|
How Megalodon possibly looked like
|
 (06-20-2022, 09:08 PM)GuateGojira Wrote:(06-18-2022, 10:46 PM)Semyon Wrote: There is no new form to be accepted, those are only paleoartists proposions based on sheer guess like many since years. The only tested current work about meg body plan is the research from Jack Cooper. If you are not interested in this animal at all, don't reply and don't post erroneous claims. And no, there is no "one month, next month", the research is steady but there is a growing consensus anyway. You just don't know much about Otodus phylogeny, this is all recent : https://www.researchgate.net/publication...todontidae Lamnids are the closest living relatives to otodontids and together may form a superfamilly the "lamnoidae". Even Kent (2018) acknowledges that the closest taxa comparable in the vertebral count and structure are C. carcharias and I. oxyrinchus. Sorry but you have absolutely no autority to judge the quality of an article not yet published, especially since using Carcharodon carcharias as a closest analogue has been used by all the modern otodontids researchers in two decades, especially in the morphology of the backbone, lamnids centra are definitely the closest to megatooth centra. Exactly my point, there is no living marine taxa in the 10-20 m range that has the locomotion apparatus of a bottom feeding sandtiger, because this caudal and those fins can't operate properly at such a scale, read below. Yes the sandtiger body plan is not supported anywhere in the peer reviewed literature, the best two alternatives given the shape of the centra are the fusiform plan and the carangiform plan (Kent 2018). Kent in Renz (2002) : Bretton W. Kent, author of "Fossil Sharks of the Chesapeake Bay Region" believes that if Meg is more closely related to sand tiger sharks, the relationship is largely irrelevant for determining body shape. "I'm a functional morphologist by training and argue that the constraints on shape are so severe for an axial swimmer (i.e., that flexes the body to provide propulsion) of this size that a sand tiger style of body is physically impossible," says Kent. "Sand tigers have an acceleration body form and use drag to displace water when swimming. Displacement swimmers need to move a water mass equivalent to 3-4 times their body mass with each stroke of the tail to swim by this mechanism." Kent says that the problem arises at really big sizes like that of Meg. "This problem is based on classic biological scaling," he says. For objects of similar shape, doubling the length causes surface area (e.g., fins) to increase four times and volume (i.e., mass) to increase eight times. Consequently, a really large sand tiger would need enormous fins to offset the tremendous increase in mass. Unfortunately, these fins would also generate an enormous amount of nonproductive drag that would impede swimming.
"The only way large axial swimmers have evolved is to switch over to a cruising body form that generates propulsion by lift rather than drag," says Kent. "Cruising fish need only displace a fraction of their body weight when swimming, relying instead on increasing the speed, rather than the mass, of the water over the tail. All of the large marine, axial swimmers (tunas, porpoises, whales, great white, mako, basking and whale sharks) use a cruising body form. As far as we know, no really large marine animal with an acceleration body shape has ever evolved. They all appear to be cruisers."
|
| Users browsing this thread: |
| 1 Guest(s) |