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Texas Echinoid: Pliotoxaster comanchei from Fredericksburg Formation

Bill Thompson

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The Pliotoxaster comanchei is a common echinoid in the Glen Rose Formation of Texas.

In the 1930's, there was a site for echinoids that is now under Lake Belton.

Smiser in 1936 studied this material and described the echinoids as Pliotoxaster comanchei from the Fredericksburg Formation.

Older names include Hemiaster comanchei (Clark 1915) and Palhemiaster comanchei (Smiser 1936).


Last month I was found about 8 specimens in the Fredericksburg Formation, Bell County.

Overall they are larger, and narrower at the bottom.


I had never seen any others from the Fredericksburg other than Smiser's hypotype at the University of Texas.


Has anybody else seen or found any specimens in the Fredericksburg?

In the photo, the left is from the Glen rose and the other 2 are from the Fredericksburg.5af21d2574678_Pliotoxastercomanchei.thumb.jpg.75bb414c37e01553253a40267f0b0e20.jpg



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Can't help, but very interesting .

Lovely fossils, too. :)

Life's Good!

Tortoise Friend.


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Can’t help, but nice echinoids! @Uncle Siphuncle might be able to help. He has a good amount of experience in the Glen Rose and associated formations. 


Correct me if I am wrong, but I am not aware of a Fredericksburg Formation in Texas. I do know of the Fredericksburg Group that, in north and central Texas, encompasses the Walnut, Comanche Peak, Edwards, and Kiamichi formations. I assume it is the group that you are referring too? Perhaps the Fredericksburg Group is also interchangeably called the Fredericksburg Formation like the Eagle Ford Group is also called the Eagle Ford Formation. If so, I just haven’t heard that usage before. 

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Can you pin down what formation in the Fredericksburg Group these came from?  There are similar echinoids that we collect at a Walnut/Comanche Peak site along Hwy 107 in Coryell County.



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Comanche Peak Formation. 


I would love to see a specimen or 2 of yours.  Maybe at the June Paleo meeting or photos before then?


(The Pliotoxaster whitei is common in the Fredericksburg and Washita.)


Thanks, Erich

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