Hello, Great-Great-Great-Aunt!

I love writing about evolution’s great transitions–from water to land, from ground to air, and so on. For our species, one of the biggest of those transitions happened when our invertebrate ancestors became vertebrates–complete with our distinctive backbone, muscles, mouths, noses, and eyes. For fifteen years, I’ve been writing about this transition, and it’s been exciting to see more fossils come to light that help us understand how our inner fish got its start.  For my new “Matter” column in the New York Times, I take a look at one of the most interesting of these fossils–what one scientist has dubbed a benchmark for our understanding of the first vertebrates. It’s called Metaspriggina, and here’s a video of an animated reconstruction. Get the rest of the story here.

2 thoughts on “Hello, Great-Great-Great-Aunt!

  1. Related story: http://news.yahoo.com/423-million-old-fish-once-earths-largest-vertebrate-144946272.html
    423-Million-Year-Old Fish Was Once Earth’s Largest Vertebrate
    LiveScience.com By By Tia Ghose, Staff Writer

    Some other related notes:
    530M (Million years ago) paper clipsize impressions “fossils of two fish that push the origin of vertebrates back … by at least 30” my.
    (Science News, Vol 156, Nov. 6, ’99, p. 292) fish named Haikouella  already displayed many vertebrate characteristics …some of the 305 fossil specimens Chen’s team has recovered are so well preserved that paleontologists practically swoon over them.

    515M Conodonts, small (2 in.), softbodied, eellike, named after their (sandgrainsized) teeth (common  “all but ubiquitous” in rocks dated from 520-515 to 208-205M), classified as vertebrates because they have true teeth and evidence of a notochord. Once considered ancestors of (all other) vertebrates/fish which weren’t thought to have evolved until 500M (see fish fossils at 530M) 23 separate species, evidence they preyed on other animals. Science Horizons Yearbook, 1996, p. 359 notes they had muscle for vertical eye movement that “appears only in vertebrates.”

    455M Fossil fish scales discovered in Colorado reveal that sharks have been haunting the seas since the middle of the Ordovician period ‘There is no known jawless vertebrate with similar scales'” (Science News, Vol. 149, 2/17/96, p.101).

    450M “scraps of acanthodianlike fossils” (spiny fishes) (Discovering Fossil Fishes, p. 72)

    ~440M+? Anaspid fish known from Early Silurian to Late Devonian, but with a 60 My gap in the middle (Discovering Fossil Fishes, p. 53)

    420-400M The great explosion in diversity of fishes (New Scientist, v 139 #1885, 7/8/93, p 23)
    AH! so our new friend Megamastax may not be so much early, but a contributor to the “explosion.”

    420-380M A number of new discoveries of body fossils suggest during the late Silurian and early Devonian, the major colonization of the land by animals took place. (New Scientist, 7/8/93, p 23)

    Given the number of fossils and different locations, it seems this effect is unlikely to be a factor, and yet stranger things have happened:
    NATURE, Vol 463, 11 February 2010, pp. 797-800
    Non-random decay of chordate characters causes
    bias in fossil interpretation
    Robert S. Sansom1, Sarah E. Gabbott1 & Mark A. Purnellz

  2. I assume these guys were vacum feeders, like many jawed fishes and turtles today, and those proto-jaws perhaps enhanced that process. I can see a selective pressure for that. I wonder too, with the eyes placed as they are, if they buried themselves in the bottom with only their eyes protruding to hide from predators?

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