Ammonite ID

[KimTexan]

I found this the last weekend of November, 2017 in Arlington Texas. It was in an area that is marked Woodbine, but Grayson formation fossils are mixed in. So, I’m not sure which it is from. It was found in a tan crumbly soft clay like soil. I sat down to try to ID it, but it seems pretty worn down. So I am not sure it is even identifiable.

It is about 14 cm in diameter and has a whorl breadth of 30 mm and whorl height of 60 mm.

There appear to be 2 rows of tubercles. One on the interior edge of the whorl. There are 6 tubercles in this row. The 2nd row runs down the middle of the whorl. Those in the middle are so worn down some are missing and I’m unable to determine the tubercle count, but I can count 10 tubercles within the same space of 3.5 tubercles on the inner edge. I tend to think there should be a 3rd row of tubercles on the outer edge, but if there is a third row it is worn off. 

This was taken at an angle so you could see the tubercles better. They’re very faint bumps.

 

The tubercles in the center are most noticible, but still pretty worn.

If anyone can point me in the right direction on ID I’d appreciate it.

@BobWill and @Uncle Siphuncle and @bone2stone

[Heteromorph]

Definitely Placenticeras, not sure what species yet. 

 

EDIT: Sometimes I get too sure of myself. This could also be of the genus Engonoceras. There are two species of this genus reported from the Grayson formation, E. serentinum and E. bravoense. The later has no tubercles so that can be ruled out. The former’s ornamentation is described thus: Ribs are obscure and sinuous. Ventrolateral tubercles alternate on opposite sides of venter. Umbilical tubercles. Younger whorls are smooth. 

 

No species are reported from the Woodbine Formation. 

 

EDIT No. 2: Alright, so this is getting kinda silly, but I now have a more refined answer. The oldest Placenticeras specimens that I know of are from the Turonian, too late for your specimen. I am now quite certain (but of course very possibly wrong) that your specimen is of the genus Engonoceras. I still don't know what species. 

[KimTexan]

Thank you very much! That’s a direction I can work with.

[Darktooth]

Another good size specimen. Geez do you ever find small ones?

[BobWill]

I agree with Engooceras sp. The give-away is the ventral view which shows the wavy pattern you get because the ribs on one side do not line up with the ribs on the opposite side. It's very worn but you can still see this. Yours is on the large side of normal which makes it more likely to be E. subjectum, the biggest of the 10 or so species found in Texas.

[Heteromorph]

Here is an E. subjectum specimen. The website is in French but the pictures are useful. I need to learn French...

 

Engonoceras subjectum HYATT 1903

[Uncle Siphuncle]

Grayson fm

[BobWill]

36 minutes ago, Uncle Siphuncle said:

Grayson fm

Good point Dan. If you mean the Houston book doesn't list E. subjectum as occurring in the Grayson I can't say I've found them there either but I have found some exceptions to their lists. You probably have better references. They are listed in the Duck Creek only so if Kim is right about the formation the next biggest known to be from the Grayson is E. belviderense. Unless there's a better view of the sutures than what I'm seeing it's best to label it Engonoceras sp. anyway.

[doushantuo]

BTW(comment NOT related to the above-shown generic Engonoceras):subjectum has bituberculate flank ornament,outer flank ribs,a sinuous venter)

Mancini(1982,I think,probably Cret.Res.) and Kennedy/Gale(Cret.Res,2005) et al probably are the best references for the Grayson

Subjectum seems to be defined in Cragin's 1893 monograph

 

 

 

 

[doushantuo]

subjectum according to Hyatt(1903)

(this being "Ammonites" pierdenalis Buch 1848)

[bone2stone]

Looks as if our friends here have your species pegged.

Subjectum

[KimTexan]

On 3/10/2018 at 2:25 PM, Darktooth said:

Another good size specimen. Geez do you ever find small ones?

Yes, I found the cutest little ammonite today that was the size of a quarter. Unfortunately it was only half of it. Not more than 2.5 cm. Today I also found many tiny pyratized ammonites that were all 1 cm and under. There were a few gastropods that were under 1 cm as well.

Also, the same day I found this I found the cutest chubby little echinoid, which I posted on here in December I think.

 

@doushantuo and @bone2stone so is Engonoceras subjectum the same as Ammonites pierdenalis? If so which is the accepted name or the one in common usage? I get that the name assigned when first described generally takes precedence, but sometimes things get reclassified and what not. I have no idea how to figure out which is now the current name.

[KimTexan]

On 3/10/2018 at 10:36 PM, BobWill said:

Good point Dan. If you mean the Houston book doesn't list E. subjectum as occurring in the Grayson I can't say I've found them there either but I have found some exceptions to their lists. You probably have better references. They are listed in the Duck Creek only so if Kim is right about the formation the next biggest known to be from the Grayson is E. belviderense. Unless there's a better view of the sutures than what I'm seeing it's best to label it Engonoceras sp. anyway.

This is not from the same ammonite, but they are fragments that were found nearby in the same layer/formation. They show suture lines quite clearly. So with that would you say it is subjectum or belviderense?

 

 

@Heteromorph Thank you so very much for your input and the work you did to help ID it!!! I truly appreciate it. I’m also impressed with you skill at being able to ID this. From my understanding of your hunting grounds it isn’t likely that you’ve had opportunity to come across one of these in your own hunting. To ID something you haven’t encountered personally is a talent and gift. It also takes time and study. I appreciate the time and study you put into it.

I hope you consider a career in paleontology or related field. I’m sure you’d be fantastic at it.

[BobWill]

 

17 minutes ago, KimTexan said:

@doushantuo and @bone2stone so is Engonoceras subjectum the same as Ammonites pierdenalis? If so which is the accepted name or the one in common usage? I get that the name assigned when first described generally takes precedence, but sometimes things get reclassified and what not. I have no idea how to figure out which is now the current name.

Good question. I always thought that when a reanalysis that passes review can show that somethings fits better in another genus or even family that this becomes an accepted change until someone changes it again. Maybe someone who was in class that day can help us.

[BobWill]

32 minutes ago, KimTexan said:

This is not from the same ammonite, but they are fragments that were found nearby in the same layer/formation. They show suture lines quite clearly. So with that would you say it is subjectum or belviderense?

 

 

@Heteromorph Thank you so very much for your input and the work you did to help ID it!!! I truly appreciate it. I’m also impressed with you skill at being able to ID this. From my understanding of your hunting grounds it isn’t likely that you’ve had opportunity to come across one of these in your own hunting. To ID something you haven’t encountered personally is a talent and gift. It also takes time and study. I appreciate the time and study you put into it.

I hope you consider a career in paleontology or related field. I’m sure you’d be fantastic at it.

This is from the Houston Gem and Mineral Society's book Texas Cretaceous Ammonites which you should consider finding a copy of for these IDs.

 

[DPS Ammonite]

On 3/20/2018 at 5:48 PM, KimTexan said:

"so is Engonoceras subjectum the same as Ammonites pierdenalis? If so which is the accepted name or the one in common usage? I get that the name assigned when first described generally takes precedence, but sometimes things get reclassified and what not. I have no idea how to figure out which is now the current name."

The peer scientific community decides what name gets kept when a fossil is given a new name by a worker. Sometimes more than one name is used because of a reasonable difference of opinions.

 

Engonoceras subjectum and Ammonites pierdenalis are different species (2nd part of name) but are the same genus, Engonoceras. They are not synonyms or alternate combinations of names.

 

To find if a name is valid and accepted, I search for names on the internet to see what form is used in the recent literature, Engonoceras. Also search for both names on the Fossilworks.org website which tries to determine the current name for most fossils based on input from the scientific community and recent scientific papers.

 

Look at Engonoceras subjectum on Fossilworks where the name is at top (a valid name). A few lines down it says that the name belongs to Engonoceras according to Kennedy, 1998 (a reference).

 

Look at Ammonites pierdenalis on Fossilworks where the name is listed as an "alternate combination" which is a valid name that usually a minority of the scientific community uses. Use the name listed at the top: Engonoceras pierdenale, usually the preferred name of common usage.

 

If both species names (Engonoceras subjectum and Ammonites pierdenalis) were the considered synonyms, Fossilworks would mention that (it does not).

 

 

[doushantuo]

 

 

 

 

 

 

 

 

 

 

 

[BobWill]

Well, rats! It looks like the easiest parts of the suture to distinguish between E. subjedtum  &  E. belviderense are near the venter where yours are the most beat up. Maybe you can see something along the flanks that aren't clear from the photos. The diagrams from the HGMS book have the arrow on the ventral side pointing toward the aperture.

[Heteromorph]

Thanks Kim! That's a real encouragement. I do hope to go into the field of paleontology someday. I have been fossil hunting since around the age of 6 and have enjoyed it ever since. 

 

To me the sutures that you showed most resemble E. subjectum because the saddles of E. belviderense have a more zigzag pattern on their sides while the saddles of E. subjectum, like both of the specimens that you show, have more round, smooth, and club shaped saddles. But that is just from what I can tell. I am now quite wary of using the word "definitely."   

 

You might already have a copy of this and @doushantuo already posted a page of it here, but here is the open access PDF copy of Hyatt's 1903 monograph Pseudoceratites of the Cretaceous (Monographs of the United States Geological Survey). The description of E. subjectum is on pages 168 - 171 and illustrations of it are on Plate XXI and Plate XXII. The description of E. belviderense is on pages 158 - 159 and it is illustrated on Plate XVIII. 

 

 

[KimTexan]

22 hours ago, BobWill said:

This is from the Houston Gem and Mineral Society's book Texas Cretaceous Ammonites which you should consider finding a copy of for these IDs.

 

I recently acquired that book. It is maybe 30 yrs old, but very helpful.

[KimTexan]

3 hours ago, Heteromorph said:

Thanks Kim! That's a real encouragement. I do hope to go into the field of paleontology someday. I have been fossil hunting since around the age of 6 and have enjoyed it ever since. 

 

To me the sutures that you showed most resemble E. subjectum because the saddles of E. belviderense have a more zigzag pattern on their sides while the saddles of E. subjectum, like both of the specimens that you show, have more round, smooth, and club shaped saddles. But that is just from what I can tell. I am now quite wary of using the word "definitely."   

 

You might already have a copy of this and @doushantuo already posted a page of it here, but here is the open access PDF copy of Hyatt's 1903 monograph Pseudoceratites of the Cretaceous (Monographs of the United States Geological Survey). The description of E. subjectum is on pages 168 - 171 and illustrations of it are on Plate XXI and Plate XXII. The description of E. belviderense is on pages 158 - 159 and it is illustrated on Plate XVIII. 

 

 

Once again thank you very much! This is helpful.

 

I need to make a fossil hunting trip post. I went yesterday with another TFF member from out of town and found oodles of new stuff. I must have found 30 ammonites, maybe 3-4 species of them. I brought them all home.

 

While it sounds astounding I have to qualify it with they are all mini ones under 1 cm, all pyratized, but oh so cute! It sounds awesome until you hear they are all that small. LOL

I think I found 30-40 urchins if not more. I haven’t counted them. The are normal to large, not mini.

[BobWill]

7 hours ago, Heteromorph said:

To me the sutures that you showed most resemble E. subjectum because the saddles of E. belviderense have a more zigzag pattern on their sides while the saddles of E. subjectum, like both of the specimens that you show, have more round, smooth, and club shaped saddles. But that is just from what I can tell. I am now quite wary of using the word "definitely."  

 

Good eye! I have trouble finding points of comparison like that. Looking back I see where this was my first guess so I should have gone with that. The faunal lists in the Houston book represent what the authors found and not what is possible so I'm going to pencil in E.subjectum on their list for the Grayson Formation and add that formation to the comparison chart for the genus based on Kim's finds and your ID.

[doushantuo]

[KimTexan]

17 hours ago, doushantuo said:

Thank you for that article. I have a few pyratized micros from the Grayson, but the ones I found Tuesday are from the Duck Creek Formation in Tarrant County. I’m not sure how common those are. I have heard of them being in the Paw Paw, but I haven’t heard people talk about them from the Duck Creek. I’ll wait to explore that avenue when I post the trip report. I’m not sure if I’ll have time to do it tonight though. I’ve got something I need to do this evening.