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Post by sharkboy101 on Oct 21, 2019 3:08:50 GMT 5
The only scenario that should be taken out from the sympatric versus scenarios is Deinosuchus vs Tyrannosaurus. Both these animals were separated by about 5 million years or so.
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Post by Infinity Blade on Oct 21, 2019 3:15:42 GMT 5
Did not know it was in hypothetical scenarios. Or that we even had a Deinosuchus vs. Tyrannosaurus. Thanks. It's been moved.
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Post by dinosauria101 on Oct 21, 2019 3:20:11 GMT 5
Yes, pardon my error. That was made when I thought it was sympatric.
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Post by theropod on Oct 21, 2019 3:26:12 GMT 5
Anyway, regarding their sizes
There are two partial dentitions from the Lee Creek Mine (measurements from Purdy 2001):
USNM 299832 is complete from A1-L5, with summed tooth width of 552 mm USNM 411881 is complete from A2-L8, with summed tooth width of 528 mm
The summed tooth width of A2-L5 in USNM 299832 is 483 mm, in USNM 411881 it is 417 mm, the former is ~1.16 times the size of the latter. Scaling down the first anterior of the smaller tooth set from that gives a width of ~60 mm for the A1. Assuming the L9 is as much smaller compared to L8 as L8 is compared to L7, it would be ~23 mm wide. Total width of the dentition would thus be about 610 mm, or 1221 mm for both sides. The 16% larger dentition would hence likely have a summed tooth width of 1414 mm.
The larger dentition, assuming 15% interdental spacing, would be from a 9.4 m shark based on Lowry et al. (95% CI 8.7-10.3 m). Based on the regressions for white sharks, that shark would be ~8.6 t (range 7.7-9.4t).
Matching this specimen up with the largest specimens of Purussaurus at around 10 m may be somewhat interesting, although even in that scenario I think the shark still has a distinct size advantage. However using larger specimens of C. subauriculatus, or smaller ones of Purussaurus could quickly make this a mismatch.
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Post by dinosauria101 on Oct 21, 2019 3:37:18 GMT 5
So, average vs average is 6.2 vs 8.6 tons. Similar size ratio to GWS vs saltie, which is fairly close. I give an edge to the shark due to size advantage.
But yes, a megalodon-sized subauriculatus or Purussaurus neivensis/mirandai would make this a mismatch.
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Post by theropod on Oct 21, 2019 3:46:32 GMT 5
Average vs average? Who ever said that?
6.2 tons for a 10 m crocodilian seems a little optimistic, and even then a 10 m Purussaurus brasiliensis is the largest specimen, not average.
I don't know if this dentition is average. It might very well be a relatively small specimen. As I said, really drawing the line between C. subauriculatus and megalodon is a bit problematic, and this affects making size estimates. That's why I refrain to declaring an average size for now.
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Post by dinosauria101 on Oct 21, 2019 3:50:38 GMT 5
Average vs average? Who ever said that? 6.2 tons for a 10 m crocodilian seems a little optimistic, and even then a 10 m Purussaurus brasiliensis is the largest specimen, not average. That's what I gleaned from your post. And don't the smaller Purussaurus fossils belong to the other 2 species? (could be wrong, but I've seen that on YouTube).
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Post by theropod on Oct 21, 2019 3:52:36 GMT 5
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Post by dinosauria101 on Oct 21, 2019 4:08:33 GMT 5
Oh, right.
Then yes, this may be a bit onesided.
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Post by Life on Oct 23, 2019 3:38:13 GMT 5
Carcharocles chubutensis and Carcharocles subauriculatus refer to the same shark, but former identity is rather popular. C. chubutensis represent a stage of evolution just before the Megalodon. Relevant study: www.tandfonline.com/doi/full/10.1080/02724634.2018.1546732"From a macroevolutionary perspective, the gradual progression in tooth morphology from the Paleocene Otodus obliquus to the Mio-Pliocene Carcharocles megalodon could be linked to a shift in diet and feeding style. Over this roughly 50-million-year interval, teeth of this lineage shift from, arguably, a tearing-grasping type to a cutting-dominant dentition. Teeth of Otodus obliquus have a complete cutting edge lacking serrations, a robust root and crown, and broad, triangular lateral cusplets. In stark contrast, teeth of Carcharocles megalodon have fully serrated cutting edges, a less robust root, and lack lateral cusplets."
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Post by theropod on Oct 23, 2019 3:56:32 GMT 5
Carcharocles chubutensis and Carcharocles subauriculatus refer to the same shark, but former identity is rather popular. C. chubutensis represent a stage of evolution just before the Megalodon. Relevant study: www.tandfonline.com/doi/full/10.1080/02724634.2018.1546732"From a macroevolutionary perspective, the gradual progression in tooth morphology from the Paleocene Otodus obliquus to the Mio-Pliocene Carcharocles megalodon could be linked to a shift in diet and feeding style. Over this roughly 50-million-year interval, teeth of this lineage shift from, arguably, a tearing-grasping type to a cutting-dominant dentition. Teeth of Otodus obliquus have a complete cutting edge lacking serrations, a robust root and crown, and broad, triangular lateral cusplets. In stark contrast, teeth of Carcharocles megalodon have fully serrated cutting edges, a less robust root, and lack lateral cusplets." As I think I pointed out, only nomenclatural precedence is not determined by popularity of a name (or even etymological correctness, take for example Basilosaurus), it is determined by seniority. See here: www.iczn.org/the-code/the-international-code-of-zoological-nomenclature/the-code-online/Note in particular article 23.1 "Principle of priority". Since C. subauriculatus (Agassiz) was named earlier than C. "chubutensis" (Ameghino) and both are (it seems universally) agreed to be synonyms, the latter is a junior synonym, and therefore invalid, while the former is the correct name for the species.
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Post by Life on Oct 23, 2019 5:01:43 GMT 5
Carcharocles chubutensis and Carcharocles subauriculatus refer to the same shark, but former identity is rather popular. C. chubutensis represent a stage of evolution just before the Megalodon. Relevant study: www.tandfonline.com/doi/full/10.1080/02724634.2018.1546732"From a macroevolutionary perspective, the gradual progression in tooth morphology from the Paleocene Otodus obliquus to the Mio-Pliocene Carcharocles megalodon could be linked to a shift in diet and feeding style. Over this roughly 50-million-year interval, teeth of this lineage shift from, arguably, a tearing-grasping type to a cutting-dominant dentition. Teeth of Otodus obliquus have a complete cutting edge lacking serrations, a robust root and crown, and broad, triangular lateral cusplets. In stark contrast, teeth of Carcharocles megalodon have fully serrated cutting edges, a less robust root, and lack lateral cusplets." As I think I pointed out, only nomenclatural precedence is not determined by popularity of a name (or even etymological correctness, take for example Basilosaurus), it is determined by seniority. See here: www.iczn.org/the-code/the-international-code-of-zoological-nomenclature/the-code-online/Note in particular article 23.1 "Principle of priority". Since C. subauriculatus (Agassiz) was named earlier than C. "chubutensis" (Ameghino) and both are (it seems universally) agreed to be synonyms, the latter is a junior synonym, and therefore invalid, while the former is the correct name for the species. Jean Louis Rodolphe Agassiz identified this shark as Carcharodon subauriculatus. However, identity of this shark was revisited at a later stage with a far better understanding of shark evolutionary patterns, and it is now Carcharocles chubutensis. Therefore, Carcharocles chubutensis is common/popular reference in recent scientific literature. Although some authors identify the same shark as Otodus chubutensis. I think WE can settle for Carcharocles chubutensis in this forum for convenience and in line with how this shark is identified in recent scientific literature.
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