Texas Upper Cretaceous Ammonite?

[BobWill]

I think I may have posted this several years ago but didn't get an ID so I'm trying again. It's from the North Sulphur River which is the Ozan Formation. The sulcate (grooved) venter reminds me of Neodimorphoceras texanum from the Pennsylvanian of north Texas but this is Upper Cretaceous so definitely not a goniatite. I realize it's not much to go on and I need to find a bigger piece but I thought maybe somebody who collects there may have found some better examples to show. Any ideas?

[Guguita2104]

Nice find!

If you prep this fossil, it would be better to get an ID (we can just see the ventral bord).

Regards

[BobWill]

Thanks for replying Guguita. I just realized it's not clear from the photos that this is all there is of the fossil except for a small portion still in the matrix. That is what I meant by needing to find a bigger piece and hoping someone else had better examples.

[Guguita2104]

You are welcome!

I researched again and I find an ammonite with a ventral bord similar to yours :Drakeoceras sp.Try to compare.

Regards,

Edited September 16, 2015 by Guguita2104

[BobWill]

Thanks Guguita. I looked first at the Houston Gem and Mineral book on Texas Cretaceous ammonites and only found a reference to Drakeoceras drakei which was changed to Mortoniceras drakei and indeed has a ventral keel, ribs and tubercles similar to other Morts. Then when I googled Drakeoceras I found a link to a fossil posted by our own Foshunter in his gallery on April 27th 2012 that looks more like mine but there's no image showing the venter clearly to make sure it is sulcate. It does not have the prominent ribs or tubercles or keel like the fossil I saw in the HGMS book. I'll send a PM to Foshunter to see if he can help. Thanks for putting me on the right (I hope) track.

[Ptychodus04]

Rather small (juvenile) specimens of Placenticeras from the Britton formation (Cenomanian/Turonian) have a sulcate venter that becomes rounded with maturity.

[Guguita2104]

Pytchodus, your post was very informative and interesting.However Placenticeras (wich was one of my first possibilties) is much more compressed than this amonite.

Regards,

[Guguita2104]

Thanks Guguita. I looked first at the Houston Gem and Mineral book on Texas Cretaceous ammonites and only found a reference to Drakeoceras drakei which was changed to Mortoniceras drakei and indeed has a ventral keel, ribs and tubercles similar to other Morts. Then when I googled Drakeoceras I found a link to a fossil posted by our own Foshunter in his gallery on April 27th 2012 that looks more like mine but there's no image showing the venter clearly to make sure it is sulcate. It does not have the prominent ribs or tubercles or keel like the fossil I saw in the HGMS book. I'll send a PM to Foshunter to see if he can help. Thanks for putting me on the right (I hope) track.

Nice idea Bob!

You can't see the tubercles ,because you only have the upper part of the ventral bord. Those type of ornamentation are located in the sides of it.

[BobWill]

Guguita, please google "drakeoceras images" and notice that most of the images resemble many Mortoniceras ammonites we see in Texas. We certainly can't rely on google to make good IDs bit I'm wondering if any of those ammonites are similar to the genus you know about or whether you can supply a picture of it. The first one displayed with the maroon colored sutures is very different from the others. It's hard to tell from that side view how compressed it is or what the venter looks like but it has more resemblance to my specimen which tapers away from the venter rather quickly suggesting a profile closer to Placenticeras. Any tubercles at the ventro-lateral margin would show if it were more like the species similar to Mortoniceras.

[Guguita2104]

I researched and I'll changed my Id from Mortoniceras drakei to Mortoniceras equidistans.

This one is identifyied as Mortoniceras sp., but for me the specie is equidistans because of the ribs.

[Guguita2104]

http://bcfas.org/museum2/Meander/2010/FOSSIL%20COLLECTING%20REPORT%20Feb%202010.pdf

Regards,

[Uncle Siphuncle]

Guguita

M. equidistans has 3 prominent tubercles on each flank, the middle one being "equidistant" from the other 2. Please see attached photo. Also, it is an Albian form, a bit older than Bob's Campanian specimen, which I also believe to be Placenticeras. My best guess at the image in your last post is M. drakei.

[BobWill]

If Kris and Dan say it's Placenticeras that's good enough for me. All the ones I've found have a flat or sharp venter but are probably more mature than this one as Kris said. I asked Foshunter about the Drakeoceras from his gallery and he hasn't gotten all of his fossils unpacked since moving from Florida but he will have a look when he can to see what the venter looks like just to be sure but the picture of it in his gallery doesn't even have much in the way of ribs so it may be mislabeled.

[Foshunter]

Bob,

Looked for the Drakeoceras without luck but it doesn't fit into the Sulphur R. ammonites. Drakeoceras was found at Lake Texoma, Duck Creek which is much younger. Ammonites in the Sulphur aren't numberous, so not many candidates. I agree that it is Placenticeras sp. Pictured is P. planus from the river with a close-up of the keel. Hope this helps

Tom

[BobWill]

Of course that makes sense about the age Tom. Thanks for looking though. Now that Kris told us about the early whorls we'll know these when they come along.

[Ptychodus04]

If Kris and Dan say it's Placenticeras that's good enough for me.

Even a blind pig finds a root every now and then!

[Foshunter]

Even a blind pig finds a root every now and then!

Kris,

Thought it was, every now and then a blind pig finds a acorn?? LOL

Tom

[Uncle Siphuncle]

Bob,

Looked for the Drakeoceras without luck but it doesn't fit into the Sulphur R. ammonites. Drakeoceras was found at Lake Texoma, Duck Creek which is much younger. Ammonites in the Sulphur aren't numberous, so not many candidates. I agree that it is Placenticeras sp. Pictured is P. planus from the river with a close-up of the keel. Hope this helps

Tom

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Kris was spot on in noting the similarity to morphology of the Upper Britton Placenticeras keel. I was thinking the same thing and he beat me to the punch. I have a few of these cool little ammos as well. They are rare but present in the Desmoceras scotti zone. Of course Bob's specimen is 12 or 15 million years younger than the Britton, so it is probably a different species, but the Britton form makes for good comparison.

[Uncle Siphuncle]

Even a blind pig finds a root every now and then!

Tom, you don't know how accurate your statement truly is! Blind pig describes me quite well. Age is catching up with me...let's see if I can do it with grace.

[Ptychodus04]

Kris,

Thought it was, every now and then a blind pig finds a acorn?? LOL

Tom

Tom, you are correct. But, judging from the amount of digging feral hogs do, I think they like roots better!

Of course, I prefer when they have an acute onset of lead poisoning... yum, ham, yum, sausage... great! Now I'm hungry.

[Foshunter]

Tom, you are correct. But, judging from the amount of digging feral hogs do, I think they like roots better!

Of course, I prefer when they have an acute onset of lead poisoning... yum, ham, yum, sausage... great! Now I'm hungry.

It's funny you mentioned feral hogs. I am a senior hunter, back in the day and before I moved to Florida in 2000, never say many signs of them in the Sulphur. I hunted the river constantly from the late 70's to 2000. My how things can change. Have for years packed a pistol when down there, will continue to do so

Tom

[Ptychodus04]

Yah, they have pretty much taken over the state.