Coniacian Glyptoxoceras?

[Heteromorph]

Is anyone aware of any Glyptoxoceras sp. in the Coniacian? 

 

@doushantuo, I know that you are good at digging up information like this. Can you find anything? 

[Fruitbat]

I rounded up all of the usual suspects and couldn't find a thing about Glyptoxoceras in the Coniacian.  There are a number of mentions of that genus in the Santonian.

 

Maybe doushantuo can ferret out something for you!

 

-Joe

[DPS Ammonite]

Fossilworks implies that they occur in a range of time that includes the Coniacian. Look around the page for more details and references: http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=14933

[caterpillar]

I find a lot of Glyptoxoceras in santonian and campanian of southwest France but never in coniacian

[The Amateur Paleontologist]

The oldest record of Glyptoxoceras I've seen on Fossilworks is from the Early Turonian of Colombia (link) - so a Conacian Glyptoxoceras is entirely possible..

 

 

[DPS Ammonite]

Here is another reference. A Glyptoxoceras from the Early Turonian in Venezuela. Note, Hamites indicum is a synonym of Glyptoceras indicum. A search for early Austin Chalk Hamites species might be useful.

 

http://fossilworks.org/bridge.pl?a=collectionSearch&taxon_no=313280&max_interval=Cretaceous&country=Venezuela&is_real_user=1&basic=yes&type=view&match_subgenera=1

[Heteromorph]

32 minutes ago, DPS Ammonite said:

Here is another reference. A Glyptoxoceras from the Early Turonian in Venezuela. Note, Hamites indicum is a synonym of Glyptoceras indicum. A search for early Austin Chalk Hamites species might be useful.

 

http://fossilworks.org/bridge.pl?a=collectionSearch&taxon_no=313280&max_interval=Cretaceous&country=Venezuela&is_real_user=1&basic=yes&type=view&match_subgenera=1

When you click Glyptoxoceras indicum in the species list of the paper in the link, it takes you to this page with the lists of synonyms for G. indicum. It has a detailed description from Kennedy and Henderson (1992), which states that G. indicum is from the Maastrichtian. They don’t list any confirmed occurrences of that species before that. But that doesn’t mean it isn’t of the genus Glyptoxoceras, which does push it back quite a bit. Thanks! 

 

Hopfully looking up Austin Chalk Hamites will be productive. Thanks for the recommendation! 

 

2 hours ago, The Amateur Paleontologist said:

The oldest record of Glyptoxoceras I've seen on Fossilworks is from the Early Turonian of Colombia (link) - so a Conacian Glyptoxoceras is entirely possible..

 

 

Thanks! With these two references, the early Turonian does seem to be when this genus starts occurring, which is much earlier than I expected. 

 

@PFOOLEY, I know you that you have found Glyptoxoceras in the Santonian of New Mexico. Have you found any in the Coniacian or earlier? 

[PFOOLEY]

36 minutes ago, Heteromorph said:

Have you found any in the Coniacian or earlier?

I have not...but if you are working on tracking its evolution, I will be following! 

[Heteromorph]

23 hours ago, PFOOLEY said:

I have not...but if you are working on tracking its evolution, I will be following! 

In an unprofessional way I am, out of personal interest. The main reason why I started this topic is because I have found two Glyptoxoceras sp. in the upper Coniacian of the Austin Chalk of North Texas that were identified as being Glyptoxoceras by William James Kennedy at Oxford from pictures emailed to him and I was wondering if an age that early had been reported for this genus before. The upper Coniacian age of the first specimen I found has been definitively confirmed by inoceramids from the same layer identified by Dr. Ireneusz Walaszczyk, a Polish inoceramid expert. The first specimen and the inoceramid specimens come from an extremely fossiliferous 9” thick layer that has many other rare ammonite species. The second specimen came from a layer that may be just a few feet lower stratigraphically, but it is probably also upper Coniacian. I don’t know what species they are, but G. ellisoni has been reported from the Santonian of the Austin Chalk as well as the base of Campanian. But I am not aware of any reports of that species being found in the Coniacian. It does have occasional constrictions like mine does.

 

The first specimen I found is a long fragment with multiple constrictions. The second specimen I found is a shorter fragment that is only an impression. It is, however, an impression from a more mature whorl section. I can’t see any constrictions on it, though it is not very long so it may have had them. 

 

This is just my hypothesis, but assuming that Glyptoxoceras first originated in the Early Turonian, perhaps the genus first originated near the equator, like Venezuela and Columbia. Then in the Coniacian it spread northward, which is why I am finding my specimens in the Austin Chalk of North Texas. Then in the Santonian it had a major radiation event that made it an almost worldwide genus till the end of the Cretaceous. Again, this is just my hypothesis based on my limited knowledge. Just a thought. 

[doushantuo]

As Wiedmann had noticed,there might not be much daylight between Diplomoceras and Glyptoxoceras

below: indeterminate G. fragments,Cretaceous of Limburg

 

The original Forbes figuration(6a/b/c)(Transact.Geol.Soc.1846)

 

 

I DON'T have 'the 1926 vol.out of the Spath multivolume monograph,and McLachlan's 2016 piece on Nostoceratid and Diplomoceratid systematics(which MIGHT be useful)

is paywalled.

Can we entertain the thought of the possibility that the great Kennedy could be wrong?

It hardly bears thinking about...

 

Fabre-Taxy's piece (1963,or thereabouts/on the French Coniacian ammofauna of the Provence))in Annales de Pal. is paywalled,naturellement

 

below:(from Mikhailov et al)

 

[PFOOLEY]

Fig. 13. Hypothesised evolution of the Nostoceratidae, Diplomoceratidae and Baculitidae from the Russian Pacific coast during the mid- and Late Cretaceous.

 

 

...from Ammonite evolution, bio-events and links with lithofacies, phylogeny and homoeomorphy

[PFOOLEY]

16 hours ago, Heteromorph said:

...Just a thought.

I like it! Looks like you found a subject with a giant gap of information that needs to be filled in. I'm going to go search some Coniacian outcrops tomorrow...thanks for the inspiration.

 

[Heteromorph]

On 7/3/2018 at 8:04 AM, PFOOLEY said:

I like it! Looks like you found a subject with a giant gap of information that needs to be filled in. I'm going to go search some Coniacian outcrops tomorrow...thanks for the inspiration.

 

Thanks! I hope to learn more about this genus. And please post what you found on your Coniacian trip! I always enjoy your trip reports.

[PFOOLEY]

On 7/5/2018 at 11:49 AM, Heteromorph said:

...please post what you found on your Coniacian trip...

I posted a few things here, from my excursion to the Coniacian...no ammonites yet, but will definitely search there again.  

 

On 7/5/2018 at 11:49 AM, Heteromorph said:

I hope to learn more about this genus

My specimen is from very low in the Santonian. I know it is not much, but I would be more than happy to lend it to you for your studies...best of luck in your research.

[Heteromorph]

5 hours ago, PFOOLEY said:

My specimen is from very low in the Santonian. I know it is not much, but I would be more than happy to lend it to you for your studies...best of luck in your research.

Thank you very much for the offer, but I wouldn't want to bother you with the hassle of shipping. However, would you be willing to post a few pictures of it from multiple angles on this thread? My two Coniacian specimens seem to have some kind of keel/ventral ornamentation, and I am wondering if your Lower Santonian specimens do as well. 

[PFOOLEY]

6 hours ago, Heteromorph said:

...would you be willing to post a few pictures of it from multiple angles on this thread...

 

specimen is 1.5 cm in length.

[PFOOLEY]

6 hours ago, Heteromorph said:

Thank you very much for the offer, but I wouldn't want to bother you with the hassle of shipping

You are welcome...and I leave that offer on the table (in-hand comparisons are the most informative). Institutions lend fossils for Paleontological research...I've been daydreamin' about a community of independent researchers doing the same.

 

[Heteromorph]

1 hour ago, PFOOLEY said:

 

specimen is 1.5 cm in length.

Thanks for the pictures! Beautiful sutures. I assume the 3rd picture is of the venter? 

 

1 hour ago, PFOOLEY said:

You are welcome...and I leave that offer on the table (in-hand comparisons are the most informative). Institutions lend fossils for Paleontological research...I've been daydreamin' about a community of independent researchers doing the same.

 

I greatly appreciate your willingness to allow your specimens to be studied. I know of many collectors who would be hesitant to do such. Right now I am “working” (though they are doing most of the work) with Keith Minor and a few of his colleagues on a paper on the rare heteromorph sites I have found in the Upper Coniacian Austin Chalk. It probably won’t be published until 2019-2020. I don’t know how much constructive study of your specimen that I could do now, but perhaps as this paper is being written your specimen could have some relevance, since it is not too much younger than the two Glyptoxoceras sp. that I found at my heteromorph sites. It could be useful for comparison. 

 

Thank you for the offer! I will keep it in consideration. 

[PFOOLEY]

@Heteromorph

 

The Geological Society of America Memoir 71: UPPER CRETACEOUS OF THE PACIFIC COAST

 

There are a number of Diplomoceratids mentioned in here (though none of the genus Glyptoxoceras)...some from the Turonian and Coniacian.

[FossilDAWG]

I would not put too much weight in the fact that Glyptoxoceras was not mentioned.  Andersen's taxonomy is notoriously suspect, and anyway at the time Hamites was used as a catch-all for many diplomocerids.

 

Don

[Heteromorph]

On 7/17/2018 at 9:35 AM, PFOOLEY said:

@Heteromorph

 

The Geological Society of America Memoir 71: UPPER CRETACEOUS OF THE PACIFIC COAST

 

There are a number of Diplomoceratids mentioned in here (though none of the genus Glyptoxoceras)...some from the Turonian and Coniacian.

Thank you very much! Somehow I have never come across this paper before. 

 

On 7/17/2018 at 9:57 AM, FossilDAWG said:

I would not put too much weight in the fact that Glyptoxoceras was not mentioned.  Andersen's taxonomy is notoriously suspect, and anyway at the time Hamites was used as a catch-all for many diplomocerids.

 

Don

Thanks! Good to know. 

 

Here are the pictures of my two Glyptoxoceras sp. Sorry about the picture quality. I had to use my phone camera because my good camera, a Nikon COOLPIX P520, decided to die about two months ago. 

 

I have been hunting at the site where I found these two Glyptoxoceras sp. since April of 2017. It is in the lower part of the Austin Chalk Group, in the Middle/Upper Coniacian. Keith Minor thinks it is the lower Bruceville formation, but from what I am seeing from multiple geological surveys in the area, this site should be well within the Atco formation. I could be wrong, but more research will give a clearer stratigraphic picture. At this site, and other sites nearby in the same zone, I have found many regular and other heteromorph ammonite species, some echinoids of different species, and so far only one vertebrate specimen. 

 

I found the first Glyptoxoceras sp. on April 6, 2018. It is a gently curving fragment consisting of the positive and both negatives. The negatives are longer than the positive is, so the rest of that part of the positive got lost in rubble during excavation. The specimen, including the positive and both negatives as a whole, has a max whorl height of 7mm and a rib index of 5.

 

The positive (Figs 1 - 12) is 35 mm long, has a max whorl breadth of 3 mm, and has two constrictions with 10 ribs between them. It has 21 preserved ribs. As presented in Fig 1, the right end is adapical from the left end. The specimen is a bit crushed resulting in it having a more compressed whorl section than it did in life (Figs 11 - 12). It seems to have some type of ventral keel, best seen in Fig 4, that turns into a groove in the venter after the first constriction from the left. Whether this transition is from some kind of post-mortem distortion, natural growth, or pathology, I don’t know. I am not sure if this really is a keel, but I see similar structures (Figs 26 - 29) on Diplomoceras specimens in the paper that PFOOLEY posted. I am not aware of Glyptoxoceras having a keel, and from what I can tell from the pictures, PFOOLEY’s specimen is lacking one. The keel/groove/thing is present on the venter except on those areas affected by constrictions. 

 

The longest part of the specimen (Figs 13 - 18) is a negative 50 mm long and has 33 ribs preserved. It shows three constrictions, with 10 ribs between the left and middle constrictions, and 15 ribs between the middle and right constrictions. The right end is adapical from the left end. The orange object to the left of the specimen is an inoceramid. 

 

The last part of the specimen (Figs 19 - 20) is a negative 40 mm long and has 26 ribs preserved. It only shows two constrictions with 10 ribs between them, but it is still longer than the positive. The left end is adapical from the right end. 

 

The second Glyptoxoceras sp. (Figs 21 - 25) is only a negative. It was found on April 10, 2018 within a few hundred yards of the first specimen. It 42 mm long, has a max width of 14 mm, and 13 ribs preserved. The depth of the impression is 3 mm. It is from a much more mature whorl section that my first specimen. It is strange in that it has a very pronounced line running down most of the length of it that makes a 35 degree turn on the 8th rib from the top. The line is positive, indicating that it was originally some kind of groove in the specimen, perhaps like on the venter in my first specimen. 

 

Here are the pictures:

 

FIG. 1

 

FIG. 2

 

FIG. 3: The venter. 

 

FIG. 4: Ventrolateral view. The “keel” is especially visible in this photo. 

 

FIG. 5: Ventrolateral view of other side. 

 

FIG. 6: Dorsum. 

 

FIG. 7: Angled view of dorsum, this and next picture. 

 

FIG. 8. 

 

[Heteromorph]

FIG. 9

 

FIG. 10

 

FIG. 11: Abapical end.

 

FIG. 12: Adapical end. 

 

FIG. 13: Longest negative. 

[Heteromorph]

FIG. 14

 

FIG. 15

[Heteromorph]

FIG. 16

 

FIG. 17

 

FIG. 18 

[Heteromorph]

FIG. 19: Last negative of the first specimen. 

 

FIG. 20

 

FIG 21: My second Glyptoxoceras sp. 

 

FIG. 22: Notice the line running down most of the specimen.