Possible mammoth tooth my son found?

[Andrew Boden]

My son found this in a deep washout in Adair county Iowa. Rock hounds have pointed in the direction of mammoth tooth but not sure.

[jikohr]

Hi,

welcome to the fossil forum!

 

What you have there is......pretty interesting. I definitly see why Mammoth tooth was suggested but after looking at the photos closer I'm not so sure. Aside from the "chewing surface" the rest of the piece looks like regular rock where as a Mammoth tooth would have other structures visible. Mammoth and elephant teeth are made up of plates of enamel stacked next to each other and held to gether by a natural cement. If this was a Mammoth tooth either the smooth cover cement that holds the plates to gether would be visible or you would be able to see the enamel sticking through on the side as well if the cement had weathered away. Also the "chewing surface" looks off. It usually looks like parralel sets of squigly lines instead of parallel semicircles like yours. Here's a picture of one for reference.

 

I'm personally going to go with not Mammoth but if I had to guess something else I'd say part of an invertebrate shell, maybe an Ammonite or a Nautiloid on a rock with the cross section of the shell polished just enogh by nature to look like a Mammoth tooth at first glance.

 

Though hopefully someone else will provide eveidence to the contrary because that would be way more exciting than what I'm thinking.

Edited July 24 by jikohr
punctuation

[ynot]

This piece looks like a speleothem to me, a weird one , but can not think of any other possibility.

See if it will fizz when acid (vinegar) is applied.

[Mahnmut]

Hi and welcome to the forum.

I am not familiar with the region, but think this looks like part of an invertebrate, cephalopod or rudist maybe?

Best regards,

J

[minnbuckeye]

Definitely NOT Mammoth. If you look closely at the second picture, there is a crinoid segment clearly visible in the second from the bottom groove, left half. I am slightly in the cephalopod camp. Interesting piece for sure!

[Fossildude19]

Orthocone cephalopod for me.

They could get quite large.

[ynot]

49 minutes ago, Fossildude19 said:

Orthocone cephalopod for me.

They could get quite large.

That was my first thought also, but, the "septia" are sitting on a flat surface with no (apparent) shell separation from the bedrock backing.

There is inconsistent spacing between them, and no sign of a siphuncle.

[Fossildude19]

1 minute ago, ynot said:

That was my first thought also, but, the "septia" are sitting on a flat surface with no (apparent) shell separation from the bedrock backing.

There is inconsistent spacing between them, and no sign of a siphuncle.

 

Siphuncle may or may not be there - it isn't a deal breaker.

As a cross section, especially as it may be a section of the edge of the shell,  it probably would not feature a siphuncle. 

Siphuncles are generally in the center, and not the edge of the shell. 

 

 

I'm seeing something similar to this:

 

  

[FossilDAWG]

The siphuncle is there, you can see a couple of segments in the left side of the specimen.  This is probably some kind of an actinocerid nautilod, given the large (relative to the size of the shell) and bead-like siphuncle.

 

Don