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Nautiloid? Help Id please


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PaleoOrdo

I think it is this (pict. 1) almost round shape near the top of the shell which is the connecting rings showing a part of the siphuncle, and not the two forms in the middle left (they are not aligned in position with the former). The shape not displays any lunettes (as I see it), yet another reason to suggest it is a oncocerid and not an discosorid. Compare with this form (pict. 2-3), with the bulette form of another discosorid nautiloid I displayed the whole shell earlier in this thread above. It is puzzling that only one ring is shown in the first.

Pict. 1 enlarged connecting ring of oncocerid (the shape is similar to a brachiopod but I not believe it is that)

665636978_sirkularnautLFd.jpg.a6c968e44fcfb86a1f3afd70284c10f6.jpg

Pict. 2 Connecting rings of discosorid (I wonder if the top form smaller half-sircle of it, which I mark with arrow from the "?", is marking the beginning of the sipuncle and that we see here the apex or the "birth chamber"?)

612814660_02patternonnaut2LUNNERF.thumb.jpg.009da200cf0d9c83bf5e6afa13230226.jpg 

 

 

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PaleoOrdo
Posted (edited)

I must be mistaken to suggest it is the apex. It must rather be the last mature or living chamber, because in discosorids the bullettes is pointing or hanging towards the apex. The small half-circle then maybe marks the living chamber. It is more "logical", because in the living chamber I guess the siphuncle is not present or only present partly or narrowing (the same with the oncocerid). 

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PaleoOrdo
Posted (edited)

Another argument for my theory of the tapering connecting rings and siphuncle in the living chamber is the fact that the aperture of the shell of oncocerids and discosorids are tapering towards the aperture, or especially the living chamber is smaller, which also is seen in my speciemens above.

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PaleoOrdo
Posted (edited)

What has happened with this nautiloid? I wonder which shape this nautiloid (same Katian formation) had originally and which order or family it belongs to. Is it compressed or just eroded? What remains of it seems to not go very deep into the stone. It is very broad compared to the length. Could it have been longer originally?

92187318_COMPRESSEDORTHBREVICONEA.thumb.jpg.7c61ac518cb2fa7c3264ad7e2482039d.jpg 

 

The near aperture part:

1802490632_COMPRESSEDORTHBREVICONEB.thumb.jpg.56a109e5d3392db3b0d7204575cee22a.jpg

The part near apex, see the broken suture lines in the bottom of this picture, is very compressed:

IMG_20210521_113351.thumb.jpg.547d035c9319b247058cd1d0f63dfffd.jpg

Edited by PaleoOrdo
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Dimitar
5 hours ago, PaleoOrdo said:

What has happened with this nautiloid? I wonder which shape this nautiloid (same Katian formation) had originally and which order or family it belongs to. Is it compressed or just eroded?

 

It has been compressed. In addition the rock with it has split / broke, so we see only the last fragments of it.  This one is similar to the last specimen that I asked about.

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PaleoOrdo
Posted (edited)

Yes, I agree, it is obviously compressed, and more so in the lower places or at edges of the stone, where the lines are broken or deformed. But I not think it have been much longer. It seems to be orthoconic brevicone in shape, but maybe an oncocerid, because they are known to have many forms? It is difficult to imagine, in view of the size of the siphuncle and shell, that this was a good swimmer. I wonder if one can estimate the size of the siphuncle by the size of the seen connecting rings? If so, then the siphuncle is relative small.

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PaleoOrdo
Posted (edited)
On 5/14/2021 at 9:00 PM, PaleoOrdo said:

Oncoceroids have bullettes with two layers and broader connecting rings.

Above in this thread, in this sentence I wrote wrong, it should rather be: Discosorids have bullettes with two layers and broader connecting rings. And in fact, this apply not to all genera of discosorids, but they have thicker and more composite layers of rings.

On 5/14/2021 at 9:33 PM, PaleoOrdo said:

Bullettes, in itself or simply, are distinctive or special for the orders of oncoceroids and discosoroids.

Another mistake. The oncocerids have not bullettes, but something called lunettes.

The only other nautiloid order which has something similar (a thickening around the end of the septal neck) to bullettes are Ascocerids, where the "bullettes" are not rounded as in Discosorids, but a more pointed structure, sharply pointed towards the siphuncular cavity. The difference is illustrated in pictures here:

(PDF) Siphuncular structure in Silurian discosorid and ascocerid nautiloids (Cephalopoda) from Gotland, Sweden: Implications for interpretation of mode of life and phylogeny (researchgate.net)

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PaleoOrdo
Posted (edited)

I used some time today sorting my photos of the nautiloids of this late Katian-Ordovician formation into folders and sub-folders, according to identified orders, some of them into genus and even species. In this way it will be easier to count the numbers of each order and compare to what is usual for this shallow water habitat other places. Then I recognized it is one speciemen from this formation which I have not presented yet in this forum - and it is a puzzling one. It should, however, be not impossible to ID somehow, because the siphuncle is clearly visible, as is also the connecting rings with some odd structure (similar to bullettes, but probable not the same; it cannot be bullettes if it is an orthocerid or endocerid). The shape of the conch is not obvious. Some parts is better preserved than others, but the preserved parts show nice curved suture lines. Maybe it was longer in real. The top is the apex part, the living chamber or chambers close to it is the lower part. I wonder if it is an orthocerid or an endocerid, or maybe another nautiloid order?

298070839_ENDOORORTHOA.thumb.jpg.0ee21e98025d119aa8953091dd8641f8.jpg

879303417_ENDOORORTHOA2.thumb.jpg.6ed49b77fb7c3f0c23199182eb779f45.jpg

Some of the connecting rings are visible:

560668996_ENDOORORTHOB.thumb.jpg.bef97825995ef1d880af6ee3fe844980.jpg

Pictures more close up on the connecting rings:

1464138151_ENDOORORTHOB3(2).thumb.jpg.cede196196c956efd9b94b39b49cfa8f.jpg

887354049_ENDOORORTHOB3.thumb.jpg.ef48f85d3876c5dc518c155c0817f0ff.jpg

Next, the under side or cross-section, shows the siphuncle at or near the shorter side. Also the curved septa?

1672772991_ENDOORORTHOC2.thumb.jpg.26d983687e5b606c306da6cd381dc6c9.jpg

Close up on the siphuncle:

1980359141_ENDOORORTHOC3SIPH.jpg.4f6e01fc7f29f9c2ae2061e841e6f5e3.jpg 205416153_ENDOORORTHOC3.jpg.49e7d97ee228893493798ea1a7ec1714.jpg

Edited by PaleoOrdo
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PaleoOrdo

A more close up picture of two of the conncting rings show more structures:

456708214_ENDOORORTHOringsB3.jpg.057588c679783be487261c840c1d87b5.jpg

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PaleoOrdo

Last week I went again to the same formation in Norway and found several nautiloid, of which I will show a few. 

First, this nice specimen, which has a small broken part (see arrow to apex in Pic. 2); I believe it is an orthoconic nautiloid, although the shell has an oval shape (the same rock has two more similar speciemens not so well preserved):

Pic 1

nau.thumb.jpg.73e3ae47c248743a4e147015a2dd5ad8.jpg

Pic 2 (a thicker line of crystal layer is made post-mortem along the two broked edges):

1140043046_bapexbrokenpartarrow.thumb.jpg.43152b2a586f6a4653e996f19f3a4fab.jpg

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PaleoOrdo

Next, two rocks with two orthoconic nautiloids and one relative small discoceras where the central parts is missing.

Pic 3

208341633_sizesev.thumb.jpg.45c1058c822669396a9da8832617ac46.jpg

Pic 4 and 5, close up pictures:

discoceras.thumb.jpg.9dc1accccd13aa9f95b6a56b2ebeeb3c.jpg

The specimen to the right has a diameter expanding faster than any other orthoconic nautiloid I have seen or found (the left speciemen maybe is a crinoid stem?):

595482623_closeup.thumb.jpg.771e7d09ef32f497f774d4aa15c0f15e.jpg

 

 

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PaleoOrdo
Posted (edited)

Next, a strange speciemen on the edge of a rock. Could it be an Ascocerid?

Pic 6

ASCOSERID.thumb.jpg.7cb65a8828058adfdf6b270e46fc2cfd.jpg

Pic 7 - the right side:

174959775_ASCOSERIDB.thumb.jpg.c14c2ce48dba8ee003cb57c3970addfa.jpg

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  • 4 weeks later...
PaleoOrdo
Posted (edited)

I visited the area again last week, from the same location and late Katian, Upper Ordovician period I found these nautiloids:

Pict. 1-2. Maybe an oncocerid?

1840273635_FARM1NEDRE.thumb.jpg.bda8fb79810f7ac64aa6a820f7e0663c.jpg

1648828734_FARM1NEDRE(2).thumb.jpg.e6b63586b3cfedc8437848f9933bd5dd.jpg

Pict. 3 - a small nautiloid, not well preserved, but a suture line on the top and two connecting rings or the siphuncle is visible, maybe an oncocerid or a actinocerid? 

1759105749_FARM1NEDRE(3).thumb.jpg.804a04ae72e8fc153af4a57309994e71.jpg

Pic. 4-7 - The next nautiloid is puzzling, because the siphuncle is not visible in the cross section part. The suture lines are visible and curved, or could it be that we only see the siphuncle and not the shell? I tend to belive it is the shell. The 'shell' seems slightly bended, and the shell is tapering in both ends, so maybe it belong to the discosorid or onconcerid order. Any further specification is maybe impossible.

1638780991_usipFARM1ANEDRE.thumb.jpg.57489dc7f526601c48af24b96deab125.jpg527120149_usiphFARM1D.thumb.jpg.c770e868198594906d209f778ddcc287.jpg

577744587_USIPHFARM1F.thumb.jpg.d5a62175ba883cb5f19751e826d6b1dd.jpg

 

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PaleoOrdo

Last weekend I visited another location in the Kalvsjøen formation and found this rock which I left in the field as it was too big to bring home. It includes a curved nautiloid and some other fossil, maybe a bryozoan? The nautiloid have a texture which look similar to something made of plastic, but it is a nautiloid and seems for me to be an oncocerid or a discosorid. No connecting rings are visible, so maybe we just see the siphuncle?

248522373_IMG_20210712_163111lunnersrforjernbstjKALVSJFORMASJONEN.thumb.jpg.e4d9db8622f7f0f3161269d44250163b.jpg

 

IMG_20210712_163135.thumb.jpg.d8d864fd23fdebbc179b9dcb14ca668c.jpg

 

IMG_20210712_163142.thumb.jpg.cdfacf573c56f958f76a9231fc230e00.jpg

 

IMG_20210712_163145.thumb.jpg.b716e950770eb17b43ebad922e060ecc.jpg

The reason I think we just see the siphuncle is that the "suture" or siphuncle lines are not seen deeper in the fossil speciemen, as seen in this picture: 

IMG_20210712_163206.thumb.jpg.cb05a9d1eb89d0f3bb78ca76b737113c.jpg

 

IMG_20210712_163341.thumb.jpg.529ed5ac8128aa31f69c81207f7f4ac4.jpg

 

Some of the bryozoa part:

IMG_20210712_163150.thumb.jpg.736765ce16b35405b816c11fb86fc43e.jpg

 

 

 

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  • 4 weeks later...
PaleoOrdo

Last week I found some more nautiloids in the Kalvsjøen formation at another location (if I read the geological map correctly, the area have many formation divided as in a maze of parts, because of the many fault lines), Hadeland, in the Oslo-field. The first one seems to be a part of a cross section of a Discoceras. But the shape is unusual (the broad sentral -?- part) and doesn't match any of the shapes drawn by Strand in Plate II, p.121-122: NGT_14_1_2_001-117.pdf (geologi.no)

Pict.1

994340619_1CROSSSECT.thumb.jpg.e594b6b7934eedc00b28f81dfac52519.jpg

 

184189197_CROSSSECTB.thumb.jpg.88e12237311aa347926ea3963d5c61bf.jpg

 

The next one is also a spiral formed nautiloid, a Discoceras? It is also unusual in it overall oval shape. Is it a cross section or is some part of it hidden in the rock?

Pict. 3

448293631_kalvsjenform.thumb.jpg.5b301c1628be69e4566a3d467de144ab.jpg

Pict. 4

1387925135_kalvsjenformatiob.thumb.jpg.a2fa3e531bc533c16c4f8678152eb639.jpg

The next one seems be an orthoconic nautiloid.

Pict.5

1284397977_KALVSJFORMASJONEN3.thumb.jpg.0d7ea6128dfbb6bafb9b361a6d6f773a.jpg

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PaleoOrdo

More nautiloids from the same late Katian Kalvsjøen formation:

Pic. 1 & 2 - a small orthoconic and probably an orthocerid nautiloid  

IMG_20210627_134523.thumb.jpg.1b8246a9df34fd353689b486e6e2da43.jpg

IMG_20210627_134533.thumb.jpg.5e869f072644864348cb644abe5c845c.jpg

Pict. 3-7 - a Discoceras with the outer whorles preserved not so well or better in cross section at one or two of the sides of the speciemen, the inner whorle better and more comple preserved.

IMG_20210627_135008.thumb.jpg.6e796e61ef74e6c6aaa65be3a45ba8b4.jpg

Other side of the rock:

IMG_20210627_134910.thumb.jpg.7a4e7da94fbf8f7179b64b9b5dda5c4d.jpg

I divided the rock in two parts, the suture lines not seen here, the inner whorle has very smooth surface

IMG_20210627_135104.thumb.jpg.5e29829ea3d6c6615f874e0ba0af82a1.jpg

Next, the other side of the rock (here shown not divided), which shows suture lines and the cross section. The overall structure of the specimen seems somehow curved, and sihuncle is visible and by its size, bigger to the left than to the right (position of the siphuncle is near the ventral or inner side of the shell, and it is relative small in diameter) it seems that the left side is closer to the living chamber:

IMG_20210627_134942.thumb.jpg.ad8d816a0d7eb064ccd079e6fb180d3b.jpg

The same side from opposite direction, showing in cross section 2 or 3 inner and outer whorles? And some sircular lines inside one of the whorles:

IMG_20210627_134951.thumb.jpg.f2a1a7e574b09b2145b9685a56494e71.jpg

 

 

 

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PaleoOrdo
Posted (edited)

Here is a better picture of one of the above displayed nautiloids. I wonder how it looked like in real. It must have been a spirally formed one, but maybe not flat spiral, to judge my its middle part?

IMG_20210707_203239.thumb.jpg.5e1eb8d2871f56169cfdf1f5951a1f03.jpg

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PaleoOrdo
Posted (edited)

Maybe that question is impossible to answer in this case, since a cross section of a spiral nautiloid like Discoceras could look differently if the cross section is cut across the middle of the shell compared to if it is cut across some distance away from the center part.

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PaleoOrdo

One more nautiloid, together with some gastropods and bryozoa in the same rock, found in the same Late Ordovician Kalvsjøen formation in Hadeland, Norway (445-447 MY). I believe the nautiloid belong to the discosorid order becauce conch is curved and the connecting rings of the siphuncle are placed on the ventral side of the conch and the speciemen seems to have bullettes inside the rings (the latter which are a special mark of discosorids):

IMG_20210809_142545.thumb.jpg.243c31f29e4041cec427d95be76c3140.jpg

 

IMG_20210809_142656.thumb.jpg.c1ee8e247a0c877d85d5b7eb1950e76c.jpg

 

IMG_20210809_142602.thumb.jpg.fcc6b80fe522d47187c4f0d36ab5835b.jpg

 

IMG_20210809_142834.thumb.jpg.318f33cef94c73903ae55596e1aa7ba7.jpg

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FossilDAWG

Do you have a faunal list for the formation?  That would help a lot to narrow down possibilities.  If I found this one in the Ontario or Manitoba formations I have collected, I would be thinking of Diestoceras or Westonoceras or Cyrtogomphoceras or some near relative to those.

 

Don

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PaleoOrdo
On 9/7/2021 at 5:56 PM, FossilDAWG said:

Do you have a faunal list for the formation?  That would help a lot to narrow down possibilities.

Thank you, Don, that is an excellent advice. I have looked through the articles of Trygve Strand and Walter Sweet on the nautiloid fauna of this (and other in mid- to upper Ordovicium) formations in the Oslo field. Diestoceras have been found in this formation, the hight of the chambers and the shell is very similar in size, but the species of Diestoceras in the articles are oval in shape (I not know if this is always so for this genus), while my speciemen is slightly endogastric. Moreover, Diestoceras is an oncocerids which not have bullettes, but lunettes (if I am right lunettes look different, although I am not sure precicely how they look). Westonoceras, but not Cyrtogomphoceras (in Strand's old article), is found in the formation. However, Strand describes the one and only speciemen of Westonoceras in this formation this way: 'In dorso-ventral outline the dorsal margin is only very faintly convex, while the ventral (siphuncular) margin is strongly convex'. Since that is an exogastric shell, an oncocerid, it cannot be same as my endogastric speciemen.

   We should still not rule out Cyrtogompoceras as an option. Both Cyrtogomphoceras and Protophragmoceras (the latter have been found in the formation) look very similar in overall shape to my speciemen. The shell is fusiform in profile, reaching maximum width at or near the base of body chamber, which narrows toward the aperture, as do my speciemen. The siphuncle of Cyrtogompoceras is large and slightly removed from the ventral side, that with the concave longitudinal profile. Siphuncle segments are short, as are chambers. The same applies to Protophragmoceras Tyriences, also called Strandoceras species (which I have found a similar speciemen of before in this formation, my avatar, also displayed above in this thread, which I now believe was a little wider and more curved in real because of erosion made it thinner). But the latter is not typical for Protophragmoceras, which in general which is longer or is not brevicone (Strand mentions one which is 15 cm long , while my speciemen is 5-6 cm long). But Strand also mentions another 'almost complete' Strandoceras which is 7.7 cm long, 10 chambers and at the base of the living chamber the dorso-ventral diameter is 57 mm and the lateral 50 mm; while my speciemen is a little shorter, it also has 10 chambers and about the same diameter. The genus population Cyrtogomphoceras seems to be derived from the discosorid Strandoceras (both belong to the family Cyrtogomphoceratidae) by a reduction in the degree of endogastric curvature. It seems difficult decide if it is the one or the other. Still, I think my speciemen should be Cyrtogomphoceras. I should maybe be cautious for this conclusion, becauce (1) while Protophragmoceras in general is more heavily curved and not so breviconic, some species are described by Strand as less curved and shorter (as is my avatar), and (2) Cyrtogompoceratidae are according to some websites reported found only in Greenland and America (but one species are found in East-Europe Baltica).  (3) Moreover, a big part of the nautiloid fauna at this period is know to be endemic. (4) The siphuncle segments is oval in shape (also for both genera?). On the other hand, it is a distinctive mark of the Cyrtogomphoceras family to be breviconic. Strandoceras is also know from the Middle Ordovician and must have developed into something else in the Upper Ordovician. Finally, Sweets explains that Strandoceras (and Protogramgoceras in general?) is 'lachrymiform in transverse section' (cross-section form of conch like a pear), while the top chamber of my speciemen displays a circular or rounded shape. These are the main reasons for my conclusion: it is an Cyrtogomphoceras. If I am right, it may be the first of this species or genus which is found in Norway or Scandinavia from this (or any) period. But I need check that out more, since Strand's article is old.

   In any case, I think my speciemen is complete in lenght, although eroded in width. It is interesting to note that this family were among the few who survived the end-Orovician extinction event, and this formation is very close to the extinction time, the next formation being the Hirnatian.

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Walter Sweet writes in an article in 1957 that no speciemen of Cyrtogomphoceras have been found outside Greenland and North America, but in another article in 1959 he report one speciemen found in Norway in the same formation as mine, the first one of this genus ever found in Baltica, but at another location, a Cyrtogomphoceras similar to C. thompsoni Miller & Furnish (but unique since it has endocones), came from the Upper Ordovician Gastropod limestone (substage 5a) of the Ringerike district.  But this species is different than the one I found, because it has no bullettes and a very broad siphuncle. As far as I know, my species is not found before in Norway and Baltica. Moreover, a different but similar species to the one Sweet reported from Upper Silurian is found in the Lower Silurian in Norway, belived to descend from it, through the end-O. exctinction.

Source: Ordovician and Silurian Cyrtogomphoceratidae (Nautiloidea) from the Oslo Region, Norway Author(s): Walter C. Sweet Source: Journal of Paleontology, Vol. 33, No. 1 (Jan., 1959)

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I have checked more the litterature on Cyrtogomphoceras and so far not found any identical species as my OP. The ventral side of my speciemen is more similar to Strandoceras (both being concave in mid-venter and toward apperture) than other Cyrtogophoceras as I have seen in pictures of the latter, because these Cyrtogomphceras is not concave in the middle part of the short venter side (they are just partly convex on one side and strictly convex on the other side). After all, Cyrtogompoceras got its name, I suppose, because it is similar to Gompoceras (a questionable nautiloid genus assigned to the Oncocerida), which is generally short but rapidly expanding, straight to slightly endogastric, with a gibbous shape such that all sides are convex. On the other hand, my speciemen is more strongly curved on the dorsal side than Strandoceras (by «dorsal side» I mean the longest side of the conch, by «ventral» the shorter; the words are sometimes used in the scientific litterature in a different meaning). I still think it is a discosorid Cyrtogomphoceras, but with some oncoserid-like attributes: I am thinking of the tapering of the part of the conch which is near the body chamber, because other pictures of Cyrtogomphoceras show a longer conch and a more strongly tapering towards apperture than OP. The biggest Cytogomphoceras reported by Flower and Teichert is 35 cm long, while other species can be much smaller. They also write: «Strangely, without knowledge of the position of the siphuncle, and consequently, of orientation, some species look very much like Westonoceras or Winnipegoceras.» The two latter belong to the discosorid order, while T. Strand before thought they are oncocerids. And their siphuncle is placed on the longest side, the opposite side of OP. Also these are not so brevicone as my speciemen. For me is seems my speciemen is different than any other I have seen in the litterature.

Here is a Cyrtogomphoceras baffiinense for comparison:

 

54770630_cyrtbaffiense.jpg.3473e830bc2445f27a7770bac808c378.jpg

Source: THE CEPHALOPOD ORDER DISCOSORIDA By ROUSSEAU H. FLOWER and CURT TEICHERT

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