Shark vs. Sea Turtle--Who Has the Better Odds of Being Whale-Sized Planktivores?

In a hibernating speculative evolution project called The Speculative Dinosaur Project, the "speccers" feature a species of shark called Jasconius pelaganax, the Gigamouth, which is basically a megamouth the size of a Blue Whale.

Want visual proof? Here it is:

However, it is stated in the article that

with a skeleton composed of cartilage rather than bone, and with much smaller fat reserves, the shark is probably substantially lighter than a comparably sized whale. In one of nature's biggest ironies, while Spec may be a world filled with giants, the greatest animal of all time is from the other timeline.

In another alternate Earth, there is another whale-sized filter-feeder, but this time, the candidate is a dermochelyid sea turtle. Considering that dermochelyids (leatherbacks) feast on soft-bodied jellyfish, it shouldn't be much of a stretch for a whale-sized sea turtle to suck up plankton.

These two candidates are, of course, fiction, but how "fictional" could either scenario be? Does either candidate have what it takes to be the size of a blue whale? Or do both have biological limitations that would make this impossible?

posted almost 7 years ago

JohnWDailey‭

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