Megalodon not as big as we once thought!

[BorneanTiger]

(09-01-2020, 06:07 AM)GuateGojira Wrote:

(08-27-2020, 08:59 PM)BorneanTiger Wrote: Yes, but either way, it's not unusual to use modern creatures to imagine or reconstruct the looks, behaviour or ecology of prehistoric animals, even if in a minor way. For instance, if sharks didn't exist today, then we wouldn't have this reconstruction, would we? Credit: Harry the Fox

*This image is copyright of its original author

*This image is copyright of its original author

Good images, but the information is now outdated. New information shows that these sharks were not close to the white shark, but much different, not only in the body itseld but also in the tail form.

It is known that sharks normally do not leave fossils of the body because they do not have bones, but in some cases there are exceptional specimens that leave very good fossils. The closer known relative of the Carcharocles (Otodus) megalodon is the Cretolamna appendiculata, a relative medium sized shark and we have one of the best fossils of this species, check this:

*This image is copyright of its original author

Under this image, Paleontologist know that the "megalodon" was not a fast hunter as the white shark but a slow swimer as the modern sand tiger shark or the basking shark:

*This image is copyright of its original author

*This image is copyright of its original author

These sharks have heterocercal tails, which means that the uper lobule is very elongated and measn that the can make short burst of spead but not a prolonged fast travel, like the fish that have homocercal tails (lobules about the same size) characterized for fast swimers fish like sword fish or tuna. White shark and makos are closer to the homocercal than to the heterocercal, check again the tail of Cretolamna appendiculata. Newer reconstructions must and are taking this in count, check this out:

*This image is copyright of its original author

Reconstruction from "Palaeos" and Paleontologist Roberto Díaz Sibaja from 2020. However he scalated the animal at 18 m long, which is too large for the modern estimation of size (he also said that too). Compare it with the 6 m long female white shark.

*This image is copyright of its original author

Art from Christopher Chávez, also from 2020. Good image but somewhat too pointed in the nose.

*This image is copyright of its original author

And this one from Jaime Bran, again from 2020. Escalated at 15 meters long.

As you can see, slowly but strongly, the idea of how the "megalodon" looked is changing and like the Spinosaurus, sooner or late the new form will be accepted.

I have discovered that it's not even as simple as that, because for instance, another prehistoric mega-toothed shark that is considered to be a close relative of Megalodon (hence considered to belong to the same genus as Megalodon) is Carochles angustidens / Otodus angustidens, and in 2001, the discovery of what was said to be the best-preserved angustidens specimen to date by two scientists, Michael D. Gottfried and Ewan Fordyce, had been presented by the team as evidence for close morphological ties with the extant great white, and so the team argued that angustidens (along with all other related megatooths, including Megalodon) should have been assigned to Carcharodon, as was done before by Louis Agassiz: https://www.tandfonline.com/doi/abs/10.1...2.0.CO%3B2

Basically, the issue of which shark is closely or distantly related to the Megalodon and other megatooths is a controversial topic, with different models of evolution giving different answers.

A tooth of Carcharocles / Otodus angustidens measuring 4.25 inches (10.795 cm), found in the Edisto River of South Carolina's Lowcountry, image by user Crazy Uncle Jim (16th of August, 2007):
   

2 teeth belonging to another species (Carcharocles / Otodus auriculatus): USNM & PAL-537807. Credit: E. Emmons (1858), North Carolina Geological Survey Report, pages 231–234, Figures 57–58; P. Bartsch & A. R. Barwick (1941), Copeia (1): 40–41; from Craven County, North Carolina; posted by The Smithsonian (2nd of June, 2009): https://collections.si.edu/search/detail...term=shark
   

A tooth belonging to Carcharocles / Otudus sokolovi from Dakhla (Morocco), measuring 3 inches (7.62 cm), with a feeding damage to the tip and some "lightning strikes", image by user Whodaman HD (11th of December, 2019):
   

A chipped tooth belonging to Carcharocles / Otodus subauriculatus (also chubutensis), which was thought to have evolved into Megalodon. Dated to the Early – Middle Miocene (~ 18–15 million years ago), it had a slant height of 2.25 " (57 mm), and was found by Jayson Kowinsky (2011) in Chesapeake Bay Area (on the border of the States of Maryland, Virginia and Delaware): https://www.fossilguy.com/sites/calvert/calv_meg.htm
   

Lingual and labial view of a lateral tooth belonging to a Megalodon, which was found by Kowinsky at Calvert Cliffs, in Maryland's portion of Chesapeake Bay. Dated to the same period as above, it had a slant height of 2 ⅜ " (60 mm):
   

A tooth of the Megalodon with 2 teeth of the great white, by user "Broken In a Glory":
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