Cretaceous "Fish nodule" - Help me understand what I'm looking at

[FossilSloth]

I bought two unprepared fish nodules from a dealer at a show and have started to prepare them. I'm a total noob when it comes to preparation. I've prepared a few trilobites from wheeler shale but that's about it. I have a Paleo Aro and a Paasche air eraser. Can you all take a look at what I've done so far, and help me to understand what I'm seeing? Obviously I just got a fin, but I don't understand what the big long part is in the middle, or how the fish is oriented. A lot of the black/brown layer has chipped off while I've been working on it. Is this an actual 3-dimensional fossil? I expected it to be just like a thin plate, like Green River fish. I have only used the Aro, haven't tried messing around with the air eraser yet, although wouldn't the air eraser chip off the thin brown layer just as badly? 

[ynot]

Looking good so far!

 

[FossilDudeCO]

These fish from Brazil are nothing like Green River fish unfortunately!

They are 3-D fossils that are prepped as such. Most that I have seen are prepped from the side, it looks like you prepped yours from the bottom!

The big long part in the middle above his fin is his head!

 

Looking good so far, keep it up.

[doushantuo]

You think this one's from Crato?

[fossilized6s]

It looks as though you're uncovering the ventral side of the fish. And it does look like a three dimensional preservation. But the head has more boney plates to preserve that way. You may be looking at something slightly different with the body. I don't think it will be flat like a Green River fish preservation, just not as robust as the head. 

 

All i can suggest is to take your time and have a very delicate touch. Your prep tool should never really touch the fossil. I will usually coat my fossils with a diluted clear elmers glue if I'm afraid of them exploding or chipping away while prepping. This can easily be removed later. The glue will hold most pieces together and intact if you were to hit them on accident. Then you can just lightly use a super glue or paleobond to glue it back in place and keep on prepping. 

 

Lookin' good.

[Fossildude19]

5 hours ago, doushantuo said:

You think this one's from Crato?

 

I think it probably is, although there is a slight chance it is from Morocco. 

It looks like it might be a Rhacolepis buccalis,

 

I would echo Charlie's advice - go slow, and avoid actually touching the fossil. Patience is your most important tool, here.  

Air abrasion would be best for removing any matrix actually still adhering to the fish. 
 

With the air abrasion, just practice with the matrix, and see how much comes off with different pressures, and with different media, before actually starting on the fish. Use the unprepped side, to get an idea of what you should use for a technique. 

 

Good luck, hope to see it when it is finished.

Regards,

 

[Ptychodus04]

Definitely the ventral side of the fish. If it winds up actually being 3D preserved, you can prep the whole thing out while leaving matrix to support the extended fins. That would look pretty cool.

 

Slow is best. I would also add magnification. You need a minimum of 3x to lessen the chance of hitting the specimen with the scribe. 10X is very helpful. I've gone as far as 30X while prepping delicate specimens in the Perot's lab. You can see individual grains of matrix at that magnification.

[jpc]

I second ptych's advice... magnification.  Invest in a 3x or 5x Opivisor.  You will be happy you did.  And you will use it a lot as you find more fossils to prep.

[Fossildude19]

Here is your fish:

 

   

 

And a few examples of ventral prep from the internet :

 

Your's is more compressed, than this one.                           And this one is more of a 3/4 type of view, from the bottom. 

 

                       

 

 

Hope those help you understand your fossil better.  

Good luck!

Regards,

[RJB]

Some really great advice from our members here.  The only thing no one mentioned is that you should have sold it to me.  Ha!!       Just kidding.   have fun.  Would love to see it finished.

 

RB

[oilshale]

10 hours ago, doushantuo said:

You think this one's from Crato?

 

Not quite - these nodules can be found in the Romualdo Member of the Santana Formation and not in the Crato Member of the Santana Formation.

Try this paper:    Preservation of Fish in the Cretaceous Santana Formation of Brazil.

[FossilSloth]

Here's what I ended up with. It's body seems to be sort of hollow. I was a little too rough with the air pen and punched through it at some spots. Not sure if I should do anything else. Maybe try a micro blaster on the thin layer of matrix still over the lower body? Or maybe actually completely go through the body and leave the hollow section to display. 

[Ptychodus04]

I would start dumping PVA or Butvar into the hollow body to stabilize it and then go after it with the abrasive. I wouldn't open it up unless you can get a peek at the bones through the holes you have. Might be cool if that's the case.

[RJB]

Ditto to what Ptychodus04 said !!!

 

RB

[RJB]

I Think this fish is from Morocco? 

 

RB

[FossilSloth]

Yes, it's from Morocco. Any idea on the species?

[Fossildude19]

What is the size of the specimen? 

I see similarities to Notelops brama.

But ID is difficult from  a ventral view. 

Regards,

[FossilSloth]

Roughly 8 inches in length

[FossilSloth]

Here's a gallery of the prep and the finished product. The next one will be much better, I'm sure. https://imgur.com/gallery/lUJjc