Upper Del Rio Clay Large Echinoid ID

[LSCHNELLE]

Scouted Bear Creek in Travis Co., TX today for Eagle Ford outcrop. No luck. Plenty of nodular Buda limestone. At dry creek bottom saw two feet of blue-gray clay/marl beneath the oyster/beach shell basal Buda layer. Could it be upper Del Rio? Then, I saw this 70mm partly crushed echinoid. Usually, I just get pieces of echinoids in the Del Rio Clay. I wonder if it is a Tetragramma. Any ideas?

[fifbrindacier]

Wow, that's a big one !

[JustPlainPetrified]

Beautiful! Great find!

[JohnJ]

That's a great find, Lee. Hard to say from the photos, but it looks more like a Pedinopsid.

[FossilDudeCO]

Great find, congrats!

[LSCHNELLE]

Thanks! JohnJ, in my non-expert opinion,I think you could be correct with Pedinopsis sp. The fossil is worn somewhat. I looked at Lance's North TX fossil page and he found something very similar in better condition in Justin,TX on August 16, 2008 in upper Goodland fmn.

[Guguita2104]

Congrats on your fantastic regular echinoid (can't help you further, sorry )!

Regards,

[LSCHNELLE]

Correction,Lance said his Pedinopsis (texanus?) was found in Grayson or Mainstreet formations. The Grayson formation is considered equal to Del Rio Clay. So, that appears to match the biostratigraphy.

[sharko69]

Very cool find! Congratulations!

[sixgill pete]

Great find. What a fantastic echinoid.

[LSCHNELLE]

Here is one better picture of the algae coated side after cleaning. Plus pics from "Some Cretaceous Echinoids of America" (C. Wythe Cooke (1955) - Plate 19 (extractions) :

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwi53MfWvMfOAhVM7yYKHWW7CssQFggmMAI&url=http%3A%2F%2Fpubs.usgs.gov%2Fpp%2F0264e%2Freport.pdf&usg=AFQjCNEwicXbmCNO2s6B8KYA3wnZV5NOsQ

The lower/upper echinoid plating and Cenomian Mainstreet Limestone origin (equal to Buda Limestone/Del Rio Clay) Age all seem to be a good match for it being a Pedinopsis texanus.

[JohnJ]

Looks good, Lee. Well done, sir.

[erose]

Was able to see that thing in hand last night at the PSA meeting. Despite being a distorted/crushed specimen it is rather spectacular. Definitely one of the largest regular echinoids I have seen come out of our Texas Cretaceous rocks.

[LSCHNELLE]

JohnJ. Can I enter this in the FOTM for August? Do I need to resubmit it thru that forum? Or, can you use this Fossil ID discussion?

[JohnJ]

JohnJ. Can I enter this in the FOTM for August? Do I need to resubmit it thru that forum? Or, can you use this Fossil ID discussion?

You found it this month, so you can enter it HERE.

[LSCHNELLE]

"Fossil Echinoids of Texas" by Bill Thompson, Jr.  (new pictorial book) released this month has 5 Pedinopsis for Texas.  Bill thinks this is a P. pondi.  Pics attached.  But, that key specimen was found in Austin Chalk.  The closest Austin Chalk is 1/2 to 3/4 miles upstream from the outcrop on Bear Creek. The subject fossil appears to have a yellow limey matrix on it, which would match basal Buda Limestone colors from the "beach"  deposit.   Has anyone else beside Lance of North Texas found Pedinopsis in the Cenomian stage of the Upper Washita Group? 

[LSCHNELLE]

I hope you can forgive my insatiable curiosity.  But,  USGS reports that the Pedinopsis pondi holotype fossil was found only one mile downstream (on Onion Creek) from where I found the recent one.  I have observed basal Buda outcrops (similar to where I found this fossil) near Twin Creek Road about halfway downstream to the holotype fossil. 

 

So,  I am convinced this was a basal Buda fossil or it is common to both Austin Chalk and Buda.  So,  maybe we can find a few more.  Please beware on Bear Creek and Onion Creek.  Much, if not all of it, is private property. 

[Bill Thompson]

Great to see you sharing your great find.

Beautiful echinoid.

I've only seen one other and it was the Holotype at the Smithsonian.

 

Bill Thompson

 

[fossilized6s]

Wonderful specimen. Thanks for sharing.

[LSCHNELLE]

I am convinced that the holotype echinoid found in Onion Creek was part of an upthrown graben of basal Buda Limestone  - not Austin Chalk as stated by the USGS geologist.  It should be reclassified as Washita Group. 

 

The five below facts support this position:

(1) It is a very rare find. 

(2) The above Bear Creek echinoid test was found at the downstream end of a 300' to 400' long basal section of Buda/Del Rio contact Gryphaea mucronata oyster limestone with Del Rio Clay underneath. No other fossilerous zones were noted nearby. Multiple ammonites and neithea were noted at the formation boundary - more evidence of a beach storm deposit. This is mentioned in Keith Young's 1977 guidebook - "The Buda Limestone in the Austin area represents shallow subtidal and intertidal deposits. The basal limestone represents a shell or shoal of beach that transgressed across the Del Rio Formation and scoured it at the top". 

(3) A similar fault graben sequence with potential for Basal Buda Limestone under alluvium is reported by USGS on their Webviewer just upstream and very near where the Pedinopsis pondi holotype was reportedly found. 

(4) Lance Hall found a similar sized Pedinopsis test in 2008 at a construction site near Denton where the Grayson Marl and Goodland Limestone are exposed. His test appears to have been extracted from a marl. And, the Grayson Marl is equivalent to the Buda Limestone and Del Rio Clay of Austin area.

(5) Lance's fossil has a very similar test pattern. But, it is NOT Austin Chalk origin.