Re: Megalania question - DNA

[Jura <pristichampsus@yahoo.com>]

> Total length estimates in particular will depend largely on
> the length of 
> the tail, which lacking any complete fossil specimens will
> usually be 
> conjecture. Mass is probably a better way of comparing
> 'size', since a tail 
> ending with a long thing whip-like structure won't
> increase the mass much, 
> but could potentially add a metre or three to the total
> length. 
> 
> Earlier one-tonne-plus mass estimates (Auffenberg gave the
> heaviest, at 2.2 
> tonnes) were almost certainly incorrect. I haven't read
> Molnar's book, but 
> I'd be interested to know which specimens gave the 7m
> length estimate. Hecht 
> gave a similar length estimate in 1975, which he
> extrapolated from a single 
> phalanx! 
> 
> ___________________________________________________________________
> 
> 
> Dann Pigdon

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Molnar determined length by going over the skeleton of a lace monitor (_Varanus 
varius_) and looking for relationships between bones and overall body size (the 
lace monitor was used because it was a complete skeleton of a monitor, that was 
available on hand, and not for any phylogenetic reason). Dr. Molnar also 
measured the skeletons of other monitors in the Queensland museum. He found a 
relationship between dorsal vertebral breadth, and total body length. His 
results appeared to reliably indicate total body lengths within 5% of actual 
results.

Molnar also goes into great detail into the tail length problem, and how widely 
ranging these results can be depending on length estimates. He mentioned that 
if _Megalania prisca_ had a tail that was 2.3 times bodylength, like in 
_V.varius_ then the largest specimen would have clocked in around 7.9 meters. 
If, as Hecht suggested, the tail was half SVL, then the largest individual 
would have been 5.2 meters. 

However, since no living monitor shows a tail that is less than SVL, this 
latter estimate is probably wrong. In the end Molnar assumed a tail length that 
was equal to body length (like in oras), which resulted in a 7 meter 
individual. 

In the end it was a best guess estimate, but one with plenty of caveats that 
are worth keeping in mind. 

The book, by the way, is a great read. Easily the most comprehensive view of 
this beast ever written.

Jason

"I am impressed by the fact that we know less about many modern [reptile] types 
than we do of many fossil groups." - Alfred S. Romer