Winner: National Science Teachers Association "Outstanding Science Trade Books for Students K–12: 2008" Award
Parent's Choice 2008 Award Recommendation For Non-Fiction
Finalist: AAAS/Subaru Science Books and Films Prize for Excellence in Science Books, Young Adult Science Books
NEW UPDATES FOR JANUARY 2010: Silesauridae, Megaraptora, Tawa, fuzzy heterodontosaurs, and much much more! See the notation "NEW January 2010:" for the appropriate update.
2008 Genus List now available; Winter 2010 genus list coming soon.
Greetings,
This website is provided especially for readers of my recent book Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages (illustrations by Luis Rey; Random House, published 2007). In the Introduction I begin by saying "The world of dinosaurs is changing", and indeed it has been! In fact, to quote from p. 5:
The purpose of this website is provide you with an update of information on dinosaurs. I'll try to hit the highlights of recent discoveries in the field, chapter by chapter. And I will update these periodically (with dates of new additions listed before the appropriate section). (The initial list of updates date to October 2007, when the book was released).
Additionally, I will provide a link at the bottom to an updated version of the Appendix: Dinosaur Genus List, containing newly named dinosaurs and revised classifications. Additionally, I will provide the complete introduction to that Appendix, explaining what I meant by the various size and weight classes.
SUPPLEMENTARY INFORMATION TABLE OF CONTENTS:
CHAPTER UPDATES
Chapter 3: Fossils and Fossilization
Chapter 4: Geologic Time
Chapter 11: The Origin of Dinosaurs
More significantly, though, are several finds related to the reptile
Silesaurus shown in Chapter 11. One of these is
Sacisaurus
of the Late Triassic of Brazil, about 5 feet (1.5 meters) long. The first description of this near-dinosaur was published in October 2006. These two represent a distinct group of herbivores very closely related
to the dinosaurs. Like true Dinosauria their pubis and ischium bones are very long; unlike true dinosaurs, their hands do not seem to have been
large and grasping, nor do their hips have an open socket. Sacisaurus seems to have a pair of small bones in front of the dentary, similar
to the larger single predentary bone of ornithsichian dinosaurs.
Based on comparisons with the more complete skeletons of Silesaurus and Sacisaurus, it turns out that a number of previously-known
creatures from the Triassic belong to this group of "silesaur" near-dinosaurs. These include Lewisuchus and Pseudolagosuchus of the
Middle Triassic of Argentina (possibly the same species!) and Technosaurus and Eucoelophysis of the American Southwest. Additionally,
some species known only isolated teeth of the Late Triassic Southwest (Crosbysaurus, Galtonia, Krzyzanowskisaurus,
Lucianosaurus, Pekinosaurus, and Protecovasaurus) might be from silesaurs, or they might be from a newly-recognized group
of herbivorous crocodile relatives the revueltosaurs. In fact, the near-dinosaur silesaurs and the near-crocodilian revueltosaurs
represent two of the most important groups of herbivorous reptiles of the Middle and Late Triassic, and they weren't even known five years ago!
NEW January 2010: Silesauridae--the group described in the previous two paragraphs--has been formally named. Many analyses now show
this group to be the closest known relatives to the first dinosaurs.
Chapter 12: Saurischians (Lizard-Hipped Dinosaurs)
NEW January 2010: In December 2009 this debate may have come to an end. Specifically, discovery of a new primitive theropod dinosaur
named Tawa from the Late Triassic of New Mexico has helped to answer some
of the old questions. Tawa shows features
shared by more advanced theropods and those of primitive saurischians like Herrerasauria and Eoraptor. With all this new information,
it now appears that Herrerasauria is a group of very primitive theropod; that Eoraptor is a slightly more advanced form; that Tawa
is more advanced still, and is in fact the closest known relative to Coelophysis plus later theropods. (This last group--Coelophysis
plus later theropods--is technically known as Neotheropoda.)
Chapter 13: Coelophysoids and Ceratosaurs (Primitive Meat-Eating Dinosaurs)
There is still confusion about the relationships between the primitive theropods. Some studies support the breakdown that I use in the book:
the coelophysoids as the first major branch, and a second group of ceratosaurs more closely related to the tetanurines than to the coelophysoids.
However, there are some researchers who have evidence that the old 1980s-1990s idea that coelophysoids and ceratosaurs are each other's closest
relatives in a a grander Ceratosauria. To make it even more confusing, still other evidence points to a different arrangement. In this third
scheme, the slender small coelophysoids such as Coelophysis, Megapnosaurus, Procompsognathus, Segisaurus, and the like
represent the first branch separate from group of larger forms. These larger dinosaurs, the Early Jurassic Dilophosauridae, containing
newly-discovered Dracovenator of South Africa, Dilophosaurus of western North America, and "Dilophosaurus" sinensis of
China. In fact, work first published in September and October 2007 by Nathan Smith (graduate student at the Field Museum of Natural History in Chicago and the University of Chicago) and
his colleagues shows that Cryolophosaurus of Early Jurassic of Antarctica is also a member of this group. I think that Smith and
his colleagues probably have the closest approximation to the truth so far when it comes to primitive theropods.
In this new hypothesis, these 16.5 to 21 foot (5-7 m) long dilophosaurids were more closely related to the ceratosaurs and tetanurines
than they were to the "true" coelophysoids. I find this a really interesting idea, and look forward to future research that might resolve
this issue. Whether the Late Triassic Zupaysaurus and Gojirasaurus turn out to be early representatives of the
dilophosaurids, or big true coelophysoids, or something in between the two remains to be seen.
The oldest true ceratosaur in the restricted sense, Berberosaurus of northern Africa, was first described by Ronan Allain (Muséum national d'Histoire
Naturelle, Paris) and colleagues in September 2007. This dinosaur shows that true
ceratosaurs (that is, the group including Ceratosaurus, Elaphrosaurus, noasaurids, abelisaurids, but not coelophysoids of
any sort) were already around by the Middle Jurassic.
NEW July 2008: A major restudy of the ceratosaurs has been published by Matt Carrano (Smithsonian Institution) and Scott Sampson (University of
Utah). Among other discoveries, they found that Deltadromeus, previously thought to be a giant noasaurid, is more likely a primitive ceratosaur.
NEW January 2010: There has been a lot of work on the dinosaurs covered in this chapter. The newly-discovered Tawa of the Late Triassic
of New Mexico shows a mixture of primitive theropod and neotheropod features; when it is added into our studies, it shows that even the reduced version
of "Coelophysoidea" mentioned in the paragraphs above is not a natural group either. Instead, "coelophysoids" simply represent "the primitive
phase of the Neotheropoda."
And while Herrerasauria and Eoraptor seem to be more clearly moving INTO Theropoda, Guaibasaurus is moving out: see notes for
Chapter 22.
Among the primitive ceratosaurs, the most important new discovery is Limusaurus.
This dinosaur from the earliest Late Jurassic of Xinjiang, China (the same site as the early tyrannosauroid Guanlong) shares many
features in common with Elaphrosaurus, but is known from more complete fossils. Most significantly, it has a
toothless beak very similar to the later ornithomimid coelurosaurs and extremely short arms with stubby
hands with only two fingers. These two features suggest that it was not a carnivore at all, but instead a herbivore (or at best an omnivore that
ate mostly plants and small animals.)
Skorpiovenator from the Late Cretaceous of Argentina
was first named in 2008, and represents one of the mostly completely known skeletons of an abelisaurid so far discovered.
Chapter 14: Spinosauroids (Megalosaurs and the Fin-Backed Fish-Eating Dinosaurs)
On p. 92, the name "Calvadosaurus" is a mistake: the dinosaur in question is properly called Dubreuillosaurus.
NEW January 2008: The prosauropod behind Cryolophosaurus on p. 90 now has a name: Glacialsaurus.
NEW January 2010: WOW!! There have been some major discoveries and re-analyses within this part of the theropod family tree in
the last couple years, many of them due to graduate student Roger Benson of Cambridge University in England. Most of this work was a result of
Benson's detailed study of Megalosaurus itself. He and his co-authors have argued that the dinosaurs in this chapter should more accurately
be called "Megalosauroidea" rather than "Spinosauroidea", and if I do a new edition of this book I will be using that name.
Here are some of Benson and colleagues discoveries:
Chapter 15: Carnosaurs (Giant Meat-Eating Dinosaurs)
As mentioned in the update to Chapter 14, Monolophosaurus has been moved out of Carnosauria into Megalosauroidea. Also, several European
dinosaurs that were previously considered megalosaurids or other primitive tetanurines (Poekilopleuron, Lourinhanosaurus,
Metriacanthosaurus) are now recognized to be part of Sinraptoridae; because of this, sinraptorids are not strictly Asian dinosaurs anymore.
More significantly,
however, has been the recognition of a whole new branch of carnosaur: the Neovenatoridae and its subgroup the Megaraptora. Neovenatoridae is
a newly-recognized sister group to Carcharodontosauridae (together they form Carcharodontosauria.) Neovenatorids have rather large thumb claws, among
other features. Neovenator and gigantic Chilantaisaurus are primitive neovenatorids, while the rest form a group of
slender forms called Megaraptora. Megaraptora includes: Fukuiraptor of the Early Cretaceous of Japan; Megaraptor itself (and thus it belongs in Chapter 15, not Chapter 14!);
Aerosteon of the Late Cretaceous
of Argentina (this is the "unnamed Argentine carcharodontosaurid" mentioned on p. 104);
Australovenator of the Early Cretaceous of Australia; and Orkoraptor of the latest Cretaceous of Argentina. Since Orkoraptor
belongs in this group, the carnosaurs actually did make it to the end of the Cretaceous.
In other news, new studies show that Shaochilong (previously called "Chilantaisaurus" maortuensis) is a carcharodontosaurid,
and thus this group is now known to have lived in Asia.
Chapter 17: Tyrannosauroids (Tyrant Dinosaurs)
NEW January 2010: 2009 was a spectacular year for tyrant dinosaur discoveries. New examination of the skull of Middle Jurassic Proceratosaurus of
England shows that it is a very primitive tyrannosauroid, and possibly a close relative of Guanlong. From the later Early Cretaceous of
China comes long-snouted Xiongguanlong and
tiny Raptorex which help us fill in the spaces
of the tyrant family tree. Among other things, Raptorex shows that the dinky arms and pinched foot (arctometatarsus) of Tyrannosauridae evolved
in smaller bodied ancestors.
Among true Tyrannosauridae comes the most-complete skeleton of Alioramus
yet discovered. Isn't it pretty? (Maybe just to me...)
Chapter 18: Ornithomimosaurs and Alvarezsaurs (Ostrich and Thumb-Clawed Dinosaurs)
More significantly, though, these paleontologists observe that with the exception of some deinonychosaurs, all of the dinosaurs in this
part of the family tree show signs of eating at least some non-meat (mostly plants, but also insects and/or small bodied vertebrates). The
simplest explanation would be that their common ancestor (which would have split off from the common ancestor of the meat-eating compsognathids and
tyrannosauroids some time before the Middle Jurassic) began to eat things other than dinosaurs. (It also means that meat-eating deinonychosaurs
like Deinonychus and Velociraptor evolved from omnivorous ancestors!)
A flock of the ostrich dinosaur Sinornithomimus
was found in China by Dave Varricchio and colleagues. These poor dinosaurs got stuck in some very sticky mud and died, which was bad for them
but great for paleontologists! None of them were fully grown, but none were babies either. This suggests that perhaps during the brooding season,
when parents were nesting with the new generation of babies the "kids" and "teenagers" hung out together without a parent around. For a modern
example of this, visit almost any shopping mall...
Chapter 19: Oviraptorosaurs and Therizinosauroids (Egg-Thief and Sloth Dinosaurs)
What did Gigantoraptor eat? Well, other oviraptorosaurs seem to have eaten both plants and small animals, and the same may be
true of Gigantoraptor. However, to this big theropod, "small animals" may have included sheep-sized ceratopsians and jackal-sized
dromaeosaurids!
With the discovery of Gigantoraptor, we now recognize that practically all the groups of coelurosaurian theropods produced giants
bigger than 1 ton: the tyrannosaurids (of course); Deinocheirus for the ornithomimosaurs; Gigantoraptor for the oviraptorosaurs; and
Therizinosaurus for the therizinosaurs.
Some taxonomic notes: Following a new scheme, the name "Therizinosauroidea" would be restricted to the more stump-footed sloth dinosaurs, so
that the larger category (including slender-footed Falcarius) would be "Therizinosauria". Also, the larger group of Oviraptorosauria
plus Therizinosauria (if they do form a group together) would be Oviraptoriformes.
NEW January 2010: As I mentioned in the notes to Chapter 18, new studies suggest that Therizinosauria and Oviraptorosauria are not each
others closest relatvies. Instead, Oviraptorosauria seems to be more closely related to Deinonychosauria and Avialae.
Chapter 20: Deinonychosaurs (Raptor Dinosaurs
While no one has found the actual feathers of Velociraptor yet (the rocks in which it is found do not preserve feather impressions), a
very recent discovery (September 2007) shows that it probably had very big arm feathers. Like little Rahonavis and Microraptor, Velociraptor
had "quill nodes": bumps on its ulna (forearm bone) where big feathers attached. While Velociraptor would not be able to fly, it may
have used its arm feathers as a help in turning quickly; while brooding its nests; for display; and (while a young one) for Wing-Assisted Incline
Running.
NEW January 2008: Footprints of a large (Achillobator-sized) dromaeosaurid have been found from the
Early Cretaceous of China, showing that they did indeed walk with their sickle-claws raised (as Luis Rey illustrated them in the book.)
NEW January 2010: Despite what I said on p. 154, it now appears that Pedopenna and Epidendrosaurus (and newly discovered
Epidexipteryx
So, let's see what's new with the dinosaurs:
Extraordinarily well preserved "dinosaur mummies" have been in the news. These include "Dakota",
an Edmontosaurus, and "Leonardo", a Brachylophosaurus. These two
hadrosaurines provide a great amount of information about the "soft tissues" (muscles, skin, etc.) that don't normally preserve. But no, these
aren't like Egyptian mummies or the freeze-dried mammoths of the polar regions: the muscles and skin are mineralized, not just dried.
NEW January 2008: This doesn't affect the main portion of the book, but the International Commission on Stratigraphy (the organization
in charge of the names of geologic time units) has announced that they will be restoring the old "Quaternary Period" (although somewhat longer
than the old version: 2.588 million years ago to the present). So the Cenozoic Era will have three periods: Paleogene, Neogene, and Quaternary.
A considerable amount of new discoveries have been made concerning the closest relatives of Dinosauria. One of the more primitive relatives
of dinosaurs is little Dromomeron from the Late Triassic of New Mexico, close kin to the earlier Lagerpeton of Middle Triassic
Argentina. Together these primitive dinosaur relatives form the group Lagerpetonidae.
Debate continues on whether Eoraptor and Herrerasauria are actually theropods or simply primitive saurischians. (Also, note that the
new proper term for the larger group containing Herrerasaurus and the other herrerasaurids is "Herrerasauria").
Late Triassic Guaibasaurus of Brazil may actually be a true theropod: if so, it is the most primitive of all. For example, it lacks the
three-toed foot typical of all more advanced theropods.
As mentioned in the comments for Chapter 13, new research shows that the Early Jurassic dinosaurs "Dilophosaurus" sinensis (which will
eventually get its own genus name!) and Cryolophosaurus are not primitive tetanurines, but rather part of the Dilophosauridae.
NEW January 2010: As with the previous chapter, a whole heckuva lot of new discoveries in this part of the dinosaur family tree. In this
case one of the main contributors has been Stephen Brusatte (currently a graduate student at Columbia University and the American Museum
of Natural History in New York City).
NEW January 2008: Last year there were many news reports about the finding that Tyrannosaurus rex "had three fingers". Unfortunately,
those reports were not correct. In fact, the real find was a well-preserved third metacarpal (long bone of the palm of the hand) for T. rex:
nota surprise as these were already known in other two-fingered tyrannosaurids. In fact, you can see this little bone on the hand skeleton of
Tyrannosaurus on the bottom of page 120.
NEW January 2010: New studies by Lindsay Zanno of the Field Museum in Chicago and her colleagues, based on a new species of the therizinosaur
Nothronychus, suggest a new relationship among the dinosaurs of this chapter and the next, and a new understanding of their
diet and history. In particular, Zanno and colleague's work shows that ornithomimosaurs, therizinosaurs, alvarezsaurs, oviraptorosaurs,
deinonychosaurs, and avialians branched off in that order. So if I ever do a new edition of the book, I would probably include therizinosaurs
in this chapter (and possibly move alvarezsaurs into the next).
One of the biggest discoveries (literally) among these dinosaurs is the new giant oviraptorosaur
Gigantoraptor of the Late Cretaceous of Asia. Xu Xing (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing) and
his colleagues first published on this giant in June 2007. As big as tyrannosaurids like Albertosaurus and Gorgosaurus, Gigantoraptor was one of the
largest dinosaurs in its environment. And yet it had long slender legs: longer and more slender than those of tyrannosaurids, in fact,
so it may have been the swiftest of big dinosaurs.
2007 has seen the discovery of several new small Asian dromaeosaurs, including Shanag and
Mahakala. The first of these is the oldest known (and first Asian example) of the unenlagiines; the second is a very small primitive
dromaeosaurid no bigger than Archaeopteryx.
The "giant unenlagiine" discovered by Fernando Novas mentioned on pp. 155-156 has been named: it is Austroraptor (seen in the linked image with Novas himself!) At the other size extreme, little Hesperonychus of the Late Cretaceous of Canada is the smallest known theropod (other than birds) from North America, and the first North American microraptorine. Studies included these new dromaeosaurid have caused some shifting among the various subgroups of dromaeosaurids, which will be included in the 2010 genus list update.
On the troodontid side of things, little Anchiornis shows that troodontids a) were present in the Middle Jurassic; b) had long leg feathers like primitive dromaeosaurids and primitive avialians; and c) were cute.
Also, with regards to the discussion of brains on p. 161: new studies show that Troodon's brain was exceptionally big even for a troodontid, so it (rather than Troodontidae as group) may indeed have been the brainiest Mesozoic dinosaur.
Chapter 21: Avialians (Birds)
New Mesozoic birds continue to be found and described. I have included a more up-to-date classification of early bird groupings in the revised
version of the genus list.
One aspect of the new discovery of early birds, and of bird-like primitive deinonychosaurs, is that it is getting less and less certain that Archaeopteryx really WAS a bird: that is, that it was more closely related to today's birds than were deinonychosaurs.
Work by American paleontologist Julia Clarke and her Chinese colleagues Zonghe Zhou and Fucheng Zhang in 2006 has shown that the typical modern bird tail (with a fan of feathers coming off of a pygostyle) actually shows up later in bird evolution than we used to think. Confuciusornis and the enantiornithines seem to lack this adaptation, which modern birds use to help them steer in flight and in landing.
NEW January 2008: The flying ability of early avialians (like Confuciusornis) and possible avialians (like Archaeopteryx) may not have been very good at all. A recent study by Phil Senter (Fayetteville State University) shows that these early feathered dinosaurs could not effectively flap their arms in the right way to generate lift, so that they couldn't have had any sort of sustained powered flight. True powered flight would have shown up later, among the common ancestors of enatiornithines and more specialized birds.
Chapter 22: Prosauropods (Primitive Long-Necked Plant-Eating Dinosaurs)
Many important new studies of these dinosaurs were published in 2006 and 2007. Here are some of the highlights:
Most recent phylogenetic analyses agree that there are three basic types of "prosauropod". There are the early small-bodied primitive forms like Saturnalia, Efraasia, Thecodontosaurus, and Pantydraco (the last one was still considered a species of Thecodontosaurus when the book went to the printers!). There are the "core prosauropods": larger dinosaurs including Plateosaurus, Massospondylus, Riojasaurus, Lufengosaurus, Coloradisaurus, and their closest relatives. And there are the "near-sauropods": Yunnanosaurus, Anchisaurus, Melanorosaurus and other dinosaurs more similar to sauropods than to "core prosauropods". The different analyses disagree mainly on whether the core prosauropods from their own group (with all members more closely related to each other than to other types of dinosaurs), or if some are closer to true sauropods and some are more distantly related.
Great new skeletons of all three types of prosauropod have been found, and have given us a better view of their anatomy. For example, the primitive sauropodomorphs may have lacked a cheek, but the core prosauropods and the near-sauropods seem to have had a smaller version of the skin or muscular cheek that ornithischians independantly evolved. This would help them keep food in their mouths as they ate. Also, analyses of the forelimbs of these dinosaurs by Matt Bonnan (Western Illinois University), Phil Senter (Fayetteville State University), and Adam Yates (University of Witwatersrand) show that the primitive sauropodomorphs and the classic prosauropods were probably strictly bipedal, and not the "sometimes bipedal, sometimes quadrupedal" dinosaurs that I wrote about and Luis Rey illustrated. On the other hand (so to speak), the near-sauropods seem to have been capable of walking on all fours, and so were more like they were shown in the book.
While the vast majority of the prosauropods died out by the end of the Early Jurassic, the first Middle Jurassic prosauropod (a new species of the near-sauropod Yunnanosaurus of China) has been described.
NEW January 2008: A newly-discovered core prosauropod or near-sauropod, Lamplughsaura of the Early Jurassic of India, is one of the most completely-known early sauropodomorphs. Study of it will help us understand the evolution of the long-necked plant eaters.
NEW January 2010: Yet more discoveries in this part of the tree. Panphagia from the Late Triassic of Argentina (in fact, the same rocks that Eoraptor, Herrerasaurus, and Pisanosaurus come from) is now the most completely known primitive sauropodomorph. Ongoing studies by Martín D. Ezcurra (Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina) and his colleagues suggest that Panphagia forms a group of successful very primitive sauropodomorphs with other genera previously considered theropods (like Guaibasaurus) or sauropodomorphs (like Saturnalia) or even non-dinosaurs (like Agnosphitys).
At the other end of the "prosauropod" range is 7 m long Aardonyx of the Early Jurassic of South Africa. This is the most advanced of the bipedal sauropodomorphs: the next branch known were capable of some quadrupedal walking. It had lost the cheeks that seem to have been present on most other primitive sauropodomorphs (including primitive sauropods), and thus could "bulk browse" like more advanced sauropods: that is, open its jaws wide and chomp down on a lot of food quickly.
Chapter 23: Primitive Sauropods (Early Giant Long-Necked Dinosaurs)
Depending on how you classify them the "near-sauropods" mentioned in the previous section are considered early sauropods by some paleontologists.
While it is true that most sauropods had the tooth-to-tooth bite I wrote about, newly described jaws from the most primitive sauropods show that they had a bite more similar to prosauropods (with a wraparound overbite and a small cheek). The later sauropods (called the Eusauropoda, or "true sauropods") evolved the tooth-to-tooth contact and lost their cheeks in favor of a jaw that could open much wider. This makes sense when one considers that the heads of eusauropods were about the same size as the heads of the more primitive sauropods and near-sauropods, but the bodies of the eusauropods were MUCH bigger than the other two! They had to chomp and gulp down food as quickly as they could, and not worry about chopping it up in their jaws.
A whole new group of primitive sauropod (in fact, of primitive eusauropod) was announced while the book was at the presses! First described in December 2006, this group is the Turiasauria, a Jurassic-to-Early Cretaceous clade of dinosaurs from Europe containing gigantic Turiasaurus (at 48 tons the largest known European dinosaur and one of the largest sauropods) as well as Galveosaurus and Losillasaurus. Also, new phylogenetic analyses suggest that at least some of the Middle-to-Late Jurassic extremely long necked Chinese sauropods that I wrote about (such as Omeisaurus and Mamenchisaurus) belong to a clade that also includes Middle Jurassic English Cetiosaurus, Middle Jurassic Argentine Patagosaurus, and Early Jurassic Indian Barapasaurus. (Long-necked Euhelopus may be related to these, but more analyses still place it as close kin to the titanosaurs within Macronaria).
NEW January 2010: One of the newest discoveries among the primitive sauropods is the nearly-complete skeleton of Spinophorosaurus of the Middle Jurassic of Niger. Interestingly, like Shunosaurus, Spinophorosaurus has a spiked club on its tail.
On-going work has not resolved yet if Turaiasauria represents a natural group or not. Mamenchisauridae (the group containing Omeisaurus and Mamenchisaurus) does appear to be well-supported, but Euhelopus is not part of it: instead, this other long-necked Chinese form is close to the ancestry of the Titanosauria.
Chapter 24: Diplodocoids (Whip-Tailed Giant Long-Necked Dinosaurs
NEW January 2008: On p. 199 I wrote "At the time of this writing, no one has put together a complete rebbachisaurid skull or skeleton,
so we aren't sure what they looked like." That has changed, thanks to Paul Sereno (University of Chicago), Jeff Wilson (University of Michigan), and
their team. They have finally put together the skeleton and
utterly-bizarre skull of
Nigersaurus. And it is even stranger than Luis drew and I wrote about in our book! Its teeth were apparently replaced at a rate of about
once a month: twice as fast as duckbills, which were previously thought to have the fastest rate of tooth replacement in dinosaurs by far.
The snout of Nigersaurus was normally head facing straight downwards. It was little
(for a sauropod: only the size of an Indian elephant).
Learn a lot more about Nigersaurus on this website.
NEW July 2008: David Lovelace (University of Wyoming), Scott Hartman (Wyoming Dinosaur Center), and William Wahl (Bighorn Basin Foundation) have recently described Jimbo the Supersaurus, a specimen that demonstrates that Supersaurus is its own distinct genus and that was an apatosaurine (that is, it was a diplodocid that was more closely related to Apatosaurus than to Diplodocus). Additionally, their study shows that "Seismosaurus" is not a distinct genus or species, but is just a very very old, very very large individual of Diplodocus longus.
Chapter 25: Macronarians (Big-Nosed Giant Long-Necked Dinosaurs)
The biggest new discovery (September 2007) for this chapter is 106 to 112 feet (32-34 m) and 70 or more ton
Futalognkosaurus, a rival with fellow titanosaurs Argentinosaurus and Puertasaurus for the "Largest Dinosaur of Them All" title.
Unlike its giant cousins, however, a good percentage of the skeleton is actually known. Its 46 to 50 foot (14-15 m) long neck is the longest
of any dinosaur currently known.
Many new titanosaurs have been discovered, and the relationships between the various groups is still being worked out. It is likely that the relatively simplistic version I used in the book (with a bunch of primitive titanosaurs and the advanced saltasaurids) will be replaced by a classification with multiple groups of advanced titanosaurs. I have used such a system (based on the phylogenetic analysis of Kristi Curry Rogers (Science Museum of Minnesota) and using names already available from previous classifications) in the revised appendix. In this scheme, Titanosauria includes primitive forms like Phuwiangosaurus, Janenschia, Andesaurus, and the gigantic Argyrosauridae (containing Argyrosaurus and Paralititan); the brachiosaurid-like Antarctosauridae (including Argentinosaurus, Alamosaurus, and Antarctosaurus, as well as some titanosaurs whose names DON'T begin with "A"...); and the Lithostrotia. The latter batch are the forms known to have armored backs (not definitely known in the previously-listed types). Among the lithostrotians are the relatively small Saltasauridae (like Saltasaurus and Neuquensaurus) and the more diverse broad-snouted Nemegtosauridae (including Rapetosaurus, Nemegtosaurus, and spike-backed Augustinia, among many others). However, with all the new titanosaurs showing up around the world, our understanding of the diversity of the titanosaurs is going to change even more!
NEW July 2008: Many new titanosaurs have been found in South America. Among them, Futalognkosaurus and Mendozasaurus form a group that has been named the Lognkosauria, or "chief reptiles."
NEW January 2010: Jobaria does not seem to be a macronarian, but instead a more primitive form. Also, it and the megalosaurid Afrovenator are NOT from the Early Cretaceous as long thought: instead, the rocks they are found in come have been redated to the Middle Jurassic.
Re-examination by Mike Taylor of the true North American Brachiosaurus altithorax and the African species typically called "Brachiosaurus" brancai confirms that the latter is distinct from Brachiosaurus proper, and thus is more properly called Giraffatitan.
A comment on p. 205 of the book led to this discussion on the Sauropod Vertebra Picture of the Week blog.
Chapter 26: Ornithischians
Everything you know about early ornithischians is wrong! Okay, that's an overstatement... But recent work in 2006 and 2007 by the team of Randall Irmis (University of
California, Berkeley), Sterling Nesbitt (American Museum of Natural History), William Parker (Petrified Forest National Park), and various colleagues
have revolutionized our identification of Triassic ornithischian dinosaurs. Basically, a re-examination of the evidence shows that most of the
previously described Triassic "ornithischians" turn out to be from either the near-crocodilian revueltosaurs
or the near-dinosaurian silesaurs, two non-dinosaurian
types of herbivorous archosaur they we didn't even know about a few years ago. The only remaining definite Triassic ornithischian is the oldest and
most primitive one, Pisanosaurus, and an unnamed Triassic member of the Heterodontosauridae.
Oh, wait: turns out another Triassic ornithischian showed up in June 2007! This is Eocursor, a Late Triassic South African ornithischian. Like heterodontosaurids and saurischians, but unlike all the other ornithischians, Eocursor still had the relatively large grasping hand of the earliest dinosaurs. In their initial description of this new dinosaur, Richard Butler (Cambridge University and the Natural History Museum, London), Roger Smith (Iziko South African Museum), and David Norman (Cambridge University) also reanalysed the relationships between various ornithischians, and found that heterodontosaurids are indeed very primitive ornithischians and not ornithopods at all.
NEW January 2010: A couple of important new discoveries among the heterodontosaurids. One of these is tiny Fruitadens of the Late Jurassic of western North America. This is one of the smallest ornithischian dinosaurs ever found: only 70 cm (not quite 28 inches) long!
More spectacular--or maybe just more surprising--is Tianyulong. It was first thought to come from the Early Cretaceous, but now is known to date to the Middle Jurassic. That's not the surprising thing, though. What is the surprising thing is that it had protofeathers along its back (at least). Now up until this discovery there was no definite evidence of feathers or protofeathers outside of the coelurosaurian theropods. (It is true that Psittacosaurus had its quills, but these were not clearly derived from the same anatomical features as protofeathers.) Now we've got fuzzy ornithischians. This means that the common ancestor of all dinosaurs may have sported some fuzz, and that Luis Rey's fuzzy Leaellynasaura on p. 248 may turn out to be accurate!
Chapter 28: Stegosaurs (Plated Dinosaurs)
NEW January 2010: A bizarre new discovery is Miragaia of
the Late Jurassic of Portugal: a stegosaur with a long flexible neck like a sauropod.
Chapter 29: Ankylosaurs (Tank Dinosaurs)
The first definite Asian members of Nodosauridae have been described: Zhejiangosaurus and Zhongyuansaurus.
NEW January 2010: Biomechanical studies led by graduate student Victoria Arbour of the University of Alberta calculated the force that ankylosaurids could generate with their club tails. The short answer: they could indeed break bone, especially the big ones.
Chapter 30: Primitive Ornithopods (Primitive Beaked Dinosaurs)
The analysis of ornithischian dinosaurs by Butler, Smith and Norman (see the comments on Chapter 26 above) indicates that
"Othnielia" (recently renamed Othnieliosaurus by Peter Galton), Agilisaurus,
and Hexinlusaurus are all non-ornithopods, but are simply Jurassic relatives of the Ornithopoda and Marginocephalia. Jeholosaurus, on the other hand,
may be a true ornithopod.
Bob Bakker (currently at the Houston Museum of Natural History) once speculated that the primitive ornithopod (or ornithopod-like dinosaur) Drinker was a burrower. More recently, a newly discovered (first described in March 2007) Early Cretaceous ornithopod Oryctodromeus was found actually buried inside its burrow.
Chapter 31: Iguanodontians (Advanced Beaked Dinosaurs)
"Iguanodon" aetherfieldensis was slender European iguanodontian once considered a species of Iguanodon. However, recent work
by Gregory Paul suggests it is actually more closely related to hadrosaurids than to Iguanodon proper, and so in late 2006 he gave it its own
genus name: Mantellisaurus. We will have to see if that name stands, or if instead this species turns out to be the same as the
previously-named but poorly-known Vectisaurus.
In the past, when you have seen the skull of the Late Jurassic iguanodontian Camptosaurus, it turns out you've seen the wrong dinosaur! Re-examination of the skull by Kathleen Brill and Kenneth Carpenter (Denver Museum of Nature & Science) published in late 2006 shows that the long, squared off skull that everyone (including I and Luis Rey) thought was Camptosaurus was really from a younger, Early Cretaceous dinosaur. Brill and Carpenter have given this dinosaur the name Theiophytalia. Thankfully, however, the actual Camptosaurus skull is now known from a nearly complete specimen, and it is found to be more triangular (something like the head of Dryosaurus, only larger).
Although it is in the genus list in the book, I think it is worth mentioning one of the strangest iguanodontians here as well. That is Lanzhousaurus of Early Cretaceous China. While most iguanodontians evolved more but smaller teeth over time, Lanzhousaurus decided to "buck the trend" and developed fewer but enormous teeth. In fact, these are the largest teeth known of any herbivorous dinosaur.
NEW January 2008: Greg Paul has additionally recognized two new Early Cretaceous dinosaurs that were once considered species of Iguanodon: slender Dollodon bampingi of Belgium and Dakotadon lakotaensis of the United States.
Chapter 32: Hadrosauroids (Duckbilled Dinosaurs)
NEW January 2010: Some changes in terminology for future editions of this chapter: I will probably call the whole chapter "Hadrosauria", and
where I used "Hadrosaurinae" I will use "Saurolophinae" following work by Albert Prieto-Marquez of the American Museum of Natural History. (Hadrosaurus
may actually be more distantly related to other "hadrosaurines" than the lambeosaurines are!) These changes, and some changes among the
interrelationships of the duckbills, will be reflected in the revised 2010 genus list.
A new discovery is the primitive Italian hadrosaurian Tethyshadros, one of the most complete skeletons of a large Mesozoic dinosaur from Europe.
Chapter 33: Pachycephalosaurs (Domeheaded Dinosaurs)
Jack Horner (Montana State University) has recently suggested that Pachycephalosaurus, Stygimoloch, and Dracorex are all
different growth stages (basically adult, "teenager", and kid) of the same
species. I think that this idea has a lot going for it, and look forward to this study being presented in more detail. (As I mention in the
book, dinosaurs had a lot of growing up to do in their life, so they went through a lot of different sizes and shapes between hatchling and
adulthood. So many different "species" of dinosaurs will likely turn out to be just different growth stages).
NEW January 2010: Related to the above study, new work suggests that Homalocephale is just the juvenile stage of Prenocephale.
Chapter 34: Primitive Ceratopsians (Parrot and Frilled Dinosaurs)
Plenty of new primitive ceratopsians have been discovered, including the first European ceratopsian fossils (teeth only, but resembling most closely
those of leptoceratopsids, announced in July 2007). As more and more of these are discovered, they highlight the fact that ceratopsians spent most of their history
as small dinosaurs under the shadows of sauropods, thyreophorans, and iguanodontians. It is only at the very end of the Age of Dinosaurs, and
only in western North America, that they became a major group of large-bodied dinosaur.
Chapter 35: Ceratopsids (Horned Dinosaurs)
NEW January 2008: Eotriceratops
xeriinsularis is a newly described ceratopsine very closely related to Triceratops (heck, possibly even ancestral to that
later and more famous dinosaur!).
NEW January 2010: With the discovery that primitive centrosaurines (like Albertaceratops) and advanced non-ceratopsid ceratopsians (like Zuniceratops) had long brow horns suggests that poorly-known Ceratops itself may not be closely related to the other dinosaurs that are called "Ceratopsinae" in the book. Therefore, in future versions I will stick to more common use and call Triceratops, Chasmosaurus, and their kin "Chasmosaurinae".
It has been suggested that Turanoceratops from Uzbekistan is a chasmosaurine ceratopsid: if true, it would be the first true ceratopsid from outside of western North America. However, it might be a Zuniceratops-like near-ceratopsid.
On-going research is suggesting that Torosaurus may not be a distinct type of dinosaur, but rather just a fully-adult Triceratops. This is an interesting idea, and I await the full analysis of this idea.
Chapter 36: Dinosaur Eggs and Babies
In September 2007, an assemblage of Psittacosaurus fossils found together was described. This collection of skeletons of the little
ceratopsian were buried together under volcanic ashes. Examination of the fossils by Zhao Qi (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing),
Paul Barrett (The Natural History Museum, London), and Dave Eberth (Royal Tyrrell Museum of Palaeontology) indicates two different age
groups of youngsters: some about 1 and a half years old and the others about 3 years old. This shows that they were born at two
different times, but the fact that they were buried together may indicate that they lived together as a big family.
II. Updated Dinosaur Genus List
The genus update is available here.
III. Reviews of the book
IV. Frequently Asked Questions
V. Website Links
Some other dinosaur-rich museums are:
Some non-Museum-based Sites of Interest:
On-Line Interactive Activities
A list of answers to frequently asked questions is available here. (Not yet mounted online).
Below are some links to websites about dinosaurs and topics related to dinosaur science:
Many natural history museums have websites about dinosaurs. Among them are:
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