Tetrapod Zoology

Tetrapod Zoology

Amphibians, reptiles, birds and mammals - living and extinct

21st Century Dinosaur Revolution


Front cover of the A & C Black edition.

A recent tour of the Natural History Museum (London) bookshop reminded me that my 2009 book, The Great Dinosaur Discoveries (A & C Black in the UK, University of California Press in the USA), is still on sale and in demand. Buy it here on amazon and here on Thoughts on this book (including on its mostly fair coverage in reviews) have been covered before on Tet Zoo (see What they’re saying about The Great Dinosaur Discoveries). I still like it. Naturally, it’s becoming increasingly out of date, and many of the illustrations we had to use aren’t my ideal choices. But overall I’m pleased with the reviews I provided of various key dinosaur discoveries, and of the historical overviews I wrote about the different stages of our knowledge evolution about Mesozoic dinosaurs.

As an example of the latter, below I’ve published the introductory text from the book’s last chapter, titled ‘The 21st Century’. Seeing as this text was written in 2009, it’s lacking reference to numerous discoveries made since. And constraints of space and word count also mean that it doesn’t credit everything it should: no mention of the Ornithischian Revolution, for example. Anyway, the text below appears as it does in the book (Naish 2009). However, I’ve added citations to relevant papers (though not all of them), something I didn’t do in the book for obvious reasons (it’s a popular book, not a semi-technical or technical one).

It's not from The Great Dinosaur Discoveries, but - seeing as I just mentioned ornithischians - I thought I may as well recycle this now somewhat dated cladogram, from Naish & Martill (2001). Back then, we were excited by the possibility that heterodontosaurids might be close to Marginocephalia (yikes, here they're shown as >part of< Marginocephalia). (1) Ornithischia; (2) Lesothosaurus; (3) Genasauria; (4) Thyreophora; (5) Scelidosaurus; (6) Eurypoda; (7) Ankylosauria; (8) Stegosauria; (9) Cerapoda; (10) Marginocephalia; (11) Heterodontosauridae; (12) Pachycephalosauria; (13) Ceratopsia; (14) Ornithopoda; (15) Hypsilophodon; (16) Iguanodontia. Diagram by Darren Naish.

The 21st Century

Primary achievement of the 21st Century: MEMES. This from John Conway's series on Hypsilophodon.

Spectacular dinosaur discoveries continue to be made today. China and Argentina have produced a flurry of unusual new species, but the new generation of palaeontologists specializing in dinosaurs have contined to describe new species from Europe, North America, and elsewhere. Since 2000, we have seen such wonders as the long-snouted maniraptoran Austroraptor, the strange theropod Masiakasaurus, the abelisaurs Rugops, Rajasaurus and Skorpiovenator, the gigantic sauropod Turiasaurus, the dwarf sauropod Europasaurus, and the basal ceratopsians Liaoceratops and Yinlong.

The early 21st century also saw the emergence of a new biomechanics movement, stimulated by new techniques and technologies, that sought to test many of the old assumptions about dinosaur function and behaviour. The bite strength, head postures, neck mobility, arm strength, and running ability of many dinosaurs have been analysed. This work should be seen as part of a broader approach to form and function in animals. The general thinking during much of the 1990s* was that scientists had nothing new to learn from anatomy, and that genetics remained the only biological frontier, but this view has proved mistaken: it turns out that plenty of very basic questions about the anatomy of living animals have never been analysed – and dinosaurs are at the heart of this anatomical revolution.

* This isn’t really correct: the text originally said “late 20th century” and was meant to be a reference to the last few decades of the 20th century, not the 1990s in particular.

Theropod insights

Scipionyx doesn't even get mentioned in The Great Dinosaur Discoveries (hey, nothing personal - it was going to get its own full spread!). Definitely worthy of mention here is the amazing, comprehensive, 281-page monograph on the specimen, published in 2011. A must-own for those seriously interested in Mesozoic theropods.

The discovery of Sinosauropteryx, Caudipteryx and Protarchaeopteryx in the 1990s proved that small theropods were feathered (or, at least, possessed quill-like “proto-feathers”). Beautifully preserved, complete or near-complete small theropods continued to be found during the following decade. Most of these fossils came from the Lower Cretaceous Yixian Formation in China’s Liaoning Province, and most were described by Xu Xing and his colleagues, of the Institute of Vertebrate Paleontology and Paleoanthropology.

The bizarre Microraptor – a small dromaeosaur with long feathers on its hind limbs as well as the forelimbs – was named in 2000; the tiny, long-fingered Epidendrosaurus saw print in 2002; poorly known Yixianosaurus was described in 2003; and a small troodontid preserved in a sleeping posture, Mei long, was named in 2004. Many other such dinosaurs were named as well, and new, feathered dromaeosaur, oviraptorosaur and therizinosauroid specimens provided much new information on the anatomy and feathery covering of these animals.

Given their position in the theropod cladogram, several groups, including tyrannosauroids and ornithomimosaurs, were believed to have started their history with feathers. This hypothesis was confirmed in 2004 with the description of the basal tyrannosauroid Dilong, yet another new small theropod from Liaoning (Xu et al. 2004). The early history of tyrannosauroids had long been poorly known, but several primitive forms were described during the first decade of the 21st century. Eotyrannus was named from England in 2001, Guanlong from China in 2006, and a new, English species of StokesosaurusS. clevelandi langhami– in 2008*.

Did I mention Eotyrannus? Here's the newest version of my skeletal recontruction (a few newly recognised elements make it look different from prevously published versions). From the Naish & Cau monograph, to be published some time in 2014.

* Since this text was written, Dilong and Guanlong have been recovered as non-tyrannosauroids in some analyses (Turner et al. 2007). Meanwhile, Stokesosaurus langhami has been given the new name Juratyrant.

Prosauropod progress

Here's the cover of the 2007 volume alluded to in the adjacent text: Barrett & Batten's multi-authored Special Papers in Palaeontology volume Evolution and Palaeobiology of Early Sauropodomorph Dinosaurs.

New theropod discoveries routinely make the headlines due to the popularity of these dinosaurs with the public, but a substantial amount of work on a somewhat less charismatic group of dinosaurs – the basal sauropodomorphs or “prosauropods” – has appeared since 2000. A prosauropod “research renaissance” is in progress, and in 2007 an important, multi-authored volume on this group appeared.

This renaissance involved not only descriptive work, but exciting investigations of dinosaurian biology, growth, and lifestyle. South African Massospondylus embryos, described in 2005, showed that juveniles were fundamentally different from adults (Reisz et al. 2005), and analysis of the forelimb anatomy of Massospondylus and Plateosaurus revealed that these animals could not use their forelimbs in regular walking (Bonnan & Senter 2007), as was thought. A 2005 study on bone growth in Plateosaurus showed that different individuals grew at different rates (Sander & Klein 2005). Some matured quickly, and others grew slowly, at rates comparable to those of living crocodiles.

Sauropod studies

Antetonitrus (from Yates & Kitching 2003), a key taxon in our understanding of sauropod gait and limb evolution. Isn't this also a key taxon in the PhyloCode contributions on Sauropodomorpha? Huh, I guess we'll never know (certainly seems that way, grr). Click to enlarge.

The biology and diversity of the giant sauropodomorphs, the sauropods, with their column-like limbs, also became the focus of renewed palaeobiological work. Questions on the evolution of the unusual limbs and hands of these giant dinosaurs were illuminated by the discovery of primitive forms such as Antetonitrus. Studies on growth rates deduced from the internal structure of bone confirmed that sauropods grew astonishingly quickly (Sander et al. 2004). Particularly interesting new sauropods described during the early 21st century include the giant brachiosaur Sauroposeidon*, the short-necked diplodocoid Brachytrachelopan, and the highly atypical Xenoposeidon, currently known only from a single vertebra fundamentally distinct from those of all other sauropods (Taylor & Naish 2007). New discoveries also showed that titanosaurs, which are traditionally regarded as restricted mainly to the southern continents, also have a good Asian fossil record.

* D’Emic & Foreman (2012) argued that Sauroposeidon ain’t no brachiosaur, but that it’s a somphospondylan instead (Somphospondyli is the titanosauriform clade that includes Euhelopus and titanosaurs). Furthermore, it seems to be synonymous with Paluxysaurus (the latter was named in 2007, versus Sauroposeidon’s 2000), in which case we have a lot more than three neck vertebrae to go on.

The Great Dinosaur Discoveries (Naish 2009) spread on Sauroposeidon... though, no mention of Paluxysaurus of course. Famous boy-in-a-footprint at far right; images from Matt Wedel at left, Acrocanthosaurus by Julius Csotonyi at top right.

For previous Tet Zoo articles on The Great Dinosaur Discoveries and some of the other dinosaur-themed issues mentioned here, see...

Refs - -

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

D’Emic, M. D. & Foreman, B. Z. 2012. The beginning of the sauropod dinosaur hiatus in North America: insights from the Lower Cretaceous Cloverly Formation of Wyoming. Journal of Vertebrate Paleontology 32, 883-902.

Naish, D. 2009. The Great Dinosaur Discoveries. A & C Black, London.

- . & Martill, D. M. 2001. Ornithopod dinosaurs. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 60-132.

Reisz, R. R., Scott, D., Sues, H.-D., Evans, D. C. & Raath, M. A. 2005. Embryos of an Early Jurassic prosauropod dinosaur and their evolutionary significance. Science 309, 761-764.

Sander, P. M. & Klein, N. 2005. Developmental plasticity in the life history of a prosauropod dinosaur. Science 310, 1800-1802.

- ., Klein, N., Buffetaut, E., Cuny, G., Suteethorn, V. & Le Loeuff, J. 2004. Adaptive radiation in sauropod dinosaurs: bone histology indicates rapid evolution of giant body size through acceleration. Organisms, Diversity & Evolution 4, 165-173.

Taylor, M. P. & Naish, D. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50, 1547-1564.

Turner, A. H., Pol, D., Clarke, J. A., Erickson, G. M. & Norell, M. A. 2007. A basal dromaeosaurid and size evolution preceding avian flight. Science 317, 1378-1381.

Xu, X., Norell, M. A., Kuang, X., Wang, X., Zhao, Q. & Jia, C. 2004. Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids. Nature 431, 680-684.

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

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