Dinosaurs Without Bones

by Anthony J. Martin

  p. 107 “Forests were farther away from the nesting grounds, as was an active volcano that occasionally erupted and helped to preserve both the trees of these forests and dinosaur bones.” Roberts, E.M., and Hendrix, M.S. 2000. Taphonomy of a petrified forest in the Two Medicine Formation (Campanian), northwest Montana: implications for palinspastic restoration of the Boulder Batholith and Elkhorn Mountains volcanics. Palaios, 15: 476-482.

  p. 108 “This is a behavioral trait shared with nesting sea turtles, crocodilians, and birds, in which mothers come back repeatedly to the same nesting site… .” (1) Ruckdeschel and Shoop (2006). (2) Thorbjarnarson, J.B., and HernaÅLndez, G. 1993. Reproductive ecology of the Orinoco crocodile (Crocodylus intermedius) in Venezuela. I. Nesting ecology and egg and clutch relationships. Journal of Herpetology, 27: 363-370. (3) Hepp, G.R., and Kennamer, R.A. 1992. Characteristics and consequences of nest-site fidelity in wood ducks. The Auk, 109: 812-818.

  p. 108 “… I later did a study with Varricchio on fossil insect nests near the Troodon nesting sites.” Martin, A.J., and Varricchio, D.J. 2011. Paleoecological utility of insect trace fossils in dinosaur nesting sites of the Two Medicine Formation (Campanian), Choteau, Montana. Historical Biology, 23: 15-25.

  p. 109 “Horner originally conjectured that these cocoons, which were also near the Maiasaura nest sites, were those of carrion beetles, which he imagined fed on hatched eggs, or dead eggs and hatchlings.” Horner, J.R., and Gorman, J. 1988. Digging Dinosaurs: The Search that Unraveled the Mystery of Baby Dinosaurs. Workman Publishing Company, New York: 210 p.

  p. 109 “Thus it was not surprising that one of the same people who studied the Troodon nests and eggs with Varricchio in Montana, Frankie Jackson, later noticed and defined similar structures… .” Chiappe et al. (2004).

  p. 110 “Instead, some of these nests had about the same width and depth of the Troodon nests… .” (1) Varricchio et al. (1999). (2) Chiappe et al. (2004).

  p. 110 “… the titanosaur nests were longer than they were wide, giving them oblong or kidney-bean profiles.” Chiappe et al. (2004).

  p. 111 “Complicating matters further, the expansion and contraction of soils around the eggs fractured and moved them… .” Jackson, F.D., Schmitt, J.G., and Oser, S.E. 2013. Influence of vertisol development on sauropod egg taphonomy and distribution at the Auca Mahuevo locality, Patagonia, Argentina. Palaeogeography, Palaeoclimatology, Palaeoecology, 386: 300-307.

  p. 111 “Even more odd is how the ungual on the first digit of the rear foot of a sauropod … is significantly larger than all of the others.” Fowler, D.W., and Hall, L.E. 2011. Scratch-digging sauropods revisited. Historical Biology, 23: 27-40.

  p. 112 “This same skewed orientation shows up in well-preserved sauropod tracks… .” Fowler and Hall (2011).

  p. 112 “Interpretations of these pedal oddities, which paleontologists had noted since the 19th century, have been quite varied and include… .” Fowler and Hall (2011).

  p. 112 “This was an intriguing clue, because some tortoises, such as the gopher tortoise of the southeastern U.S. (Gopherus polyphemus), are magnificent burrowers… .” Martin, A.J. 2013. Life Traces of the Georgia Coast. Indiana University Press, Bloomington, Indiana: 692 p.

  p. 112 “To get a better idea of how sauropods might have dug out their nests, Fowler and Hall read many accounts of tortoises digging nests and watched videos of tortoises making nests… .” Fowler and Lee (2011).

  p. 113 “For example, paleontologists who studied the Argentine sauropod nests do not think these eggs were actively buried by the sauropods.” Chiappe et al. (2004).

  p. 113 “Still, other sauropod eggshells have the right kind of pore structure for having been buried and incubated under a layer of sediment, just like in tortoises.” Chiappe et al. (2004).

  p. 114 “… even though one sauropod urination trace fossil has been interpreted from Late Jurassic rocks in Colorado, explained in a later chapter.” Sorry, you’re going to have to hold your curiosity for now, but I promise to relieve you with that reference soon. horizons with fossil eggs, which they classified as megaloolithid, an egg type affiliated with sauropods.” Vila, B., Jackson, F.D., Fortuny, J., SelleÅLs, A.G., and Galobart, AÅL. 2010. 3-D modelling of Megaloolithid clutches: insights about nest construction and dinosaur behaviour. PLoS One, 5: e10362. doi:10.1371/journal.pone.0010362

  p. 115 “All the same, Fowler and Hall thought about this problem too, and conjectured that large unguals in the front feet of sauropods may have been used for getting a grip… .” Fowler and Hall (2011).

  p. 115 “For instance, from a full standing position, a mother titanosaur’s cloaca might have been as high as 4 to 5 m (13–16 ft) above the ground.” These heights can be imagined easily by looking at a mounted skeleton of a titanosaur, in which the upright postures correspond with leg lengths, which in turn are 80–90% of cloacal height. Look just below the base of the tail, and that is where the cloaca would have been located.

  p. 116 “Alternatively, these mothers may have had an anatomical attribute, such as an extendable tube that projected from the cloaca and thus brought the eggs closer to the ground without the sauropod mother having to squat.” Fowler and Lee (2011).

  p. 117 “We don’t know an answer for sure yet, although some sauropod tracksites show a wide range of sizes in their tracks—from very small to extra large—suggesting that young sauropods and parents may have been in the same place and time.” (1) Bird (1985). (2) Lockley (1991).

  p. 118 “One of the most impressive dinosaur nest sites with other trace fossils to address these questions is in Early Jurassic rocks of South Africa from about 190 mya.” Reisz et al. (2012).

  p. 118 “Massospondylus was not a massive dinosaur, probably weighing about 130 to 150 kg (285–330 lbs)… .” Seebacher, F. 2001. A new method to calculate allometric length-mass relationships of dinosaurs. Journal of Vertebrate Paleontology, 21: 51-60.

  p. 118 “Paleontologists had known about Massospondylus embryos and eggs since at least the 1970s… .” Reisz, R.R., Evans, D.C., Sues, H.-D., and Scott, D. 2010. Embryonic skeletal anatomy of the sauropodomorph dinosaur Massospondylus from the Lower Jurassic of South Africa. Journal of Vertebrate Paleontology, 30: 1653-1664.

  p. 118 “… summarized in a report published by Robert Reisz and four other paleontologists in 2011, were spectacular.” Reisz et al. (2012).

  p. 119 “The first embryos and eggs were discovered at this site in 1976 in loose rocks on the ground… .” Reisz, R.R., Scott, D., Sues, H.-D., Evans, D.C., and Raath, M.A. 2005. Embryos of an Early Jurassic prosauropod dinosaur and their evolutionary significance. Science, 309: 761-764.

  p. 119 “The nests were on four horizons and close to one another, which the paleontologists interpreted as good reasons to infer site fidelity and nesting colonies.” Reisz et al. (2012).

  p. 120 “These four-toed tracks, preserved as natural casts on blocks of rock that fell from the roadcut, just happened to match the front and rear feet of a sauropodomorph like Massospondylus.” (1) Farlow et al. (2012). (2) Reisz et al. (2012).

  CHAPTER 5: DINOSAURS DOWN UNDERGROUND

  p. 123 “Alligators are represented by two species that live in widely separated places… .” (1) Ouchley, K. 2013. American Alligator: Ancient Predator in the Modern World. University of Florida Press, Gainesville, Florida: 160

  p. (2) Thorbjarnarson, J., and Wang, X.M. 2010. The Chinese Alligator: Ecology, Behavior, Conservation, and Culture. Johns Hopkins University Press, Baltimore, Maryland: 288 p.

  p. 124 “Both are burrowers, especially the Chinese alligators… .” Thorbjarnarson and Wang (2010).

  p. 124 “In their evolutionary history, Chinese and American alligators shared a common ancestor not too far back in the geologic past… .” Brochu, C.A. 2003. Phylogenetic approaches to crocodilian history. Annual Review of Earth and Planetary Sciences, 31: 357-397.

  p. 125 “Furthermore, no convincing evidence has revealed that dinosaurs lived underground because
no dinosaur has ever been found in a burrow, nor have any burrows been attributed to them.” Martin (2006). (P.S.: What an idiot.)

  p. 128 “A few other dinosaurs had anatomical attributes that could have helped them to dig, such as the small Late Cretaceous theropod Mononykus of Mongolia… .” Senter, P. 2005. Function in the stunted forelimbs of Mononykus olecranus (Theropoda), a dinosaurian anteater. Paleobiology, 31: 373-381.

  p. 128 “Moreover, one specimen of the Early Cretaceous ceratopsian, Psittacosaurus, was found with 34 juveniles… .” Meng et al. (2004).

  p. 128 “More recently, in 2010, trace fossils attributed to predatory dromaeosaurs—such as Deinonychus—were interpreted as dig marks… .” Simpson et al. (2010).

  p. 128 “… mammals that live part or most of their lives underground will result in hundreds of species … from Oldfield mice (Peromyscus polionotus) to grizzly bears (Ursus arctos).” Elbroch (2003).

  p. 129 “For a few animals, such as lungfish or some toads and turtles, these burrows serve as aestivation or hibernation chambers… .” Hembree, D.I. 2010. Aestivation in the fossil record: evidence from ichnology. Progress in Molecular and Subcellular Biology, 49: 245-262.

  p. 130 “Anyway, Bakker speculated that Othnielia and Drinker … must have been living in burrows of their own making.” Bakker, R.T. 1996. The real Jurassic Park: dinosaurs and habitats at Como Bluff, Wyoming. The Continental Jurassic: Museum of Northern Arizona Bulletin, 60: 35-49. David Varricchio also saw Bakker present this idea in a talk and he was influenced by it (Varricchio, personal communication with me, November 2013).

  p. 130 “As discussed earlier, most scientists now accept that a large meteorite hit the earth about 65 mya, landing in the area of what is now the Yucatan Peninsula.” Alvarez (2008).

  p. 131 “So large animals likely died the soonest after the impact, and yes, I am talking about dinosaurs… .” McKinney, M.L. 1997. Extinction vulnerability and selectivity: combining ecological and paleontological views. Annual Review of Ecology and Systematics, 28: 495-516.

  p. 132 “Lastly, burrowing is a behavior present in every major group of vertebrates that made it past the mass extinction… .” Robertson, D.S., McKenna, M.C., Toon, O.B., Hope, S., and Lillegraven, J.A. 2003. Survival in the first hours of the Cenozoic. GSA Bulletin, 116: 760-768.

  p. 133 “This region of Montana had outcrops of the Blackleaf Formation, which was composed of mudstones and sandstones… .” Dyman, T.S., and Nichols, D.J. 1988. Stratigraphy of mid-Cretaceous Blackleaf and lower part of the Frontier Formations in parts of Beaverhead and Madison Counties, Montana. USGS Bulletin, 1773: 1-27.

  p. 134 “… expressed succinctly in a quote by famed science fiction writer Isaac Asimov: ‘The most exciting phrase to hear in science’… .” I have to admit that, however much I love this statement attributed to Asimov, and as often as you will find it connected to him in Internet searches, I’ve had a tough time finding exactly when and where he originally said it. So for now, I’ll enjoy its sentiment regardless of whether he said it or not.

  p. 138 “For example, modern gopher tortoise burrows play host to 200 to 300 species of other animals… .” Kinlaw, A., and Grasmueck, M. 2012. Evidence for and geomorphologic consequences of a reptilian ecosystem engineer: the burrowing cascade initiated by the gopher tortoise. Geomorphology, 157-158: 108-121.

  p. 138 “As a Russian saying goes, ‘Trust, but verify… .’” Доверяй, но проверяй, or transliterated as “Doveryai, no proveryai,” which also rhymes.

  p. 140 “The study of modern traces—also known as neoichnology—had been kind to us, with the gopher tortoise burrows of Georgia supplying a sensible explanation… .” Martin (2013).

  p. 142 “The latter synced beautifully with previous work done by Dave’s advisor, Jack Horner, who had proposed that Maiasaura raised its young in their nests… .” (1) Horner and Makela (1979). (2) Horner (1982).

  p. 142 “First, one of the bones integral to its shoulder—the scapulocoracoid—had attachment sites for large muscles.” Varricchio et al. (2007).

  p. 142 “Second, the bone on the front of its snout—the premaxilla—was fused, an unusual feature in a dinosaur.” Varrichio et al. (2007).

  p. 142 “Third, when compared to its closest relatives (other small ornithopods), its hip had an extra vertebra.” Norman, D.B. 2004. Basal Iguanodontia. In Weishampel, D.B., Dodson, P., and Osmólska, H. (editors), The Dinosauria (2nd Edition). University of California Press, Berkeley, California: 393-412.

  p. 143 “In a study published the same year the dinosaur was discovered (2005), a zoologist compared the cross-sectional areas of burrows made by a wide variety of modern burrowing animals… .” White, C.R. 2005. The allometry of burrow geometry. Journal of Zoology, London, 265: 395-403.

  p. 144 “Granted, the burrow was a close fit, but this situation also applies to many modern burrowing and denning mammals… .” Varricchio et al. (2007).

  p. 144 “Gopher tortoise burrows display exactly the same sort of strategy, in which these at first run straight down… .” Martin (2013).

  p. 147 “For example, in a paper published in late 2006, the author David Loope proposed small dinosaurs as possible burrowmakers… .” Loope, D.B. 2006. Burrows dug by large vertebrates into rain-moistened, Middle Jurassic dune sand. Journal of Geology, 114: 752-763.

  p. 150 “Australians have a long tradition of ill-fated expeditions, and I felt like I had unwittingly instigated one of these.” In fact, when I originally wrote these words, I had not realized that “ill-fated expedition” is a cliché phrase in Australia, especially when applied to the infamous 1860-1861 Burke and Wills expedition to the central desert of Australia; both namesakes died during this foray. However, at least some science came out of their journey: Joyce, E.B., and McCann, D.A. (editors). 2010. Burke and Wills: The Scientific Legacy of the Victoria Exploring Expedition. CSIRO Publishing, Collingwood, Victoria: 368 p.

  p. 150 “Based on plate-tectonic reconstructions, the rocks in this part of Australia were originally formed near the South Pole, when southern Australia was connected to Antarctica… .” Rich, T.H., Vickers-Rich, P., 2000. Dinosaurs of Darkness. Indiana University Press, Bloomington, Indiana: 222 p.

  p. 150 “Nearly all of the dinosaur bones and teeth in strata there were from small dinosaurs, and most of these were hypsilophodonts.” Rich, T.H., and Vickers-Rich, P. 1999. The Hypsilophodontidae from southeastern Australia. In Tomada, Y., Rich, T.H., and Vickers-Rich, P. (editors), Proceedings of the Second Gondwana Dinosaur Symposium. National Science Museum Monographs, 15: 167-180.

  p. 151 “In a paper they and other co-authors published in the journal Science in 1988, they proposed that hypsilophodonts and other dinosaurs in the region were likely endothermic… .” Rich, T.H., Rich, P.V., Wagstaff, B.E., McEwen-Mason, J., Douthitt, C.B., Gregory, R.T., and Felton, E.A. 1988. Evidence for low temperatures and biologic diversity in Cretaceous high latitudes of Australia. Science, 242, 1403-1406.

  p. 151 “Not all paleontologists were so accepting of the idea that dinosaurs were less like reptiles and more like birds… .” Probably no book title of the time summarized those feelings better than this: Thomas, R.D.K., and Olson, E.C. 1980. A Cold Look at the Hot-Blooded Dinosaurs. Westview Press, Boulder, Colorado: 514 p.

  p. 151 “With the possible exception of the Allosaurus sp., all of the animals were small enough to have found shelter readily by burrowing.” Quoted from Rich et al. (1988).

  p. 155 “For one, the Cretaceous rocks of Victoria abounded with evidence for hypsilophodonts… .” Rich and Vickers-Rich (1999).

  p. 155 “For another, such dinosaurs were too small to have migrated long distances between seasons.” Bell, P., and Snively, E. 2008. Polar dinosaurs on parade: a review of dinosaur migration. Alcheringa 32: 271-284.

  p. 155 “Thirdly, many modern polar vertebrates, from puffins to polar bears, burrow into dirt or snow to take refuge in those harsh environments.” Davenport, J. 1992. Animal Life at Low Temp
eratures. Chapman & Hall, London: 246 p.

  p. 157 “Gratifyingly, the editor accepted the paper the following week, which had the title… .” Martin (2009). p. 157 “As of this writing, the video had the most views of any in the history of my university, and the press attention was flattering.” The video includes good footage (shot by my wife, Ruth Schowalter) at Knowledge Creek, with me talking about them, at: http://www.youtube. com/watch?v=S8gahKh1l9A

  p. 158 “So in an experiment straight out of the popular TV show Mythbusters, Woodruff joined PVC piping… .” Woodruff, D.C., and Varricchio, D.J. 2011. Experimental modeling of a possible Oryctodromeus cubicularis (Dinosauria) burrow. Palaios, 26: 140-151.

  p. 159 “… the hypothesis that this Oryctodromeus cubicularis was a burrowing, denning dinosaur still stands.” This hypothesis was further supported in a study done by Jamie Fearon, a graduate student of Varricchio’s. She determined that the forelimb anatomy on Oryctodromeus really was different from that of other ornithopods, and was suited for digging: Fearon, J., and Varricchio, D. 2012. Comparative pectoral and forelimb morphology of Ornithopoda: does Oryctodromeus cubicularis exhibit specialization for digging? Journal of Vertebrate Paleontology, SVP Program and Abstracts, 2012: 92-93.

  CHAPTER 6: BROKEN BONES, TOOTHMARKS, AND MARKS ON TEETH

  p. 162 “Although this scenario was imagined, the trace fossil evidence for all such behaviors is real.” (See the references related to this scene under Chapter 1 endnotes.)

  p. 163 “Although this ‘skin’ was actually just a natural cast of the original skin, it was closely associated with the bones of Edmontosaurus annectens. …” Rothschild, B.M., and Depalma, R. 2013. Skin pathology in the Cretaceous: evidence for probable failed predation in a dinosaur. Cretaceous Research, 42: 44-47.

  p. 164 “These unusual body fossils were normally formed first as impressions against soft sediment, and then naturally cast in sandstone, similar to how many dinosaur footprints were preserved.” Martin (2006).