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Forwarded from Richard Butler

With regards to yesterday's discussion of Fruitadens, the first author
asked me to forward the following. Michael Erickson has already replied to
me that he was mistaken--and sorry--about his rant yesterday.  Butler
wanted a chance to more fully explain the size issue in Drinker,
Fruitadens, etc.


Dear members of the DML;

I am glad to see that our recent paper on the new heterodontosaurid
Fruitadens has been the subject of discussion and debate; however, I
felt that I had to respond to comments by list member Michael Erickson
in which he accuses us (the authors of the paper) of lying and
unethical behaviour. There is absolutely no evidence to support these

In his accusation, Michael Erickson suggested that Robert Bakker had
estimated a body length of 25 cm for the small ornithopod Drinker
nisti, and that we had ignored this. This claim is a complete
falsehood. Drinker nisti was described by Bakker et al. (1990). On
pages 12-14 Bakker et al. say:

"The linear dimensions of the type of Drinker are nearly all within
+/- 7% of those given by Galton for the subadult Hypsilophodon
specimen BMNH R196 (Galton, 1974), an animal 1.36m long, snout to tail
tip. The type of Drinker is not fully adult; all the arches had
separated from the centra in the dorsal and anterior caudal vertebrae.
A slightly larger Drinker specimen, CPS 197, shows nearly complete
coalescence of the centrum-arch suture, thereby establishing an adult
total length of slightly less than 2.0 m."

Thus Bakker estimated a body size range of 1.36-2 metres for Drinker,
very significantly larger than the 65-75 cm that we estimated for
Fruitadens. I have no idea where Michael Erickson got his information
from, but it is wrong. Foster (2003) estimated a mass of just under
10kg for Drinker, again much larger than our 0.75 kg estimate for

Bakker et al. went on to discuss the material of Fruitadens
("exceedingly small ornithopods from the Morrison at Fruita") and
suggest that it might represent juveniles. Our histological analyses
indicate that growth was beginning to slow in the largest individuals,
and that they were probably close to adult size. The ESM of our paper
contains a discussion of body size in all other ornithischians. We
acknowledge in the paper and the ESM that the heterodontosaurids
Echinodon and Tianyulong might be of similar size to Fruitadens, but
at present we don't have good data on the ontogenetic stage of these

Thanks to Tom Holtz for already pointing much of this out, and
apologies for reiterating his comments. In light of the very strongly
worded and false nature of the attack I felt a brief response was

If anyone wants further information on Fruitadens and our research
please feel free to contact me.

All the best,


Bakker, R.T., Galton, P.M., Siegwarth, J., and Filla, J. (1990). A new
latest Jurassic vertebrate fauna, from the highest levels of the
Morrison Formation at Como Bluff, Wyoming. Part IV. The dinosaurs: A
new Othnielia-like hypsilophodontoid. Hunteria 2(6): 8-14.

Butler, R. J., Galton, P. M., Porro, L. B., Chiappe, L. M., Henderson,
D. M., & Erickson, G. M. (2009). Electronic supplementary material to
"Lower limits of ornithischian dinosaur body size inferred from a new
Upper Jurassic heterodontosaurid from North America. Proceedings of
the Royal Society B.

Foster, J.R. (2003). Paleoecological Analysis of the Vertebrate Fauna
of the Morrison Formation (Upper Jurassic), Rocky Mountain Region,
U.S.A. New Mexico Museum of Natural History and Science Bulletin 23.

Dr Richard J. Butler

Alexander von Humboldt Research Fellow
Bayerische Staatssammlung für Paläontologie und Geologie
Richard-Wagner-Str. 10
80333 Munich, Germany


Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661

Faculty Director, Earth, Life & Time Program, College Park Scholars
Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA