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readinghiker

Asking for more squalicorax help

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readinghiker

I have done some more research on the squalicorax that I posted about a few weeks ago.  I ended up 

examining 886 teeth or fragments thereof.  Of these, 79 showed a fossilization process in which the

serrations (and sometimes the whole cusp) was covered with a white mineral.  48 were so worn that sometimes

the serrations could barely be made out.  254 were too small or fragmented to be of any use (which does not preclude

that they were of the same species as the rest).  The remaining 632 all had the ornamentation that is so unusual.  They can

be found only on the labial side of the cusp (forgive my previous posts saying that they were on the lingual side...a stupid

mistake on my part), and the majority are on the mesial edge of the cusp, although a smaller percentage have the

ornamentationon the distal edge, and even fewer have them on both.  .  There are three types of ornamentation, the least common

being a horizontal band below the top of the cusp.  The second type consists of a small circular indentation, and can be found anywhere

on the serration.  The most common is a vertical triangle, with the apex of the triangle towards the top of the serration.  

I have no clue as to whether this is due to ontological heterodonty, sexual dimorphism, placement within the jaw, or something else.

If anybody could check their S. falcatus examples (the closest that these teeth resemble), or any other Coniacian squalicorax, and see if

this ornamentation is found beyond the fauna I am working on.  I have corresponded with Mike Everhart  (Oceans of Kansas), and this is 

new to him.  All help will be greatly appreciated!  I will post two pictures here, then two more immediately after.  Thanks again!

Randy

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readinghiker

More pictures... 

thanks!

Randy

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ynot

Interesting questions.

Because of the lack of compleat shark fossils, the variation of individual species and the overlap between differing species, seems like You are looking for an answer that is undefinable.

 

Good luck with Your quest.

Tony

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readinghiker

Tony,  

  Thanks for your reply.  Respectfully,  the study of prehistoric sharks and other selachians is very robust.  Cappetta, Shimada, and dozens of others are actively trying to make sense of the untold numbers of these creatures (the genus squalicorax has more than 20 species, with many paleontologists saying that the species falcatus should be divided up into many more

 [Bourdon, et. al.]).  What I am currently looking at is a species with teeth having very unusual ornamentation which I cannot find in the literature.  Hopefully, someone else might help me find a paper that describes this ornamentation and could point me to an already named species of squalicorax.  Lacking this, I must assume that this could very well be a new species.

I appreciate you taking the time to respond!

    Randy

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ynot

@MarcoSr @Al Dente @siteseer

What is Your take on this?

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MarcoSr
2 hours ago, ynot said:

@MarcoSr @Al Dente @siteseer

What is Your take on this?

 

The pictures are not detailed enough for me to see the ornamentation being described.  EDIT You need high magnification pictures of individual serrations showing the features you are seeing.  A lot of what I see looks to me to be caused by the lighting.  The teeth are in such bad condition that what is being observed by readinghiker may be the result of damage after fossilization.  The ornamentation could also be the result of feeding damage.  It is really hard to comment any further when I really don't see the features being described.

 

Marco Sr. 

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readinghiker
On October 7, 2018 at 7:11 PM, MarcoSr said:

 

The pictures are not detailed enough for me to see the ornamentation being described.  EDIT You need high magnification pictures of individual serrations showing the features you are seeing.  A lot of what I see looks to me to be caused by the lighting.  The teeth are in such bad condition that what is being observed by readinghiker may be the result of damage after fossilization.  The ornamentation could also be the result of feeding damage.  It is really hard to comment any further when I really don't see the features being described.

 

Marco Sr. 

Marco,

 

  You were right.  The Dinolight I was using was casting shadows.  I always had a nagging suspicion, and I ended up using a Zeiss microscope to look at some of the same teeth.

Guess what... no indentions!  So.....the squalicorax will be described in the paper that will eventually come out of this fauna as Squalicorax cf. falcatus, since there is widespread belief that falcatus is a species that needs to be broken apart (Bourdon, Welton & Farrish) by someone far more knowledgable than myself.

Thanks for your input, it is always helpful.  Now to tackle the cretolamnids and scapanorhynchids, of which I have multiple thousands.  Not looking forward to this part!

Randy

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