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Tetrapod Zoology

Tetrapod Zoology

Amphibians, reptiles, birds and mammals - living and extinct

Greg Paul s Dinosaurs: A Field Guide

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Paul (2010): cover of the A & C Black edition.

ResearchBlogging.org

Greg Paul is an independent researcher who specialises on dinosaurs; he’s well known for his popular articles and books and his technical papers, but in particular for his hugely influential artwork. Paul’s most recent book – the 2010 Dinosaurs: A Field Guide (aka The Princeton Field Guide to Dinosaurs) – is, simply put, the ultimate Greg Paul book. It’s a large (320 pp.), heavily illustrated catalogue of over 400 reconstructed skeletons, accompanied throughout with life restorations and brief chunks of text that present data on the world’s Mesozoic dinosaur species. The idea that this book might function as a “field guide” is of course fanciful, and indeed it’s stated early on that the book is intended to be “in the style of a field guide”. A lengthy introductory section reviews dinosaur anatomy, biology, evolution, behaviour, and the climate, atmosphere and palaeogeography of the Mesozoic.

Most basic pieces of biographical information about Paul are already well known. Studying informally under the famously iconoclastic Robert Bakker at Johns Hopkins University during the 1970s and 80s, Paul became interested both in the idea that most dinosaurs were metabolically similar to extant mammals and birds, and that dinosaurs (and other fossil archosaurs) were being portrayed inaccurately by other artists. Under Bakker’s guidance, and inspired by the work of Charles Knight and other artists interested in anatomy, Paul honed a distinctive visual style for both the high-fidelity skeletal reconstructions he has become famous for, and for his reconstructions of dinosaurs in their environments.

One of Greg Paul's most famous scenes: the giant Tendaguru brachiosaur Giraffatitan brancai, with the diplodocoid Dicraeosaurus at left. Image (c) Greg Paul.

It is difficult to overstate the impact and significance of Paul’s work. Like it or not, when most of us think about dinosaurs (or other Mesozoic archosaurs), the images we have in our minds are generally “Greg Paul dinosaurs”. Paul wasn’t the first to depict slim-limbed, fully terrestrial sauropods, galloping ornithischians, or theropods with horizontal bodies and tails, drumstick-like shank muscles, or feathery pelts – Bakker did all of this in his articles from the 1960s and 70s. But the fact that Paul did this consistently, produced both black and white illustrations and colour paintings, and became published across popular mainstream sources, soon made him a dominant force in the world of dinosaur art. While many palaeontologists dislike or disagree with what Paul says about dinosaurs and their biology and evolution, I think that his role in the dinosaur renaissance, and especially in the way dinosaurs are portrayed in art and the media, should always be credited (Naish 2009).

Greg Paul's skeletal reconstructions of the iguanodontians Dollodon bampingi (top) and Mantellisaurus atherfieldensis (below). The status of the former is controversial. Images (c) Greg Paul, used with permission.

Furthermore, Paul’s massive influence mostly comes from the fact that his reconstructions have always been based on an underlying, apparently empirical effort to depict anatomy. In an ideal world, all attempts to reconstruct fossil animals would proceed this way; alas, most illustrators of prehistoric life have done their work by looking at mounted skeletons, guessing the limits of the surrounding soft tissue, and producing the final product with little or no recourse to the anatomy of extant animals. Historically, even those who knew anatomy well – Charles Knight is a classic example – thought it ok to imagine dinosaurs with massive, flabby bodies and (paradoxically) small, lizard-like muscles, despite substantial skeletal evidence to the contrary. In articles, papers and books, Paul argued that one should strive to produce multi-view skeletal reconstructions of fossil archosaurs, and that a good understanding of the overlying musculature should result in a reconstructed form that – bar integument – is essentially that of the living animal (Paul 1987, 1988, 1991). His 1987 ‘rigorous how-to guide’ on the reconstruction of dinosaurs and other Mesozoic archosaurs (Paul 1987) remains a classic that has not really been bettered, even if it does now require substantial update.

The Mongolian deinonychosaurs Velociraptor (l) and Saurornithoides (r) squabble over a Protoceratops carcass. Image (c) Greg Paul.

On the subject of integument, Paul has always been careful to restore his archosaurs with the sort of skin known from certain rare fossils – not with the imaginary wrinkled, elephant-like skin so often given to big dinosaurs by naïve artists – or, in the case of smaller or especially bird-like taxa, with feathery or furry plumes, crests or coats. I’m not alone in recalling a time when certain palaeontologists decried the reconstructing of small dinosaurs as feathery or furry as wholly unscientific and as evidence of the obviously inferior intellect and experience of Paul and his artist colleagues, but look where we are now.

Paulian dinosaurs, but not by Greg Paul. This scene - depicting Therizinosaurus, Tarbosaurus and some remarkably stupid avimimid oviraptorosaurs - is by Luis Rey.

In view of all of this, a distinctive ‘Paulian’ style is present throughout the dinosaur art world today, with many artists producing animals clearly inspired in form, pose and posture by – or even direct copies of – Paul’s dinosaurs. The Jurassic Park dinosaurs are Paulian (though, shame about those unfeathered dromaeosaurs and the burly, tree-trunk-like limbs on the brachiosaur): in fact, we even see a Greg Paul skeletal reconstruction in the movie. In view of this movement, artists who produced non-Paulian dinosaurs as late as the 1980s or 90s seemed anachronistic even at the time.

As Paul explains, it has long been an aim to reconstruct, and publish together, the skeletons of “almost all dinosaur species for which sufficient information is available” (Paul 2010, p. 6). A previous effort to produce a compilation of Paulian dinosaurs – the Japanese volume The Complete Illustrated Guide to Dinosaur Skeletons (Paul 1996) – is far less comprehensive, and is also hard to obtain. This new volume is a guide to (nearly) all valid, non-avialan Mesozoic dinosaur species published at the time of going to press. Some species aren’t illustrated because Paul decided that published or illustrated information was insufficient to allow a reconstruction, but all are provided with a brief description. This consists of data on the taxon’s size, age and distribution, but it also includes an ‘Anatomical characteristics’ section.

Ceratosaurus pages from Paul (2010), from Princeton University Press site.

Dinosaurs: A Field Guide really is the sumptuous visual treat that dinosaur fans, and fans of Paul’s artwork and reconstructions, have long wished for. Numerous dinosaurs never before reconstructed by Paul, nor (in cases) by anyone, are present, including the theropods Juravenator, Sinocalliopteryx, Mei long, Jinfengopteryx, a scansoriopterygid (Paul calls it Scansoriopteryx, whereas the name Epidendrosaurus is probably more appropriate), the sauropodomorphs Jingshanosaurus and Gongxianosaurus, the ankylosaurs Saichania and Pinacosaurus, Pachycephalosaurus, and Olorotitan and numerous other hadrosaurs. Surprises come in the form of the apparently ridiculous Atlasaurus, Beipiaosaurus (but see below), the absurdly shaped Gastonia and the impressively long neural spines of Hypacrosaurus altispinus. Paul describes in the Preface how the recent explosion of new dinosaur discoveries – concerning new feathered theropods, new data on dinosaur pigmentation, skin texture, and bizarre new groups like therizinosaurs – make the modern world of dinosaur research radically different from the one he first got to know.

Three negative points

One of the stegosaur pages from Paul (2010), from NHBS site.

Three main points stand out as areas that could definitely have been improved upon. The first concerns the descriptive text, the second the volume’s format, and the third the taxonomy and classification that Paul uses throughout. At this point it has to be noted that this book will primarily be used by artists; it will not be used by, nor is it intended for, technical scientists, the majority of which seem to have little interest in, or knowledge of, inferred dinosaur life appearance.

Negative point 1: descriptive text

On that note, the ‘Anatomical characteristics’ section included in the descriptive text for each species is frequently all but useless, failing to include material that seems appropriate. I think this is because Paul’s general aim was to describe the overall form of the animal as if it were alive, and not to refer to autapomorphies or other distinctive bony attributes. The tendency to describe species as “standard” for their group, or as “uniform” or “fairly uniform” is frustrating, but refers I suppose to the fact that the respective animal is inferred to be typical for its group in general shape. The reference to contemporaneous species as “enemies” is slightly irksome. Should “friends” have been listed as well?

The pages of field guides.

Negative point 2: format

On the second negative point, the book’s format is also frustrating. ‘Field guides’ do not have illustrations of animals scattered throughout: rather, similar species are illustrated together such that the reader can best appreciate their similarities and differences. I really wish that this format had been used in Dinosaurs: A Field Guide – it would have made it so much earlier to compare related animals. To give one example: apatosaurine sauropod skeletons are spread across three pages, making it hard to appreciate how Apatosaurus ajax compares in limb and body proportions to the three species that Paul considers similar enough to be grouped together as ‘Brontosaurus morph’ apatosaurines.

It is also unfortunate that specimen numbers and scale bars are not included alongside the reconstructions. This would have increased the volume’s value enormously and would make it look more authoritative. It’s not as if there wasn’t the room for the inclusion of such data: there are enormous white spaces alongside every single reconstruction. Paul does say early in the book that the specimen numbers of all reconstructed individuals are provided in an online appendix, archived at http://press.princeton.edu/titles/9287.html. A link available through that site does include specimen numbers, but they’re listed in connection with size estimates – it isn’t immediately clear that they refer to the same specimens used in the reconstructions, but I suppose they must.

Negative point 3: taxonomy, phylogeny, nomenclature

How many 'genera' do you see, one or three? It doesn't matter, so long as we know what we mean. Most workers would interpret these three skulls as (clockwise from top left) representing Centrosaurus, Styracosaurus and Pachyrhinosaurus. Images from wikipedia: see below.

On the third negative point, one of the first rules about this book is that Paul’s taxonomy should be ignored. We all know that Greg has his own views on which taxa should be congeneric, but the use of names across the book is misleading and totally confusing, especially for non-specialists. Paul has argued before (e.g., Paul 1988) that dinosaur genera are oversplit and that tyrannosaurid and ornithomimid species, various of the centrosaurine horned dinosaurs, some of the crested lambeosaurine duckbills and so on should really be placed in the same genera, in part because (say) Styracosaurus and Pachyrhinosaurus are (in Paul’s view) more similar to one another than are species included in such extant genera as Varanus. [In composite image above, Centrosaurus by Sainterx, Styracosaurus by Claire Houck, Pachyrhinosaurus by Sebastian Bergmann.] Authors are of course free to reclassify species based on their own understanding or interpretation of phylogenetic relationships (this is itself an unfortunate consequence of the fact that Linnaean binomials frame a specific hypothesis for a taxon’s affinities; they are not just labels). But authors should only do this when they can justify or explain their reclassifications. Paul doesn’t do this, and in fact his reclassifications seem mostly based on whimsy.

But a little of the morphological variation present within Varanus. Top to bottom: Komodo dragon (V. komodoensis), Savannah monitor (V. exanthematicus), Green tree monitor (V. prasinus).

In any case, it is both naïve and futile to imagine that the entities we term genera should be somehow consistent across different animal clades. It doesn’t make any difference as goes our understanding of diversity or phylogeny whether the name Centrosaurus is understood to be unique to the species apertus, or to apply to all species within the clade typically called Centrosaurinae, or whether Centrosaurus encompasses the same amount of morphological disparity as Varanus, Loxodonta or Cricetus; what matters is that researchers within a given subject area use a consistent nomenclature. Many people – and remember that this is a popular volume, not written just for dinosaur nerds and technical specialists – just won’t get it should they see, for example, the Argentinean Giganotosaurus referred to as a species of the otherwise African Carcharodontosaurus. All in all, the taxonomy that Paul opts to use in his volume represents a real failure of communication. Readers will be perplexed, not enlightened. [In adjacent composite, Komodo dragon photographed at ZSL London Zoo, Savannah monitor image by Shizhao, tree monitors by El Cattivo86.]

On a related note, the way in which Paul classifies the species is frustrating, not necessarily because he is idiosyncratic, but rather because the placements he favours are not explained or justified. To take just one example… Sapeornis chaoyangensis – a long-armed, short-skulled, short-tailed theropod with a pygostyle and reversed hallux – is generally regarded as part of Avialae, close in phylogenetic position to the root of Pygostylia (Zhou & Zhang 2002). Yet Paul regards it as an oviraptorosaur – a placement that many of us have considered informally but one which has yet to be supported by any character analysis. The idea that the long-winged, presumably volant Sapeornis might be an oviraptorosaur is, needless to say, an exciting speculation in view of Paul’s idea about the repeated evolution of flightlessness in Mesozoic maniraptorans (Paul 1988, 2002), but that’s all it is - a speculation. The classification of Epidexipteryx hui within Oviraptorosauria also requires explanation, and why is Epidexipteryx regarded as an oviraptorosaur while the extremely similar Epidendrosaurus is not?

In a few cases, Paul uses new names for certain clusters of species. I can understand that one might need to lump animals together into paraphyletic grades for the purposes of a book like this, but I think it’s misleading to refer to (say) non-lithostrotian titanosaurs as ‘baso-titanosaurs’ (as Paul does), since this immediately creates the impression that such a name is in widespread use (it isn’t) and will be understood by others (it won’t). Minmi and Liaoningosaurus are grouped together as ‘minmids’ and what exactly are ‘paxceratopsians’? So far as I can tell, the latter name is wholly novel (Paul uses it for psittacosaurs and neoceratopsians).

One of my favourite Greg Paul pieces: pair-bonded, nesting azhdarchids with altricial chicks fend off a tyrannosaurid. Image (c) Greg Paul. Art like this is controversial specifically because it is bold and daring. And, no, that doesn't mean that I support the behavioural hypotheses depicted in this painting.

In a work of this size, particularly one containing both novel skeletal reconstructions and a huge amount of controversial re-naming and re-classifying, it’s inevitable that numerous small matters of contention will arise. Some researchers say that the very raison d’etre of this work – Paul’s body of high-fidelity skeletal reconstructions – is problematic, with the underlying reconstructive process being subjective, prone to bias and misinterpretation, and far more artistic than Paul makes clear (Mallison 2010, Norman 2011). Producing skeletal reconstructions of this sort involves extrapolation, interpretation and a degree of guesswork, so perhaps it would be helpful – and this is not a specific criticism of Paul, but one that could be directed at all technical skeletal reconstructions – if the reconstructions were framed as hypotheses where some (SOME, not all) of the details are open to alternative interpretations. Indeed, some of the things that look intuitively reasonable in reconstructions – Paul’s quadrupedally bounding plateosaurian sauropodomorphs are a good example – are unlikely to be correct, in this particular case because, among other things (e.g., Mallison 2010), plateosaurs could not pronate the manus (Bonnan & Senter 2007) and were thus likely incapable of quadrupedal walking or running.

Life reconstruction of Guanlong wucaii, by Renato Santos (from wikipedia).

On more trivial matters, I especially disliked seeing the tyrannosauroid Guanlong included among the allosauroids as a second species of Monolophosaurus (note that Monolophosaurus itself is no longer regarded as an allosauroid by other workers: Benson 2010, Brusatte et al. 2010). This idea only has its origin in a conference abstract and its associated presentation (Carr 2006) and the full argument has yet to be presented in print. Whether it withstands scrutiny or not (I agree with Brusatte et al. (2010) that it seems unlikely to be correct), Paul shouldn’t have reclassified Guanlong on the basis of a conference presentation. Neovenator, an uncontroversial allosauroid allied with carcharodontosaurids, is said by Paul to be the centre of a disagreement over whether it’s a tyrannosauroid or allosauroid. Unless I’ve missed something, this is incorrect.

Therizinosaur Beipiaosaurus, with 'dorsal fin' visible above its dorsal vertebrae.

What’s with the crazy ‘dorsal fin made of fuzz’ depicted on the therizinosaur Beipiaosaurus? Paul illustrates another, later therizinosaur – Nothronychus – with a subtriangular ridge in the middle of its back (that is, with the peak of the ridge being mid-way along the length of the torso), but here the ridge is formed by tall neural spines. My hypothesis is that Paul is hinting at the possibility that therizinosaurs found mid-dorsal fins highly fashionable, and swapped soft-tissue ones for bony ones at some point during their evolution (elsewhere in the book, Beipiaosaurus gets referred to as “a refugee from a Warner Brothers’s cartoon” (p. 12)). But is there any evidence for a ‘dorsal fin’ in Beipiaosaurus? An excellent referred specimen preserves the subtriangular patch of integument that Paul has restored as a ‘dorsal fin’ (Xu et al. 2009), but, like other integument-bearing patches preserved adjacent to the specimen, I don’t think you can confidently infer that it represents a soft-tissue structure in life position. The Liaoning Province fossils are mostly flattened. Like most fossils with soft tissues attached, their outlines are not sharp and life-like, but messy and the result of decomposition and compression. Taphonomic experiments have shown that, when the bodies of modern birds are crushed flat, large feathery crests not present in life typically result (Foth 2011).

Reconstructed skull of Nemegtosaurus (though - controversially - given 'cheeks'), by palaeozoologist (NOT by Paul).

Paul puts the Nemegtosaurus skull on the Opisthocoelicaudia body [adjacent skull illustration by palaeozoologist]. This is objectionable if you follow phylogenies where the two are recovered as but distantly related (e.g., Curry Rogers 2005), and it isn’t supported by any overlapping material (see discussion in Wilson 2005). For now, it’s an interesting idea, but not a ridiculous one, especially in view of the fact that – the more we learn about sauropod skulls – the more samey they appear. Also on sauropods, Paul’s idea that the raised tails present in some mamenchisaurid specimens might represent the actual life condition has so far proved unpopular (I know: I brought it to attention at a recent meeting devoted to sauropods). I’ll leave this idea for those with more experience of sauropods and their tails.

The panel-mounted chasmosaurine NMC 8538 as we're used to seeing it. Skull comes from a different specimen and the ribs are scrunched up on right side. Photo courtesy of ReBecca Hunt-Foster.

Styracosaurus albertensis (Centrosaurus albertensis of Paul’s usage) is illustrated with an enormously long, tapering nasal horn, despite the fact that Ryan et al. (2007) showed the actual horn to be about half as long as the one reconstructed on mounted specimens. Also on ceratopsids, we now know that the wonderfully complete ‘Anchiceratops ornatus’ skeleton NMC 8538 (shown here), reconstructed by Paul, is a composite (the skull is a cast from another specimen). Furthermore, it turns out that it was only ever identified as Anchiceratops by default, not because it can be convincingly referred to this taxon (Mallon & Holmes 2010). On the subject of ceratopsians, Cerasinops is inadvertently featured twice in the book, and Paul accepts the proposal that Torosaurus is a growth stage of Triceratops, not a separate taxon. On ornithopods, we now know that the cranial crest of Tsintaosaurus spinorhinus is not just a sub-vertical spike as classically depicted, but a more complex structure. I think that some of the dryosaurids in the book are incorrectly labelled.

Another of my favourite Greg Paul paintings. Giraffatitan and Ceratosaurus ingens contemplate one another; pterosaurs and a mammal are in the foreground. The full version includes several diplodocids at far right. Image (c) Greg Paul.

It’s a matter of taste whether you like or dislike Paul’s artwork. The flat horizons, low viewer angle, and tendency of animals to be depicted in tidy profile are features disliked by some. And a minor artistic and scientific movement away from ‘shrink-wrapped’, Paul-style dinosaurs (that is, those where the edges of many of the skull bones, and the distinct margins of the bony skull openings, are far more distinct than they are in any living animals) is currently underway. Anyway, those who enjoy Paul’s colour pieces will be happy to see several new ones included here. Paul also includes modified, ‘colourised’ versions of pieces that were either originally produced in black and white, or originally showed the animals standing alone, without any obvious background. These haven’t worked at all in my opinion (e.g., Lesothosaurus diagnosticus on p. 216, Euoplocephalus tutus on p. 235). The many small life reconstructions of animal’s heads suffer from their fuzzy outlines – a real contrast to the typically sharp lines of Paul’s artwork.

Some of the spelling is sloppy. ‘Ornithsichians’ are mentioned on p. 273 and Paul’s own taxon Dollodon bampingi is consistently referred to as Dollodon bambingi (pp. 289-290). Then there’s Crylophosaurus (p. 11) (= Cryolophosaurus), Pacycephalosaurus (p. 22) (= Pachycephalosaurus), Archiornis (p. 52) (= Anchiornis), Pycnoneosaurus (p. 79) (= Pycnonemosaurus), Aerosteons (p. 99) (= Aerosteon), Ansermimus (p. 113) (= Anserimimus) and so on.

What is the purpose of this book? People will enjoy looking at it, for sure, but doesn’t Paul produce those high-fidelity skeletal reconstructions so that other scientists and artists have access to excellent, useable data on the animals that Paul reconstructs? Well, no, apparently not, for the great irony is that a major ruckus erupted in the dinosaur art world at about the same time as this book appeared in print.

The 'no GSP' logo you can find online. I won't say who produced it.

Apparently inspired by the fact that he was losing paying work to competitors, Greg Paul spent considerable time and effort during 2011 demanding that other artists stop using his work as reference points for their own art, that people compensate him adequately should they use or pass his reconstructions on to others, and that those who produce skeletal reconstructions of their own should ensure that the poses they choose are visually distinct from the Greg Paul standard. Paul’s proposals understandably caused great animosity from many quarters: an enormous amount of discussion is archived online on this issue at blogs and the dinosaur mailing list and I don’t wish to cover it here. Suffice to say that, while Paul should get appropriate credit for his work and art, he cannot and will not stop people from using his published work as an available resource.

Princeton University Press cover.

Any lengthy piece of work by Greg Paul is likely to attract a degree of criticism, either because of his taxonomic and phylogenetic proposals, because of certain controversial or uncertain details of his reconstructions or art, or because of his outspoken views on dinosaur physiology or behaviour. But, then, these areas are part of the appeal. People like reading what Paul writes because he is well known for being controversial; for promoting new and sometimes daring and weird ideas about dinosaur evolution, biology, locomotion and behaviour. This is the person who was arguing for feathered theropods and fuzzy ornithischians before such ideas went mainstream, argued for the evolution of widespread secondary flightlessness across maniraptoran theropods, and worked to emphasise the idea that watching live dinosaurs would be like watching modern animals on the Serengeti – there would be dust in the air, interspecies conflicts, occasional herbivory in predators and occasional carnivory in herbivores. If Dinosaurs: A Field Guide is anything, it is indeed a visual treat, with reconstructions of tens of species representing most of Mesozoic dinosaur diversity as we currently understand it. What’s more, the book is extremely affordable for its size and quality. Bottom-line: most people interested in dinosaurs will value it, despite its problems.

The book comes in two editions. The US version, published by Princeton University Press, features two running tyrannosaurs on the cover and is properly titled The Princeton Field Guide to Dinosaurs. The UK version, published by A & C Black, is black with six life restorations on the cover. The cover image shown at the very top of this article has three ostrich dinosaurs at the top and I’m not sure if this version exists in the real world: the one I have with me here now features Leptoceratops, Euoplocephalus and Shantungosaurus at the top.

Paul, G. S. 2010. Dinosaurs: A Field Guide. A & C Black (London). Hardback, index, refs, pp. 320. ISBN 978-1-4081-3074-2.

For previous Tet Zoo articles relevant to some of the stuff discussed here, see...

Refs - -

Benson, R. B. J. 2010. A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society 158, 882-935

Bonnan, M. F. & Senter, P. 2007. Were the basal sauropodomorph dinosaurs Plateosaurus and Massospondylus habitual quadrupeds? Special Papers in Palaeontology 77, 139-155.

Brusatte, S. L., Benson, R. B. J., Currie, P. J. & Zhao, X. 2010. The skull of Monolophosaurus jiangi (Dinosauria: Theropoda) and its implications for early theropod phylogeny and evolution. Zoological Journal of the Linnean Society 158, 573-607.

Carr T. 2006. Is Guanlong a tyrannosauroid or a subadult Monolophosaurus? Journal of Vertebrate Paleontology 26, 48A.

Curry Rogers, C. 2005. Titanosauria: a phylogenetic overview. In Curry Rogers, C. & Wilson, J. A. (eds) The Sauropods: Evolution and Paleobiology. University of California Press (Berkeley), pp. 50-103.

Foth, C. (2011). On the identification of feather structures in stem-line representatives of birds: evidence from fossils and actuopalaeontology Paläontologische Zeitschrift DOI: 10.1007/s12542-011-0111-3

Mallison, H. 2010. The digital Plateosaurus II: An assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount. Acta Palaeontologica Polonica 55, 433-458.

Mallon, J. C. & Holmes. R. 2010. Description of a complete and fully articulated chasmosaurine postcranium previously assigned to Anchiceratops (Dinosauria: Ceratopsia). In Ryan, M. J., Chinnery-Allgeier, B. J. & Eberth, D. A. (eds) New Perspectives on Horned Dinosaurs: the Royal Tyrrell Museum Ceratopsian Symposium. Indiana University Press (Bloomington and Indianapolis), pp. 189-202.

Naish, D. 2009. The Great Dinosaur Discoveries. University of California Press (Berkeley and Los Angeles).

Norman, D. B. 2011. Ornithopod dinosaurs. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 407-475.

Paul, G. S. 1987. The science and art of restoring the life appearance of dinosaurs and their relatives - a rigorous how-to guide. In Czerkas, S. J. & Olson, E. C. (eds) Dinosaurs Past and Present Vol. II. Natural History Museum of Los Angeles County/University of Washington Press (Seattle and London), pp. 4-49.

- . 1988. Predatory Dinosaurs of the World. Simon & Schuster (New York).

- . 1991. The many myths, some old, some new, of dinosaurology. Modern Geology 16, 69-99.

- . 1996. The Complete Illustrated Guide to Dinosaur Skeletons. Gakken.

- . 2002. Dinosaurs of the Air: the Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press (Baltimore), pp. 536.

- . 2010. Dinosaurs: A Field Guide. A & C Black (London).

Ryan, M. J., Holmes, R. & Russell, A. P. 2007. A revision of the late Campanian centrosaurine ceratopsid genus Styracosaurus from the Western Interior of North America. Journal of Vertebrate Paleontology 27, 944-962.

Wilson, J. A. 2005. Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous sauropod diversity. Journal of Systematic Palaeontology 3, 283-318.

Xu, X., Zheng, X. & You, H. 2009. A new feather type in a nonavian theropod and the early evolution of feathers. Proceedings of the National Academy of Sciences 106, 832-834.

Zhou, Z. & Zhang, F. 2002. Largest bird from the Early Cretaceous and its implications for the earliest avian ecological diversification. Naturwissenschaften 89, 34-38.

The views expressed are those of the author and are not necessarily those of Scientific American.

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