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Pushing more modern animals back to the Ediacaran

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  • Pushing more modern animals back to the Ediacaran

    An interesting paper came out recently:
    https://www.nature.com/articles/s41559-022-01807-x

    It's about the earliest cnidarians, a group that currently includes things like corals, anemones, and jellyfish. They're quite different from animals like ourselves - radially symmetric, no clear brain, but nerves and muscles that indicate we share a common ancestry. But that ancestry almost certainly predates the Cambrian, given that bilaterians do, and based on molecular evidence.

    We now have Ediacaran fossils of cnidarians that back that up. And the fossil is pretty spectacular. It's got the polyps of a coral, but the tentacles of a jellyfish.

    So, it seems like all sorts of interesting life forms had evolved ahead of the Cambrian, but it's taking a while to find them, probably because the global glaciations wiped out a lot of the sediments that might otherwise have preserved them.
    "Any sufficiently advanced stupidity is indistinguishable from trolling."

  • #2
    Originally posted by TheLurch View Post
    An interesting paper came out recently …
    If you want to be really evil, you can tell me you didn’t have to slog through that paper looking up every third word. But if you want to make amends, you could try to explain to me how this affects the timing of the so-called Cambrian explosion. As in, how long do we generally figure the Cambrian explosion lasted, and by how much does this extend that time span.

    Comment


    • #3
      Originally posted by TheLurch View Post
      An interesting paper came out recently:
      https://www.nature.com/articles/s41559-022-01807-x

      It's about the earliest cnidarians, a group that currently includes things like corals, anemones, and jellyfish. They're quite different from animals like ourselves - radially symmetric, no clear brain, but nerves and muscles that indicate we share a common ancestry. But that ancestry almost certainly predates the Cambrian, given that bilaterians do, and based on molecular evidence.

      We now have Ediacaran fossils of cnidarians that back that up. And the fossil is pretty spectacular. It's got the polyps of a coral, but the tentacles of a jellyfish.

      So, it seems like all sorts of interesting life forms had evolved ahead of the Cambrian, but it's taking a while to find them, probably because the global glaciations wiped out a lot of the sediments that might otherwise have preserved them.
      That cnidarians date from before the Cambrian is nothing new but the new fossil discovery is major league



      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)
      "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
      "Of course, human life begins at fertilization that’s not the argument." --Tassman

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      • #4
        Originally posted by Juvenal View Post

        If you want to be really evil, you can tell me you didn’t have to slog through that paper looking up every third word. But if you want to make amends, you could try to explain to me how this affects the timing of the so-called Cambrian explosion. As in, how long do we generally figure the Cambrian explosion lasted, and by how much does this extend that time span.
        The whole "Cambrian Explosion" notion is an outdated misnomer that should be scraped like "missing link."

        Donald Prothero makes a great case for why it ought to instead be referred to as the "Slow Fuse."

        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)
        "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
        "Of course, human life begins at fertilization that’s not the argument." --Tassman

        Comment


        • #5
          Originally posted by rogue06 View Post
          The whole "Cambrian Explosion" notion is an outdated misnomer that should be scraped like "missing link."

          Donald Prothero makes a great case for why it ought to instead be referred to as the "Slow Fuse."
          I'd be somewhat kinder to the idea of a Cambrian Explosion. It's a real phenomenon, but we've done a poor job of understanding exactly what the phenomenon is. There's several aspects to that:
          - it's difficult for most people to comprehend the scale of tens of millions of years.
          - global glaciations wiped out many of the Cambrian and Ediacaran fossil beds, leaving us with an even more incomplete picture than usual.
          - lack of a good picture of Ediacaran fossils leave us with a poor understanding of what organisms predate the Cambrian.
          - Lots of the interpretation of the Cambrian took place before molecular and DNA data provided indications of the relations between some groups of species and when splits took place.
          - Our interpretations are biased by which groups survived subsequent mass extinctions.

          What I'd say is that this doesn't change our sense of the timing of the Cambrian Explosion at all - the Cambrian remains the Cambrian. What it does is tell us more about what was present when the Cambrian started, and thus gives us a clearer picture of what was involved in the Explosion. and, along with most other recent discoveries, it makes it clear that it was less an "origin" event, and more a diversification.
          "Any sufficiently advanced stupidity is indistinguishable from trolling."

          Comment


          • #6
            Originally posted by TheLurch View Post
            I'd be somewhat kinder to the idea of a Cambrian Explosion. It's a real phenomenon, but we've done a poor job of understanding exactly what the phenomenon is. There's several aspects to that:
            - it's difficult for most people to comprehend the scale of tens of millions of years.
            - global glaciations wiped out many of the Cambrian and Ediacaran fossil beds, leaving us with an even more incomplete picture than usual.
            - lack of a good picture of Ediacaran fossils leave us with a poor understanding of what organisms predate the Cambrian.
            - Lots of the interpretation of the Cambrian took place before molecular and DNA data provided indications of the relations between some groups of species and when splits took place.
            - Our interpretations are biased by which groups survived subsequent mass extinctions.

            What I'd say is that this doesn't change our sense of the timing of the Cambrian Explosion at all - the Cambrian remains the Cambrian. What it does is tell us more about what was present when the Cambrian started, and thus gives us a clearer picture of what was involved in the Explosion. and, along with most other recent discoveries, it makes it clear that it was less an "origin" event, and more a diversification.
            That "it's difficult for most people to comprehend the scale of tens of millions of years" is perhaps one of the better arguments for abandoning the use of the term "Explosion." It leads to misunderstandings.

            That was the reason "Missing Link" got dropped although it still appears from time to time (particularly in the popular press).

            Moreover, the "Cambrian Explosion," was but one in a series of major evolutionary radiation events that have taken place with the last being at the end of the Cretaceous. That is not meant to minimize the importance of this first one, as it is arguably the most important, but that should not come at the cost of minimizing all the other ones.

            Finally, I really don't want this to degenerate into a squabble over terminology, so I won't say anything more about this.

            In this thread at least

            PS: Nice to see you again.

            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)
            "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
            "Of course, human life begins at fertilization that’s not the argument." --Tassman

            Comment


            • #7
              Originally posted by rogue06 View Post
              PS: Nice to see you again.
              After a few scans, I was given the ok to resume stressful activities, so I figured risking discussing evolution with Lee was an option again.
              "Any sufficiently advanced stupidity is indistinguishable from trolling."

              Comment


              • #8
                Originally posted by TheLurch View Post
                So, it seems like all sorts of interesting life forms had evolved ahead of the Cambrian, but it's taking a while to find them, probably because the global glaciations wiped out a lot of the sediments that might otherwise have preserved them.
                But cnidarians are known (as rogue06 said) before the Cambrian. And I would say that "all sorts of interesting life forms had evolved ahead of the Cambrian" is a stretch, given that we don't have the evidence for this.

                P.S. Thankful you're better, hope you enjoy good health...
                "What I pray of you is, to keep your eye upon Him, for that is everything. Do you say, 'How am I to keep my eye on Him?' I reply, keep your eye off everything else, and you will soon see Him. All depends on the eye of faith being kept on Him. How simple it is!" (J.B. Stoney)

                Comment


                • #9
                  Originally posted by lee_merrill View Post
                  But cnidarians are known (as rogue06 said) before the Cambrian. And I would say that "all sorts of interesting life forms had evolved ahead of the Cambrian" is a stretch, given that we don't have the evidence for this.

                  P.S. Thankful you're better, hope you enjoy good health...
                  This is basically for school kids, but more importantly looks a bit dated.

                  Nevertheless, it should get the point across regarding "all sorts of interesting life forms had evolved ahead of the Cambrian"

                  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)
                  "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
                  "Of course, human life begins at fertilization that’s not the argument." --Tassman

                  Comment


                  • #10
                    "Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte (505 million years ago) of British Columbia." (Wikipedia)

                    Was this supposed to be an Ediacaran picture?

                    Blessings,
                    Lee
                    "What I pray of you is, to keep your eye upon Him, for that is everything. Do you say, 'How am I to keep my eye on Him?' I reply, keep your eye off everything else, and you will soon see Him. All depends on the eye of faith being kept on Him. How simple it is!" (J.B. Stoney)

                    Comment


                    • #11
                      Originally posted by lee_merrill View Post
                      "Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte (505 million years ago) of British Columbia." (Wikipedia)

                      Was this supposed to be an Ediacaran picture?

                      Blessings,
                      Lee


                      I thought I posted this

                      6179880.jpg


                      Although either of these would have done.




                      ediacara-white-sea-assemblages.jpg1-precambrian-illustration-spencer-sutton.jpg

                      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)
                      "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
                      "Of course, human life begins at fertilization that’s not the argument." --Tassman

                      Comment


                      • #12
                        Originally posted by lee_merrill View Post
                        P.S. Thankful you're better, hope you enjoy good health...
                        Appreciated.

                        Originally posted by lee_merrill View Post
                        But cnidarians are known (as rogue06 said) before the Cambrian. And I would say that "all sorts of interesting life forms had evolved ahead of the Cambrian" is a stretch, given that we don't have the evidence for this.
                        I suppose "interesting" is a matter of personal judgement, and you could always claim that all the species in Rogue's images, along with many others, just aren't interesting to you.

                        I notice you're not commenting on the fact that this organism has features that are found in different major groups of cnidarians today, consistent with its relatives being ancestral to them. I wonder why you're choosing to ignore that?

                        Although I guess it's consistent with you citing stem groups - something you don't think exists - as evidence when it happens to be convenient.
                        Originally posted by lee_merrill View Post
                        "Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte (505 million years ago) of British Columbia." (Wikipedia)
                        "Any sufficiently advanced stupidity is indistinguishable from trolling."

                        Comment


                        • #13
                          Originally posted by TheLurch View Post
                          Appreciated.


                          I suppose "interesting" is a matter of personal judgement, and you could always claim that all the species in Rogue's images, along with many others, just aren't interesting to you.

                          I notice you're not commenting on the fact that this organism has features that are found in different major groups of cnidarians today, consistent with its relatives being ancestral to them. I wonder why you're choosing to ignore that?

                          Although I guess it's consistent with you citing stem groups - something you don't think exists - as evidence when it happens to be convenient.
                          I guess it's to each his own, but I, for one, find organisms such as Dickinsonia, Spriggina and even Tribrachidium quite interesting for a variety of reasons. But Lee's position pretty much forces him to minimize all Ediacaran biota, so naturally, they aren't of much interest to him.


                          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)
                          "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
                          "Of course, human life begins at fertilization that’s not the argument." --Tassman

                          Comment


                          • #14
                            Originally posted by TheLurch
                            I suppose "interesting" is a matter of personal judgement, and you could always claim that all the species in Rogue's images, along with many others, just aren't interesting to you.
                            Originally posted by rogue06 View Post
                            I guess it's to each his own, but I, for one, find organisms such as Dickinsonia, Spriggina and even Tribrachidium quite interesting for a variety of reasons.
                            But I was thinking "interesting" meant "interesting Cambrian creatures from the Ediacaran".

                            Originally posted by TheLurch
                            I notice you're not commenting on the fact that this organism has features that are found in different major groups of cnidarians today, consistent with its relatives being ancestral to them. I wonder why you're choosing to ignore that?
                            Well, it didn't seem to have a bearing on your main point. But it is, well, interesting...

                            Blessings,
                            Lee
                            "What I pray of you is, to keep your eye upon Him, for that is everything. Do you say, 'How am I to keep my eye on Him?' I reply, keep your eye off everything else, and you will soon see Him. All depends on the eye of faith being kept on Him. How simple it is!" (J.B. Stoney)

                            Comment


                            • #15
                              Originally posted by lee_merrill View Post
                              But I was thinking "interesting" meant "interesting Cambrian creatures from the Ediacaran".
                              You'd expect the ancestors of Cambrian creatures plus a lot of unrelated stuff in the Ediacaran, given the two were separated by a mass extinction.

                              Amazingly, that appears to be what we're seeing.

                              Originally posted by lee_merrill View Post
                              Well, it didn't seem to have a bearing on your main point. But it is, well, interesting...
                              It's kind of central to my main point. But, as indicated above, you don't seem to understand it.
                              "Any sufficiently advanced stupidity is indistinguishable from trolling."

                              Comment

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