Announcement

Collapse

Natural Science 301 Guidelines

This is an open forum area for all members for discussions on all issues of science and origins. This area will and does get volatile at times, but we ask that it be kept to a dull roar, and moderators will intervene to keep the peace if necessary. This means obvious trolling and flaming that becomes a problem will be dealt with, and you might find yourself in the doghouse.

As usual, Tweb rules apply. If you haven't read them now would be a good time.

Forum Rules: Here
See more
See less

Fossils of squirrel-like creatures push back origin of mammals millions of years

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Fossils of squirrel-like creatures push back origin of mammals millions of years

    The discovery of the fossilized remains of three different long extinct squirrel-like creatures in northeastern China that are roughly 160 myo (Middle Jurassic) is providing evidence that mammals arose millions of years earlier than some scientists have thought.

    The remains were unearthed from a rock outcropping in a cornfield that is part of the Tiaojishan Formation by private collectors and amateur paleontologists over the past few years at the Daxishan site of Linglongta, Liaoning province of China.

    The discovery consists of six extremely well-preserved nearly complete fossil specimens, which included skulls, skeletons and teeth, that are from three different extinct species belonging to a poorly understood group of Mesozoic animals called Haramiyida, or haramiyids. The remains were so well preserved that not only were the remains of the bones and teeth fossilized but so were some of the soft parts including fur and the animal's guts.

    The researchers say that these remains demonstrate that they clearly belong in the mammal family tree as well as show that different sort of body plans were emerging rather early on in contrast to the traditional view that all early mammals were shrew-like creatures.

    Haramiyids appear to have originated during the Late Triassic and went extinct during the Late Jurassic. Their remains have predominantly been found in Europe but more recent discoveries place them in Greenland, Africa, Mongolia and China as well.

    "For decades, scientists have been debating whether the extinct group, called Haramiyida, belongs within or outside of Mammalia," explained one of the authors of the paper describing the creatures, Jin Meng, a curator in the American Museum of Natural History's Division of Paleontology in New York.

    Meng continued, "Previously, everything we knew about these animals was based on fragmented jaws and isolated teeth. But the new specimens we discovered are extremely well preserved. And based on these fossils, we now have a good idea of what these animals really looked like, which confirms that they are, indeed, mammals."

    Prior to the discovery debate centered on whether haramiyids were a basal group of true mammals or mammaliaformes, their closest relatives. While known about for well over a century, until now, as Meng indicated, their remains were essentially limited to jaw and tooth fragments which wasn't enough to make any sort of conclusive identification.

    But now the researchers, led by Shundong Bi of the Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences in Beijing and the Biology Department of Indiana University of Pennsylvania (IUP)[1], have enough material to make a much more certain identification.

    Key among the finds are the skulls which reveal clear evidence of mammalian middle ear -- regarded as the defining characteristic for determining what is and what isn't a mammal. The middle ears of mammals are distinctive in that they have three bones, the malleus, incus, and stapes (also known respectively as the hammer, anvil and stirrup).

    The new findings also presents evidence for their closest known relatives being rodent-like creatures known as multituberculates which existed for some 120 million years -- from 35 to 153 mya (Late Jurassic-Oligocene). Neither of these groups having any living descendants meaning that while these new discoveries may resemble modern squirrels they aren't related to them but are the result of convergent evolution.

    What makes this discovery important is that by placing them firmly in the mammal group this indicates that the earliest mammals first arose some 208 mya during the Triassic.

    While the majority of earlier studies had concluded that true mammals had originated somewhere between 161 and 176 mya (Middle Jurassic) several other studies along with DNA research suggested the earlier date was more likely.

    When alive these animals weighed between 28 to 300 grams (1-11 oz.) or, as Meng put it, from "a house mouse to a small squirrel" in size.

    The largest of the three previously unknown species is named Shenshou lui, with the genus name "shenshou" coming from combining the Mandarin Chinese words for "deity" (shen) with "animal" (shou) making "divine beast." The species name, "lui," refers to the scientist who collected the holotype specimen, Lu Jianhua. Aside from being the largest of the three it had more prominent incisors than the others.

    The smallest of the group, weighing approximately 40 grams (1.4 oz.) was named Xianshou songae with the genus name essentially meaning "celestial beast" while the second or species name was named in honor of Rufeng Song, the collector of the specimen.

    The last, which weighed approximately 83 grams (just under 3 oz.) was extracted from a chunk of siltstone and named Xianshou linglong with the species name being derived both from linglong, the Chinese word for "exquisite" as well as a reference to the town of Linglongta, where the specimen came from. Its sharper cusps and ridges of its upper molars allow it to be distinguished from Shenshou and Xianshou songae.

    All three possessed slender light builds, long (probably prehensile) tails, limbs and elongated feet that indicate they were arboreal (tree dwellers). Meng said that "they were good climbers and probably spent more time than squirrels in trees." He pointed out that "their hands and feet were adapted for holding branches, but not good for running on the ground."

    Their teeth, while differing from one another, were alike in that they had many cusps, or raised points, on the crowns. It is commonly thought that mammals evolved from a common ancestor that had three cusps but these newly discovered species possessed two parallel rows of cusps on each molar -- with up to seven cusps on each side. The researchers said that they don't know how this complex tooth pattern evolved in relation to those of other mammals.

    Be that as it may, the teeth strongly indicate that these creatures omnivorous, eating insects, nuts and fruits -- much like other members of their clade (Euharamiyida) are thought to have done.

    Jurassic_mammals1.jpg
    Left: holotype specimen of Senshou lui Top right: specimen of Xianshou linglong
    Bottom right: specimen of [/i]Xianshou songae[/i]


    Jurassic_mammals3.jpg
    Paratypes 1 and 2 of Shenshou lui

    Jurassic_mammals2.jpg
    Artist's reconstruction of Xianshou songae



    Further Reading:

    Three new Jurassic euharamiyidan species reinforce early divergence of mammals Abstract

    See What Our Earliest Mammal Ancestors Looked Like

    Ancient Squirrel-Like Creatures Push Back Mammal Evolution

    Chisel-Toothed Beasts Push Back Origin of Mammals

    Mammals Originated Much Earlier than Previously Assumed

    Squirrel-like Jurassic critters shed light on mammal origins

    Squirrel-like critters lived alongside Jurassic age dinosaurs, study says

    When did mammals evolve? Fossils of an extinct squirrel-like animal reveal the answer

    Fossils of New Squirrel-like Species Support Earlier Origin of Mammals



    1 The confusing sounding name comes from the fact that the university is located in Indiana County, Pennsylvania.

    I'm always still in trouble again

    "You're by far the worst poster on TWeb" and "TWeb's biggest liar" --starlight (the guy who says Stalin was a right-winger)
    "Of course, human life begins at fertilization that’s not the argument." --Tassman

  • #2
    Any rabbits in the Cambrian yet?


    Comment


    • #3
      Originally posted by Cerebrum123 View Post
      Any rabbits in the Cambrian yet?


      from the links
      "...Many scientists had suggested that mammals originated in the Middle Jurassic, which ranged from 174 million to 164 million years ago....
      "The oldest known haramiyids date to the Late Triassic period about 220 million to 200 million years ago. This suggests mammals are at least that old, "earlier than much previous research predicted,"
      LIVESCIENCE

      "Previous research had suggested that mammals originated in the middle Jurassic (between 176 and 161 million years ago). The current study states that mammals were roaming the earth as early as the late Triassic period (between 235 and 201 million years ago)..."
      NATURE WORLD NEWS

      that like jumps from 14% (IF 176 to201 jump)
      .....to 46% (IF 161 to 235 jump)

      is Haldane getting nervous

      (50 years in the grave, I guess he already knows whats the deal)
      To say that crony capitalism is not true/free market capitalism, is like saying a grand slam is not true baseball, or like saying scoring a touchdown is not true American football ...Stefan Mykhaylo D

      Comment


      • #4
        Originally posted by jordanriver View Post
        from the links
        "...Many scientists had suggested that mammals originated in the Middle Jurassic, which ranged from 174 million to 164 million years ago....
        "The oldest known haramiyids date to the Late Triassic period about 220 million to 200 million years ago. This suggests mammals are at least that old, "earlier than much previous research predicted,"
        LIVESCIENCE

        "Previous research had suggested that mammals originated in the middle Jurassic (between 176 and 161 million years ago). The current study states that mammals were roaming the earth as early as the late Triassic period (between 235 and 201 million years ago)..."
        NATURE WORLD NEWS

        that like jumps from 14% (IF 176 to201 jump)
        .....to 46% (IF 161 to 235 jump)

        is Haldane getting nervous

        (50 years in the grave, I guess he already knows whats the deal)
        You YECs still have 300 million years to go.

        So sorry.

        K54

        Comment


        • #5
          Originally posted by klaus54 View Post
          You YECs still have 300 million years to go.

          So sorry.

          K54
          just a matter of time
          To say that crony capitalism is not true/free market capitalism, is like saying a grand slam is not true baseball, or like saying scoring a touchdown is not true American football ...Stefan Mykhaylo D

          Comment


          • #6
            Originally posted by jordanriver View Post
            just a matter of time
            A million years here, a million years there, and it finally adds up to some deep time.

            Comment


            • #7
              Originally posted by jordanriver View Post
              from the links
              "...Many scientists had suggested that mammals originated in the Middle Jurassic, which ranged from 174 million to 164 million years ago....
              "The oldest known haramiyids date to the Late Triassic period about 220 million to 200 million years ago. This suggests mammals are at least that old, "earlier than much previous research predicted,"
              LIVESCIENCE

              "Previous research had suggested that mammals originated in the middle Jurassic (between 176 and 161 million years ago). The current study states that mammals were roaming the earth as early as the late Triassic period (between 235 and 201 million years ago)..."
              NATURE WORLD NEWS

              that like jumps from 14% (IF 176 to201 jump)
              .....to 46% (IF 161 to 235 jump)

              is Haldane getting nervous

              (50 years in the grave, I guess he already knows whats the deal)
              Hardly.

              It has long been known that the lineage that led to the mammals split off from the one that led to reptiles a long, long time ago (Early Permian IIRC). The question has been just how soon did the first true mammals originate from it.

              I'm always still in trouble again

              "You're by far the worst poster on TWeb" and "TWeb's biggest liar" --starlight (the guy who says Stalin was a right-winger)
              "Of course, human life begins at fertilization that’s not the argument." --Tassman

              Comment


              • #8
                Originally posted by rogue06 View Post
                Hardly.

                It has long been known that the lineage that led to the mammals split off from the one that led to reptiles a long, long time ago (Early Permian IIRC). The question has been just how soon did the first true mammals originate from it.
                Very true, the ancient origins of mammals in the Permian has been well known and documented for more then 50 years. This discovery simply fills in a significant gap in the evidence for the intermediates in mammal evolution. Great discovery!!!, but in reality nothing new, nor unexpected, and predicted from previous fossil evidence.

                I can see the anti-evolution fundamentalists responding in confusing rhetoric like the scattering of a flock of burning Cambrian rabbits.
                Last edited by shunyadragon; 09-13-2014, 08:23 AM.
                Glendower: I can call spirits from the vasty deep.
                Hotspur: Why, so can I, or so can any man;
                But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

                go with the flow the river knows . . .

                Frank

                I do not know, therefore everything is in pencil.

                Comment

                Related Threads

                Collapse

                Topics Statistics Last Post
                Started by Juvenal, Yesterday, 04:47 PM
                2 responses
                24 views
                1 like
                Last Post Seeker
                by Seeker
                 
                Started by rogue06, 11-28-2020, 12:54 PM
                4 responses
                37 views
                0 likes
                Last Post shunyadragon  
                Started by shunyadragon, 11-26-2020, 09:46 PM
                0 responses
                12 views
                1 like
                Last Post shunyadragon  
                Started by lee_merrill, 11-23-2020, 10:25 PM
                5 responses
                50 views
                1 like
                Last Post Seeker
                by Seeker
                 
                Started by rogue06, 11-22-2020, 08:25 AM
                5 responses
                74 views
                3 likes
                Last Post rogue06
                by rogue06
                 
                Working...
                X