’s a fact.

    The wooly mammoths laughed when we discovered spears, fire and barbeque sauce. Look where they are now. I’m suspicious these rat-squirrels may have made some similar kind of evolutionary improvements, perhaps even a walnut sauce, which is why they’re making a comeback after 11 million years. You should be too. Don’t scoff! They look evil and cunning.

    I’m just glad that, so far, our species is doing well. I mean, we’re the ones making the others extinct! I’d hate for it to be the other way around! Whew! It seems to me that finding this rat-squirrel-thingy is a set back for all of us. It’s still alive and using our resources. We took millions of years to claw our way to the top of the food chain and I, for one, say, “The less species we have to compete with, the better!” Don’t let our little competitors get a foothold! Act now! Exterminate them while their numbers are few! Working together, we can bring death to the rat-squirrels!!! Who’s with me?

    GO HUMANS!
    WE’RE NUMBER ONE!
    WE’RE NUMBER ONE!
    WE’RE NUMBER ONE!

  11. #11 Dan
    March 12, 2006

    I say, “Who cares about the stupid rat-squirrels?” The ecosystem will get along just fine without them. If they do become extinct, another species will simply evolve to fill the gap, right?

    Besides, if these rat-squirrel-thingies can’t compete with all the rest of us animals, who are we to try change the path of Evolution? Aren’t we an equal part of the Evolutionary Ecosystem? If we make them extinct, isn’t that, “natural selection” and “survival of the fittest”? Don’t we have just as much right to win as other species?

    We have to look out for ourselves. No one else will do it for us. I certainly don’t recall any other species building the Navajo Indian code-talkers, for instance, a preserve, a sanctuary or even including them on a single stinking endangered species list! Given a chance, any bear, lion, schnauzer or rat-squirrel would kill and eat us all. That’s a fact.

    The wooly mammoths laughed when we discovered spears, fire and barbeque sauce. Look where they are now. I’m suspicious these rat-squirrels may have made some similar kind of evolutionary improvements, perhaps even a walnut sauce, which is why they’re making a comeback after 11 million years. You should be suspicious of them, too. Don’t scoff! They look evil and cunning.

    I’m just glad that, so far, our species is doing well. I mean, we’re the ones making the others extinct! I’d hate for it to be the other way around! Whew! It seems to me that finding this rat-squirrel-thingy is a set back for all of us. It’s still alive and using our resources. We took millions of years to claw our way to the top of the food chain and I, for one, say, “The less species we have to compete with, the better!” Don’t let our little competitors get a foothold! Act now! Exterminate them while their numbers are few! Working together, we can bring death to the rat-squirrels!!! Who’s with me?

    GO HUMANS!
    WE’RE NUMBER ONE!
    WE’RE NUMBER ONE!
    WE’RE NUMBER ONE!

  12. #12 Dan
    March 12, 2006

    I say, “Who cares about the stupid rat-squirrels?” The ecosystem will get along just fine without them. If they do become extinct, another species will simply evolve to fill the gap, right?

    Besides, if these rat-squirrel-thingies can’t compete with all the rest of us animals, who are we to try change the path of Evolution? Aren’t we an equal part of the Evolutionary Ecosystem? If we make them extinct, isn’t that, “natural selection” and “survival of the fittest”? Don’t we have just as much right to win as other species?

    We have to look out for ourselves. No one else will do it for us. I certainly don’t recall any other species building the Navajo Indian code-talkers, for instance, a preserve, a sanctuary or even including them on a single stinking endangered species list! Given a chance, any bear, lion, schnauzer or rat-squirrel would kill and eat us all. That’s a fact.

    The wooly mammoths laughed when we discovered spears, fire and barbeque sauce. Look where they are now. I’m suspicious these rat-squirrels may have made some similar kind of evolutionary improvements, perhaps even a walnut sauce, which is why they’re making a comeback after 11 million years. You should be suspicious of them, too. Don’t scoff! They look evil and cunning.

    I’m just glad that, so far, our species is doing well. I mean, we’re the ones making the others extinct! I’d hate for it to be the other way around! Whew! It seems to me that finding this rat-squirrel-thingy is a set back for all of us. It’s still alive and using our resources. We took millions of years to claw our way to the top of the food chain and I, for one, say, “The less species we have to compete with, the better!” Don’t let our little competitors get a foothold! Act now! Exterminate them while their numbers are few! Working together, we can bring death to the rat-squirrels!!! Who’s with me?

    GO HUMANS!
    WE’RE NUMBER ONE!
    WE’RE NUMBER ONE!
    WE’RE NUMBER ONE!

  13. #13 Edin Najetovic
    March 13, 2006

    Dan,

    Though I wholeheartedly share your disgust at conservationists, you are the other end of the spectrum. And though it may be a joke (which I doubt with a triple post), your post is a tad over the top. But just shouting that evolution is a race to dominate other kinds is distinctly untrue. Evolution is a race to pass on genes and I don’t see how one squirrel-rat can stop us from doing so. Or facilitate it for that matter, but for the few people among us that are biologists we can let it live for a while longer before we start eating it ;)

  14. #14 Brenton
    August 4, 2006

    I am very intirested in the Coelecanth. I have been researching the species and following the expeditions to find both the living and the fossilized specimens. I thought the comment posted by MJ Memphis, on March 10, 2006 at 12:11 PM, was quite comical and intiresting-the Coelecanth being sold in fish markets! I would like to look into that and see how whoever was selling the fish ever got their hands on enough to sell at a fish market! So, MJ Memphis, do you think you could possibly send me an email, telling me where the Coelecanth were being sold at a market, who was selling them, and how/where did you find out about it? My email address is brent00720032000@yahoo.com. Any information you could offer me would be much obliged.

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