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RE: Megalania question - DNA



One of the conclusions Molnar (2004) reached about _Megalania prisca_ is
that it is a species of _Varanus_, i.e. he sunk the genus. Nobody since
Fejervary, afaik, has argued for a phylogenetic position outside _Varanus_,
so it was about time this was done formally. 'Megalania' is a beautiful word
though, and I'm all for keeping it around as the 'common name' for _Varanus
priscus_ (Owen).  (Similarly, _Montypythonoides_ Smith & Plane, 1985
achieved wide name-recognition for a Miocene python from Riversleigh, which
turns out to be phylogenetically within the extant genus _Morelia_ Gray).

The original question was about most-recent age, presence in caves, and
potential for DNA recovery.  While the giant goanna does occur in cave
deposits (Wellington, NSW, and Naracoorte, SA; Reed & Hutchinson 2005), it
seems the climate, chemistry and relatively great age (mostly >>40ka) of
Australian Pleistocene deposits with megafauna makes the prospects for
ancient DNA pretty poor. There was discussion on this with Alan Cooper at
the 2005 CAVEPS in Naracoorte; I presume he's still looking, but as far as
the titles listed at http://www.adelaide.edu.au/acad/publications/ indicate,
there is still no Pleistocene DNA of any organism known in the whole
continent. 

References:
Molnar, R.E.  2004.  The long and honourable history of monitors and their
kin.  In E.R. Pianka, D.R. King and R.A. King (eds), Varanoid Lizards of the
World, 10-67.  Indiana University Press, Bloomington & Indianapolis. 

Reed, E.H., and M.N. Hutchinson.  2005.  First record of a giant varanid
(Megalania, Squamata) from the Pleistocene of Naracoorte, South Australia.
Memoirs of the Queensland Museum 51: 203-213.

-----------------------------------------------
Dr John D. Scanlon, FCD
Riversleigh Fossil Centre, Outback at Isa
riversleigh@outbackatisa.com.au
http://tinyurl.com/f2rby
 
"Get this $%#@* python off me!", said Tom laocoonically.

-----Original Message-----
From: Dann Pigdon [mailto:dannj@alphalink.com.au] 
Sent: 03 June, 2008 4:05 PM
To: dinosaur@usc.edu
Subject: Re: Megalania question - DNA

Jura writes: 

> 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.

It'd be interesting to compare the proportion of total length the tail makes

up with total mass in a range of living varanids, to see whether there's a 
nice neat relationship (tails getting proportionally shorter as mass gets 
bigger, for instance). If there is a nice neat trend, then scaling up to 
Megalania-size might then result in a tail that is less than the 
snout-to-vent length. 

Of course in the absence of actual fossil material, it's still just another 
method of interpolation. 

___________________________________________________________________ 

Dann Pigdon
GIS / Archaeologist              http://geo_cities.com/dannsdinosaurs
Melbourne, Australia             http://heretichides.soffiles.com
___________________________________________________________________