fossils
pharyngula | July 11, 2012If you ever get a chance, spend some time looking at fish muscles in a microscope. Larval zebrafish are perfect; they're transparent and you can trace all the fibers, so you can see everything. The body musculature of fish is most elegantly organized into repeating blocks of muscle along the length of the animal, each segment having a chevron ("V") or "W" shape. Here's a pretty stained photo of a 30 hour old zebrafish to show what I mean; it's a little weird because this one is from an animal with experimentally messed up gene expression, all that red and green stuff, but look at the lovely…
pharyngula | April 25, 2012A while back, I told you all about this small piece of the biochemistry of the fly eye — the pathways that make the brown and red pigments that color the eye.
I left it with a question: if even my abbreviated summary revealed considerable complexity, how could this pathway evolve? Changing anything produces a failure or change in the result. Before I answer, let's make the problem even harder, because I love a challenge (although actually, I'm cheating — it's going to turn out that complexity is not a barrier, but an opportunity).
The pigment pathways above are far downstream: they operate…
pharyngula | December 29, 2011I've written about the spectacular phospatized embryos of the Doushantuo formation before. It's a collection of exceptionally well preserved small multicellular organisms, so well preserved that we can even look at cellular organelles. And they're pre-Cambrian, as much as 630 million years old.
They've been interpreted as fossilized embryos for which we have no known adult forms. They certainly look like embryos, but one thing has always bothered me — they all look like blastula-stage embryos at various points in their early divisions, and the absence of later stages was peculiar: how did…
pharyngula | December 20, 2011Look with your puny camera eyes! Some new specimens of Anomalocaris, the spectacular Cambrian predator, have been discovered in South Australia. These fossils exhibit well-preserved eyes, allowing us to see that the bulbous stalked balls on their heads were actually fairly typical compound eyes, like those of modern insects.
Anomalocaris eyes from the Emu Bay Shale. a-d, Eye pair, SAM P45920a, level 10.4 m. a, b, Overview and camera lucida drawing. Scale bars, 5 mm. Grey fill in b represents visual surface, the proximal part in the upper eye extrapolated from the lower eye. c, Detail of…
pharyngula | December 15, 2011A few weeks ago, PLoS One published a paper on the observation of preserved chitin in 34 million year old cuttlebones. Now the Institute for Creation Research has twisted the science to support their belief that the earth is less than ten thousand years old. It was all so predictable. It's a game they play, the same game they played with the soft tissue preserved in T. rex bones. Here's how it works.
Compare the two approaches, science vs. creationism. The creationists basically insert one falsehood, generate a ludicrous conflict, and choose the dumbest of the two alternatives.
The…
pharyngula | October 10, 2011At first I thought this discovery was really cool, because I love the idea of ancient giant cephalopods creating art and us finding the works now. But then, reality sinks in: that's a genuinely, flamboyantly extravagant claim, and the evidence better be really, really solid. And it's not. It's actually rather pathetic.
It consists of the discovery of ichthyosaur vertebrae lying in a flattened array. They look like this.
Photo shows shonisaur vertebral disks arranged in curious linear patters with almost geometric regularity. The arranged vertebrae resemble the pattern of sucker discs on a…
pharyngula | September 16, 2011Emily Baldry is six years old. Emily has a little plastic shovel. Emily dug up a 160 million year old cephalopod.
I'm 54, I have a little plastic spoon, and I'm eyeing the backyard. There used to be cephalopods swimming around in this neighborhood…of course, there were also some annoying glaciers that scoured the landscape. But I can dream!
(Also on FtB)
pharyngula | September 3, 2011Ann Coulter is back to whining about evolution again, and this week she focuses on fossils. It's boring predictable stuff: there are no transitional fossils, she says.
We also ought to find a colossal number of transitional organisms in the fossil record - for example, a squirrel on its way to becoming a bat, or a bear becoming a whale. (Those are actual Darwinian claims.)
Darwin postulated that whales could have evolved from bears, but he was wrong…as we now know because we found a lot of transitional fossils in whale evolution. Carl Zimmer has a summary of recent discoveries, and I wrote…
pharyngula | August 28, 2011I raised a few questions about those 3.4 billion year old bacterial fossils, primarily that I was bugged by the large size and that they cited a discredited source to say that they were in the appropriate range of diameters for bacteria. Now my questions have been answered by Chris Nedin, and I'm satisfied. In particular, he shows data from 0.8 and 1.9 billion year old fossils in which the bacterial sizes are in the same range. It's also a good review of the other evidence used to infer that they actually are bacterial microfossils.
(Also on FtB)
pharyngula | August 24, 2011Both Jerry Coyne and Larry Moran have good write-ups on the recent discovery of what are purportedly the oldest fossil cells, at 3.4 billion years old. I just have to add one little comment: a small, niggling doubt and something that bugs me about them. All the smart guys are impressed with this paper, but this one little thing gives me pause.
I'm a microscopist — I look at micrographs all the time, and one of the things I always mentally do is place the size of things in context. And I was looking at the micrographs of these fossils, and what jumped out at me is how large they are. They're…
pharyngula | August 14, 2011This is one beautiful plesiosaur, Polycotylus latippinus.
(Click for larger image)
(A) Photograph and (B) interpretive drawing of LACM 129639, as mounted. Adult elements are light brown, embryonic material is dark brown, and reconstructed bones are white. lc indicates left coracoid; lf, left femur; lh, left humerus; li, left ischium; lp, left pubis; rc, right coracoid; rf, right femur; rh, right humerus; ri, right ischium; and rp, right pubis.
The unique aspect of this specimen is that it's the only pregnant plesiosaur found; the fore and hind limbs bracket a jumble of bones from a juvenile…
pharyngula | July 28, 2011A lovely new dinosaur fossil from China is described in Nature today: it's named Xiaotingia zhengi, and it was a small chicken-sized, feathered, Archaeopteryx-like beast that lived about 155 million years ago. It shares some features with Archaeopteryx, and also with some other feathered dinosaurs.
(Click for larger image)a, b, Photograph (a) and line drawing (b). Integumentary structures in b are coloured grey. cav, caudal vertebra; cv, cervical vertebra; dv, dorsal vertebra; fu, furcula; lc, left coracoid; lfe, left femur; lh, left humerus; li, left ilium; lis, left ischium; lm, left manus…
pharyngula | July 12, 2011That's not hyperbole. I really mean it. How else could I react when I open up the latest issue of Bioessays, and see this: Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules. Just from the title alone, I'm immediately launched into my happy place: sitting on a rocky beach on the Pacific Northwest coast, enjoying the sea breeze while the my wife serves me a big platter of bacon, and the cannula in my hypothalamus slowly drips a potent cocktail of cocain and ecstasy direct into my pleasure centers…and there's pie for dessert. It's like the…
pharyngula | July 6, 2011Phil Senter has published the most deviously underhanded, sneaky, subtle undermining of the creationist position I've ever seen, and I applaud him for it. What he did was to take them seriously, something I could never do, and treat their various publications that ape the form of the scientific literature as if they actually were real science papers, and apply their methods consistently to an analysis of taxonomy. So on the one hand, it's bizarre and disturbing to see the like of Ken Ham, Jerry Bergman, and Henry Morris get actual scientific citations, but on the other hand, seeing their…
pharyngula | June 30, 2011I got a letter from a creationist today, claiming that "Darwinism is falsified," based on an article in Nature. It's kind of amazing; this article was just published today, and the metaphorical digital ink on it is barely metaphorically dry, and creationists are already busily mangling it.
It's a good article describing some recent fossil discoveries, found in a 515 million year old deposit in South Australia. Matthew Cobb has already summarized the paper, so I'll be brief on the details, but it's very cool. What was found was a collection of arthropod eye impressions, probably from cast-off…
pharyngula | March 10, 2011It's a real shame. Forty million years ago, this pair of mites, Glaesacarus rhombeus, had just buckled down to a happy grind, when plop, a drop of tree sap fell on them and entombed them in flagrante delicto. Also, coitus interruptus. And as long as we're slinging around the Latin, Perfututum!.
Notice that they mate butt-to-butt. This is probably the preferred position when your partner has a face like an arachnid.
pharyngula | August 5, 2010I'm going to break another webcam, aren't I? While you can, you can actually watch a dinosaur dig in progress in Svalbard, Norway. (Strictly speaking, though, it looks like they're excavating pliosaurs and ichthyosaurs, not dinosaurs.)
I'm amused that it looks exactly like the the big construction project on the county courthouse in Morris, Minnesota: a lot of people standing around watching one person with an itty-bitty trowel pushing dirt around. Except that these guys are all wearing coats in August.
But seriously, it looks like they're having a good time — bring the kids around so they…
pharyngula | July 15, 2010
Sometimes, I really hate fossils. I hate them with the passion of a spurned lover, one who is consumed with desire but knows that he will never, ever be satisfied. They drive me mad.
Right now we're at a point in our technology where we can take a small sample from a living organism and break it down into amazing detail — we can extract every gene, throw them into a computer, and compare them with every other gene that has been similarly sampled. We can look for the scars of evolution, we can analyze and figure out where on the tree of life this cell resides, we can even figure out what…
grrlscientist | June 24, 2010tags: evolution, biogeography, phylogeography, animals, Here Be Dragons, How the Study of Animal and Plant Distributions Revolutionized Our Views of Life and Earth, Dennis McCarthy, book review
I'm happy: another book review of mine was just published, this time, by Science magazine. This book, Here Be Dragons: How the Study of Animal and Plant Distributions Revolutionized Our Views of Life and Earth (Oxford University Press: Oxford; 2009), is by Dennis McCarthy, a researcher at the Buffalo Museum of Science in Buffalo, New York. In short, I liked the book and I thought it was generally well-…
pharyngula | May 26, 2010
Well, more like great-great-many-times-great-aunt of all squid, but it's still a spectacular fossil. Behold the Cambrian mollusc, Nectocaris pteryx.
(Click for larger image)Reconstruction of Nectocaris pteryx.
This was one of those confusing, uninterpretable Cambrian animals, represented by only one poorly preserved specimen. Now, 91 new specimens have been dug up and interpreted, and it makes sense to call it a cephalopod. It has two camera eyes — not arthropod-like compound eyes — on stalks, an axial cavity containing paired gills like the mantles of modern cephalopods, and a flexible…