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Theropod body size estimated from tooth marks using Komodo dragons



From: Ben Creisler
bscreisler@yahoo.com
 
In the new issue of Paleobiology:
 
 
Domenic C. D'Amore and Robert J. Blumenschine (2012)
Using striated tooth marks on bone to predict body size in theropod dinosaurs: 
a model based on feeding observations of Varanus komodoensis, the Komodo 
monitor.
Paleobiology 38(1):79-100
doi:10.5061/dryad.99qj3 
http://www.bioone.org/doi/abs/10.1666/09079.1
 
Mesozoic tooth marks on bone surfaces directly link consumers to fossil 
assemblage formation. Striated tooth marks are believed to form by theropod 
denticle contact, and attempts have been made to identify theropod consumers by 
comparing these striations with denticle widths of contemporaneous taxa. The 
purpose of this study is to test whether ziphodont theropod consumer 
characteristics can be accurately identified from striated tooth marks on 
fossil surfaces. We had three major objectives (1) to experimentally produce 
striated tooth marks and explain how they form; (2) to determine whether body 
size characteristics are reflected in denticle widths; and (3) to determine 
whether denticle characters are accurately transcribed onto bone surfaces in 
the form of striated tooth marks. We conducted controlled feeding trials with 
the dental analogue Varanus komodoensis (the Komodo monitor). Goat (Capra 
hircus) carcasses were introduced to captive, isolated
 individuals. Striated tooth marks were then identified, and striation width, 
number, and degree of convergence were recorded for each. Denticle widths and 
tooth/body size characters were taken from photographs and published accounts 
of both theropod and V. komodoensis skeletal material, and regressions were 
compared among and between the two groups. Striated marks tend to be regularly 
striated with a variable degree of branching, and may co-occur with scores. 
Striation morphology directly reflects contact between the mesial carina and 
bone surfaces during the rostral reorientation when defleshing. Denticle width 
is influenced primarily by tooth size, and correlates well with body size, 
displaying negative allometry in both groups regardless of taxon or position. 
When compared, striation widths fall within or below the range of denticle 
widths extrapolated for similar-sized V. komodoensis individuals. Striation 
width is directly influenced by the
 orientation of the carina during feeding, and may underestimate but cannot 
overestimate denticle width. Although body size can theoretically be estimated 
solely by a striated tooth mark under ideal circumstances, many caveats should 
be considered. These include the influence of negative allometry across taxa 
and throughout ontogeny, the existence of theropods with extreme denticle 
widths, and the potential for striations to underestimate denticle widths. This 
method may be useful under specific circumstances, especially for establishing 
a lower limit body size for potential consumers.