Fossil tooth, vertebra, cephalopod? Ames, IA

[Peto Lithos]

Found these and a few other things, including petrified wood, modern bone, old looking mineralized bone and new looking mineralized bone, and brachipods in small chunks of limestone. All found in a streambed in Ames, IA just north of Des Moines. Vertebra is flattened, and I'm fairly sure the thing in the middle is a crushing shark tooth. New to the area, geologic map said pleistocene deposits only. Thank you

[Tidgy's Dad]

I think the top one is a fish vertebra, you might be right about number two but I can't quite make it out. Nor number three. 

[patelinho7]

Speaking purely from frequently browsing others’ Ptychodus posts… of which I have no expertise, the second fossil looks a bit like a Ptychodus tooth. No clue which exact species though

[Peto Lithos]

Sorry about the pictures, these should be a bit better.

[Scylla]

The new pics are better. The Ptycodus ID guide is pinned at the top of the ID section here. Maybe you can ID the species there?

 

Agree with cephalopod for that limestone fossil, but no way that's pleisteocene. Reworked strata.

[LSCHNELLE]

@Peto Lithos

Ptychodus would be found in the stream beds and Cretaceous deposits far NW of Ames or in the NW half of Iowa (such a the Dakota Shale and Niobrara Chalk). It would not be in a stream bed north of Ames where the exposed formations are Mississippian and Permian in age. That being said, it looks like you have either a Ptychodus decurrens (flatter crown) or Ptychodus occidentalis (higher crown).

Edited June 5, 2023 by LSCHNELLE
Clarification

[Peto Lithos]

14 hours ago, LSCHNELLE said:

@Peto Lithos

Ptychodus would be found in the stream beds and Cretaceous deposits far NW of Ames or in the NW half of Iowa (such a the Dakota Shale and Niobrara Chalk). It would not be in a stream bed north of Ames where the exposed formations are Mississippian and Permian in age. That being said, it looks like you have either a Ptychodus decurrens (flatter crown) or Ptychodus occidentalis (higher crown).

This is the source of my confusion, because even if the stream had cut deeper than the sources I read had implied, it still shouldn't be bringing this material in. Could the glacier have carried this in from further North?

[LSCHNELLE]

I think that is possible. Glaciers often pulverize the material they push ahead of them (glacial moraine deposit).

 

But, it's possible that larger boulders of Cretaceous material made their way farther south. I think that the vertebra and Ptychodus tooth might have come from the same formation. Was there any matrix associated with either fossil? Or, were they already loose from the matrix and associated with stream gravel/sand/silt?

[Peto Lithos]

They were loose. I've tried gravel banks in a neighboring stream and haven't found any more of the material, but I will be heading upstream at some point to see if I can find where these are from.

[LSCHNELLE]

The light green (Cretaceous) areas in this screenshot of Iowa geology have the potential of producing Ptychodus teeth. If any of them are upstream from the area you were hunting in, then that could be the explanation.

[Peto Lithos]

Hmm, none of those are upstream, and even if they were they would need to travel tens of miles down a narrow creek to get here. I wouldn't expect much to survive that journey.

[LSCHNELLE]

The geologic history of this area appears to include the Dakota Shale (Kd) deposits being put on top of the Mississippian age Paleozoic strata. The Ptychodus that you found is likely of Cenomanian age youngest Dakota Fmn. So, that matches well. It is possible that in your area most of the Kd deposits have been washed into the stream valleys. They are no longer present as matrix on hilltops. So, you might have found a remnant piece of the Kd in your area. The other possibility is that someone brought some into your creek area and left it behind. That seems less likely but it's still possible.

[Al Dente]

4 hours ago, Peto Lithos said:

Could the glacier have carried this in from further North?

Yes. When I lived in eastern Iowa I would find occasional Cretaceous shark teeth that were glacially transported, probably from somewhere in Minnesota.

[LSCHNELLE]

Ames, Iowa is within the Des Moines Lobe of the last glacial advance. So transport by glacier is a possibility along with hilltop Kd erosion as I previously mentioned. I think larger chunks of Cenomanian age formations would be the most likely mode of transport. But, it seems less likely that it was transported by glacier or that it came from Minnesota. As a geologist, I think that it's more likely that it was just Dakota Shale from NW Iowa that was formerly on the hilltops in the area or that was moved  southeastward into the Ames area by a glacier.

Edited June 7, 2023 by LSCHNELLE
Added map

[fifbrindacier]

On 6/3/2023 at 11:47 PM, patelinho7 said:

Speaking purely from frequently browsing others’ Ptychodus posts… of which I have no expertise, the second fossil looks a bit like a Ptychodus tooth. No clue which exact species though

I agree with that and with @LSCHNELLE's statement.

[LSCHNELLE]

On 6/3/2023 at 5:47 PM, patelinho7 said:

Speaking purely from frequently browsing others’ Ptychodus posts… of which I have no expertise, the second fossil looks a bit like a Ptychodus tooth. No clue which exact species though

 

 

My opinion as a student of Shawn Hamm, it looks like you have either a Ptychodus decurrens (flatter crown) or Ptychodus occidentalis (higher crown). Both likely Cenomanian age.

[Peto Lithos]

Thank you all, and sorry for the late reply. I have searched this streambed several times since, and have found no more of this material so it seems quite sparse. That said, the two pieces pictured above were within a few feet of each other, so I suspect a single piece of shale was dumped in the area and weathered by the stream.