Gastropod ID from the Grayson Formation

[KimTexan]

I found this last weekend in the Grayson Formation in Tarrant county, Texas. I have never found a Cretaceous gastropod that was so squatty. Most that I find are elongated to some degree or another, but there is no elongation to this one.

This was posterior end down in the creek bed embedded in the limestone. I popped it out, but I guess part of it remained in the limestone. I tried to prep the matrix off, but I can’t tell where the matrix ends and the shell begins since it appears to be a steinkern.

 

There is no ornamentation on it at all.

It is about 36 mm at the widest whole part, but looks like it was at least 50 mm wide at one time. I can’t tell how wide the aperture or last whorl was.

The total height of the gastropod is 20 mm tall.

The overall shape is lenticular. I don’t think there are many lenticular gastropods in the book I have. I couldn’t find one that matched it.

Top view (which is actually the posterior end of the shell)

 

Side view

 

Bottom view (which I believe is the anterior end of it)

 

Any help at all would be appreciated.

[DPS Ammonite]

On 12/9/2018 at 10:52 PM, KimTexan said:

 

Side view

Bottom view (which I believe is the anterior end of it)

Any help at all would be appreciated.

Probably Gyrodes which is a near form genus for similiar gastropods.

 

Here is a good reference for similar aged Texas fossils: 

 

Stanton, 1947. Studies of some Comanche pelecypods and gastropods. USGS Professional Paper 211    link

 

 

[KimTexan]

Thank you John. I was looking at the Gyrodes, but none that I saw were listed in the Grayson or any Washita group or in Tarrant county that I recall, but I’ll go back and verify that is the case. I know that doesn’t exclude them though.

Thanks for the link too.

[-AnThOnY-]

I agree with Gyrodes

[abyssunder]

17 hours ago, KimTexan said:

Most that I find are elongated to some degree or another, but there is no elongation to this one.

I'm not familiar with the gastropods of the Grayson Formation, so I'm just wondering if specimen can't be something like Gyrodes rotundus.

 

 

picture from here

 

 

 

 

 

[KimTexan]

I looked at Gyrodes again. There are only 2 listed that would fall within the geologic group and age. It is from a Cenomanian group. The G. rotundus is from the Maastrichtian. 

The lower left is from the right stage and county, but wrong geological group. The top right one is from the right geological group but not reported in the county it was found in and wrong stage, but the geological group spans 2 stages. It definitely looks more like the top right one, but the height on the example of that one is 42 mm x 50 mm wide. The width fits mine, but not the height. I guess the bottom of the last whorl is missing. Still the curve and thickness looks different than either of them.

[doushantuo]

repost:

JOURNAL OF PALEONTOLOGY, V. 61, NO. 1, P. 70-100, 7 FIGS., JANUARY 1987
GYRODIFORM GASTROPODS FROM THE PACIFIC COAST
CRETACEOUS AND PALEOCENE
W. P. POPENOE, L. R. SAUL AND TAKEO SUSUKI

please note :about 30 MB
this might or might not further the case...

[DPS Ammonite]

Don’t forget that yours is a steinkern. Genus should suffice. Species is more speculative. You also could be more conservative and call it a naticoid.

 

Another genus around that time that is a possible candidate is Natica. See reference that Ben just posted; I believe that it includes Naticas.

[doushantuo]

it does,DPS

[erose]

On 12/9/2018 at 10:14 PM, KimTexan said:

Thank you John. I was looking at the Gyrodes, but none that I saw were listed in the Grayson or any Washita group or in Tarrant county that I recall, but I’ll go back and verify that is the case. I know that doesn’t exclude them though.

Thanks for the link too.

Indeed. I have so many gastropods that are a match for genus in every way except the known stratigraphic occurrence or range.  Two weeks ago I found a HUGE Tylostoma in the Walnut Formation here in Austin. It's easily as big as the largest Glen Rose species.  I love the HGMS books and the one on gastropods is a great resource but I take the stratigraphy with a grain of salt.

 

Oh, And the Stanton publication is a must-have for all Texas collectors...