Belemnite spikes?

[KingSepron]

Are these Belamnite Spikes? Found at Lyme Regis.

 

It is an early Jurassic area.

[TqB]

Yes.  (More properly, pieces of belemnite rostrum or guard.)

[Rockwood]

Internal, ya know. 

[Kato]

@Rockwood @TqB

 

Learning question(s) here.

 

(1) The mantle is rarely preserved? Seems sort of backward. One would have thought the mantle would be more 'preservable'.

 

(2) How about phragmocones? Are they ever preserved?

 

I've found belemnites in the upper Devonian here recently. Mine presented as very nondescript like the larger specimen shown.  The smaller one has a different vibe due to dissimilar shapes and geometry.

 

I'm also very confused as to how one might tell a belemnite like the smaller one above from a very tiny pseudorthoceras. I can pose these questions over in Questions&Answers if that is better. 

[Rockwood]

(1) I think a mantle would be soft tissue, making it in the realm of exceptional preservation.

(2) Yes. It is rare but they are known.

Upper Devonian occurrences of belemnites have not been reported. Gaurds are quite dense (solid) and have a radially arranged structure.  

[Kato]

1 hour ago, Rockwood said:

(1) I think a mantle would be soft tissue, making it in the realm of exceptional preservation.

(2) Yes. It is rare but they are known.

Upper Devonian occurrences of belemnites have not been reported. Gaurds are quite dense (solid) and have a radially arranged structure.  

@Rockwood

 

Thanks!  Okay, I think the best thing is to post this pic of two in a glauconite formation. Found just above the Devonian, possibly the lower Mississippian?  The first place I've found the boundary exposed locally so still learning.

 

I did find small loose specimens appearing as the larger of the 2 specimens in the original post above. I do note the ones in my photo seem to have segmentation to them, though. Perhaps they are poorly preserved orthocones of some kind.

 

 

 

[Rockwood]

The shape is right but the composition is quite different from that seen in belemnite gaurds.

I remember being surprised to learn that some crinoids had spikes. I have had no experience with them, but I think the fractures look similar to those in the post that surprised me.

[TqB]

10 hours ago, Kato said:

@Rockwood @TqB

 

Learning question(s) here.

 

(1) The mantle is rarely preserved? Seems sort of backward. One would have thought the mantle would be more 'preservable'.

 

(2) How about phragmocones? Are they ever preserved?

 

I've found belemnites in the upper Devonian here recently. Mine presented as very nondescript like the larger specimen shown.  The smaller one has a different vibe due to dissimilar shapes and geometry.

 

I'm also very confused as to how one might tell a belemnite like the smaller one above from a very tiny pseudorthoceras. I can pose these questions over in Questions&Answers if that is better. 

1) As Rockwood said, mantles are soft tissue and very rarely preserve.

 

2) Phragmocones often preserve a short initial length within the rostrum and can be seen in broken sections, with their chambers. They regularly preserve more completely at some localities but are generally rather scarce at Charmouth/Lyme Regis (pyritised ones are reasonably common finds on the beach).

 

3) Pre-Jurassic belemnoids are a complicated subject - to summarise, the earliest belemnoids (Protaulacoceras) are from the Lower Devonian Hunsrückschiefer and various types have been found in the Carboniferous, all rare. I'm pretty sure the specimens in your photo aren't belemnoids - you don't get them looking like that so early. Not sure what they are though! The points are of course an illusion caused by the matrix cover.

(By the way, the earliest true belemnites, with a clearly radiating fibrous rostrum structure, are  Jurassic or possibly Triassic. The earlier belemnoids have a much less differentiated structure.)

 

4) As Rockwood also said, your rostrum specimens have a fibrous structure which clearly differentiates them from orthocone nautiloids.

With isolated phragmocones though, it can be more difficult. Belemnite siphuncles are ventral whereas most orthocone nautiloids are more or less central.

Otherwise, it can be difficult and specialist - you may need microstructure of the outer layers. Belemnite/belemnoid phragmocones have a thin layer of rostral calcite on much of the surface and there are supposed to be other differences.   

[Kato]

3 hours ago, TqB said:

1) As Rockwood said, mantles are soft tissue and very rarely preserve.

 

2) Phragmocones often preserve a short initial length within the rostrum and can be seen in broken sections, with their chambers. They regularly preserve more completely at some localities but are generally rather scarce at Charmouth/Lyme Regis (pyritised ones are reasonably common finds on the beach).

 

3) Pre-Jurassic belemnoids are a complicated subject - to summarise, the earliest belemnoids (Protaulacoceras) are from the Lower Devonian Hunsrückschiefer and various types have been found in the Carboniferous, all rare. I'm pretty sure the specimens in your photo aren't belemnoids - you don't get them looking like that so early. Not sure what they are though! The points are of course an illusion caused by the matrix cover.

(By the way, the earliest true belemnites, with a clearly radiating fibrous rostrum structure, are  Jurassic or possibly Triassic. The earlier belemnoids have a much less differentiated structure.)

 

4) As Rockwood also said, your rostrum specimens have a fibrous structure which clearly differentiates them from orthocone nautiloids.

With isolated phragmocones though, it can be more difficult. Belemnite siphuncles are ventral whereas most orthocone nautiloids are more or less central.

Otherwise, it can be difficult and specialist - you may need microstructure of the outer layers. Belemnite/belemnoid phragmocones have a thin layer of rostral calcite on much of the surface and there are supposed to be other differences.   

@TqB @Rockwood

 

Thanks to both of you. The formation where these are at is relatively remote but I hope to get back there in the next week. Perhaps, with some luck I can retrieve some decent specimens. When I found it I didn't have a hammer and chisel in my pack.

 

The smaller one on the left is definitely a point and it is tapering in size. Also, I did find some 1" long pointed tips but they were pretty banged up and inconclusive so I didn't bring any home.

 

I agree the larger one on the right presents as an illusion. That glauconite isn't going to give up any samples easily. For now I will keep them marked as mysteries.

[Pemphix]

4 hours ago, TqB said:

1) As Rockwood said, mantles are soft tissue and very rarely preserve.

Depends on the location and kind of lagerstätte....

https://www.urweltmuseum.de/urweltmuseum/zoo/belemniten/

https://www.solnhofen-fossilien.de/fossilien.php?ordnungid=16

https://www.naturkundemuseum-bw.de/sites/default/files/publikationen/serie-b/B273.pdf

[Rockwood]

45 minutes ago, Pemphix said:

Depends on the location and kind of lagerstätte..

Doesn't being part of a conservation lagerstätte sort of equal being rare ?

 

[Rockwood]

16 hours ago, Kato said:

One would have thought the mantle would be more 'preservable'.

It's work product is usually what is preserved.

Maybe the pattern seen on gaurds represents a mantle attachment site ?

[doushantuo]

KingSepron, below you'll find  some informaton of a technical/scientific nature,that might be helpful in understanding belemnites.

But: if yo've never read anything like that,the going might be tough

This has proven useful through the years

saelfunctiobiomindiagenesreview!!!rostruvol32_part4_pp765-797.pdf

G.Saelen :Diagenesis and construction of the belemnite rostrum

Palaeontology,32-4/1989

 

 

 

 

recommended

ALSO useful

(-------------------------->>>>>out of copyright,public domain)

Naef's Die Fossilen Tintenfische(about 22 MB)

( A cephalopod classic if there ever was one,IN GERMAN BTW  )

 

BELOW:

from:

Hoffmann, R, Richter, DK, Neuser, RD, Jöns, N, Linzmeier, BJ, Lemanis, RE, Fusseis, F, Xiao, X &
Immenhauser, A 2016, 'Evidence for a composite organic–inorganic fabric of belemnite rostra: Implications
for palaeoceanography and palaeoecology' Sedimentary Geology, vol. 341, pp. 203-215

(also recommended,BTW)

AND>>

back to the classics: for a nice overview of the interplay between ontogeny and biomineralization style:

Neues Jahrbuch fur ,Mineralogie ,Geologie und Palaontologie,Beilageband LI/1925

E.Christensen

Neue Beitrage zum Bau der Belemniten

[Pemphix]

1 hour ago, Rockwood said:

Doesn't being part of a conservation lagerstätte sort of equal being rare ?

 

No, the chance to find such things is much higher in a conservat lagerstätte than elsewhere.

So indeed there are a couple of finds known from Holzmaden and Solnhofen.

And "rare" depends always on the point of view: in Holzmaden finding an Ichthyosaur or larger remains of it is more possible than to find a belemnite with such preservation, but finding a complete plesiosaur skeleton in holzmaden is much more rare than that....so always depends on.....

[Notidanodon]

Definitely belemnites but too worn to I’d 

[Rockwood]

1 hour ago, Pemphix said:

No, the chance to find such things is much higher in a conservat lagerstätte than elsewhere.

So indeed there are a couple of finds known from Holzmaden and Solnhofen.

And "rare" depends always on the point of view: in Holzmaden finding an Ichthyosaur or larger remains of it is more possible than to find a belemnite with such preservation, but finding a complete plesiosaur skeleton in holzmaden is much more rare than that....so always depends on.....

Calculate the raw number of such fossils as a likely percentage of the number that ever lived and I bet they start to look rare.

[Mark Kmiecik]

This video https://www.shapeoflife.org/video/molluscs-survival-game will clear up a few things regarding the "mantle" (but says nothing of maris).