Story of a softshell turtle (Apalone sp.) from start to finish

[digit]

Here is a photo heavy and (for me) text light posting showing the sequence of Tammy and I finding a partial softshell turtle (Apalone sp.) carapace in the field at Montbrook (which was jacketed and removed on the last day of the spring digging season). I pulled the jacked and prepped the carapace over the course of a few months. The jacket was made in the field on 5-May-2021 and I retrieved the jacket (#573) from the storage area on 10-Jun-2021 and completed the prep today 23-Sep-2021. Lots of excavation into the jacket and cleaning and re-attaching parts. The pectoral girdle (scapula and corocoid bones) as well as the first cervical vertebra were left in the position where they were found to preserve the taphonomic information. A fun project that taught me a lot about fossil prep.

 

Cheers.

 

-Ken

 

         

 

         

 

         

 

         

 

         

 

         

 

         

 

         

 

 

[ClearLake]

Ken, very cool! Nicely done by both you and Tammy. Is the Fall digging season at Montbrook still limited to a relatively small group of volunteers?

[sharkdoctor]

Wow, that's a beauty! Great photo journalism too :-) Thanks for sharing.

[fossilsonwheels]

Hi Ken

 

SUPER COOL and TOTALLY AWESOME. I can’t really say anything else lol 

 

 

[Brett Breakin' Rocks]

Fantastic prep Ken, how long does it take to train and qualify to take on such an important task at the museum ? The prep looks great !

 

Cheers,

Brett

[Manticocerasman]

incredible job, congrats 

[Ludwigia]

Excellent!!

[Bobby Rico]

Now that’s something quite  lovely. Great find , post and prep work.
Cheers Bobby 

[ziggycardon]

Cool find and I love the prep result! 
Amazing job!

[pachy-pleuro-whatnot-odon]

What a great find! And the result after preparation is just astonishing! You wouldn't be able to recognize it from the original find any more! Well done!

[RJB]

  Wow.  What a cool find.  Nice job on the prep too.

 

RB

[tombk]

Totally cool find and amazing work extracting and prepping!

[digit]

11 hours ago, ClearLake said:

Ken, very cool! Nicely done by both you and Tammy. Is the Fall digging season at Montbrook still limited to a relatively small group of volunteers?

The museum has hopes that we'll be open for a full volunteer season once again. The starting date will likely be sometime toward the end of October or definitely sometime in November. It will depend on water levels at the site. I have heard that the current target is to dig a limited number of days per week for the autumn session and that they are planning on being out in the field for a 3-day block (Friday-Sunday) each week. This will provide the entire weekend for volunteers who can only dig on the weekends. When the season has a definite start date I'll surely make a post here on the forum to alert anyone interested in finding their own turtle.

 

 

Cheers.

 

-Ken

[digit]

7 hours ago, Brett Breakin' Rocks said:

Fantastic prep Ken, how long does it take to train and qualify to take on such an important task at the museum ?

Funny that!

 

The prep lab in Dickinson Hall on campus had been closed during the pandemic. Jason Bourque the head preparator had been working on specimens from home during the duration. When campus opened up again earlier this year I was there the first day Jason returned to the prep lab. I have a reputation for detail work (borderline OCD and years of being a computer programmer and editor) and Jason was aware of this fact. He started me out on several projects that were started (some years ago) by students and other volunteers who had lost interest (or graduated) and as a result were mostly done but required the final clean-up detailed work to complete the projects.

 

Jason showed me around the lab and introduced me to the tools--mostly dental picks and brushes with Butvar (B72) to consolidate/glue and acetone to remove excess B72. Then it was mostly me figuring out the techniques that worked best for me. Jason was always there for consultations and explanations of what he'd do that has worked best for him in the past. Questions to Jason tapered off as I got the hang of things. Each new project has had new challenges and required new techniques with the coincident learning of new skills.

 

I started out with an 18 Ma tiny 3-toed horse jaw from the Thomas Farm site that had been sitting in a box on a shelf for some time and needed some TLC. The jaw looked to be missing most of its teeth and needed a good dental hygiene cleaning. Turned out the jaw was full of unerupted teeth and turned out to be a very nice specimen.

 

Cheers.

 

-Ken

 

          

 

         

 

[jpc]

NIce work, Ken.  What, pray tell, have you done to the specimen between exposing it and plastering it?  6th photo, way up top.  Are you guys using some sort of mud as a separator?  

[Pagurus]

   Congratulations on the find, Ken, and thanks for the documentary.

[digit]

1 hour ago, jpc said:

Nice work, Ken.  What, pray tell, have you done to the specimen between exposing it and plastering it?  6th photo, way up top.  Are you guys using some sort of mud as a separator?  

When we find a specimen in the field that is not just a disarticulated bone or something that is likely too fragile and needs more consolidation and prep in the lab, we decide to make a plaster jacket instead of pulling out the fossil and tossing it into our bone bag for the day. We have a large (roughly gallon size) plastic bag that has a label in it (protected inside a tiny zip-top bag). The label contains the site information, the date, the grid coordinates within site site and the name of the collector. These bone bags are brought back to the museum where they are washed and air dried. Then they are repacked into clean(er) bags and driven up to the vertebrate paleontology warehouse (where I get the fun task of sorting through them to see which pieces are good enough to be cataloged and which fragments go into archive boxes).

 

For specimens that merit a plaster jacket we spend time trenching around the specimen wide enough and deep enough to create a pedestal. Our matrix is mostly sandy/silty/clay and so it is much easier to create the trench than it would be in hard rock paleontology like you are familiar with out west. When we are ready to make the jacket we finish off the pedestal with a slight undercut around the base which hopes to contain the contents when the jacket is flipped. For larger jackets (gomphothere femurs, articulated alligators, etc.) we use burlap strips and we mix batches of plaster to dunk them into. We usually mix a couple of batches of plaster so that it doesn't harden while we are working on a sizeable jacket. For smaller jackets we use rolled bandages that are impregnated with dried plaster. You can tear of strips of an appropriate length and then simply dunk them in a bucket of water and squeeze out the excess water gently before applying to the pedestalled fossil. Much quicker and easier than burlap but more expensive so we only use it for smaller jackets.

 

To answer your question (finally! ) about the separator to keep the plaster from touching the fossil, we use clean sand. While making the trench we set aside some of the clean sand (without pebbles or lithified bits) and just before jacketing we dampen the sand and apply a not-too-thick layer of the dampened sand over the top of the specimen. This not only helps to provide separation so the plaster does not get on the bone but it also helps to even out the surface and provide a smoother and flatter surface. The jackets turn out better if they are smoothly convex and they sit more stably once rotated if they have a flatter top (which becomes the base).

 

Once the plaster is set we use trowels (on smaller jackets) or little trenching shovels (on larger jackets) which are pushed (or hammered) underneath the jacket's base to break through the pedestal and free the jacket. A quick flip secures the contents for storage. We often scrape out some of the matrix from the open end of the jacket (what would have been below the specimen when it was in situ). This helps to reduce the weight when carrying jackets up and out of the pit.

 

Quite often jackets can sit in storage for some time before being prepped. During the last week of the season Tammy and I found not only this front part of an Apalone carapace but enough of the rear portion of the same species that we wondered if the two came from the same individual. The rear portion was in the same grid square not very far at all from this front piece. I pulled both jackets and prepped them somewhat simultaneously to see if they might match-up (which would have been spectacular). Unfortunately, once they were both out of their jackets and could be examined closer, the back half of the carapace was thicker than the front and so had to come from different individuals. The two would have been just about a perfect fit if it were not for that. I knew that this potential association would be lost to memory if the jackets sat on a shelf in storage for too long and so I suggested I prep them both. Jason (the head of the prep department) specializes in turtles and tortoises and so I did not have to try hard to convince him to let me prep these two jackets.

 

Jason is starting to gather specimens for a book project he's starting covering fossil turtles. He said this one turned out nice enough that it will likely be pictured in this book when it is finally written.

 

 

Now, I'm working on re-assembling an alligator skull from the Thomas Farm site that has been sitting partially prepared since shortly after its discovery 25 years ago in 1994. It was not adequately stabilized and (like many Thomas Farm specimens) is coming apart in chunks. They'd like to scan this specimen for an upcoming paper and so I'm doing a re-build on this one so that it can be handled and scanned in 3D.

 

 

Cheers.

 

-Ken

[jpc]

I like that idea... sand as a a separator. 

 

 

[fossilhunter21]

Awesome find! Nice job on the prep!

[Mainefossils]

Amazing prep @digit! Your projects came out quite well - I really like the carapace of your soft-shell turtle. I had one question though: how rare do you think a find of this nature is? I myself have never seen (digitally) such a nice carapace from this formation, and the association makes it more extraordinary to me. Either way, congratulations on the beautiful fossils, and for the expertise that enabled a prep worthy of them! 

[digit]

4 hours ago, jpc said:

I like that idea... sand as a a separator. 

Cheap and plentiful.  We use sand from nearby as we often screenwash the matrix removed when prepping a jacket. This keeps any separator sand micro-fossil finds in the same grid square as the rest of the matrix in the jacket.

 

 

2 hours ago, Mainefossils said:

I had one question though: how rare do you think a find of this nature is? I myself have never seen (digitally) such a nice carapace from this formation, and the association makes it more extraordinary to me.

We have a few partial carapace and complete plastrons (fewer bones) from the Apalone species at the Montbrook site. Mostly, (as expected) we tend to have fragmentary elements (mostly broken costals). I was amazed to find a complete costal (in pieces) and bagged that within a smaller nested bag inside my bone bag for the square. When I spotted a complete second costal a few minutes later I then changed my digging and explored to see if there was more articulated further in (which there was).

 

This was the articulated rear section of (another) Apalone found in the same square days apart. The preservation was a bit different but that can happen on opposite ends of a single piece. It was the difference in thickness that make it clear that these two parts were not from the same individual. These two articulated pieces of carapace are the most complete Apalone specimens I've found at the site--fairly rare in this amount of completeness but not uniquely so.

 

Cheers.

 

-Ken

 

 

[Pixpaleosky]

Thank you very much for showing us the prep stages. Which kind of bond did you use to glue the rib at the end ?

And thank you for all the tips you already shared .

 

[Top Trilo]

Nice find and fantastic prep, what a cool fossil. You really do great at explaining things. When someone asks a question you answer it fully teaching all of us, with plenty of detail. Thanks Ken for sharing this with us.

 

[digit]

16 hours ago, Pixpaleosky said:

Thank you very much for showing us the prep stages. Which kind of bond did you use to glue the rib at the end ?

And thank you for all the tips you already shared .

It was find of fun to gather together and look at the images (from the many I took) to show the progress from the field to the jacket and its final preparation

 

In general, we use B72 to glue together separate bones along their suture lines. For fragmented bones we tend to use cyanoacrylate (CA or "super glue") to either tack the pieces together and finish of with B72 or sometimes completely glue together the fragments. Quite often, you have to leave some flexibility when lining up several individual elements like the costal (rib) bones so they can fit together in the best way possible. The carapace is slightly flattened and spread out with sand-filled gaps between the line of neural bones and the adjoining costals to either side. I could have tried to detach all of the costals from the neurals and cleaned out the sandy fill in an attempt to get a tighter fit but messing with the neurals would likely have caused the pieces of the vertebrae to become loosened and fall apart. As a result the separated costals were re-attached so they aligned with the best possible fit to the neighboring costals and the gap between the proximal ends and the neurals was filled with sandy matrix from the jacket and then solidified with an application of B72. I used modeling clay (which we have in the prep lab for various purposes) pressed along the outside of the carapace to span the gap needing to be filled and provide a base. I am then able to sprinkle in some dried sandy matrix to fill the gap. A brush wetted with acetone helps to dampen the sand and help it pack in tightly. I can then drip in some B72 to help lock the sandy matrix in place. Should this ever need to be removed to re-align things, the B72 can easily be softened by applying more acetone to dissolve the B72.

 

 

12 hours ago, Top Trilo said:

When someone asks a question you answer it fully teaching all of us, with plenty of detail.

Part of the enjoyment of learning new information (or techniques) is in sharing that knowledge to a receptive audience.

 

 

Cheers.

 

-Ken

[RuMert]

Excellent prep