At long last, I’ve posted to flickr my images of the Royal Ontario Museum’s new dinosaur gallery, with several shots of their new exhibit, the Barosaurus.
PZ Myers recommends some basic books about evolution: “Read these!
This is not an onerous demand. These books are not overly technical, they aren’t part of the specialist literature, they are just general introductions to the ideas and evidence of evolution.”
I’ve read At the Water’s Edge and Your Inner Fish. Both were informative, enjoyable, and convincing as they explained some of the history of evolution. At the Water’s Edge describes the history of tetrapods’ conquest of the land, with the evidence we have. Shubin’s Your Inner Fish shows the traces of our fish ancestry in our bodies.
Casey Luskin, a lawyer for the Discovery Institute, hasn’t yet discovered that eponymous means having the same name as. When “Garth Brooks” puts out a debut album called “Garth Brooks,” it’s referred to as his eponymous album. And when Neil Shubin, the author of a scientific paper describing his discovery, refers to the bones in Tiktaalik’s reinforced fin as being homologous to the eponymous wrist bones in tetrapods, he means the bones with the same names. And Casey complains that the author hasn’t specified which bones.
Previously, he quote-mined:
Shubin has another paper in Nature specifically on Tiktaalik‘s fin, entitled, “The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb.” In this paper, there’s much more discussion of the “wrist,” as the first sentence of the abstract contains a confession of retroactive ignorance that states, “Wrists, ankles and digits distinguish tetrapod limbs from fins, but direct evidence on the origin of these features has been unavailable.”
That’s right, Casey. There has been plenty of circumstantial evidence. Shubin evaluated it and went looking for direct evidence in rocks of the right age and ecological circumstances; and he found it. What’s to carp at?
He makes much of the fact that Ahlberg and Clack in 2006 were careful to point out that these are still fin bones and not digits. Very good, Casey! They aren’t claiming that legs appeared “fully formed” from fins. It’s a transitional form–functional in its swampy environment, but not on dry land. In fact, he argues as if Shubin hadn’t already called Tiktaalik’s limb a fin in the title of his paper. He tries to turn scientific accuracy into a weakness: as rhetoric, that stinks like a dead fish.
Finally, Casey goes for the stale authority. He quotes another paper from fifteen years ago, stating that modern lungfishes and others have sturdier fins than ancient fishes in “the forms that we know.” The lesser point is that no one says that the modern lungfishes etc. are the same as ancient fossils. They have been evolving too and are not relevant. The main point is that Tiktaalik was not known 15 years ago. It’s a newly discovered form that is more developed, lived in a different environment, and had sturdier limb-fins. I’d call this argument a pair of red herrings.
Shubin et al. go on to acknowledge, “Limb skeletons differ from those of fins mainly by the presence of bones that comprise mobile wrists, ankles and digits.” It would thus indeed be very impressive to find a fish with a wrist, ankle, or digits in its fin. Does Tiktaalik have these bones?
No, and Shubin doesn’t say that it does. He says that there are bones in arrangements and places that could develop into wrists and digits, and that those bones allow extension and flexion is a similar way to tetrapod joints. Casey claims that modern fish that prop themselves up out of water have similar mechanisms for extension and flexion. The ones I’ve seen use straight fins.
Casey, flogging his straw man again, calls for a diagram comparing Tiktaalik’s limb to a tetrapod limb. Then he shows Shubin’s diagram, in which Tiktaalik is placed neatly between the extinct fish Panderichthyis and the extinct tetrapod Acanthostega, with its “eight little piggies” made famous by Stephen Jay Gould. Apparently Casey doesn’t understand standard zoology diagrams of homologous bones, either.
I guess Casey hasn’t studied either discography or zoology.
Researchers have examined a well-preserved amphibian fossil and found that it fills the gap between frogs and salamanders. Gerobatrachus hottoni, “Hotton’s old frog,” has a mosaic of features such as a salamander’s walk and a tail but a wide, froggy head. It comes from a time, 280 million years ago, before frogs and salamanders became separate branches on the tree of life.
their research, published in Thursday’s issue of the journal Nature, settles a long and hot debate in scientific circles as to just how these species evolved.
“This fossil is the most like the modern amphibian that you find and it’s from incredibly ancient times,” said principal investigator Jason Anderson, an assistant professor of veterinary anatomy at the University of Calgary who specializes in vertebrate paleontology.
“So what this does is provide conclusive evidence that frogs and salamanders have an origin among one particular group of extinct fossil amphibians,” he said Wednesday from Calgary. “This fossil falls right into a gap in the fossil record between one archaic group of amphibians and the earliest examples of the modern amphibians, frogs and salamanders.”
The fossilized remains were discovered in 1995 in the scrub land of north-central Texas by the late Nicholas Hotton of the Smithsonian Institution, the man for whom the long-extinct creature is named.
Hotton, who died two years later, knew he had made a significant find, said Anderson.
“With a slip of paper found with the specimen and in his handwriting is the nickname ‘Froggie.’ So he recognized the specimen for what it was immediately after he found it.”
The slab of silt stone bearing the 12-centimetre-long creature’s imprint had languished in the Smithsonian’s collection for some time before a U.S. colleague brought it to Anderson’s attention; he jumped at the chance to create a team to partially raise it from its rocky grave.
Co-author Robert Reisz, a professor of biology who heads a vertebrate paleontology research lab at the University of Toronto, came on board to lay bare the creature’s skeleton, delicately chipping away at the chalk-like rock in which it was embedded.
It has small teeth, a reduced number of vertebrae, salamander ankle bones, a frog’s ear, and a lightly built skeleton.
The first frog fossils date from about fifty million years later.
Complete specimen in ventral view, photograph (left) and interpretive outline drawing (right). Abbreviations: bc, basale commune; cl, cleithrum; cv, clavicle; dm, digital elements of the manus; dt3, distal tarsal 3; fe, femur; h, humerus; ic, intercentrum; il, ilium; is, ischium; op, olecranon process of ulna; pc, pleurocentrum; r, radius; sr, sacral rib. [Diagram from Pharyngula]
Sauropod Vertebra of the Week: get a look at this beauty: Xenoposeidon proneukos, a new English dinosaur. The XenoposeIdon vertebra is shown here:
This partial vertebra was collected in the 1890s and stored away in the London Museum of Natural History until recently, when palaeontologist Mike Taylor discovered that it was unusual. He asked Darren Naish of Tetrapod Zoology about it, and Darren had a partially written review article, so they decided to collaborate on a new description. The bone turned out to belong to a very large, unknown dinosaur which was different enough to be placed in its own genus. There’s a whole week of posts about it in the link, plus another link to a web-friendly page with lots of detailed images and a simple connecting narrative. Enjoy!
This reminds me of the Barosaurus found by the Royal Ontario Museum last year in its own closet:
I just stumbled upon this lovely image: Eurasian griffon vulture by Linda Wright.