There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
Just to show the approximate size of Livyatan, I found this comparative image were the author tried to show the three diferent estimations of size reported by Lambert et al. (2010), he kept the same skull and head size and just increased the body lenght and massiveness, here is the image:
*This image is copyright of its original author
There we can see how the body proportions change based in the estimation. From my point of view the lower estimation looks ok taking in count that this is an "sperm whale" (bias based in the current species?). The lenght of 16.2 m works only if Livyatan present a morphology close to the moder orcas, where they have skulls or less than 130 cm but bodies of up to 9 meters. The largest one of 17.5 cm, personally looks odd, but until we found a more or less full specimen, it is just a posibility that is based in another posibility (the size of Zygophyseter is still not clearly defined).
Now, following this line, I made a comparative image now, using the "conservative" body size estimated (the lower one) from Zygophyseter (the one in the paper of Bianucci & Landini, 2006) and the one based in the new proportions estimated from the skeleton of Brygmophyseter (no measurements from the holotype are involved, just a side-to-side estimation). Finally I included the biggest sperm whale actually measured and reported by scientists and also the biggest orca actually confirmed. Here is the image:
*This image is copyright of its original author
I kept the size of the head in the same form as the first image, but I had to increase the bulkiness of the animal for obvious reasons. On the body mass, the heaviest sperm whale is a male of 57.1 tonnes (total length of 18.1 m) weighed in pieces, but the heaviest male weighed complete was a male that weighed 53 tonnes (18 m), so for the largest males of over 20 m reported in litterature a maximum of 60 tonnes is not out of question. For the orca the heaviest male actually weighed was of 6.6 tonnes (7.65 m) as far I remember, but the biggest specimens of up to 9 m had been estimated up to 10 tonnes, and based in the massiveness of this animal that weight is completelly plausible.
Now, on the body mass of Livyatan, there is no document where they actually worked on it. Villafaña & Rivadeneira (2014) did not calculated any body mass or made any formula, they just estimated a weight of 57 tonnes based in a length of 1750 cm, so is just a pure guess. As we don't know the proportions of this animal, is simply impossible to estimate its body mass at this moment, BUT if we use the sperm whales as a modern surrogate, we can make a partial estimation, although with a good margin of error because of differences in the morphology of both species. I got a sample of 47 males with total length and body mass and I found that there is a regional difference, with males from south been heavier on average than those from north:
One male of 49.3 tonnes (15.4 m) was discarded in the regional differences as the location was not provided, but including it in any of the samples creates no significant difference.
Now, I created three ecuations usefull to estimate the body mass of male sperm whales: Overall r2=0.7168, North r2=0.8118, South r2=0.8173) and if we applied them to this specimen of Livyatan, here are the results:
For a length of 16.2 m
Overall: 40.7 tonnes
North: 38.0 tonnes
South: 45.4 tonnes
For a length of 12.5 m
Overall: 21.3 tonnes
North: 19.2 tonnes
South: 21.6 tonnes
So, based on this, the body mass of Livyatan melvillei, using the modern male sperm whale (Physeter macrocephalus), could be between 19 - 22 tonnes (total length of 12.5 m) or 38 - 45 tonnes (total length of 16.2 m). However based in the bulkiness of the specimen compared with the sperm whales, is possible that the body mass could be higher than this calculations.
