Dinosaurs Without Bones (55 page)

p. 15
   “This relatedness has been certified through many lines of evidence, including fossilized feathers directly associated with the skeletons of more than thirty species of theropods.” Godefriot, P., Cau, A., Dong-Yu, H., Escuillié, F., Wenhao, W., and Dyke, G. 2013. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature, doi:10.1038/nature12168.

p. 15
   “A similar behavior can be inferred from tracks in Early Cretaceous rocks of east Texas, in which the footprints of a large theropod paralleled and then crossed those of a sauropod, apparently shadowing it.” Farlow, J.O., Chapman, R.E., Breithaupt, B., and Matthews, N. 2012. The scientific study of dinosaur footprints. In Brett-Surman, M.K., Holtz, T.R., Jr., and Farlow, J.O. (editors), The Complete Dinosaur (2nd Edition). Indiana University Press, Bloomington, Indiana: 713-759.

p. 15
   “Other compelling theropod trackways include some from the Cretaceous of China that tell of six theropods, equally spaced and all moving in the same direction, which very much looks like evidence of pack hunting.” Li, R., Lockley, M.G., Makovicky, P.J., Matsukawa, M., Norell, M.A., Harris, J.D., and Liu, M. 2008. Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China. Naturwissenschaften, 95: 185-191.

CHAPTER 2: THESE FEET WERE MADE FOR WALKING, RUNNING, SITTING, SWIMMING, HERDING, AND HUNTING

p. 17
   “Thus far, dinosaur tracks have been found in eighteen states of the U.S. and on every continent except for Antarctica, with thousands of newly discovered ones each year.” Although a little dated, the following three books give a geographic sense for where one might find dinosaur tracks: (1) Lockley, M.G. 1991. Tracking Dinosaurs: A New Look at an Ancient World. Cambridge University Press, Cambridge, U.K.: 267 p. (2) Lockley, M.G., and Hunt, A.P. 1995.
Dinosaur Tracks and Other Fossil Footprints of the Western U.S.
Columbia University Press, New York: 338 p. (3) Lockley, M.G., and Meyer, C. 2000.
Dinosaur Tracks and Other Fossil Footprints of Europe.
Columbia University Press, New York: 360 p.

p. 18
   “Ideally, then, each recognizable dinosaur bone can be correlated with about six broad groups of dinosaurs… .” The latest two publications explaining dinosaur classifications in detail are
The Complete Dinosaur
and
The Dinosauria
, both in their second editions: (1) Brett-Surman, M.K., Holtz, T.R., Jr., and Farlow, J.O. (editors),
The Complete Dinosaur
(2nd Edition), Indiana University Press, Bloomington, Indiana: 1112 p. (2) Weishampel, D.B., Dodson, P., and Osmólska, H. (editors). 2004.
The Dinosauria
(2nd Edition). University of California Press, Berkeley, California: 861 p.

p. 19
   “For example, the hypothetical ‘first dinosaur,’ which would have evolved about 235
mya
and was the common ancestor to both saurischians and ornithischians… .” Figuring out what animal constituted the “first dinosaur” is likely impossible, but two of the earliest known dinosaurs are
Eodromeus
and
Eoraptor
, discussed here: Martinez, R.N., Sereno, P.C., Alcober, O.A., Colombi, C.E., Renne, P.R., Montañez, I.P., and Currie, B.S. 2011. A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea.
Science
, 331: 206-210.

p. 19
   “For the major evolutionary groups of dinosaurs, the following modes of movement and digit numbers, with only a few exceptions, can be applied to help with identifying their tracks.” Farlow, J.O., Chapman, R.E., Breithaupt, B., and Matthews, N. 2012. The scientific study of dinosaur footprints.
In
Brett-Surman, M.K., Holtz, T.R., Jr., and Farlow, J.O. (editors),
The Complete Dinosaur
(2nd Edition). Indiana University Press, Bloomington, Indiana: 713-759.

p. 20
   “These were unusual theropods, so unusual that no self-respecting dinosaur paleontologist discussing them can complete a sentence with these as the subject without also saying ‘strange’… .” Although slightly out of date now, a good overview of therizinosaurs is here: Clark, J.M., Maryanska, T., and Barsbold, R. 2004. Therizinosauroidea.
In
Weishampel, D.B., Dodson, P., and Osmólska, H. (editors),
The Dinosauria
(2nd Edition). University of California Press, Berkeley, California: 151-164.

p. 20
   “As of this writing, a few therizinosaur tracks are known, with the most astonishing recently found in Cretaceous rocks of Alaska.” Fiorillo, A.R., and Adams, T.L. 2012. A therizinosaur track from the Lower Cantwell Formation (Upper Cretaceous) of Denali National Park, Alaska. Palaios, 27: 395-400.

p. 21
   “Dromaeosaurids … were bipedal theropods with three toes retained on their rear feet, but only two of those digits contacted the ground.” One of the best summaries of theropod traits, including those of dromaeosaurids, is: Holtz, T.R., Jr. 2012. Theropods. In Brett-Surman, M.K., Holtz, T.R., Jr., and Farlow, J.O. (editors), The Complete Dinosaur (2nd Edition), Indiana University Press, Bloomington, Indiana: 347-378. Once you’ve read that, you’ll be better prepared to focus on the traits of dromaeosaurids: Norell, M.A., and Mackovicky, P.J. 2004. Dromaeosauridae. In Weishampel, D.B., Dodson, P., and Osmólska, H. (editors), The Dinosauria (2nd Edition). University of California Press, Berkeley, California: 196-209.

p. 21
   “Pachycephalosaurs … often nicknamed ‘bone-headed dinosaurs’ because of their thick, bony skulls, share a common ancestor with those other big-headed dinosaurs, ceratopsians.” For seeing how big-headed ceratopsians and pachycephalosaurs were related through their anatomy: Mackovicky, P.J. 2012. Marginocephalia. In Brett-Surman, M.K., Holtz, T.R., Jr., and Farlow, J.O. (editors), The Complete Dinosaur (2nd Edition). Indiana University Press, Bloomington, Indiana: 524-549.

p. 22
   “But the easiest way to tell the difference between a theropod track and an ornithopod track is to apply three criteria… .” (1) Lockley, M.G. 2009. New perspectives on morphological variation in tridactyl footprints: clues to widespread convergence in developmental dynamics. Geological Quarterly 53: 415-432. (2) Also see Farlow et al. (2012).

p. 22
   “However, many prosauropod tracks also show them walking on their rear feet only.” Rainforth, E.C. 2003. Revision and re-evaluation of the Early Jurassic dinosaurian ichnogenus Otozoum. Palaeontology, 46: 803-838.

p. 22
   “So where we originally had none, we now frolic in the land of plenty, as sauropod tracks have been found on all continents except for Antarctica, and in rocks ranging from the Late Triassic (230 mya) through the Late Cretaceous periods (65 mya).” (1) Lockley, M.G., Wright, J.L., Hunt, A.P., and Lucas, S.G. 2001. The Late Triassic sauropod track record comes into focus. New Mexico Geological Society Guidebook, 52nd Field Conference: 181-190. (2) Carrano, M.T., and Wilson, J.A. 2001. Taxon distributions and the tetrapod track record. Paleobiology, 27: 564-582.

p. 23
   “For example, the first undoubted stegosaur tracks were not found
until 1994, in Middle Jurassic (about 170
mya
) rocks of England.” Whyte, M.A., and Romano, M. 1994. Probable sauropod footprints from the Middle Jurassic of Yorkshire, England.
Gaia Revista de Geociencas
, 10: 15-26.

p. 23
    “Now stegosaur tracks are becoming more readily recognized, also having been found in Spain, Portugal, Morocco, and the exotic far-off land of Utah.” (1) Pascual, C., Canudo, J.I., Hernández, N., Barco, J.L., and Castanera, D. 2012. First record of stegosaur dinosaur tracks in the Lower Cretaceous (Berriasian) of Europe (Oncala group, Soria, Spain).
Geodiversitas
, 34: 297-312. (2) Mateus, O., Milàn, J., Romano, M., and Whyte, M.A. 2011. New finds of stegosaur tracks from the Upper Jurassic Lourinhã Formation, Portugal.
Acta Palaeontologica Polonica
, 56: 651-658. (3) Belvedere, M., and Mietto, P. 2010. First evidence of stegosaurian
Deltapodus
footprints in north Africa (Iouaridène Formation, Upper Jurassic, Morocco).
Palaeontology,
53: 233-240. (4) Milàn, J., and Chiappe, L.M. 2009. First American record of the Jurassic ichnospecies
Deltapodus brodricki
and a review of the fossil record of stegosaurian footprints.
Journal of Geology,
117: 343-348.

p. 23
   “Some of these tracks even include skin impressions, the first known glimpse at the scaly feet of stegosaurs.” Mateus, O., Milàn, J., Romano, M., and Whyte, M.A. 2011. New finds of stegosaur tracks from the Upper Jurassic Lourinhã Formation, Portugal.
Acta Palaeontologica Polonica
, 56: 651-658.

p. 23
   “Now their tracks are documented from places as widespread as Bolivia, British Columbia (Canada), Colorado (USA), and elsewhere… .” McCrea, R.T., Lockley, M.G., and Meyer, C.A. 2001. Global distribution of purported ankylosaur track occurrences.
In
Carpenter, K. (editor),
The Armored Dinosaurs
. Indiana University Press, Bloomington, Indiana: 413-454.

p. 24
   “The current claim for ‘oldest dinosaur from the fossil record’ … lies with
Eodromeus
(‘dawn runner’).” Martinez
et al.
(2011).

p. 25
   “Other dinosaur fossils from rocks of nearly the same age in Argentina includes one other theropod,
Herrerasaurus
, a basal sauropodomorph,
Eoraptor
, and a primitive prosauropod,
Panphagia
.” Martinez, R.N., and Alcober, O.A. 2010. A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha.
PLoS One
, 4: e4397. doi:10.1371/ journal.pone.0004397. A new article by some of the same authors also concluded that
Eoraptor
, long considered as a primitive theropod, was actually a sauropodomorph: Sereno, P.C., Martínez, R.N., and Alcober, O.A. 2013. Osteology of
Eoraptor lunensis
(Dinosauria, Sauropodomorpha). Basal sauropodomorphs and the vertebrate fossil record of the Ischigualasto Formation (Late Triassic: Carnian-Norian)
of Argentina.
Journal of Vertebrate Paleontology Memoir,
12: 83-179 DOI:10.1080/02724634.2013.820113

p. 25
   “Sure enough, three- and four-toed tracks similar to those predicted for primitive dinosaurs are fairly common in some Middle Triassic rocks.” (1) Demathieu, G.R. 1989. Appearance of the first dinosaur tracks in the French Middle Triassic and their probable significance. In Gillette, D.D., and Lockley, M.G. (editors), Dinosaur Tracks and Traces. Cambridge University Press, Cambridge, U.K.: 201-207. (2) A good, critical review of Early and Middle Triassic dinosaur-like tracks in the U.K. was provided by: King, M.J., and Benton, M.J. 1996. Dinosaurs in the Early and Mid Triassic? The footprint evidence from Britain. Palaeogeography, Palaeoclimatology, Palaeoecology, 122: 213-225.

p. 26
   “Some of this disrespect for all things ichnological was allayed in 2010 when a team of paleontologists, led by Stephen Brussatte… .” Brussatte, S.L., Niedźwiedzki, G., and Butler, R.J. 2010. Footprints pull origin and diversification of dinosaur stem lineage deep into the Early Triassic. Proceedings of the Royal Society of London, B, 278: 1107-1113. An update on their research into dinosauromorph tracks in the Triassic rocks of Poland is here: Niedźwiedzki, G., Brusatte, S.L., and Butler, R.J. 2013. Prorotodactylus and Rotodactylus tracks: an ichnological record of dinosauromorphs from the Early-Middle Triassic of Poland. Lyell Collection, Special Publications of the Geological Society of London, 379, published online April 23, 2013: doi: 10.1144/SP379.12.

p. 26
   “… footprints are often ignored or largely dismissed by workers focusing on body fossils, and are rarely marshaled as evidence in macroevolutionary studies of the dinosaur radiation.” Brussatte et al. (2010) discuss this oversight of ichnological evidence, which is also addressed in Carrano and Wilson’s (2001) paper.

p. 26
   “A ghost lineage is one for which we have evidence that ancestral members of a clade and their descendants lived at a certain time in the geologic past… .” Cavin, L., and Forey, P.L. 2007. Using ghost lineages to identify diversification events in the fossil record. Biology Letters, 3: 201-204.

p. 27
   “However, a few dinosaurs mixed it up, switching from bipedal to quadrupedal and back again… .” Wilson, J.A., Mariscano, C.A., and Smith, R.M.H. 2009. Dynamic locomotor capabilities revealed by early dinosaur trackmakers from southern Africa. PLoS One, 4(10): e7331.doi:10.1371/journal.pone.0007331

p. 27
   “In a dinosaurian sense, though, a change from a four-legged to a two-legged gait meant that a dinosaur was facultatively bipedal (became bipedal when it wanted) and a normally two-legged dinosaur going on all fours was—you guessed it—facultatively quadrupedal.” See Farlow et al. (2012).

p. 28
    “We also can get a better understanding of gaits by measuring distances between alternating feet (pace), between the same foot (stride), and the width of the trackway (straddle).” Basic tracking terms can be very confusing when applied by different trackers, but are approaching some standardization. Two scientifically well-done books on mammal tracking that clearly define these and other terms are: (1) Halfpenny, J., and Biesiot, E. 1986. A Field Guide to Mammal Tracking in North America. Johnson Publishing, Boulder, Colorado: 161 p. (2) Elbroch, M. 2003. Mammal Tracks and Sign of North America. Stackpole Books, Mechanicsburg, Pennsylvania: 778 p.

p. 29
   “Speaking of sauropod trackways, their patterns can be further placed into two categories based on their widths: narrow gauge and wide gauge.” (1) Farlow, J.O. 1992. Sauropod tracks and trackmakers: integrating the ichnological and skeletal records. Zubia, 10: 89-138. (2) Wilson, J.A., and Carrano, M.T. 1999. Titanosaurs and the origin of “wide-gauge” trackways: a biomechanical and systematic perspective on sauropod locomotion. Paleobiology, 25: 252-267.

p. 29
   “Take the length of a theropod or ornithopod track and then multiply it by four. The resulting number gives the approximate hip height of the dinosaur… .” Henderson, D.M. 2003. Footprints, trackways, and hip heights of bipedal dinosaurs: testing hip height predictions with computer models. Ichnos, 10: 99-114.