Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
She’s gone. I was at the Field Museum on Wednesday for the first time since the previous month, and the removal of Sue the Tyrannosaurus rex has been completed.
Stanley Field Hall, where Sue used to be.
Viewed from the balcony above, visitors walk through Stanley Field Hall, seemingly unaware of the ghostly white outline of Sue’s now departed plinth.
Where Sue used to be, from above.
A sign explained where Sue will eventually show up.
Sue’s actually not gone away entirely, for the second floor balcony display, featuring Sue’s real skull, remains in place. [JAC: the skull was always up there as it was too heavy to mount on the skeleton downstairs.]
The second floor display also includes touchable, life-size, bronze models of various parts of Sue, including the (relatively) tiny forearm. Devotees of the concept of unity of type, and Neil Shubin‘s Your Inner Fish in particular, will recognize the “one bone, two bones, many bones” pattern found throughout the tetrapod vertebrates and their piscine forebears.
A bronze model of Sue’s forearm.
A closeup of the digits; the two distalmost phalanges of the outer (lower, in this photo) digit were among the few bones missing from Sue’s skeleton, and the ones in the model are based on Albertosaurus, a related theropod dinosaur.
Sue’s fingers.
From up on the balcony, I could also get a better look at the model of Pteranodon longiceps hanging from the ceiling.
Pteranodon longiceps in the Field Museum.
And zooming in a bit.
Does the position of this model mean that Pteranodon is Ceiling Reptile?
Sue, the iconic Tyrannosaurus rex that has inhabited the Field Museum of Natural History‘s Stanley Field Hall since 2000, is coming down. But, shortly after she comes down, she’ll be going up– upstairs that is. The Museum announced plans last year to replace Sue in Stanley Field Hall with a model of Patagotitan mayorum, a much larger dinosaur than Tyrannosaurus rex. At the same time, they’ll be adding plants and pterosaurs to the Hall. Bill Simpson (who for some reason appears to be being assisted by Ricky Gervais) explains what’s going to happen to her in this video. (And continue watching the next video, also featuring Bill, that comes up after the first finishes.)
A similar model of Patagotitan has been on display at the American Museum of Natural History in New York for a couple of years now. It doesn’t even fit in the dinosaur hall there, and its head and neck poke out into the hall way to greet visitors arriving by elevator! Sue will be moving upstairs to the Field’s second floor, whose balconies overlook the Hall, where she’ll join the rest of the dinosaurs in the Evolving Planet exhibit. Sue is a theropod, and though in the same order of dinosaurs as Patagotitan, which was a sauropod, Sue and her kin ate creatures like Patagotitan and its kin.
I had gotten to see Sue up close during the study and preparation phases prior to her being placed on exhibit, and wanted to say farewell (for a little while), so I went down to see her before the deconstruction. These are pictures from a visit in late December.
Sue towers over her human prey admirers in Stanley Field Hall.Getting closer to Sue’s business end.The better to eat you with.The somewhat old-fashioned painted reconstruction on the second floor, overlooking Sue down below. Sue’s skull, which is too heavy to be supported on the body of the mounted skeleton in Stanley Field Hall, has always resided in a separate display case on the second floor balcony, just below this painting.One of the pterosaurs is already in position.
I went down again last month, and took a few more pictures, mostly closer shots of interesting parts of her anatomy.
A closer view of her teeth.Her reduced, two-fingered, forelimbs. The functional significance of this feature is much speculated on, but unknown.Her strong, 4-toed (3 forward, 1 back) hind foot. These provided a powerful mode of locomotion.Au revoir, Sue!
The tale of how Sue got from South Dakota to the Field Museum is a long and tortuous one, and not very edifying; but that’s a story for another post.
This coming Monday, February 1, at 7 PM in the Student Union Cinema, the University of Wisconsin-Parkisde will present Luis Chiappe, Director of the Dinosaur Institute of the Natural History Museum of Los Angeles County, will speak on “Birds of Stone: Avian Fossils from the Age of Dinosaurs”.
Dr. Luis Chiappe of the LACM
Many of the features commonly associated with birds (feather, wings, hollow bones, wishbones) were inherited from their dinosaurian ancestors, and these features arose at various times during the birds’ long Mesozoic history. New fossils have laid out this evolutionary saga in great detail, allowing us to trace the changes from the earliest birds, such as Archaeopteryx, to the dawn of modern birds. The talk, part of UW-Parkside’s Science Night series, is intended for the general public.
At noon on Monday, in Molinaro Hall D 139, Dr. Chiappe will present a more technical talk at the Biological Sciences Colloquium entitled “Birding in the Mesozoic: Recent Insights on the Early Evolution of Birds”. There’s also a small exhibit in the UWP Library, “Dinosaurs and Birds: The Art of Science”, that you can stop in and see.
Both talks are free and open to the public. For the evening talk, parking in the Student Union lot is free after 6:30 PM. For the noon talk, there are metered spots, but if any WEIT readers are planning to come, email and I’ll see what we can do. The talks are presented in conjunction with the exhibit “Dinosaurs Take Flight: The Art of Archaeopteryx”, by Silver Plume Exhibitions in conjunction with the Yale Peabody Museum, at the Kenosha Public Museum, on display now through March 27th.
This is a very well done exhibit, combining fine reproductions of almost all of the eleven known Archaeopteryx specimens (the real ones almost never travel!), with an exploration of how several distinguished paleo-artists create their works, including Julius Cstonyi, whose work we’ve highlighted here at WEIT before.
Anyone from Chicago to Milwaukee is within range, and you can make a day of it– the exhibit at the KPM, two talks, and a stop in UWP’s Library. Even if you can’t make it Monday, the exhibit at KPM is well worth a trip on some other day. Here’s a tidbit– a realistic sculpture– from Dinosaurs Take Flight; I hope to post a fuller report later.
Update: An alert reader, has objected to the theory presented below, or at least the specific evidence used; he has proffered what he contends is “much more pertinent evidence”, which I append below.
Jerry posted a couple of days ago on a specimen of an early tetrapod, Ossinodus, which seems to have had a partially healed injury to the radius of its right forearm. The authors who described the injured specimen interpreted the injury as a fracture that could only have occurred on land, arguing that Ossinodus therefore is the oldest tetrapod that can confidently be said to be terrestrial. (The first tetrapods, from the upper Devonian, are considerably older than Ossinodus, which is from the following Mississippian subperiod of the Carboniferous; but these earlier tetrapods, which had caudal fins and functional gills, may not have been terrestrial.) Ossinodus is thus potentially an important point in the transition from fishes to amphibians.
Another major transition in the history of vertebrate life was that from reptiles to mammals, which we have discussed here before at WEIT. As important as the morphological changes which can be seen in the fossils, are the changes in ecology and behavior, which, along with environmental changes, lead to changes in the extent to which one group or another dominates the ecosystems of its time. Although mammals originated in the mid-Mesozoic era, it was not until the Cenozoic (colloquially known as the “Age of Mammals”) that the mammals became the dominant terrestrial vertebrates. Most ideas on the rise of mammals to ecological dominance focus on the fate of dinosaurs and other large reptiles at the end of the Cretaceous, when the disappearance of the latter may have been caused or accelerated by the impact of an extraterrestrial body. I was recently forwarded another theory, visually expressed, about how it was that mammals replaced reptiles as the dominant land animals on Earth.
A mammal and reptile engage in a vigorous contest for dominance.
And now, the more pertinent evidence:
Leo battles velociraptor.
I will allow as the mammal in the new evidence does seem to have a more dominant position over the reptile.
Earlier this year my friend Chris Noto and his colleagues Derek Main and Stephanie Drumheller published a paper describing injuries to turtle and dinosaur bones from the Cretaceous that show evidence that they were preyed upon by crocodiles. Besides the irresistible alliteration, their paper serves to show that we can sometimes learn much more about extinct animals than merely their skeletal morphology, and, with the right sorts of evidence, can learn about their behavior, ecology, and physiology as well.
The fossils were recovered at a site in Texas known as the Arlington Archosaur Site. Modern crocodilians feed on turtles, and also on dinosaurs, if you think of birds as dinosaurs (which, in a sense, they are). They will seize turtles side to side (as shown in the reconstruction) or top to bottom. American alligators are particularly fond of turtles, and, compared to some other crocodilians, their rear teeth are especially blunt and peg-like (sort of like molar teeth). This helps to crush the shells of turtles they are eating (which, I have been told, break with a popping sound). E.A. McIlhenny, the great naturalist of hot sauce fame, wrote:
I have seen alligators catch large terrapins and turtles of considerable size and crush their hard shells as if they were made of paper, swallowing them whole.
Tooth scars on a turtle shell (above) and a dinosaur leg bone (below).
Noto et al’s study is a nice example that shows we can learn about more than just the morphology of extinct creatures, but can also learn about thier biology and the paleocommunities they lived in, including (in other studies) ecology, behavior, and even color (see, for example, Matthew’s recent post here, and earlier posts by Jerry here and here).
McIlhenny, E.A. 1935. The Alligator’s Life History. Christopher Publishing House, Boston. (Reissued in a facsimile edition in 1976 by the Society for the Study of Amphibians and Reptiles, with a foreword by the great herpetologist and conservationist, Archie Carr.)
Noto, Christopher R., Derek J. Main, and Stephanie K. Drumheller. 2012. Feeding traces and paleobiology of a Cretaceous (Cenomanian) Crocodyliform: Example from the Woodbine Formation of Texas. Palaios 27:105-115. (abstract)
Jerry gave a talk yesterday at the MCZ which most WEIT readers couldn’t attend (although you can get a general idea of it by watching this video of an earlier talk by Jerry), so I thought I’d give folks the opportunity see another evolution talk, “Why Study Fossils?” by Chris Noto. (The audio is a bit faint, so turn up the volume.)
Chris is a paleontologist specializing in Mesozoic reptiles who has recently joined my department. His talk was given last month as part of our Science Night series, which Jerry has also spoken in.
Bruce Woollatt, who posts under the handle “Your name’s not Bruce?” won an autographed copy of WEIT by coining the term “faitheist.” I have had some correspondence with him, and learned that one of his avocations is dinosaurs. He has an artistic bent, too, and has built models of dinos for the Children’s Museum in London, Ontario. I thought I’d post, with his permission, some photos of his latest project, especially because it includes a cat.
First the cat, who is used as a scale for Bruce’s modelling. As he tells it:
Amber has been a part of our family since the summer of 2001. We think she is about ten years old. She was dumped with her litter of kittens in my mother-in-law’s neighbourhood. She started hanging around people’s homes; people started to feed her. Her kittens were caught and homes were found for all of them through a local organization called Animalert. Mom, however eluded capture, for a while at least. Then one of the neighbours phoned Animal Care and Control, who snagged her using a noose-like device. Unlike Animalert, ACC euthanizes unclaimed animals after two weeks. So my wife and I got over there as quickly as we could to pick her up and have her put into Animalert’s system. They gave her a checkup and spayed her (apparently she was pregnant again; the Animalert people told us that if Animal Care and Control had known this they might have euthanized her right away). We agreed to foster her on a temporary basis as we already had an elderly cat (C.G. for Curious George. She died the following February at age 17). Amber had other ideas. She worked her way into our hearts and “temporary” has turned into eight years. When she is not using her talents as a geophysical standard measurement she is the furry head of our household.
Fig. 1. Amber
Bruce describes his latest project, which he’s been pursuing since March (you can find his ongoing posts about the project here. (Have a look; it’s an amazingly intricate operation.)
My aim is to make an accurate, poseable 1/10 scale Tyrannosaurus rex skeleton out of cheap, safe and simple materials (cardboard, wire, wood, papier mache) using simple tools and techniques. I’m using FMNH PR2081, the specimen known as “Sue”, which is part of the collection of Chicago’s Field Museum of Natual History, as my prototype. I’m going to be using Sue’s dimensions and proportions to size up my rex. The Journal of Vertebrate Paleontology’s Memoir on T.rex osteology by Christopher Brochu is my main source of information, with details from other specimens used as needed to fill in any gaps.
Fig. 2. Current state of model, with Amber as scale
Fig. 3. Foundation of dino skull.
Fig. 4. Tail vertebrae
Figure 5. Hindlimb bones. Femur, tibia and fibula of papier mache, smaller bones of cardboard, tissue, glue, and acrylic paint
In this week’s Science we find a paper by Schweitzer et al. (total of 16 authors!) that has a quite remarkable result. (See the one page summary by Robert Service here.) The upshot is that protein-sequence data from an 80-million-year old duckbilled dinosaur supports the dinosaurian origin of birds.
This story has a bit of a tortuous background. First of all, we’ve known for a long time that birds evolved from gracile theropod dinosaurs; the fossil and anatomical evidence is given in WEIT. But for some folks, DNA-based data is more convincing than is the fossil record. And molecular evidence is what Schweitzer et al. provided.
In 2007, her group published a paper purporting to show that fragments of the protein collagen (a structural protein found in blood vessels and connective tissue), taken from a 68-million-year old fossil of T. rex, showed that the protein sequence (which reflects the DNA sequence) was more similar to that of birds than to that of modern reptiles. This strongly suggests that birds evolved from a lineage of dinosaurs that had already branched off of the lineage that gave rise to modern reptiles. This meant that birds and dinosaurs are each other’s closest relatives compared to say, turtles or iguanas. In fact, many systematists say that birds are dinosaurs, which is the conclusion you’re forced to if you’re a hidebound cladist. I mentioned this paper in WEIT in footnote 11 on p. 237 (this was probably the last thing I put in the book). Of course this result was no surprise to paleontologists.
As recounted by Service, this result was sharply questioned by other researchers, who claimed that the protein sequence was due to contamination; many others thought it was hard to believe that any protein could survive for so many millions of years. I was a bit depressed about this, because I had already put the result in my book and there was no opportunity to change it before publication. Also, it was just such a cute result — the kind of new finding that gets our juices flowing as scientists.
Well, Schweitzer and her team persisted, and her new result supports the old one. This time the group extracted protein fragments from the femur of a duck-billed dinosaur, Brachylophosaurus canadensis, collected in Montana. Great care was taken to prevent contamination. They found that some of the elements in the demineralized bone bound to antibodies made against bird collagen, indicating that collagen fragments similar in sequence to those of birds were present in the bone. The same was found with antibodies for hemoglobin and two other structural proteins.
Some biochemical wizardry on bone extracts identified eight fragments of collagen, and their sequences (also determined in a separate lab to preclude contamination) were determined. Sure enough, they were similar to the T. rex fragments that were questioned earlier, and were more similar to collagen sequences of modern birds than to those of modern reptiles. (See the phylogeny below.) Note that there’s a small disparity between the fossil and biochemical evidence: T. rex, as a theropod (the group that gave rise to modern birds), should be more closely related to modern birds than is B. canadensis. This discrepancy might be an artifact of not having a complete protein sequence.
Let’s be clear: the phylogeny that we get doesn’t really tell us anything we didn’t know before. Birds are highly-evolved dinosaurs, and that was already confirmed by the fossil record. Still, it’s nice to have this molecular confirmation, and perhaps the most surprising result is the ability to determine the sequences of protein fragments that have survived for millions of years. If this can be done with other fossils, we’ve suddenly gained the ability to solve many long-standing puzzles about ancestry and evolutionary relatedness.
Phylogeny showing closer relationship between dinosaurs and birds (Gallus = chicken, Struthio = ostrich) than between either of these groups and modern reptiles (alligators and Anolis lizards). Ergo, birds are dinosaurs.
Brachylophosaurus canadensis, the duck-billed dinosaur whose proteins were sequenced. Illustrationby Julius T. Csotony from Science article.
Schweitzer, M. H. et al. 2009. Biomolecular Characterization and protein sequences of the campanian hadrosaur B. canadensis. Science 324:626-631.
One of the most exciting developments in paleontology in the past ten years or so has been the discovery that many species of theropod dinosaurs had feathers. The earliest discoveries were quite controversial. At the 1997 meetings of the Society of Vertebrate Paleontology in Chicago, a paper was read criticizing the interpretation of the skin structures on these fossils as feathers. In response, Phil Currie, one of the team working on the fossils, presented an impromptu rebuttal paper later the same day, a rather unusual development for a normally tightly scheduled scientific meeting. I was not convinced they were feathers myself until a while later, when a number of fossils of the new forms were brought to the Field Museum, and I was able to see them for myself– they had feathers! One of the strangest of these feathered dinosaurs was Microraptor gui, which had both its forelimbs and hindlimbs modified into feathered wings. It seems to exemplify the remark of J.B.S Haldane, the British geneticist who was one of the founders of the modern synthesis, “that the universe is not only queerer than we suppose, but queerer than we can suppose.” Jerry highlights Microraptor in chap. 2 of WEIT, and notes a NOVA program on PBS, “The Four-winged Dinosaur”, that has a great website with interactives and videos, including the entire program. Originally airing last year, it was just recently shown again on my local PBS station, so check to see if it may be showing again in your area too.
Most of the specimens of feathered dinosaurs, as well as many true birds, have come from the fossil beds of Liaoning in northeastern China. The American Museum of Natural History has a nice website on the Liaoning fossil biota. The Liaoning deposits have become one of the most important and interesting of what are called Lagerstatten (singular: Lagerstatte), a German word for a fossil deposit with extraordinary conditions of preservation. Such deposits, because they reveal structures (such as soft parts like feathers) and organisms (those lacking hard parts) otherwise missing from the fossil record, are often of crucial importance in studying the history of life on Earth. Other famous Lagerstatten include the Pre-Cambrian Ediacara Hills of Australia, the Cambrian Burgess Shale in British Columbia and Chengjiang in China, and the Jurassic Solnhofen Limestone of Bavaria. These Lagerstatten have revealed, respectively, an early multicellular fauna, the Cambrian Explosion, including the earliest vertebrates, and Archaepoteryx, the first bird.
As I discuss in WEIT, the evidence shows that birds evolved from theropod dinosaurs–gracile, carnivorous beasts that walked on two legs. Some of the important evidence comes from Chinese fossils showing theropods with various types of feathers. The incipient stages of feather evolution appears to be filamentous feathers (T. rex might well have been covered with fluff!), implying that flight feathers originated as devices to help insulate the theropods. In a recent paper in Nature, however, F. Zhang et al. found a theropod fossil (Epidexipteryx hui), about 160 million years old, which had not only the downy feathers (feathers completely unsuitable for flight) but also four very long tail feathers that could not have been used for either flight or insulation. E. hui also showed a number of morphological features that seem to make it closely related to modern birds. The most likely explanation for these tail feathers is that they were ornaments–ornaments that evolved for either species recognition or via sexual selection. The evolution of flight, then, may have begun with feathers that were used for display. A somewhat fanciful reconstruction of the beast is shown below.
Fig. 1. Amber
Fig. 2. Current state of model, with Amber as scale
Fig. 3. Foundation of dino skull.
Fig. 6. His name is Bruce (and hers is Sue)
