PermeateFree said:
>>Both megalodons and great whites (along with some other sharks, such as the mako) are members of the mackerel shark group, also known as Lamniformes. One of the things that sets these sharks apart from others are their teeth.<<
>>In a recent international study led by the University of Vienna’s Patrick L. Jambura, however, CT scans of mackerel shark teeth revealed that in their case, the osteodentine extends up from the root and into the crown, completely replacing the orthodentine to become the only type of dentine present in the tooth. Looking back through the fossil record, the only other shark shown to have such teeth was one known as Palaeocarcharias stromeri <<
https://newatlas.com/great-white-shark-teeth-ancestor/60457/
I:m surprised. I thought that these shark teeth fossilised particularly well, which would argue that they were made from the harder orthodentine.
So either i’m wrong and osteodentine fossilises better.
Or i’m wrong and these teeth don’t fossilise well.
“Looking back through the fossil record, the only other shark shown to have such teeth … Measuring no more than about a meter long and likely hunting small fish in shallow waters up to 165 million years ago, it had a flat body resembling that of today’s bottom-dwelling carpet shark. And while it otherwise didn’t have much in common with the mackerel sharks, it is nonetheless now believed to be their distant ancestor.”
Mackerel sharks are quite distinct from requium sharks aren’t they? Checks web. Yes, that’s right.
Lamniformes: They are commonly known as the mackerel sharks. They include the goblin shark, basking shark, megamouth shark, the thresher sharks, shortfin and longfin mako sharks, and great white shark. They are distinguished by their large jaws and ovoviviparous reproduction. The Lamniformes also include the extinct megalodon.
According to wikipedia the mackerel sharks separated from the requium sharks in the Jurassic. When was this new ancestor? 165 million years ago, that’s middle Jurassic, good.