Shark Teeth

Daryl wrote this up about the shark teeth that he’s found here in Southern Minnesota.  Since he wrote this, Victoria has found some of her own too!


D’s Shark Teeth
Cretaceous Sharks of Minnesota

I live in southwestern Minnesota. Last year, in a small lake nearby, I started finding shark’s teeth – over 100 of them so far. And I’ve found one more this year, in the 3 days since the water level dropped far enough to look.

Since shark’s teeth in Minnesota are sort of unusual, to say the least, what with us being a few thousand miles from the ocean in any direction, I did some checking. It turns out that yes, it IS possible to find them here. A quick history lesson for everyone –

About 65 million years ago, in the Cretaceous period, when dinosaurs were still wandering around the earth, the continents were a lot closer together. The supercontinent Pangaea was still in the process of splitting apart, and a tremendous waterway called the Great Inland Sea covered the middle of what is now the United States, from roughly the Rocky Mountains in the west to what’s now the Mississippi River in the east, running down to the Gulf of Mexico. The climate was a lot warmer in these parts back then, and yes, sharks swam in Minnesota. Where I live used to be the coastline of the sea.

Since a) I wasn’t crazy, and b) it wasn’t just somebody playing an extremely bizarre joke on me, I did some more checking. When in doubt, consult an expert. I contacted Jim Bourdon, who not only was able to identify most of the teeth and tell me who they belonged to, but whose website, www.elasmo.com, was EXTREMELY helpful in giving me more information about prehistoric sharks. He’s done a lot of work on his site, and you can learn a LOT from it. Check it out.

What he told me was that basically I’ve found teeth from 7 different species of shark and one species of sawfish. Please keep in mind that all of the identifications were made on the basis of pictures I sent him through e-mail, and that he never physically saw any of these teeth, so all id’s are tentative. Don’t send either of us hate mail informing us of any mistakes (g).

He put the pictures I sent him and his information on a page of his site and e-mailed me the specifics. I’ve used this information for this page, and once again, I can’t thank him enough for all the help.

He asked if I was familiar with the formation these teeth are ‘coming-out’ of, and I told him “No, and nobody else in the area seems to be either. It’s part of a old river that kind of puddled up into various small lakes, and I’ve checked farther up the system and nobody there has ever seen them. Other rock-hunters at this lake have found them too, so I know I’m not just imagining all this.”

These aren’t all the teeth I’ve found, just the ones that seemed most representative or unusual. Most seemed to fall into certain groups, so it made sense to scan them that way.

That said, one last note – originally some of these teeth were part of larger pictures, but I broke them down to make it easier to look at the teeth and descriptions at the same time. I’ve noted this where it happens.

Scale: tooth #1 is 3/4″ long
My description and Jim’s ID:

  • #1 – no cusplets, non-serrated, nutrient groove
    1.1 Very worn, appears tooth may have had cusplets at one time. Could have been a Scapanorhynchus, but even in person, the condition would preclude a firm ID.
  • #2 – no cusplets, serrated, enamel is striated on front and back
    1.2. Squalicorax sp
  • #3,4 – no cusplets, non-serrated, nutrient groove, striations on enamel
    1.3. The narrowness of the crown throws me. What remains seems to be in excellent condition — no cusplets and a robust root. This would suggest Cretoxyrhina or Cretodus. I’d lean in the direstion of Cretodus, but there isn’t enough to say more.


Originally part of the above picture, scale is the same.

  • #3,4 – no cusplets, non-serrated, nutrient groove, striations on enamel
    1.4 Too little to even guess.
  • #5 – no cusplets, non-serrated, nutrient groove
    1.5 Too little to even guess.
  • #6,7 – cusplets, non-serrated, nutrient groove, very dagger-like
    1.6&7 Probably Carcharias sp


Scale: tooth #1 is 5/8″ long
Desc: one cusplet on either side, non-serrated, nutrient groove, high labial arch

  • 2.1 Archaeolamna cf kopingensis (Formerly referred to as Plicatolamna or Cretodus arcuata.)
  • 2.2 Worn, probably the same as 2.1
  • 2.3 Damaged, probably the same as 2.1
  • 2.4 Can’t say, details too worn.


Scale: tooth #1 is 3/4″ long
Desc: one cusplet on either side, no nutrient groove, non-serrated, labial side relatively flat

  • 3.1 Cretalamna cf appendiculata
  • 3.2 too damaged & worn
  • 3.3 Cretalamna cf appendiculata
  • 3.4 Looks quite damaged, but probably the same as 3.1
  • 3.5 Looks like another appendiculata

Originally part of the above picture, scale and description are the same

  • 3.6 Too worn & damaged
  • 3.7 Probably appendiculata
  • 3.8 ?Carcharias sp
  • 3.9 Cretalamna cf appendiculata
  • 3.10 Too much damage


Scale: tooth #1 is 1 1/8″ long
Desc: All teeth like this are non-serrated, but all have striations on the front and back.
Ones with bases still attached have nutrient grooves (most are broken off).

  • 4.1-3 If these are striated on both sides and when viewed on end, both side flare out, these would be sawfish rostral teeth – Ischyrhiza cf mira


Scale: tooth #2 is 7/8″ long
Desc: Non-serrated, nutrient groove, very “wavy” design (#5 is on side)

  • 5.1 & 3 Too damaged
  • 5.2,4 & 5. If these teeth have striations on the lingual crown face, they are likely Scapanorhynchus


Scale: tooth #1 is 9/16″ wide
My description and Jim’s ID:

  • #1 – no cusplets, non-serrated, no nutrient groove, wide base (Squalicorax kaupi?)
  • #2 – minor cusplet under arch, non-serrated, deeply arched base, no nutrient groove
  • #3,4 – no cusplets, fine serrations, no nutrient groove
  • #5-8 – no cusplets, non-serrated, no nutrient groove, distinct angle on blade
  • 6.1-8 All appear to be crow shark teeth.
    6.1,6 & 7 – Probably Squalicorax
    6.2,3,4 – These teeth are currently referred to as Squalicorax, will likely change in the future.
    6.5,8 Too damaged


4 thoughts on “Shark Teeth

  1. Pingback: » A Rant and Some Raves About the Science Conference Magic and Mayhem

  2. This is fascinating! Great work, Daryl. It must be exciting to find all these teeth, and then to correspond with an expert to learn more about them. I enjoyed reading this greatly, and loved to click over and see some images of ancient sharks!

    Like

  3. I just found your site while looking for info on finding shark’s teeth in MN. My daughter and I were rock hunting today in South Central MN, and she found a beautiful shark’s tooth. I had never heard of people finding teeth here, but am glad to see it does happen! I’ll have to check out the resource you used and see what they can tell us about her tooth. It doesn’t look like any of the pics you’ve posted.

    Like

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