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Post by Godzillasaurus on Nov 11, 2013 1:18:40 GMT 5
Kaprosuchus has often been stated being a lot smaller than a lot of people think, specifically around the size of the American alligator. I remember coherenstheaf on Carnivora showing us a chart displaying the animal's skull proportions:  Kaprosuchus had a mandible length of close to 24 inches (2 feet) long. I just read about a 14 foot American alligator killed in Florida with a 23.75 inch head length: www.nydailynews.com/news/national/huge-alligator-largest-head-found-florida-caught-killed-article-1.1142973The main problem with this claim is that kaprosuchus most likely did NOT have identical head to body proportions as that of the American alligator, as it was not only part of an entirely different family but also occupied a different niche being a primarily terrestrial predator. Evidence for this includes differently-shaped dentition from that of modern, semi-aquatic crocodilians (long, at least somewhat laterally compressed, and tusk-like. The enlarged sets of dentition in its maw are clearly designed for killing via powerful and fatal stabbing) and eyes that seem to have been positioned to give the animal more binocular vision (as opposed to begin in the top of the skull as seen in modern crocodilians, which is an adaptation for hunting in aquatic environments). Another clue to evolution on land could also be the heavily-armored and rugose snout of the animal, which has been theorized to have been used to take large prey down on land. More evidence of this "ramming of prey" comes from the possible presence of a tough keratinous shield on the tip of the upper jaw.Because the only fossil evidence that we have of kaprosuchus is a skull, there is no way to truly find the animal's head to body proportions. Does anybody have any sources that might shine some light on this subject? Here is the skull of kaprosuchus and the skull of an American alligator for reference (notice how the former skull is proportionally longer with a smaller snout width):   |
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Post by creature386 on Nov 11, 2013 1:26:36 GMT 5
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blaze
Paleo-artist 
Posts: 766
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Post by blaze on Nov 11, 2013 3:12:30 GMT 5
The maximum head length of Kaprosuchus is actually 20 inches but this is not how you measure crocs head length, it's from the snout to the occipital platform, this can't be measured on Kaprosuchus though, the parietal extends further back but measuring to the reconstructed occipital condyle is 46cm (18in).
It is true that we don't really know its dimensions but 6m for it is preposterous, that'll imply a head-body lenght ratio over 13.
Sincé I'm lame and can't figure out the logaritimic equation from Woodward et al. 1994 on alligator's máximum length, I'll use isometric scaling, the biggest male they captured was 4.27m long and had a head length of 60cm, that'll make Kaprosuchus just shy of 3.3m long.
The supplementary data from Sereno's 2001 Sarcosuchus paper has head length and total length measurements of 28 saltwater crocodiles, there we have two specimens with a head length of exactly 46cm and they are 3.4 and 3.5m in total length.
edited:
IMO Sereno & Larson's evidence for terrestrial habitat is pretty weak, nares slightly moved posteriorly on the skull (really?), central axis of the orbit, directed laterally more than vertically (but by how much? they didn't even make a detailed comparison for this or tried to find if it's really true beyond superficial looks) making it impossible to hide its head in water (conjecture) and that's pretty much it.
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Post by Godzillasaurus on Nov 11, 2013 5:35:54 GMT 5
If it can't be measured on kaprosuchus, then why are you representing as a definite?
That is assuming that kaprosuchus had identical proportions to that of the saltwater crocodile, which it likely did not. The specimen that was found was most likely somewhere around that size range however. We will just have to find more fossils to make the size of kaprosuchus more clear. And it would be a helluva lot easier to figure out its potential size if we found fossils that were located posterior to the head and neck with the one skull that we have.
I wasn't planning on even making this so-called detailed comparison in the first place (only a generalized comparison), as I don't have either of the animals' physical skulls to work with, and I cannot find any alligator skull dimension charts to use. No need to get mad; I did nothing wrong. Besides, I don't even know wtf occipital platforms, parietals, condyles, nares, and central axises are. I fail at this kind of stuff.
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Post by Runic on Nov 11, 2013 6:28:49 GMT 5
^ He was saying that towards the source not you lol
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Post by coherentsheaf on Nov 11, 2013 6:39:18 GMT 5
Whats the equation? Maybe I can be of service.
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Post by Godzillasaurus on Nov 11, 2013 7:00:48 GMT 5
^ He was saying that towards the source not you lol Oh, he used the pronoun "you", so I figured he was directing that at me. Would anyone be able to fully explain to me what exactly Sereno was basing the 6 meter estimate off of? I, sadly, am unable to read his paper. |
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blaze
Paleo-artist
Posts: 766
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Post by blaze on Nov 11, 2013 10:29:27 GMT 5
I did said "you" and it was directed to Sereno and Larson (2009) it worked in my head but it didn't work in reality haha I'm going to edit that.
You're right, I think I shouldn't have used the length to the occipital, mainly because that part isn't even preserved and I based it on the reconstructed skull, but generally, the dorsal head lenth is around 90% of the máximum head length, 90% of 51cm is 46cm, but 48cm could also be valid.
Sereno & Larson don't explain how they got 6m, in fact it's only mentioned once, in the diagnosis section, in this way: medium-sized (~6m) neosuchian, I wonder since when is 6m long, medium sized, it very well could be a typo but I can't remember if the press reléase repeated that claim or not.
@coherensheaf
The equation is log(TL)=2.132494 + 0.95811(log(HL))
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Post by coherentsheaf on Nov 11, 2013 17:28:53 GMT 5
@coherensheaf The equation is log(TL)=2.132494 + 0.95811(log(HL)) Using HL=50cm and assuming that natural logharithms are used I get 359cm. |
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Post by creature386 on Nov 11, 2013 22:25:20 GMT 5
I, sadly, am unable to read his paper. There's a download link below, it's a freely accessible paper. |
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Post by Godzillasaurus on Nov 12, 2013 4:25:50 GMT 5
What was the real length of mahajangasuchus (the closest known relative of kaprosuchus)? According to some sources, it had a skull length of 80 cm, yet has been estimated at having a total length of close to 3 meters.
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Post by Godzillasaurus on Nov 12, 2013 7:44:32 GMT 5
I edited my first post to describe the skull features of kaprosuchus and why it was more likely a terrestrial animal than a mainly aquatic animal.
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Post by creature386 on Nov 12, 2013 20:59:47 GMT 5
What was the real length of mahajangasuchus (the closest known relative of kaprosuchus)? According to some sources, it had a skull length of 80 cm, yet has been estimated at having a total length of close to 3 meters. Could you post these sources? The paper I posted above described Mahajangasuchidae as "Mid- to large-sized (~4–6 m) metasuchians". I doubt they would have picked 4-6 m as a range, if their eponymous member had an adult length of only 3 m. Maybe someone has the full text of the cranial description ( dx.doi.org/10.1671/0272-4634(2008)28[382:MICMCA]2.0.CO;2 ) and can search for a size estimate there. |
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blaze
Paleo-artist
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Post by blaze on Nov 12, 2013 23:59:46 GMT 5
coherentsheafThank you, it's more than I was expecting, but you did used a higher measurement than I was using. Godzillasaurus There's several specimens and the paper linked by creature386 doesn't give measurements, but measuring the skeletal in figure 2 gives a maximum head length of 59cm while the skull reconstructed in figure 9 is 61.5cm. SVL in the skeletal of figure 2 is roughly 1.9m, so the specimens figured, whichever ones they are, are around 3.8-4m long assuming a tail of equal length to SVL. This isn't very different from the proportions of alligators. They never say it had binocular vision. IMO, the impacting with prey hyphothesis sounds pretty weak, it's all based on the fact that the nares are like 2cm from the margin of the premaxilla instead of 1cm and the robust, rugose, snout, whose shape actually resembles that of Sarcosuchus in lateral view, big robust snout followed by thinner, in all dimensions, connection to the maxilla, why is the part immediately following the impact zone so fragile looking by comparison? IMO, that snout is goning to break impacting something at speed.
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Post by Godzillasaurus on Nov 13, 2013 0:45:46 GMT 5
Actually, the kaprosuchus head structure (mandible is non-inclusive) more than proves an overlap in vision.
The resemblance to the lateral view of sarcosuchus' skull is very superficial and subtle. Their skulls were so much different, and they were very different animals. Modern crocodilians don't necessarily have THAT many differences in terms of lateral skull view either, although some, like the Nile crocodile, tend to have deeper skulls than many other species with age. Plus, the lateral portion of an animal's skull most definitely does not say EVERYTHING about that said animal; kaprosuchus had a much wider snout than sarcosuchus. And even then, the dentition of the pholidosaurid and the mahajangasuchid are still very different from one another, with the former being more well designed for gripping and crushing as opposed to fatally impaling. I fail to see the relevance that sarcosuchus has here.
Kaprosuchus and sarcosuchus were two very different animals. The kaprosuchus does not have to simply "ram into" a prey animal; it can easily take something down by the legs whether it decided to bite or use its armored snout. Whether its upper jaw was enforced with a keratinous shield or not, it still wasn't weakly-built, not the least bit.
And sarcosuchus did not have weak jaws by any means
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