The Rise and Fall of the Dinosaurs

by Steve Brusatte

  I published my family tree of carcharodontosaurids (and their allosaur relatives) in 2008, in a paper written with Paul Sereno ( Journal of Systematic Palaeontology 6: 155–82). I published an updated version the following year, when I joined other colleagues to name and describe the first Asian carcharodontosaurid, Shaochilong (Brusatte et al., Naturwissenschaften, 2009, 96: 1051–58). One of the coauthors on that paper was Roger Benson, who like me was a student at the time. Roger and I became fast friends, traveled to many museums together (including an incredible trip to China in 2007), and collaborated on several research projects on carcharodontosaurids and other allosaurs, among them a monographic description of the English carcharodontosaur Neovenator (Brusatte, Benson, and Hutt, Monograph of the Palaeontographical Society, 2008, 162: 1–166). Roger invited me to take part in a further study of carcharodontosaurid/allosaur/theropod phylogeny, on which he did the vast majority of work (Benson et al., Naturwissenschaften, 2010, 97: 71–78).

  CHAPTER 5: THE TYRANT DINOSAURS

  This chapter is something of an expanded version of an article that I wrote for Scientific American of May 2015 (312: 34–41) on the story of tyrannosaur evolution. That article took its inspiration from a review paper on tyrannosaur genealogy and evolution that I published with several colleagues in 2010 (Brusatte et al., Science, 329: 1481–85). Both are good general sources of information on tyrannosaurs, as is Thomas Holtz’s chapter in the academic textbook The Dinosauria (University of California Press, 2004).

  Junchang Lü and I described Qianzhousaurus sinensis (Pinocchio rex) in a paper in 2014 (Lü et al., Nature Communications 5: 3788). The story of its discovery was recounted in a New York Times article by Didi Kirsten Tatlow (sinosphere.blogs.nytimes.com/2014/05/08/pinocchio-rex-chinas-new-dinosaur). The “weird tyrannosaur” Alioramus that I studied, which led to Junchang asking me to help him study Qianzhousaurus, was described in a series of papers: Brusatte et al., Proceedings of the National Academy of Sciences USA 106 (2009): 17261–66; Bever et al., PLoS ONE 6, no. 8 (Aug. 2011): e23393; Brusatte et al., Bulletin of the American Museum of Natural History 366 (2012): 1–197; Bever et al., Bulletin of the American Museum of Natural History 376 (2013): 1–72; and Gold et al., American Museum Novitates 3790 (2013): 1–46.

  For nearly a decade, I’ve been studying the genealogy of tyrannosaurs and building ever-larger family trees as new tyrannosaur fossils are found. This work has been done in partnership with my good friend and colleague Thomas Carr of Carthage College in Kenosha, Wisconsin. We published the first version of the family tree in the 2010 Science review paper mentioned above. In 2016 we published a fully revamped version (Brusatte and Carr, Scientific Reports 6: 20252). It is the 2016 family tree that provides the framework for the discussion of evolution in this chapter.

  The discovery of T. rex has been recounted in many popular and scientific accounts. The best source of information on Barnum Brown and his great discovery is a biography of Brown that Lowell Dingus and Mark Norell, my PhD advisor, published in 2011 (Barnum Brown: The Man Who Discovered Tyrannosaurus rex, University of California Press). Lowell’s quote that I use in the chapter comes from an American Museum of Natural History website devoted to the book. There is an excellent biography of Henry Fairfield Osborn written by Brian Rangel, which I used for information on his life (Henry Fairfield Osborn: Race and the Search for the Origins of Man, Ashgate Publishing, Burlington, VT, 2002).

  Sasha Averianov described Kileskus in a paper in 2010 (Averianov et al., Proceedings of the Zoological Institute RAS, 314: 42–57). Xu Xing and colleagues described Dilong in 2004 (Xu et al., Nature 431: 680–84),; Guanlong in 2006 (Xu et al., Nature 439: 715–18), and Yutyrannus in 2012 (Xu et al., Nature 484: 92–95). The description of Sinotyrannus was written by Ji Qiang and colleagues (Ji et al., Geological Bulletin of China, 2009, 28: 1369–74. Roger Benson and I named Juratyrant (Brusatte and Benson, Acta Palaeontologica Polonica, 2013, 58: 47–54), based on a specimen that Roger described a few years earlier (Benson, Journal of Vertebrate Paleontology, 2008, 28: 732–50. Eotyrannus, from the beautiful Isle of Wight in England, was named and described by Steve Hutt and colleagues (Hutt et al., Cretaceous Research, 2001, 22: 227–42).

  Our paper naming and describing Timurlengia from the middle Cretaceous of Uzbekistan was published in 2016 (Brusatte et al., Proceedings of the National Academy of Sciences USA 113: 3447– 52). Also joining Sasha, Hans, and me were my master’s student Amy Muir (who processed the CT scan data) and Ian Butler (fellow University of Edinburgh faculty, who custom-built the CT scanner we used to study the fossil). For information on the carcharodontosaurs that were still holding tyrannosaurs down during the middle Cretaceous, check out the papers describing Siats (Zanno and Makovicky, Nature Communications, 2013, 4: 2827), Chilantaisaurus (Benson and Xu, Geological Magazine, 2008, 145: 778–89), Shaochilong (Brusatte et al., Naturwissenschaften, 2009, 96: 1051–58), and Aerosteon (Sereno et al., PLoS ONE, 2008, 3, no. 9: e3303).

  CHAPTER 6: THE KING OF THE DINOSAURS

  The story I open with is conjectural, of course, but the details are based on actual fossil discoveries (described later in the chapter, and referenced below), with a dose of speculation about how T. rex, Triceratops, and duck-billed dinosaurs would have behaved.

  For general background on T. rex—its size, body features, habitat, and age—please refer to the general references on tyrannosaurs cited in the previous chapter. Body mass estimates come from the previously cited paper on dinosaur body size evolution by Roger Benson and colleagues.

  There is a wealth of literature on the feeding habits of T. rex. The information on daily food intake comes from two important papers on the subject: one written by James Farlow (Ecology, 1976, 57: 841–57) and the other by Reese Barrick and William Showers (Palaeontologia Electronica, 1999, vol. 2, no. 2). The idea that T. rex was a scavenger, which frustrates the hell out of many dinosaur paleontologists (especially me) whenever it rears its head to make its latest round in the press, has been thoroughly debunked by one of the most knowledgeable and enthusiastic tyrannosaur experts around, Thomas Holtz, in Tyrannosaurus rex: The Tyrant King (Indiana University Press, 2008). The fossil Edmontosaurus bones with a T. rex tooth embedded inside were described by a team led by Robert DePalma (Proceedings of the National Academy of Sciences USA, 2013, 110: 12560–64). The famous bone-filled tyrannosaur dung was described by Karen Chin and colleagues (Nature, 1998, 393: 680– 82), and the bony stomach contents were described by David Varricchio ( Journal of Paleontology, 2001, 75: 401–6).

  Puncture-pull feeding in tyrannosaurs has been studied in detail by Greg Erickson and his team, who have published several important papers on the subject (e.g., Erickson and Olson, Journal of Vertebrate Paleontology, 1996, 16: 175–78; Erickson et al., Nature, 1996, 382: 706–8). Other important studies have been presented by Mason Meers (Historical Biology, 2002, 16: 1–2), François Therrien and colleagues (in The Carnivorous Dinosaurs, Indiana University Press, 2005), and Karl Bates and Peter Falkingham (Biology Letters, 2012, 8: 660–64). Emily Rayfield’s most salient publications on tyrannosaur skull construction and biting behavior were two papers published in the mid-2000s (Proceedings of the Royal Society of London Series B, 2004, 271: 1451–59; and Zoological Journal of the Linnean Society, 2005, 144: 309–16). She has also written a very helpful primer on finite element analysis (Annual Review of Earth and Planetary Sciences, 2007, 35: 541–76).

  John Hutchinson and his collaborators have written many research papers on tyrannosaur locomotion. Chief among these are articles in Nature (2002, 415: 1018–21), Paleobiology (2005, 31: 676–701), Journal of Theoretical Biology (2007, 246: 660–80), and PLoS ONE (2011, 6, no. 10: e26037). Working with Matthew Carrano, John published an important study on T. rex pelvic and hind limb musculature ( Journal of Morphology, 2002, 253: 207–28). John has also written a general primer on studying locomotion in dinosaurs (in the Encyclopedia of Life Sciences, Wiley-Blackwell, 2005), but you can find his best writing o
n his always-entertaining blog (https://whatsinjohnsfreezer.com/).

  The efficient lung of modern birds, and how it works, is described in more detail in my book Dinosaur Paleobiology. There are also a few specialist papers on the subject worth examining (e.g., Brown et al., Environmental Health Perspectives, 1997, 105: 188–200; and Maina, Anatomical Record, 2000, 261: 25–44). The fossilized evidence for air sacs in dinosaur bones—referred to technically as pneumaticity—was expertly studied by Brooks Britt during his PhD work (Britt, 1993, PhD thesis, University of Calgary). More recently, important work on the subject has been presented by Patrick O’Connor and colleagues ( Journal of Morphology, 2004, 261: 141–61; Nature, 2005, 436: 253–56; Journal of Morphology, 2006, 267: 1199–1226; Journal of Experimental Zoology, 2009, 311A: 629–46), by Roger Benson and collaborators (Biological Reviews, 2012, 87: 168–93), and by Mathew Wedel (Paleobiology, 2003, 29: 243–55; Journal of Vertebrate Paleontology, 2003, 23: 344–57).

  Sara Burch’s research on tyrannosaur arms was described in her PhD thesis (Stony Brook University, 2013) and has been presented at annual meetings of the Society of Vertebrate Paleontology. It is currently awaiting full publication.

  Phil Currie and his crew wrote several papers on the Albertosaurus mass grave, which fill a special issue of the Canadian Journal of Earth Sciences (2010, vol. 47, no. 9). Phil’s work on pack hunting in Albertosaurus and Tarbosaurus was profiled in a popular science book with the provocative title of Dinosaur Gangs, by Josh Young (Collins, 2011).

  There has been a flood of studies using CT scans to study dinosaur brains. There are a couple of great reviews of the subject—how-to guides if you will—written by Carlson et al. (Geological Society of London Special Publication, 2003, 215: 7–22) and Larry Witmer and colleagues (in Anatomical Imaging: Towards a New Morphology, Springer-Verlag, 2008). The most important CT studies of tyrannosaurs are papers by Chris Brochu (Journal of Vertebrate Paleontology, 2000, 20: 1–6), by Witmer and Ryan Ridgely (Anatomical Record, 2009, 292: 1266–96), and by the Amy Balanoff and Gabe Bever duo and a team of collaborators (of which I am one) in PLoS ONE 6 (2011): e23393 and Bulletin of the American Museum of Natural History, 2013, 376: 1–72. Ian Butler and I published our first project on tyrannosaur brain evolution as part of our description of the new tyrannosaur Timurlengia, discussed in the previous chapter. Darla Zelenitsky’s study of olfactory-bulb evolution was published in 2009 (Proceedings of the Royal Society of London Series B, 276: 667–73). Kent Stevens has published on binocular vision in tyrannosaurs ( Journal of Vertebrate Paleontology, 2003, 26: 321–30).

  Some of the most exciting recent work on tyrannosaurs—and dinosaurs more generally—uses bone histology to understand how they grew. I highly recommend two very readable reviews on the subject: a short paper written by Greg Erickson (Trends in Ecology and Evolution, 2005, 20: 677–84) and the book-length treatment by Anusuya Chinsamy-Turan (The Microstructure of Dinosaur Bone, Johns Hopkins University Press, 2005). Greg’s landmark paper on tyrannosaur growth was published in Nature in 2004 (430: 772–75). Another important study on the topic was presented by Jack Horner and Kevin Padian (Proceedings of the Royal Society of London Series B, 2004, 271: 1875–80), and more recently the brilliant polymath Nathan Myhrvold (PhD in physics, former chief technology officer at Microsoft, frequent inventor, noted chef and author of the acclaimed Modernist Cuisine, plus a dinosaur paleontologist in his spare time) wrote an illuminating paper on the use, and sometimes misuse, of statistical techniques for calculating dinosaur growth rates (PLoS ONE, 2013, 8, no. 12: e81917).

  Thomas Carr has written many papers on how T. rex and other tyrannosaurs changed as they grew. His most important works were published in the Journal of Vertebrate Paleontology (1999, 19: 497–520) and Zoological Journal of the Linnean Society (2004, 142: 479–523).

  CHAPTER 7: DINOSAURS AT THE TOP OF THEIR GAME

  I admit that my characterization of the latest Cretaceous as the apogee of dinosaur success is a bit subjective, and some of my colleagues may quibble with some of my statements. It comes down to the difficulty of measuring diversity in the fossil record, which is always subject to various biases, many of which we don’t understand. There have been many studies of dinosaur diversity, including some that use statistical methods to estimate the total number of dinosaurs over time. These don’t always agree in detail, but do agree on one general point: the latest Cretaceous was a time of generally high dinosaur diversity in terms of the number of recorded and/or estimated species. Even if it wasn’t the absolute height of dinosaur diversity, it probably wasn’t far off. My colleagues and I used different statistical methods to compute dinosaur diversity over the Cretaceous (Brusatte et al., Biological Reviews, 2015, 90: 628–42), finding that latest Cretaceous dinosaurs were either at or very close to their Cretaceous peak in species richness. Other important studies of dinosaur diversity over time have been published by Barrett et al. (Proceedings of the Royal Society of London Series B, 2009, 276: 2667–74); Upchurch et al. (Geological Society of London Special Publication, 2011, 358: 209–240); Wang and Dodson (Proceedings of the National Academy of Sciences USA, 2006, 103: 601–5), and Starrfelt and Liow (Philosophical Transactions of the Royal Society of London Series B, 2016, 371: 20150219).

  Information on the history of the Burpee Museum can be found on the museum’s website, http://www.burpee.org. Jane—the juvenile T. rex discovered by the Burpee Museum—is currently under study by a team led by Thomas Carr. A full description has not yet been published, but the fossil has been the subject of many Society of Vertebrate Paleontology conference presentations.

  There is a wealth of information on the Hell Creek Formation. A good accessible primer is a review paper by David Fastovsky and Antoine Bercovici (Cretaceous Research, 2016, 57: 368–90). If you’re looking for more detail, the Geological Society of America has published two special volumes on the Hell Creek (Hartman et al., 2002, 361: 1–520; and Wilson et al., 2014, 503: 1–392). Lowell Dingus has also written a popular book on the Hell Creek and its dinosaurs (Hell Creek, Montana: America’s Key to the Prehistoric Past, St. Martin’s Press, 2004). There have been two important surveys of Hell Creek dinosaurs, which is where I get the percentages of different species in the ecosystem. The first was led by Peter Sheehan and Fastovsky and published in a series of papers, including two particularly important works (Sheehan et al., Science, 1991, 254: 835–39; and White et al., Palaios, 1998, 13: 41–51). The second survey was conducted more recently, by Jack Horner and colleagues (Horner et al., PLoS ONE, 2011, 6, no. 2: e16574).

  One of the best sources of information on Triceratops, and ceratopsians in general, is Peter Dodson’s semitechnical book The Horned Dinosaurs (Princeton University Press, 1996). A more technical overview of these animals can be found in Dodson’s chapter (cowritten with Cathy Forster and Scott Sampson) in The Dinosauria (University of California Press, 2004). Similarly, a prime source of information on the duck-billed hadrosaurs is the chapter by Horner, David Weishampel, and Forster in The Dinosauria, along with a recent technical book that includes several papers on the group (Eberth and Evans, eds., Hadrosaurs, Indiana University Press, 2015). There is also a chapter on the dome-headed pachycephalosaurs in The Dinosauria, written by Teresa Maryańska and colleagues, that is a good introduction to this bizarre group.

  I was part of the team that described the Homer discovery—the first Triceratops bone bed—in the scientific literature. The paper was led by Josh Mathews, one of my fellow student volunteers on the 2005 expedition, and also included Mike Henderson and Scott Williams as coauthors ( Journal of Vertebrate Paleontology, 2009, 29: 286–90). In this paper, we discuss and cite some of the other ceratopsian bone beds that had been found previously. A good review of ceratopsian bone beds, with citations to many important papers, was written by David Eberth (Canadian Journal of Earth Sciences, 2015, 52: 655–81). The Centrosaurus bone bed itself was described in a chapter coauthored by Eberth in the book New Perspectives on Horned Dino
saurs (Indiana University Press, 2007).

  The best general reference on the dinosaurs of Late Cretaceous South America (and the southern continents more widely) is Fernando Novas’s book The Age of Dinosaurs in South America (Indiana University Press, 2009). Roberto Candeiro has written many specialist papers on Brazilian dinosaurs, and some of his more important works on theropod teeth are his 2007 PhD thesis (Universidade Federal do Rio de Janeiro) and a 2012 paper (Candeiro et al., Revista Brasileira de Geociências 42: 323– 30). Roberto, Felipe, and colleagues described a jawbone of a carcharodontosaurid from Brazil (Azevedo et al., Cretaceous Research, 2013, 40: 1–12), and Felipe’s paper describing Austroposeidon was published in 2016 (Bandeira et al., PLoS ONE 11, no. 10: e0163373). The bizarre crocs of Brazil have been described in a series of publications (Carvalho and Bertini, Geologia Colombiana, 1999, 24: 83–105; Carvalho et al., Gondwana Research, 2005, 8: 11–30; and Marinho et al., Journal of South American Earth Sciences, 2009, 27: 36–41).

  For some inconceivable reason, Baron Franz Nopcsa has yet to be the subject of a major biography or a film. There have been a handful of articles on him, however. The best of these are Vanessa Veselka’s piece in the July–August 2016 issue of Smithsonian, an article by Stephanie Pain in New Scientist (April 2–8, 2005), and one by Gareth Dyke in Scientific American (October 2011). The paleontologist David Weishampel—who has spent many years excavating dinosaurs in Romania on the trail of the baron—has written often about Nopcsa. He paints an evocative picture of the baron in his 2011 book Transylvanian Dinosaurs (Johns Hopkins University Press) and also collaborated with Oliver Kerscher to collate a series of Nopcsa’s letters and publications, which also includes a short biography and background to his scientific work (Historical Biology 25: 391–544).