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mattbsharks

Trying to find the predecessors to the cretolamna shark and completing an evolution display

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mattbsharks

This is a brief evolution circle I threw together of the megalodon lineage. I’m going to put in better condition specimens of angustidens and cretolamna at some point. I was hoping to trace the lineage back even further if possible

CD1553D9-5BD6-4602-93F0-9DC2FEA59ABA.jpeg

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WhodamanHD

Missing a few chronospecies (mugodzharicus, Aksuaticus, auriculatus) but very nice teeth! Good luck in completing that set. I’m still looking for a good Aksuaticus and mugodzharicus myself.

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FossilsAnonymous

Nice set! Unfortunately, the only things in my area are C.Megalodon and C. Subauriculatus.

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WhodamanHD
29 minutes ago, FossilsAnonymous said:

C. Subauriculatus.

Not a valid species, or at least not in widespread use.

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FossilsAnonymous
1 hour ago, WhodamanHD said:

Not a valid species, or at least not in widespread use.

Would that be Chubutensis then?

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WhodamanHD
22 minutes ago, FossilsAnonymous said:

Would that be Chubutensis then?

Probably, cusped will (typically) be angustidens and reduced susp that are very close and part of the main blade are Chubs, and then megs of course have maybe little bumps where cusps used to be or none at all (except in juveniles)

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WhodamanHD
16 minutes ago, Anomotodon said:

C. appendiculata

Wait what? That’s what I called the paleocene Cretalamna I find in MD. Guess that’s gonna be sp. now 

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mattbsharks
16 hours ago, WhodamanHD said:

Missing a few chronospecies (mugodzharicus, Aksuaticus, auriculatus) but very nice teeth! Good luck in completing that set. I’m still looking for a good Aksuaticus and mugodzharicus myself.

The one at about 5 o’clock is an auriculatus. I’ll look into the other two. Does anyone know the max size for cretolamna?  I’m hoping for one about 2.6” to be the same size as the others in the display 

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TNCollector

I have several Cretaceous C. appendiculata teeth, and if I recall correctly, the biggest one is only about an inch long. I was not aware that this tooth is a predecessor to the megalodon.

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WhodamanHD

Well it’s important to note you can never really tell a direct ancestor. It’s a “best guess” with the fossils you have, and you never know if it was really an undiscovered or unfossilized creature not yet found. Hence phylogenetic trees have everything’s split up typical, and no common ancestors at junction points.

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siteseer

It's going to be tough getting a tooth of a lamniform shark from a time before Cretalamna.  Consider that the average amateur shark tooth collection runs late Cretaceous to Recent.  Some collectors live near early Cretaceous deposits so they might have some teeth from that time but the mix might not be very diverse.  You have to put effort into finding collectors with any kind of spread of early Cretaceous teeth. 

 

Even then, the vast majority of early Cretaceous teeth in a collection are going to be Albian age, the Albian (roughly 100-113 million years ago) representing the last stage of the early Cretaceous.  You get early species of familiar sharks like Cretalamna, Cretoxyrhina, and Carcharias there.  Because you can differentiate several lamniform genera by the Albian , you realize that the ancestor of Cretalamna must come from an earlier stage.

 

The next oldest stage of the Cretaceous is the Aptian (roughly 113-125 million years ago) and next one after that is the Barremian (125-129 million years ago).  Offhand, I don't know of any sites of that age in the US and really know only of a couple of Barremian-age sites in Spain (one reported in Kriwet, 1999).  When you leaf through that article and look at the illustrations, you see that the site is not very productive and the teeth you do get tend to be partials.  One Cretalamna tooth is reported but it is incomplete.  From that you get the idea that the ancestor of Cretalamna is from an earlier stage.  Unfortunately, that time interval from the Barremian through late Jurassic happens to be sort of a "phantom zone" in shark research with few known fossil sites representing marine environments - perhaps due to a lower sea level than before and after this time.  You might acquire a pre-Barremian lamniform shark tooth at some point but you couldn't be confident that it's the direct ancestor of Cretalamna.  You would be rather close, though, since the earliest lamniform appears to have evolved sometime in the first few stages of the Cretaceous.  

 

Kriwet, J.  1999.

Neoselachier (Pisces, Elasmobranchii) aus der Unterkreide (unteres Barremium) von Galve und Alcaine (Spanien, Provinz Teruel).  Palaeo Ichthyologica. 9:113-142.

 

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