Great videos!!!!!!!!!! Thanks for posting!

Great videos!!!!!!!!!! Thanks for posting!

Thanks, I put a lot of work into it. I hope this video educates a lot of new fossil collectors. Also nice cephilapod you found!

Very NICE videos and WELL done to boot, keep up the good work. George

Well I learned alot, the hard work shows

and thanks.

Nice collection! Thanks for putting that together.

Those videos were fun to watch and you summed up shark teeth very well in a short amount of time. The specimens were great examples too.

I would add that transitional great white shark teeth are also well-known from California (sites in Orange and San Diego County).

The origin of Isurus (Cosmopolitodus) planus is unclear. In California the Early Miocene mako found is I. desori (I. oxyrinchus) - Freeman Silt and Jewett Sand sites. As you move up stratigraphically into the Early-Middle Miocene (Olcese Sand and Lower Round Mountain Silt), you still find I. desori along with rare finds of I. retroflexus.

Then, in the Sharktooth Hill Bonebed, which is within the upper part of the Round Mountain Silt (Middle Miocene, approx. 15 million years ago) I. hastalis and I. planus "suddenly" appear and I. desori is less common. I have read a dissertation that points to lesser-known deposits in Mexico as containing a mako form ancestral to planus with hastalis having a separate ancestor. It is unclear if he is correct. It seems just as likely that planus diverged from hastalis, as you noted, especially since it appears that hastalis was present on the east coast of North America during the Early Miocene.

I don't know why it took so long for hastalis to appear on the west coast. It may be that it was present south of California in the Early-Middle Miocene (sites in Mexico, Central and South America perhaps) but did not move farther north for some environmental reason.

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Those videos were fun to watch and you summed up shark teeth very well in a short amount of time. The specimens were great examples too.

I would add that transitional great white shark teeth are also well-known from California (sites in Orange and San Diego County).

The origin of Isurus (Cosmopolitodus) planus is unclear. In California the Early Miocene mako found is I. desori (I. oxyrinchus) - Freeman Silt and Jewett Sand sites. As you move up stratigraphically into the Early-Middle Miocene (Olcese Sand and Lower Round Mountain Silt), you still find I. desori along with rare finds of I. retroflexus.

Then, in the Sharktooth Hill Bonebed, which is within the upper part of the Round Mountain Silt (Middle Miocene, approx. 15 million years ago) I. hastalis and I. planus "suddenly" appear and I. desori is less common. I have read a dissertation that points to lesser-known deposits in Mexico as containing a mako form ancestral to planus with hastalis having a separate ancestor. It is unclear if he is correct. It seems just as likely that planus diverged from hastalis, as you noted, especially since it appears that hastalis was present on the east coast of North America during the Early Miocene.

I don't know why it took so long for hastalis to appear on the west coast. It may be that it was present south of California in the Early-Middle Miocene (sites in Mexico, Central and South America perhaps) but did not move farther north for some environmental reason.

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Thanks for the info. You got me thinking a lot about planus and I got a new theory about those. I'll be puting a blog together about it soon. Thanks again for watching.

Enjoyed the Video's. I learned a great deal. Thanks!

Just watched these again for the second time... very informative! Thanks