Jump to content

Unknown Cretaceous Ammonite Texas


Woodgrainstone

Recommended Posts

Woodgrainstone

Recently cleaned up an Ammonite. From the Albian or Cenomanian (?) Series,  Boracho Formation, Culberson County, Texas.

 

I don't have much experience with Ammonites. The HGMS Ammonite book I own is not as helpful as I had hoped.

Thank you

 

11cm across, 9cm tall, less than 2cm thick

 

 

IMG_E1392.JPG

IMG_E1347.JPG

  • I found this Informative 3
Link to post
Share on other sites

The septa pattern looks similar to Engonoceras sp. Compare with Engonoceras serpintinum on NorthTexasFossils website:

 

http://northtexasfossils.com

A658A01C-DF00-441B-B40B-073AED1E9EF5.jpeg
 

See this reference that lists many Engonoceras species and references to them:
 

http://paleopolis.rediris.es/cg_archives/CG2010_A08/

A5D5F2F3-086A-4603-98C4-E9FB74FCE436.jpeg

Edited by DPS Ammonite
  • I found this Informative 4
Link to post
Share on other sites

You beat me to it @DPS Ammonite! I would definitely agree with Engonoceras as the genus, but since E. serpentinum are almost always pyritized or at the very least extremely small (notice the nickel in the picture from the North Texas Fossils site?), I'll have to lean towards E. pierdenale since they're the variety of Engonoceras that I find most often in limestone formations in central Texas. Ammonites are notoriously hard to ID to the species level, and it's twice as hard when trying to identify Texas ammonites since they're almost always just internal molds of the actual shell. 

  • I found this Informative 4
Link to post
Share on other sites
Woodgrainstone

Thank you both so much :) 

 

A genus is all I was really looking for.

 

Is there a decent article or website you know of that can help me to differentiate Texas Ammonites?

 

  • I found this Informative 1
Link to post
Share on other sites
Thomas.Dodson

I'm late but Engonoceras pierdenale seems the most likely based on the prominent sinuous ribs. Most Engonoceras are supposed to have obscure or no ribs and serpentium is smaller as GPayton mentioned. Which ammonite book do you have from HGMS? Texas Cretaceous Ammonites and Nautiloids has a nice table breaking down comparison of Engonoceras species (including size) and also has suture patterns if you really wanted to get down to it. North Texas Fossils like DPS Ammonite listed is a good site I've used from my limited Texas experience.

  • I found this Informative 2
Link to post
Share on other sites
Woodgrainstone

Thomas,

 

Thanks

That is the book I have. Problem for me is that it is maybe too informative.

 

Perhaps it's just me but I would put small representative drawings/pictures of all the genus' listed instead of what they have on pages 32 to 33. 

  • I found this Informative 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...