RE: cause of Gigantism in sauropods

["Thomas R. Holtz, Jr." <tholtz@umd.edu>]

> -----Original Message-----
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of Roberto Takata
> Sent: Thursday, February 10, 2011 1:09 PM
> To: DINOSAUR@usc.edu
> Subject: Re: cause of Gigantism in sauropods
> 
> Maybe dino-size was related to genome size. There is a (weak) 
> correlation in some tetrapod groups - including birds. [1]
> 
> [1] Gregory, T.R. 2002. Genome size and developmental 
> parameters in the homeothermic vertebrates. Genome 45: 833-838
> http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1480-332
1&volume=45&issue=5&startPage=833

Already tested and rejected:

http://rspb.royalsocietypublishing.org/content/276/1677/4303.abstract

Sauropod dinosaurs evolved moderately sized genomes unrelated to body size

   1. Chris L. Organ1,*,
   2. Stephen L. Brusatte2,3 and
   3. Koen Stein4

Abstract

Sauropodomorph dinosaurs include the largest land animals to have ever lived, 
some reaching up to 10 times the mass of an African
elephant. Despite their status defining the upper range for body size in land 
animals, it remains unknown whether sauropodomorphs
evolved larger-sized genomes than non-avian theropods, their sister taxon, or 
whether a relationship exists between genome size and
body size in dinosaurs, two questions critical for understanding broad patterns 
of genome evolution in dinosaurs. Here we report
inferences of genome size for 10 sauropodomorph taxa. The estimates are derived 
from a Bayesian phylogenetic generalized least
squares approach that generates posterior distributions of regression models 
relating genome size to osteocyte lacunae volume in
extant tetrapods. We estimate that the average genome size of sauropodomorphs 
was 2.02 pg (range of species means: 1.77-2.21 pg), a
value in the upper range of extant birds (mean = 1.42 pg, range: 0.97-2.16 pg) 
and near the average for extant non-avian reptiles
(mean = 2.24 pg, range: 1.05-5.44 pg). The results suggest that the variation 
in size and architecture of genomes in extinct
dinosaurs was lower than the variation found in mammals. A substantial 
difference in genome size separates the two major clades
within dinosaurs, Ornithischia (large genomes) and Saurischia (moderate to 
small genomes). We find no relationship between body size
and estimated genome size in extinct dinosaurs, which suggests that neutral 
forces did not dominate the evolution of genome size in
this group.

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
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
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