Dinosaurs Without Bones (61 page)

p. 182
“What made them think these toothmarks belonged specifically to
T. rex
stemmed from a combination of size, shape, place, and time.” Erickson, G.M., Van Kirk, S.D., Su, J., Levenston, M.E., Caler, W.E., and Carter, D.R. 1996. Bite force estimation for
Tyrannosaurus rex
from tooth-marked bones.
Nature
, 382: 706-708.

p. 183
“These artificial teeth were then used to imitate a tyrannosaur bite, but one in which the force exerted by each ‘bite’ could be measured.” Erickson
et al.
(1996).

p. 184
“Bite-force estimates came out to 6,400 to 13,400 N, which at the time were greater than those known for any living animal… .” Erickson
et al.
(1996).

p. 184
“In later experiments done on modern alligators and crocodiles, Erickson and other researchers found the largest American alligators (
Alligator mississippiensis
) had bite forces… .” Erickson, G.M., Lappin, A.K., and Vliet, K.A. 2003. The ontogeny of bite-force performance in American alligator (
Alligator mississippiensis
).
Journal of Zoology
, 260: 317-327.

p. 184
“(It was not too surprising, then, when paleontologists later found toothmarks attributable to
Deinosuchus
in dinosaur bones.)” Rivera-Sylva, H.E., Frey, E., and Guzman-Gutierrez, J.R. 2009. Evidence of predation on the vertebra of a hadrosaurid dinosaur from the Upper Cretaceous (Campanian) of Coahuila, Mexico.
Carnets de Géologie
[
Notebooks on Geology
], Letter 2009/02: 1-6.

p. 184
“This gruesome idea came about when Denver Fowler and several other paleontologists noticed, while looking at
Triceratops
bones from the Late Cretaceous of Montana… .” Fowler
et al.
(2012).

p. 186
“When paleontologist Ken Carpenter took a close look at this oddity, he saw signs of healing around the bone… .” Carpenter, K. 2000. Evidence of predatory behavior by carnivorous dinosaurs.
Gaia
, 15: 135-144.

p. 186
“Since Carpenter’s study, other healed toothmarks found in
Edmontosaurus
bones, either attributed to
T. rex
or
Albertosaurus
, have both affirmed… .” The most recent article dealing with tyrannosaurids munching hadrosaurs, which includes references to other interpreted incidents, is: DePalma, R.A., Burnham, D.A., Martin, L.D., Rothschild, B.M., and Larson, P.L. 2013. Physical evidence of predatory behavior in
Tyrannosaurus
.
Proceedings of the National Academy of Sciences
, 110: 12560-12564.

p. 186
“So this is exactly how three paleontologists—Ray Rogers, David Krause, and Kristi Rogers—discerned that
Majungasaurus
, a large theropod from Late Cretaceous rocks of Madagascar, was a cannibal.” Rogers, R.R., Krause, D.W., and Rogers, K.C. 2003. Cannibalism in the Madagascan dinosaur
Majungatholus atopus
.
Nature
, 422: 515-518.

p. 187
“Komodo dragons, crocodilians (including alligators), big cats such as lions and tigers, and bears are among the large predators that will eat their own species.” Fox, L.R. 1975. Cannibalism in natural populations.
Annual Reviews of Ecology and Systematics
, 6: 87-106.

p. 187
“Apparently so, as its rocks show the region was semi-arid while dinosaurs lived there, but with pronounced wet-dry cycles.” Rogers, R.R., Krause, D.W., Rogers, K.C., Rasoamiaramanana, and Rahantarisao, L. 2007. Paleoenvironment and paleoecology of
Majungasaurus crenatissimus
(Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar.
Journal of Paleontology
, 27, Supplement 2 (Special Issue, Memoir 8): 21-31.

p. 188
“One of the more compelling pieces of evidence for droughts in this area during the Cretaceous comes from other trace fossils, namely lungfish burrows.” Marshall, M.S., and Rogers, R.R. 2012. Lungfish burrows from the Upper Cretaceous Maevarano Formation, Mahajanga Basin, Northwestern Madagascar.
Palaios
, 27: 857-866.

p. 188
“In a 2010 study conducted by Nicholas Longrich and three other paleontologists, they examined
T. rex
bones in museum… .” Longrich, N.R., Horner, J.R., Erickson, G.M., and Currie, P.J. 2010. Cannibalism in
Tyrannosaurus rex
.
PLoS One
, 5(10): e13419. doi:10.1371/journal. pone.0013419.

p. 189
“This idea, first proposed by paleontologists Darren Tanke and Phil Currie in 1998, was based on healed bite marks they noted in skulls… .” Tanke, D.H., and Currie, P.J. 1998. Head-biting behavior in the theropod dinosaurs: paleopathological evidence.
Gaia
, 15: 167-184.

p. 190
“These scratches tell you that the hadrosaur moved its upper jaws out and to the sides while the lower jaw stayed put.” Williams, V.S., Barrett, P., and Purnell, M.A. 2009. Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding.
Proceedings of the National Academy of Sciences
, 106: 11194-11199.

p. 190
“These marks, called
microwear
, were scored on dinosaur teeth when they chewed plants containing silica or plants with grit on them.” Fiorillo, A.R. 1998. Dental microwear patterns of the sauropod dinosaurs
Camarasaurus
and
Diplodocus
: evidence for resource partitioning in the Late Jurassic of North America.
Historical Biology
, 13:1-16.

p. 191
“Phytoliths are common in many plants today, especially monocotyledons, which include all grasses, orchids, bamboo, palm trees, and many others.” Piperno, D.R. 2006.
Phytoliths: A Comprehensive Guide for Archaeologists and Paleoecologists
. Rowman Altamira, Lanham, Maryland: 238 p.

p. 191
“Monocotyledons also got their start in the middle of the Mesozoic
Era.” Daghlian, C.O. 1981. A review of the fossil record of monocotyledons.
The Botanical Review
, 47: 517-555.

p. 192
“Paleontologists who studied microwear in
Edmontosaurus
found out that this dinosaur… .” Williams
et al.
(2009).

p. 192
“But anatomical studies done on some sauropods now imply that some of these lengthy necks were maybe better suited for sweeping large areas—back and forth—across fields of low-lying vegetation.” This research on sauropod-neck flexibility has been going on for a while, but the latest paper summarizing it (along with new findings) is: Cobley, M.J., Rayfield, E.J., and Barrett, P.M. 2013. Intervertebral flexibility of the ostrich neck: implications for estimating sauropod neck flexibility.
PLoS One
, 8: e72187. doi:10.1371/journal. pone.0072187

CHAPTER 7: WHY WOULD A DINOSAUR EAT A ROCK?

p. 195
“… the Morrison Formation was rightly celebrated elsewhere in the western U.S. for yielding some of the best-loved of all dinosaurs… .” Foster, J. 2007.
Jurassic West: The Dinosaurs of the Morrison Formation and Their World
. Indiana University Press, Bloomington, Indiana: 416 p.

p. 196
“‘Gastrolith’ literally means ‘stomach stone’ (in Greek,
gastros
= stomach,
lithos
= stone), and they thus refer to rocks that somehow made it into the digestive tract of an animal.” Wings, O. 2007. A review of gastrolith function with implications for fossil vertebrates and a revised classification.
Acta Palaeontologica Polonica
, 52: 1-16.

p. 197
“For one, they can be divided into two categories:
bio-gastroliths
and
geo-gastroliths
.” Wings (2007).

p. 197
“These bio-gastroliths are deposits of calcium oxalate, which form in people’s kidneys as a result of calcium imbalances… .” Coe, F.L., Evan, A., and Worcester, E. 2005. Kidney stone disease.
Journal of Clinical Investigation
, 115: 2598-2608.

p. 197
“Gallstones, on the other hand, are more organic than mineral and are normally composed of cholesterol, although these can sometimes have calcium mixed in as well.” Attili, A.F., de Santis, A., Capri, R., Repice, A.M., and Maselli, S. 1995. The natural history of gallstones: The GREPCO experience.
Hepatology
, 21: 656-660.

p. 198
“Remarkably, some crustaceans, such as marine crabs and freshwater crayfish, secrete their own bio-gastroliths of calcium carbonate.” Greenway, P. 1985. Calcium balance and moulting in the Crustacea.
Biological Reviews
, 60: 425-454.

p. 198
“In contrast, geo-gastroliths are rocks made outside of animals’ bodies by normal geological processes… .” Wings (2007).

p. 198
“However, the width of a gastrolith seemingly never exceeds 3% the length of the animal.” Wings (2007).

p. 199
“I have watched videos of crows doing the same thing, deliberately walking along and selecting pea-sized gravel to eat.” One such video, titled “Crow (Corvus brachyrhynchos) Swallowing Gravel in Vancouver BC 10Apr2010,” is here: http://www.youtube.com/ watch?v=Gg5gGXCVNr4

p. 200
“This process, also known as
trituration
, is like having a food processor in the upper part of an animal’s digestive system.” Wings (2007).

p. 200
“In birds that use gastroliths for just this function, their alimentary canal, from top to bottom, goes like this: mouth, esophagus… .” Proctor, N.S., and Lynch, P.J. 1998.
Manual of Ornithology: Avian Structure and Function
. Yale University Press, New Haven, Connecticut: 352 p.

p. 201
“One is in predatory birds, such as hawks, which may swallow a few pea-sized rocks, keep them in their digestive tracts for a while, and then regurgitate them before hunting.” Bruce, T. 2007. Observations of stone-eating in two species of neotropical falcons (
Micrastur semitorquatus
and
Herpetotheres cachinnans
).
Journal of Raptor Research
, 41: 74-76.

p. 202
“Fortunately for these birds, though, gastroliths not only help to grind these plant fibers but also separate them enough to prevent balling up and turning into impassable objects.” Wings (2007).

p. 203
“Nonetheless, a few birds, mammals, and even humans sometimes ingest clay or soil as a digestive aid, a practice called geophagy.” Diamond, J.M. 1999. Evolutionary biology: dirty eating for healthy living.
Nature
, 400: 120-121.

p. 203
“For example, kaolinite—a white clay common in Eocene and Cretaceous sedimentary deposits of Georgia—has been long used for medicinal purposes… .” Burrison, J.A. 2007.
Roots of a Region: Southern Folk Culture
. University Press of Mississippi, Jackson, Mississippi: 236 p.

p. 203
“However, ornithologists who have studied geophagy in South American birds—such as macaws and parrots… .” Brightsman, D.J., Taylor, J., and Phillips, T.D. 2008. The roles of soil characteristics and toxin adsorption in avian geophagy.
Biotropica
, 40: 766-774.

p. 203
“It turns out that gastroliths are indeed used in a variety of swimming vertebrates, such as pinnipeds… .” (1) Taylor, M.A. 1993. Stomach stones for feeding or buoyancy? the occurrence and function of gastroliths in marine tetrapods.
Philosophical Transactions: Biological Sciences
, 341: 163-175. (2) Wings (2007).

p. 204
“… the ‘buoyancy control’
vis-á-vis
gastroliths in aquatic vertebrates was questioned in a 2003 study on alligators… .” Henderson, D.M. 2003. Effects of stomach stones on the buoyancy and equilibrium of a floating crocodilian: a computational analysis.
Canadian Journal of Zoology
, 81: 1346-1357.

p. 204
“Yet these trace fossils show up as concentrated masses of rocks in the skeletons of big, non-dinosaurian Mesozoic marine reptiles, such as plesiosaurs.” Taylor (1993).

p. 204
“These spectacular trace fossils, evident as long, wide grooves (‘gutters’) preserved in Jurassic strata of Switzerland and Spain… .” Geister, J. 1998. Lebensspuren made by marine reptiles and their prey in the Middle Jurassic (Callovian) of Liesberg, Switzerland.
Facies
, 39: 105-124.

p. 205
“This idea got more support when two Early Cretaceous plesiosaurs described in 2005 from Queensland, Australia not only had gastroliths but also stomach contents.” McHenry, C.R., Cook, A.G., and Wroe, S. 2005. Bottom-feeding plesiosaurs.
Science
, 310: 75.

p. 206
“In 2013, Laura CodorniuÅL and several other paleontologists reported on an assortment of coarse sand to fine gravel in the body cavities of two specimens… .” CodorniuÅL, L., Chiappe, L.M., and Fabricio, D.C. 2013. The first occurrence of gastroliths in pterosaurs.
Journal of Vertebrate Paleontology
, 33: 647-654.

p. 207
“A few paleontologists have suggested that if a gastrolith is found outside of the body cavity of a dinosaur … you should … instead refer to it as an
exolith.
…” (1) Wings (2007). (2) Wings, O., and Sander, P.M. 2007. No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches.
Proceedings of the Royal Society of London, B
, 274: 635-640.

p. 209
“In 2003, paleontologist Oliver Wings decided to find out under what conditions gastroliths might stay or go after the death of a dinosaur.” Wings, O. 2003. Observations on the release of gastroliths from ostrich chick carcasses in terrestrial and aquatic environments.
Journal of Taphonomy
, 1: 97-103.

p. 210
“So in the early 1990s, paleontologist Kim Manley took a look at the differences of laser-generated light scattering on genuine gastroliths… .” (1) Manley, K. 1991. Two techniques for measuring surface polish as applied to gastroliths.
Ichnos
, 1: 313-316. (2) Manley, K. 1993. Surface polish measurements from bona fide and suspected sauropod dinosaur gastroliths, wave and stream transported clasts.
Ichnos
, 2: 167-169.

p. 210
“This technique was refined in a 1994 study by other scientists who looked at gastroliths from much more recently dead avian dinosaurs, moas from New Zealand.” Johnston, R.G., Lee, W.G., and Grace, W.K. 1994. Identifying moa gastroliths using a video light scattering instrument.
Journal of Paleontology
, 68: 159-163.