Links last checked April 5, 2007. Some of the great ones had gone, including People magazine's selection of Paul Sereno as one of the world's Most Beautiful People. Rats!
Early dinosaur discoveries in North America led to feuds among paleontologists
Reconstructing Dinosaurs
Theropods
Small, late Triassic theropods from Argentina:
The earliest formal theropod group, which included Coelophysis, was the Ceratosauria.
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Coelophysis has been accused of being a cannibal, but that is not true.
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Dilophosaurus, with the story of its discovery.
The other theropods (collectively called tetanurans (diverse carnivorous dinosaurs), separated early into the allosaurs (massive, powerful predators) and the lighter and more agile coelurosaurs.
Coelurosauria were extremely bird-like dinosaurs.
Within coelurosaurs, one lineage of small, agile carnivores includes the birds (Chapter 13) and the dromaeosaurs.
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Quick survey of dromaeosaurs
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Deinonychus
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Microraptor
This is a very small dromaeosaur from the famous early Cretaceous beds of Liaoning Province, China.
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New York Times, December 2000.
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BBC News OnLine, December 2000.
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Microraptor flew like a biplane !!!???. National Geographic News, October 18, 2005. Garbage. From Sankar (Protoavis) Chatterjee. This was presented at a talk at the GSA Annual Meeting (not SVP). Anyone with the enormous registration fee can say anything. Wait for the publication...
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Sinovenator, a new little theropod dinosaur from China. Press release from the Field Museum, Chicago, February 14, 2002.. The same press release is also here.
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Velociraptor
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Now meet Megaraptor from Argentina, several times bigger than Velociraptor.
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Update, October, 2005. A new dromaeosaur Buitreraptor from Patagonia is very important. But how? It is certainly a dromaeosaur, but its closest relatives are the "bird-like" genera Unenlagia from Argentina and Rahonavis from Madagascar. Cladistic analysis puts these three together into a Gondwanan group of dromaeosaurs as opposed to the Laurasian majority we are so familiar with. In turn, that asks when the two groups separated, and where their ancestry was. It's Jurassic rather than Cretaceous.
The subplot is the fact that Rahonavis is "bird-like". A question, then: were dromaeosaurs so "bird-like" that the Gondwanan ones were evolving toward flight in Gondwana while Laurasian ones were evolving toward Archaeopteryx and all later birds? In particular, there is a largely undiscussed possibility/implication that Rahonavis was actually flying. If true, this would REALLY upset the carefully crafted stories about birds being unique. But I'm not sure what the real evidence is for ANY flight in Rahonavis, and the forelimbs of Buitreraptor are not for flight (see National Geographic story). As readers of History of Life know, I don't even think that Archaeopteryx could fly much, if at all.
So I think that the new fossil is going to be interesting for its paleogeography and for its implication that dromaeosaurs have deep roots within theropods. It also implies there are a lot of fossils still to be discovered. But maybe that's all the intellectual hurdles we have to face at the moment.
The paper is in Nature, so it is not freely available on the Web.
Building an animatronic Troodon . Article from Scientific American 2001. The movie, on YouTube .
Mononykus is a bird-like theropod from Mongolia, placed within a group called the alvarezsaurids. I write in the book that I suspect it operated rather like a megapod, for example, the brush turkey of Queensland, Australia. By the way, what happens when a brush turkey hatches out?
Ornithomimids are the so-called ostrich dinosaurs.
Tiny Theropods
Compsognathus
Scipionyx
A little theropod from Italy, Scipionyx, is beautifully preserved. (This specimen has been called "Skippy" -- irresistible!).
And on that same note, meet "Kittysaurus"! Eotyrannus, a new small theropod from England.
Giant Theropods
Some theropods evolved to giant size, and are known informally as "carnosaurs". Giant size evolved at least four times, so carnosaurs are NOT a clade:
1. Among the Jurassic allosaurs
The bite of an Allosaurus. When it was published in 2001, this paper was on open access as Nature's Feature of the Week. Well, those days are gone! You'll have to look at these other items instead:
2. Among the Cretaceous tyrannosaurs, which lived in Asia and North America.
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Tyrannosaurs through time: the best accessible summary of tyrannosaurs. Feature article in Natural History, May 2005, by Mark Norell and Xing Xu.
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Web page for the tyrannosaurs on the Tree of Life site; written by Tom Holtz, August 2000.
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The Tyrannosaurus rex page from UC Berkeley
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Recently, science has surpassed itself by turning up a coprolite from Tyrannosaurus rex.
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The most complete skeleton of T. rex is the specimen known as Sue , which had an eventful history during its life, and after its discovery too!
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Sue: The largest and most complete T. rex (so far at least) on display at Chicago's Field Museum
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Sue was the subject of a NOVA program, and you can check the Web page for the program and the the complete transcript of the TV script.
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Tellling the sex of a tyrannosaur: New Scientist, June 2005.
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Feathers on an ancestral tyrannosaur. New Scientist, October 2004.
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How fast could Tyrannosaurus run? Adults couldn't run much at all, it seems:
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National Geographic News, February 28, 2002, about a new paper in Nature. However, remember that young Tyrannosaurus could have done, and probably did.
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Physics Today, 2002
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For an awesome Web page with lots of information on this paper, click here (Cornell University).
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How fast could tyrannosaurs grow? Fast.
3. In the Cretaceous of Gondwana.
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Giganotosaurus at the Academy of Natural Sciences in Philadelphia, which proudly displays its specimen.
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The largest carnivorous dinosaur yet discovered..This is probably a new genus, related to Giganotosaurus. Story from BBC News OnLine, March 13, 2000. Includes a picture of the skull (with Phil Currie, for scale and authenticity!).
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Rajasaurus. This is a big theropod from the latest Cretaceous of India, a chronological and ecological equivalent of Tyrannosaurus.
4. In Carcharodontosaurus from North Africa.
Strange theropods
Incisivosaurus, a gnawing oviraptosaur. These are stories about a new paper in Nature. This dinosaur is from the Liaoning area of China. First assessments say it's herbivorous. It could also be gnawing into bark for insects and grubs, IMHO.
Spinosaurs
The most strangely adapted theropods are the spinosaurs, which have a head that has many crocodile-like features, probably because these theropods evolved to eat large fish. Spinosaurus itself has a sail on its back, rather like that of Dimetrodon, but a full analysis has not been done for Spinosaurus, mostly because the best specimen found before 1998 was bombed to fragments in World War II. However, the newly discovered Suchomimus is a spinosaur.
No-one properly understands therizinosaurs) yet.
There is increasing evidence that there was a radiation among abelisaurs, theropod dinosaurs that flourished in Gondwanaland, in parallel with the dominantly Laurasian coelurosaurs.
The latest new abelisaurid is Masiakasaurus, from Madagascar. (Press release from NSF).
Ornithischians
Sauropodomorphs
Prosauropods
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A new discovery, published in October 1999, means that prosauropods are now the oldest known dinosaurs, from middle- to Late Triassic beds in Madagascar, slightly older than the South American beds that yielded the earliest theropods. The new fossils are jaw pieces from prosauropods. News release.
Sauropods
The earliest sauropod: from the late Triassic of South Africa. National Geographic News, July 10, 2003.
Here is the latest largest dinosaur, in a news report from BBC News OnLine, January 19, 2000. This new unnamed dinosaur is from Argentina, and is estimated to have been 51 meters long (175 feet). Warning: the estimate is based on multiplying up from the size of two neck vertebrae.
But wait: here is another "world's largest dinosaur" (in Spain this time, but not in the plain). BBC News OnLine, February 27, 2004.
Computer reconstructions of sauropods at present give rather bizarre results: for example, the sauropod postures given in this Discover article . This is almost certainly nonsense, a victim of the "Garbage in-garbage out" rule.
Some sauropod pages:
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Introduction to the Sauropods
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What did sauropods eat?
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Details of a new titanosaur, Rapetosaurus, from Madagascar. Press release, August 2, 2001.
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A new giant sauropod, from the Cretaceous of Egypt. New York Times, June 1, 2001. The dinosaur is a titanosaur, related to the largest of them all, Argentinosaurus.
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Puertasaurus, a gigantic sauropod from Argentina. National Geographic News, Jult 2006. Here is a photo gallery of Puertasaurus, from National Geographic News.
Dinosaur Biogeography
Dinosaur Paleobiology: Life at Large Size
Posture and Habitat
Reconstructing the body attitude of sauropods is controversial. The American Museum of Natural History in New York made a bold statement in its reconstruction of Barosaurus rearing up on its hind limbs.
Growth Rate
Tyrannosaurus rex grew VERY fast. This is a study published in Nature in August 2004 (you won't find it freely available on the Web). It's from an all-star cast, lead author Greg Erickson. And it's the most thorough study yet of the growth of T. rex and other tyrannosaurids. Compared to the other tyrannosaurids, T. rex is off the scale. This means that it grew to its enormous size and was old by age 30. There seems to have been a tremendous growth spurt in T. rex and other tyrannosaurs. lasting for about 4 years in the "teens", though the implications of this for biology, sociology, maturity, diet, and locomotion can only be subjects for speculation at this point. A clean and convincing study.
Note added January 2005: Horner, J. R., and K. Padian. 2004. Age and growth dynamics of Tyrannosaurus rex. Proceedings of the Royal Society of London B 271: 18751880. Horner and Padian infer even faster growth for Tyrannosaurus rex. The actual numbers are not as important as the documentation of "mammalian" growth rate.
Web sites for the Erickson et al study:
Dinosaur Behavior
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Walking With Dinosaurs, background report on a BBC program using new animations of dinosaurs. Here is also the home page for that program.
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Dinosaur behavior can be judged by footprints; for example, the dinosaur stampede discovered in Queensland, Australia
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The world's largest collection of dinosaur footprints
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How did theropods make footprints? And how different is the trace fossil from the actual foot shape?
Movie of a (virtual) theropod making a (virtual) footprint. From Gatesy's web site.
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Trackway of a large running theropod dinosaur. BBC News OnLine, January 30, 2002, on a new paper in Nature, which is not universally available on the Web. This is the first proof that large theropods could run, though, of course, most people believed that they could on the basis of the skeleton. Reference: Day, J. J., et al. 2002. Dinosaur locomotion from a new trackway. Nature 415, 494-495.
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Sauropod tracks in England suggest herd behavior. New research, published in Nature, reported here in National Geographic News, May 30, 2002.
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Pachycephalosaurs
New research suggests that the head-butting story about pachycephalosaurs may not be correct. Update on pachycephalosaur behavior, June 2004. UC Berkeley news release.
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Triceratops horns were for display! Live Science, October 2006. Work by Mark Goodwin and Jack Horner.
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Parasaurolophus
Some hadrosaurs such as Parasaurolophus had huge crests on the head. The crests contained tubes running upward from the nostrils and back down into the roof of the mouth. When the tubes are reconstructed they look like medieval horns and can be blown to give a note. The site also offers the sounds it may have made..
Dinosaur Noses:
Dinosaur nostrils may have been reconstructed in the wrong place.
The soft tissue of dinosaurs
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Profile of Mary Schweitzer and her work on dinosaur soft tissue. Discover, April 2006
Dinosaur diseases
A dinosaur with a brain tumor. National Geographic News, November 24, 2003.
Dinosaur Coprolites
Were Dinosaurs Warm-Blooded?
Fossil Four-Chambered Heart Identified in a Dinosaur? No.
In April 2000, a group identified by CT scan an apparently four-chambered heart, fossilized inside the ribcage of a small-to-medium sized ornithischian dinosaur, Thescelosaurus. This was immediately interpreted as good evidence for an elevated metabolic rate.
However, that interpretation was denied by others, who argued that the "heart" was simply a natural concretion. Now that the excitement about the heart of Thescelosaurus has died down (I at least find the counter-arguments convincing), how does that affect arguments about warm-blooded dinosaurs? I suspect that dinosaurs had to have had four-chambered hearts to drive blood round their often huge bodies, so it doesn't matter at all. I certainly think in April 2001 that dinosaurs were warm-blooded. It is the most likely interpretation, so it's the one that I accept for now. I accept the warm-blooded interpretation based on three lines of evidence: their anatomy permitted it; many theropods were feathered; and many dinosaurs lived in polar latitudes.
P. 166. Down feathers and/or display feathers on theropod dinosaurs
P. 168. Dinosaur Eggs and Nests
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National Geographic's web site for dinosaur eggs.
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Dino Russ's dinosaur egg site, with many links
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A dinosaur with two unlaid eggs inside. This is from the Upper Cretaceous of China, and it's an oviraptorosaur.
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Dinosaur nests in Mongolia have produced fascinating science. The dinosaur Troodon apparently laid its eggs over some time (as birds do), rather than all at once (as crocodiles and turtles do).
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The Mongolian nests were naturally associated with the most abundant dinosaur in the area, Protoceratops. To everyone's surprise, when an embryo was finally discovered inside one of the eggs, it was well enough preserved to be identified not as Protoceratops, but as Oviraptor. Later, an adult Oviraptor fossil was discovered, preserved as it died crouched over its nest of Oviraptor eggs.
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Egg and embryo: photograph of real specimen.
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Discovery of major trove of fossil dinosaur eggs and embryos in Argentina.
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Brooding Eggs. A block of rock collected in Mongolia in 1993 turned out to contain an adult Oviraptor that had been buried in a sandstorm while it was crouched over a nest of Oviraptor eggs. The only reasonable explanation of this find is that the dinosaur was brooding its eggs, just as most living birds do. By 1996, three of the seven known Oviraptor adults had been discovered on or near nests. It is very unlikely that Oviraptor was cold-blooded! However, it becomes a matter of judgment how far to extend Oviraptor's body temperature to other dinosaurs.
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While we are talking about dinosaur embryos inside dinosaur eggs, let's ask how they compare to bird embryos inside bird eggs. Here is an awesome site that shows an emu embryo inside an emu egg. University of Texas CT lab.
P. 168. High-Latitude Dinosaurs
P. 170. Passive (Behavioral) Thermoregulation?
P. 172. Dinosaur respiration: they could breathe while they ran
This is new research, and in my view helps to clinch a warm-blooded interpretation. Birds have a pelvic anatomy that allows them to rhythmically move the pubic bone to help pump air in and out of the lungs. What is new is the discovery by David Carrier and Colleen Farmer that living alligators have the same adaptation. And given the phylogeny of archosaurs, that makes it likely that dinosaurs did. Reasonable reconstruction of the dinosaur pelvic anatomy makes it almost certain that they did. So dinosaurs could breathe while they ran, not in the same way as mammals can, but with a mechanism that had a different evolutionary origin, within archosaurs.
Alligators can breathe while they move (so dinosaurs could too) Press release, University of Utah, November 19, 2001, about the latest research by David Carrier and Colleen Farmer. The same press release can be found here.
Trying to explain "dinosaur graveyards".
The reference list for Chapter 12, 4th Edition, with associated Web links
Page last updated November 28, 2007.
Links all checked, October 3, 2005
[For Chapter 11, click here ]
[For Chapter 13, click here ]
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