What are you missing????

[MarcoSr]

I started collecting a new Eocene research site in Virginia this year.  I have written landowner permission to collect this site. I’m posting a few quick pictures of what I found in a single recent trip to this site.  When I’m at the site, I dig formation out and sift it in a ½ inch mesh sift in stream water.  A window screen catches what falls through the ½ inch mesh sift.  I take home the material caught by the window screen, break it down further through washing/drying cycles, and finally search the residue for fossils.  I spend about three hours per trip sifting at the site and another 3 hours or so breaking down the material that I brought home.  I want to show what I find at the site in the ½ inch sift versus what I find in the material that I bring home. For those of you who sift at a site but don’t catch what falls through your sift, I want to show you what you could be missing.  Every site is different. However, unless you bring some of the smaller material home to check it out, you will never know what you are missing.

 

The below picture shows what I found in my sift at this site in my ½ inch mesh sift during this trip.  I could use a ¼ inch mesh sift at the site to find more at the site but that dramatically increases my time looking in my sift at the site and the smaller mesh size tends to damage more (cusplets, root lobes, etc.) of the specimens that fall through the mesh.

 

 

 

Not a bad trip with some turtle bone and shell, a few sand tiger teeth, a few large bony fish vertebrae and some large fish coprolites.  For the record I usually find a few more shark teeth in my sift than I did this trip.

 

 

However, all of  the pictures below show what I found at home in the material that was caught by the window screen, a very large number of high quality fossils.

 

 

For size reference the white paper plates are 9 inches in diameter and there are two gem jar sizes, 1.75 inches and 1.125 inches in diameter.

 

 

Nice quality shark, ray, bony fish, sea snake etc. specimens:

 

 

 

 

Damaged or lower quality specimens:

 

 

 

 

Mostly odd bony fish bones:

 

 

 

 

Bony fish vertebrae:

 

 

 

 

Shark and ray vertebrae:

 

 

 

 

Bony fish jaws and partial jaws:

 

 

 

 

Ray teeth and ray dermal denticles:

 

 

 

 

Cookie cutter tooth and a few nurse shark teeth:

 

 

 

 

Fish coprolites:

 

 

 

Lignitized fruits/seeds:

 

 

 

 

Pyrite shell casts:

 

 

 

 

If I only sifted at this site and didn’t take home material caught by the window screen look at all of the fossils that I would be missing each trip.  What are you missing????

 

Marco Sr.

[jcbshark]

Excellent finds Marco, how do you distinguish the fish coprolites? I’m sure I’ve had to find a few but failed to recognize them I’ve just recently leaned to identify shark coprolites

[Ludwigia]

Sure does make a diff. Thanks for sharing your experience with us.

[MarcoSr]

1 hour ago, Ludwigia said:

Sure does make a diff. Thanks for sharing your experience with us.

 

Sometimes we miss a lot of available fossils in our collecting trips.

 

Marco Sr.

[MarcoSr]

1 hour ago, jcbshark said:

Excellent finds Marco, how do you distinguish the fish coprolites? I’m sure I’ve had to find a few but failed to recognize them I’ve just recently leaned to identify shark coprolites

 

Jeff

 

The below thread has a good number of pictures that may help you to id fish coprolites.  There are shark, ray and bony fish coprolite types in my fish coprolite picture in the above post.  Shark species have spiral and scroll valves and produce spiral and scroll type coprolites.  On spiral coprolites there is a single groove that spirals around the coprolite.  If the groove hasn't been eroded away they are fairly easy to id.  Scroll coprolites are rolled up like an ancient Greek or Roman scroll.  If the coprolite is broken the rolled pattern is fairly easy to id.  If the coprolite is complete, you only see a line on the surface of the coprolite where the scrolling stopped.  Bony fish coprolites are much more difficult to id.  Concretions and phosphate nodules can look very similar with very similar shapes.  Fish bone inclusions really help with the id.  A chemical analysis of the specimen really helps with the id.  The inclusions can be very fine bone specs to complete vertebrae and other small bones depending on how well the bony fish digestive system works at breaking the bones down.  What complicates the id process is that a few genera of ancient bony fishes have spiral valves and produce coprolites that could be mistaken for shark.  When fish coprolites are preserved in a fauna you usually see lots of them.  The more you see the easier it is to recognize them in a fauna.  When someone posts a single specimen from a marine fauna here on TFF and asks if it is a coprolite, unless fish bone inclusions are clearly visible, or you can see a spiral grove along the specimen or evidence of a scroll pattern then it is really guessing to try to id the specimen as a fish coprolite based upon the shape alone.

 

 

 

Marco Sr.

[jcbshark]

1 hour ago, MarcoSr said:

 

Jeff

 

The below thread has a good number of pictures that may help you to id fish coprolites.  There are shark, ray and bony fish coprolite types in my fish coprolite picture in the above post.  Shark species have spiral and scroll valves and produce spiral and scroll type coprolites.  On spiral coprolites there is a single groove that spirals around the coprolite.  If the groove hasn't been eroded away they are fairly easy to id.  Scroll coprolites are rolled up like an ancient Greek or Roman scroll.  If the coprolite is broken the rolled pattern is fairly easy to id.  If the coprolite is complete, you only see a line on the surface of the coprolite where the scrolling stopped.  Bony fish coprolites are much more difficult to id.  Concretions and phosphate nodules can look very similar with very similar shapes.  Fish bone inclusions really help with the id.  A chemical analysis of the specimen really helps with the id.  The inclusions can be very fine bone specs to complete vertebrae and other small bones depending on how well the bony fish digestive system works at breaking the bones down.  What complicates the id process is that a few genera of ancient bony fishes have spiral valves and produce coprolites that could be mistaken for shark.  When fish coprolites are preserved in a fauna you usually see lots of them.  The more you see the easier it is to recognize them in a fauna.  When someone posts a single specimen from a marine fauna here on TFF and asks if it is a coprolite, unless fish bone inclusions are clearly visible, or you can see a spiral grove along the specimen or evidence of a scroll pattern then it is really guessing to try to id the specimen as a fish coprolite based upon the shape alone.

 

 

 

Marco Sr.

Thanks for the insight Marco 

[Searcher78]

Very informative. I use a white basket with small holes drilled in the bottom. The dark fossils tend to stand out against the white background. The shark teeth tend to stick to the plastic basket. I know some small stuff will still get through, but I feel it works better than other sifters.

[MarcoSr]

3 hours ago, Searcher78 said:

Very informative. I use a white basket with small holes drilled in the bottom. The dark fossils tend to stand out against the white background. The shark teeth tend to stick to the plastic basket. I know some small stuff will still get through, but I feel it works better than other sifters.

 

Interesting.  I've never seen or used a sifter like that.  The white would definitely help the smaller dark fossils stand out.  What is the diameter of your bottom holes?

 

Marco Sr.

[Searcher78]

My holes are 6mm in diameter. It would be no problem to make one with smaller holes.

[MarcoSr]

6 hours ago, Searcher78 said:

My holes are 6mm in diameter. It would be no problem to make one with smaller holes.

 

Making the holes smaller wouldn't help unless you were taking material from your basket home to search under magnification.  You just wouldn't see the smaller fossils in your basket and it would dramatically increase your time looking at the material in your basket at the site.  For reference widow screen is usually around 1.75 mm maximum (diagonal of the mesh), so your holes are much larger than window screen.  Rather than make smaller holes, you might try sifting your basket over a separate window screen and take home to process/search what falls through your basket and is caught by the window screen.  You might find that what you are finding in the window screen isn't worth the effort.  However, in a number of formations, especially Cretaceous ones, the majority of the shark, ray and bony fish teeth will fall through a 6 mm diameter hole.  Cretaceous formations have lots of shark, ray and bony fish teeth down to .5 mm and a few down to .4 mm.  So with Cretaceous formations I don't use window screen because it is too large and use instead .4 mm sieves.

 

Marco Sr.

Edited August 26, 2019 by MarcoSr
changed 5 and 4 to .5 and .4 mm

[Searcher78]

Thanks for the info.  I have been thinking about making a sifter (one with a screen with small holes) that I can set up on the shore to work in conjunction with my basket.

[Daleksec]

Any fish otoliths at this site?

[MarcoSr]

14 hours ago, Daleksec said:

Any fish otoliths at this site?

 

Trevor

 

No.  There is lots of pyrite at this site.  This causes sulfuric acid with the ground water which probably dissolves the calcium carbonate otoliths.

 

Marco Sr.

[RuMert]

Incredible amount of teeth and other stuff, I've even saved the pictures

[MarcoSr]

2 hours ago, RuMert said:

Incredible amount of teeth and other stuff, I've even saved the pictures

 

I help a United States Geological Survey (USGS) emeritus with his vertebrate fauna studies.  This layer in the Nanjemoy Formation has the highest fossil density of high quality Eocene shark, ray, bony fish etc. specimens that we have studied so far in the Maryland/Virginia area of the United States.

 

Marco Sr.

[Mike from North Queensland]

Always love the small finds.

Running out of stuff at home so will have to go collecting soon. 

[MarcoSr]

4 hours ago, Mike from North Queensland said:

Always love the small finds.

Running out of stuff at home so will have to go collecting soon. 

 

Mike

 

A good number of the collecting areas in Maryland/Virginia where I collect are over collected these days.  So unless I'm at a private land site or in the middle of no where I tend to concentrate on finding the small stuff.

 

Marco Sr.

[Rowboater]

3 hours ago, MarcoSr said:

 

Mike

 

A good number of the collecting areas in Maryland/Virginia where I collect are over collected these days.  So unless I'm at a private land site or in the middle of no where I tend to concentrate on finding the small stuff.

 

Marco Sr.

 

Really agree with that!  If it weren't for computer games, I wouldn't even find the small stuff.  

 

A small change in the diameter of the screens can make a huge difference.  Using the stuff kids in the area used 30 years ago, I didn't often find much except bigger sand tiger and ray teeth. Dropping the screen holes to about one quarter the diameter, I find a lot of small teeth; don't remember many (any?) angel shark teeth or drum teeth with the old screens. 

 

Too fine (window screens), there are just too many small shell fragments and gravels to sort through.  maybe I should dump in  a bucket and go through at home? 

[MarcoSr]

6 hours ago, Rowboater said:

 

Too fine (window screens), there are just too many small shell fragments and gravels to sort through.  maybe I should dump in  a bucket and go through at home? 

 

From my experience collecting the Miocene formations of Virginia, window screens will catch the vast majority of shark and ray teeth and most of the bony fish teeth.  But I understand that you want to do what makes sense and not spend lots of time looking through shell fragments and small gravel.  I would sample your rapp creek site first.  Backpack out a couple of 1 gallon baggies of smaller material to search at home.  Use a mesh size that you are comfortable with to catch the material.  If the material was worth taking, then you can take more the next time you go to your site.  If you really don't find much in the sample, at least you know that you aren't missing much in the smaller material.  Some sites just don't have much in the smaller material. Good luck.  If you do try sampling rapp creek, let us know how you did when you post your trip.

 

Marco Sr.

[caldigger]

You might try #8-12 mesh. That should let go of much of your smaller sand/shell particals. Although I would imagine many of those Tope shark sized teeth could fall through that size.

Window screen is usually #20-16 mesh depending on distributor.

[sharkdoctor]

On 8/28/2019 at 5:50 PM, MarcoSr said:

 

From my experience collecting the Miocene formations of Virginia, window screens will catch the vast majority of shark and ray teeth and most of the bony fish teeth.  But I understand that you want to do what makes sense and not spend lots of time looking through shell fragments and small gravel.  I would sample your rapp creek site first.  Backpack out a couple of 1 gallon baggies of smaller material to search at home.  Use a mesh size that you are comfortable with to catch the material.  If the material was worth taking, then you can take more the next time you go to your site.  If you really don't find much in the sample, at least you know that you aren't missing much in the smaller material.  Some sites just don't have much in the smaller material. Good luck.  If you do try sampling rapp creek, let us know how you did when you post your trip.

 

Marco Sr.

 

In general I agree. However, it is worth checking some of the material down to a #30 sieve from time to time. Some of the shark material that was recently added to the Calvert Formation fauna (in Brett Kent's chapter in the Calvert Volume) was small enough to pass through a window screen, but caught in a #30. 

[MarcoSr]

39 minutes ago, sharkdoctor said:

 

In general I agree. However, it is worth checking some of the material down to a #30 sieve from time to time. Some of the shark material that was recently added to the Calvert Formation fauna (in Brett Kent's chapter in the Calvert Volume) was small enough to pass through a window screen, but caught in a #30. 

 

Especially when I help Dr. Weems with his Virginia vertebrate fauna studies but also when I sample a formation I go down to a .4 mm opening mesh size sieve when taking formation matrix or processing the matrix at home.  That sieve mesh size catches the really small shark and ray teeth.  Unless you are doing scientific research or are a micro vertebrate fanatic like me, window screen catches what the vast majority of collectors are interested in.  Going to the really small mesh sizes radically increases time required to process and search the matrix and if you don't use high enough magnification in your searching of the processed matrix, you will miss most of the really small vertebrate specimens anyways.  I didn't see anything new that I hadn't seen before in Kent's chapter.  However now I at least have an id for the specimens.

 

Marco Sr.