Fossil photos

[Pat Flannery]

Phil suggested I post these here; the only two I found (okay, I found the rest...but in antique and fossil shops) are the small straight-shelled nautiloid in picture one; (It is ellipsoid in cross section) and the coiled one (which looks like a gastropod; but I haven't been able to track down the type yet, unless it's a Bellerophon) marked with a "?" on the same jpg- by the way, that particular fossil taught me a very important lesson; it was found on a lake shore...I had picked up a rock that had a small fossil of coral on it, decided not to keep it, and was about to toss it into the water when it occured to me that a rock that has a fossil on the top of it might just have one on the bottom of it also; I flipped it over and found myself staring into a void in the rock with that spiral shell neatly centered in it, suspended free from the matrix by a rock attachment coming out of the aperature, and the whole being covered in small glittering crystals (the only reason I ever detached it from the matrix was to see what the other side of the fossil looked like!) the "goo" in picture four is epoxy cement holding the fossil together... it was badly damaged, but you can see the extremly complex suture lines on it if you look closely, anyone have specifics on what these all are?

 

[Architeuthoceras]

Nice fossils Pat. The ammonite in the lower left of picture 1 looks alot like Dactylioceras, but i'm not sure. Picture 2 is a specimen of Baculites and picture 4 is a scaphitoid (Jeletskytes or Hoploscaphites) both from the Late Cretaceous (check here). Picture 3 is a Paleozoic Goniatite ammonoid, I dont know the genus or specie, but a very nice specimen. Did you keep the mold the gastropod came out of? The void was where the original shell used to be, and the fossil you have is an internal mold of the snails living chamber (if that is what they call it on a snail shell). The void would be an external mold and would probably show any ornamentation the snail had, which would make it easier to identify. Hope this helps.

 

[Phil]

Thanks Pat and Kevin.

I must admit, picture 4 had me completely stumped.

Pat, for your information Baculites was a straight shelled ammonite which sometimes grew up to 2m in length. It is believed that this form of ammonite may have lived with its head facing downwards with the body hanging vertically above, perhaps in a similar manner to some modern cranchid squids. It seems that unlike the superficially similar earlier orthoconic nautiloids, Baculites had no counterweight at the apex of its shell so could not have horizontally orientated. These are some of the very latest ammonites and are datable to the late Cretaceous, thriving from approximately 90-65mya depending on the precise species.

I've found a few pictures of Dactylioceras and your mystery ammonite does indeed resemble that species (thanks Kevin!). Here's a link to a good photo you might like to compare your specimen with:

Dactylioceras.

This is quite a common ammonite to find in fossil shops so I would not be surprised if that is your specimen. One of the reasons it is easily available was that it had a worldwide distribution; the Dactylioceras dates from the end of the early Jurassic and is probably somewhere around 195-180mya making it much older than the Baculites specimen.

 

[Pat Flannery]

Regarding the gastropod- the void area was around 1/4 to 1/2 inch away from the inner cast on all sides, and showed no deatail...it wasn't a mold of the exterior, and had no detail....how exactly this happened from a geologic sense is a bit deyond me, as one would expect that any form of erosion that would destroy the detail on the mold would also destroy the detail on the internal cast, which was not the case.
I've attached a overall view of fossil number 4, showing the other, less damaged side of the shell (no sutures visible on this side; but some opalization), and the double row of oramentation knobs that wrap around the exterior of the shell's whrol about 1 cm to either side of the centerline of the exterior, and 1 cm apart in spacing at the "half-grown" point of shell age.

 

[Architeuthoceras]

Hi Pat,
If the void was not the external mold then the fossil was probably deposited in the void during deposition of the glacial deposits. Are there any signs of sutures (straight or complex) on the snail fossil? snails are usually more tightly coiled than your specimen. Is there any part of the shell preserved, or a space around the whorl where the shell would have been? If there are no traces of sutures then you are probably correct that it is a bellerophontid.

Link to Bellerophontid gastropod pics

I'll look into the scaphitoid a little later.

 

[Pat Flannery]

I haven't been able to locate any suture lines on it; and it looks like a dead ringer for Cloudia buttsi on the Bellerophon page. There is no trace of external shell left on it, and the glacial theory for the void in the rock makes a lot of sense, as I live in the part of North Dakota that was scoured over by the glaciers.