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austinswamp

small Ammonite cast

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austinswamp

This came from a gravel bed in Travis county with a large bluish shale formation nearby. Any info on the material of the rock would be appreciated as well. Thanks!

IMG_20170114_140949_238.jpg

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ynot

The rock looks like chert.

Tony

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BobWill

Almost certainly a mollusk but without more details it would be pretty hard to even say if it's a gastropod or a cephalopod. Probably an internal mold and not showing any sutures suggests one of the less common snails that coil in a stationary plane. However, sutures don't always preserve so it could be an ammonite and could even be an external cast. Look for similar fossils with more detail preserved or ask someone who is familiar with fossils from the specific area.

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austinswamp
4 hours ago, BobWill said:

Almost certainly a mollusk but without more details it would be pretty hard to even say if it's a gastropod or a cephalopod. Probably an internal mold and not showing any sutures suggests one of the less common snails that coil in a stationary plane. However, sutures don't always preserve so it could be an ammonite and could even be an external cast. Look for similar fossils with more detail preserved or ask someone who is familiar with fossils from the specific area.

It is starting to resemble Oncoceras

 

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BobWill

I think Oncoceras is from the Ordovician and that area is mostly Cretaceous. Also they are not coiled but only slightly curved.

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JohnJ

I would agree with Bob that it is likely a gastropod internal mold...and just a partial one that could have had an elevated spire.  I also think Tony is right that it is chert which means it didn't come from the blue shale.  It is most likely the eroded remnant of the local Edwards Formation - which has plenty of gastropods and plenty of chert that often contains them. 

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Ludwigia

Gastropod was also my first thought as soon as I saw this.

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Bronto

Looks like I can make out some suture in your fossil. I found a chert Ammonite yesterday.

 

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Ludwigia
4 hours ago, Bronto said:

Looks like I can make out some suture in your fossil. I found a chert Ammonite yesterday.

 

Can you please point them out and maybe show us a photo of your chert ammonite.

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