Top Dog

[Grey]

From C. McHenry.

yes, basestimating pliosaurid lengths from brachaucheniid proportions isn't a great situation but we can't do anything else until someone finds a near complete Pliosaurus. Remember that in the 90s I had to try to convince everyone else that Brachaucheniids and Pliosaurids were different... the UK researchers did not understand that. But I'd caution against using that uncertainty as a license for okaying 18 m Pliosaurus.. .we don't know which way the error goes.

About Hawthorne post :

As a principle, you can't extrapolate extremes of a giant species from specimens of a species. And you most certainly can't extrapolate from juvs... there is the small matter of allometry. émoticône smile
But the guy clearly has little biological understanding...

Then about the ratio :

( is the 1/6 or 1/7 head/body ratio he mentions correct ?)
no
1/7 - 1/8 is a crocodile!
I did head/body ratios in my thesis chapter...

[Apex]

So after this big sperm whale has been confirmed does this debunk the argument that sperm whale bulls have got bigger due to hunting?

p.s. 25 meter bull sperm whales and indication of 20+ meter pliosaurus is like a dream come true, I really hope these findings are accurate 

[blaze]

There's no new findings about 20+m pliosaurids, just some guy extrapolating to the giant teeth using a juvenile specimen and apparently not even getting the length of the skull right, inflating his own estimate. Measuring the image myself and the true length of the skull alone I only get an estimated skull length of 2.45m for those 40cm teeth (if that's an straight-line measurement), suggesting lengths of 12-15m using the 1:5 and 1:6 ratios. Comparing to the Liopleurodon specimens described in Andrews (1913) and assuming the giant teeth are 40cm along the curve you can reduce the skull length to 1.9m and total lengths of 9.5-11.4m using the same ratios mentioned before.

Grey
The paper you mention, yes it shows ct scans of the skulls, the roots go almost all the way to the middle of the snout and based on a photo you shared before in this thread it seems they also go almost all the way to the dorsal profile of the snout.

In his thesis, McHenry mentions that he knows of some late Jurassic Pliosaurids specimens with decently complete skeletons, and specifically mentions the Tübigen Liopleurodon and the Peloneustes skeleton I mentioned in the previous page, but he says that he doesn't have any proportional data on them and that's why he didn't use them.

Remember though, that he doesn't use brachaucheniid proportions (ratio ~1:4.6) for Jurassic pliosaurids but those of that museum scale model of Pliosaurus, with the skull being 19% of total length or a ratio of ~1:5.3.

[Apex]

blaze
How do these scalings work exactly?
I assume you base them from smaller specimens, but to find the length of a larger individual how do you convert the proportions from a juvenile to an adult? Is it from modern animals like crocodiles or smaller pliosaur species.
Also based on current evidence what is the length and weight of the biggest pliosaur?

[blaze]

Isometric scaling, we don't have the remains to account for allometry so that's all we can do but allometry must play a role, for example, the smallest specimen in Andrews (1913) is almost 40% larger than the one that guy used and you can already see the effects of allometry as me using that larger Liopleurodon resulted in an smaller estimate for those giant teeth.

I tend to agree with McHenry (2009) estimates of 13m and 20t.

[Grey]

Apr 10, 2015 22:43:18 GMT 5 blaze said:

McClain et al. (2015) do mention their source, the whaling records of the International Whaling Commission so yes, those measurements are definitely from whalers.

Jonsgard and Lyshoel (1969) say that when they measured orcas that had their length estimated beforehand by whalers even though most estimates were correct or almost correct there were cases where the whalers where wrong by as much as 0.6m, that's an error of ~7% an animal up to 9m long, the difficulty on measuring them accurately will definitely make the error bars grow exponentially the bigger the whale is. According to MacClain et al. (2015) there are only 9 individuals said to be larger than the official record, 9 out of a sample of over half a million, seems like the likelihood of their lengths being the result of whalers measuring/estimating them wrong is higher than them being genuine giants.

About sperm whale measurements, did you note this in McClain 2015 ?

"Size data obtained for P. macrocephalus came from the International Whaling Commission’s (IWC) whaling records (data held by IWC). Extending as far back as the 1880s, the records detail the ocean basin where individuals were caught, the specific geographical coordinates of capture, the date of capture, and the sex of each individual. The total lengths of individuals were measured from whales at rest on a flat surface, from the apex of the notch between tail flukes to the most forward part of the head."

Would the International Whaling Commission be rigorous about this though ?

[Apex]

Dec 5, 2015 3:35:35 GMT 5 blaze said:

Isometric scaling, we don't have the remains to account for allometry so that's all we can do but allometry must play a role, for example, the smallest specimen in Andrews (1913) is almost 40% larger than the one that guy used and you can already see the effects of allometry as me using that larger Liopleurodon resulted in an smaller estimate for those giant teeth.

I tend to agree with McHenry (2009) estimates of 13m and 20t.

Ok thanks that was really informative and helpful

[blaze]

Grey
Yes, the question is not if the IWC is that rigorous, is not a group of people from the IWC doing the measurements but the whalers themselves and they report them. In the case of the data from Jonsgard and Lyshoel (1969) the scientists found variation of 2ft in the whaler's measurements/estimates compared to their own measurements and remember, these are whales only up to 30ft long and that where measured on-deck, imagine the variation of much larger whales measured on the sides of vessels, specially for the 100+ year old records.

Apex
No problem!

[Grey]

Dec 13, 2015 0:01:35 GMT 5 blaze said:

Grey
Yes, the question is not if the IWC is that rigorous, is not a group of people from the IWC doing the measurements but the whalers themselves and they report them. In the case of the data from Jonsgard and Lyshoel (1969) the scientists found variation of 2ft in the whaler's measurements/estimates compared to their own measurements and remember, these are whales only up to 30ft long and that where measured on-deck, imagine the variation of much larger whales measured on the sides of vessels, specially for the 100+ year old records.

Apex
No problem!

I certainly agree about that. However what to think about the giant jawbones from Nantucket or the New Bedford Museum ? There is some discussion about that here : cameronmccormick.blogspot.fr/2008/10/sperm-whales-jaw-or-sorry-gerald-wood.html

[blaze]

Well, when using equations from the literature of body length from skull length even a 5.5m mandible does not correspond to something bigger than the 21m record by any significant margin.

[spartan]

I still wouldn't dismiss the 24m figure so easily as a measurement mistake. Even in mammals the maximum size can sometimes be as much as more than 3.5 times the average weight (although in most it seems to be around 2x or so).

[Grey]

Jan 1, 2016 4:55:01 GMT 5 spartan said:

I still wouldn't dismiss the 24m figure so easily as a measurement mistake. Even in mammals the maximum size can sometimes be as much as more than 3.5 times the average weight (although in most it seems to be around 2x or so).

That's possible but 24 m claims based on the 5.5 m mandibles are probably off.
I've recently read a paper indicating skull length is 26 % of body length in a 10 m male, then 32 % in a 16 m male.

I need to check how much of the skull length consists the mandible but skull allometry seems quite strong in Physeter.
How much of the spermaceti chamber protrudes in front of the skull needs to be known too.

But perhaps this allometry doesn't occur in all old bulls which would make 24 m possible, although maybe slightly less bulky.

Ellis (2011) reports the whalers enhanced the size their catch for reputation.

I would add that great weight variations are observed as well in reptiles (Komodo...) and fishes.

[spartan]

Jan 1, 2016 8:21:01 GMT 5 Grey said:

Ellis (2011) reports the whalers enhanced the size their catch for reputation.

I would add that great weight variations are observed as well in reptiles (Komodo...) and fishes.

True, but then there is also this

Some of the larger whales that were caught were reported to be shorter in order to create a more convincing distribution between the largest whales and the smallest whales, which were reported as longer than they were in order to meet length minimums (Ivashchenko, Clapham & Brownell, 2011).

I also didn't know that male sperm whales are growing til they are ca. 50 years old, quite fascinating for a mammal.

I would add that great weight variations are observed as well in reptiles (Komodo...) and fishes.

Absolutely. In my opinion maximum size estimates are often too conservative, but I think most of the time it's rather used in the sense of "very large, but still more or less common" instead of the freaks that represent the absolute largest size possible for the respective species.

[Grey]

But the question is, as discussed before, are the measurements made by whales +100 years ago are that reliable ?
Another question would be if these individuals are reliable, are there representative of the natural upper size within the species or were they freaks ?

[spartan]

How are freaks not "natural"?