Since there seems to be some uncertainty how large Megalania was, and there are very many dubious estimates on the internet and even the peer reviewed literature (ranging from 100-4400 kg) I will try to sort this issue out.
source of the confusionFirst an important term: SVL means as much as Snout-ventral length and is measured as indicated in the sketch:
Most modern size estimates of V.priscus (prisca?) are based on size estimates are based on estimates made by Hecht in 1975. And here lies the source of much confusion Since only a few caudal (=tail) vertebrae of the great roamer are known Hecht assumed that the total length of Megalania is 1.5 its SVL. (See sketch)
Now many people took the resulting total lengths from Hecht'sestimated SVL and compared them to modern monitor species. However modern monitors have far longer tails than that assumption with the total length being 2 or 2.5 times their SVL. If one compares a Megalnia specimen with a scaled up monitor lizard with the same total length, the megalania will have a farlonger body and would thus be much heavier. Unfortunately this effect was ignored several times in the peer reviewed literature (See for example Wroe 2002, or Fry et a. 2009).
Now that we have recognized the source of the confusion let us turn to the actual sizes:
Average size:Here are Hecht's estimates for SVLs:
as given by Molnar.
If one excludes the oversized ungual, unspecified size of a large Ora, and in the cases were there is a range of values takes the median, one gets an average SVL of 249cm and a median of 235cm, somewhat larger than the values Molnar expected.
These animals assumin Molnar's body proportions would have been 5m and 4.7m long respectively.
Now on to mass:
Blobs corrected formula forvaranid body mass asgiven by Molnar: log(bodymass)=3.435*SVL-6.009 (SVL in mm, bodymass in g) Using this formula on the previous data one gets an average of 581 kg and a median of 372kg.
Maximum size:Maximum size naturally is an even more speculative issue than average size. The lagest vertebra, QMF 2942 results in an reconstructed body lenth of 7-7.6m and in corresponding body masses of 1.5-2tonnes. However it is unclear that this truly represents the largest megalania that ever lived.
From Jessop et al. we can calculate that maximum mass of Komodo dragons is about 4.21 times the mass of the average Komodo dragon. If this ratio holds true for Megalania, the largest one would weigh in at 2446kg. However this is extrapolation way beyond the data range and almost as speculative as Megalodon maximum size estimates.
Sizes in the literature and other estimates:Wroe fails spectacularily in this regard as outlined above (note this is nothing personal, he has done wonderful research on biomechanics in general and I really like reading his papers).
Burness et al. give a body mass of 380kg, which seems quite reasonable, but they do not support that estimate with anything.
Molnar wrote the most detailed discussion but he did not actually calculate average length or mass, but smply used an SVL that he deemed apropriate. His estimate regarding the enormous specimen QMF 2942 (3.8m SVL, 7.6m total length, 1940kg) seems reasonable.
Gregory Paul lists Megalania as weighing in at 1000 kg on his website an estimate he probably did himself. Since he is very good at estimating body mass one should not simply ignore this estimate,unfortunately he does not give details regarding his methodology or which specimen this estimate was based on.
Sources:Burness, G. P., Diamond., J., and Flannery, T. F. (2001).
"Dinosaurs, dragons and dwarfs: the evolution of
maximal body size."Gregory Paul's siteS. Wroe, (2002).
"A review of terrestrial mammalian and reptilian carnivore ecology in Australian fossil faunas, and factors influencing their diversity: the myth of reptilian domination and its broader ramifications"Fry et al. (2009).
"A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) prisca"Jessop et al. (2006).
"Maximum body size among insular Komodo dragon populations covaries with large prey density"Here is my R-code, so people can replicate my calculations:
svl<-c(2.9, 3.1, 3.8, 2.3, 1.55, 2.15, 2.15, 2.35, 1.5, 2.2, 2.5, 3.25, 2.65)
mean(svl)
median(svl)
bodymass<-((svl*1000)^3.435)/10^9.009
mean(bodymass)
median(bodymass)
