Thomas Farm Volunteer Dig, Spring 2014

[Plantguy]

From what I know the Thomas Farm fossil site was a cave system where the roof collapsed to form a sink hole. The site is right down the road from Ginnie Springs and many other spring features in the area--the whole region is a karst wonderland well known to cave divers and spring swimmers. The species assemblage seems to date the site to the early Miocene Epoch (early Hemingfordian--about 18 mya). By using several indicator species found at Thomas Farm which are found at other sites where the site's age can be accurately determined (e.g. radiometric dating) it is possible to assign a reasonable estimate to this site even though no direct dating of the Thomas Farm material was possible. They think that the accumulated layers may only represent a small time slice of possibly just a few thousand years. The important thing about it is that it contains a wide spectrum of animals that were in the area at the time--from frogs to birds to bear-dogs, horses, and gators (but very, very rarely fishes).

I would suspect that the Peace River material that we usually find in our sifters would include this slice of geological time though it spans a much wider swath (up to nearly recent times). The limestone surrounding the sinkhole is of Eocene age and occasionally marine fossils are found in the matrix. In fact the coarse sand layers are in fact carbonate sand (not silica) likely from the cave system surrounding the site. I did find a small single valve of an Eocene bivalve (not yet identified) in the sandy matrix I removed while prepping the carnivore jaw to be jacketed. As the museum is not interested in invertebrate fossils I was allowed to keep this as a keepsake to go along with my photos (and memories--though photos last longer these days).

Hope this helps explain this biodiverse snapshot of Florida at about 18 mya.

Cheers.

-Ken

Thanks Ken. Regards, Chris

[Plantguy]

Nice job of explaining the processes of finding and extracting fossils at this site, Ken. You nailed it! Attached are a few more photos of fossils from the dig.

Photo 1 is a scapula of a camel (large jacket in one of your previous photos).

camel_scapula1.jpg

photo 2 is a dog femur (possibly Metatomarctus canavus)

dogfemur1.jpg

#3 is that of a dog jaw with no teeth attached.

dogjaw3.jpg

#4 is a horse tibia (Archaeohippus blackbergi).

horse_tibia1.jpg

#5 is a horse rib (probably Parahippus leonensis). Very common at this site.

horserib1.jpg

#6 is a group of bones including a horse femur, a partial horse pelvis, and part of a canid scapula (upper left corner), and a bear-dog tooth. I don't know what the large bone on top is. Bones were stacked in this corner of my square.

bones4.jpg

Enjoy.

George

Hey George, looks like you had some fun too! Very neat. Regards, Chris

[dozer operator]

Enjoyed the thread Ken thanks for Sharing your knowledge on how the professionals do it.

[digit]

Here is an update on "how the professionals do it".

I've been keeping in contact with Kristen MacKenzie, the Assistant Collections Manager with the Florida Museum of Natural History (FLMNH) in Gainesville. She was the one who jacketed the jawbone Tammy and I found while at the volunteer dig at Thomas Farm this spring (as documented above). Kristen moved from Oregon where she's been working a site she discovered that is of comparable age to Thomas Farm. Her site has a wealth of camel species (which are apparently not particularly common in Oregon) as well as several other interesting mammal species. She described working with the Thomas Farm collection at FMNH as her "dream job" and she really enjoyed her first collection season there this spring.

After all the fuss that was made about the small carnivore jawbone (expecially since there is a PhD student working on the small carnivores from the TF site), Kristen was eager to see that this mustelid (suspected Leptarctus ancipidens) dentary should get prepped and not sit on a shelf with all the other jackets waiting their turn to be prepped. I had asked Kristen to keep me appraised of the progress of this find because I wanted to follow it (both out of personal curiousity and to update this TFF topic). I requested that she try to get the person prepping the jacket to take some photos for me and my wish was granted as she snapped some images with her iPad while she worked on it.

When I returned from my birthday dig with other TFF members searching for Mazon Creek nodules up here in the Chicago area, I got a second birthday present--an email from Kristen. As great as my day digging for Mazon Creek nodules, this was to be the icing on the cake--and was butter cream no less. She said that she need to keep her prepping skills up and she didn't want this jacket to be neglected so the night before my birthday, about the time I was leaving for the airport to head to Chicago, she pulled out the jacket and started rehydrating the matrix with water to get it ready for prepping the following day. Keep in mind that she is busy with her actual job during working hours and decided to work on this jacket after work and on weekends--paleontologists can be some passionate people!

The grid square that Tammy and I had been digging had proved to be nearly fossil free till we hit the corner of the square where the jawbone turned up. Before I uncovered the jawbone I found a Parahippus tarsal and calcaneum nearby in the coarse sandy matrix layer (nothing ever seemed to turn up in the muddy clay matrix layers of our grid cell). The area immediately around the jawbone was peppered with smaller black fossil material and we had to be careful while trenching around the jawbone to create the pedestal. As it turns out the micro fossils continued within the pedestal underneath the jawbone. Kristen said that the number of specimens recovered in our grid square more than doubled due to the rich micro fossils she uncovered while prepping.

Of particular interest is a very tiny mammal molar (less than 1 mm long!) which she had Dr. Hulbert inspect. He thinks it may represent something from an entirely new species which, if true, would blow my socks off as a birthday present. She says that if it proves to be something novel that it may change the way they screen wash the sediment. Kristen was curious as to how TF matrix preps out as she's never worked this type before (and is used to much harder matrix from the John Day Fossil Beds and the even more concrete-like matrix from her southern Oregon site). She says the TF matrix is a dream to prepare.

The lab is working on getting a photo microscope so they can better take photos of specimens on the sub-millimeter scale. Kristen said that till they get that set up she may take some of the smaller specimens to one of the other labs on campus to see if she can get better photos of them (I'll post updates if she obtains better images of the micro stuff). So far the jacket has produced 6 1mm long phalanges (likely rodent), a VERY small carnivore metacarpal, numerous frog limb bones, and a 2mm astragalus in addition to the tiny mammal molar.

In addition to the news of the micro fossils it has been fun to see images of the jacket being drained away of its matrix and the jawbone making its reappearance for a second time in some 18 million years.

Below are a series of photos taken by Kristen and used with her permission.

Here is the jacket the night before prior to being rehydrated.

Four hours into the prepping and the level of the matrix visibly lower.

View of the pin vise fitted with the stainless steel needle used to work through the matrix.

-Ken

Edited June 10, 2014 by digit

[digit]

Though an iPad is not the optimal tool to photograph micro fossils here are some grab shots Kristen took while uncovering some of the tiny finds in the matrix pedestal under the jawbone. I'm hopeful that she'll be able to get me some micro photographs when she takes some of her Oregon micro fossils to one of the other labs for photos. I'll post additional photos if/when I receive them.

You'll need to zoom into these images to stand any chance at seeing what's being pointed out.

Tiny phalanx (likely rodent) in the very center of the frame.

There is a tiny rodent tooth just to the right of the needle tip.

Another micro fossil at the tip of the needle (the astragalus I believe).

-Ken

[digit]

As Kristen continued to work the matrix out of the jacket (while keeping her eye out for any other interesting micro fossils) she got to the point where she had a significant rim of the plaster cast exposed. This was about 6 hours into the prepping. To make it easier to access the matrix, the exposed walls are cut away. If this is not done there is a tendency to press down on the walls bending them and risking cracking the plaster jacket.

At the end of the day (9 hours into the prepping) the "underside" of the jawbone had been reached, The symphysis (at the front tip) and ascending ramus (at the rear cheek) were still too fragile to fully expose so she stopped there for the night. She let the specimen dry out in a controlled manner overnight so that it would be receptive to the thin polymer she would saturate it with on the following day to stabilize it before continuing the final removal phase.

After some additonal work the following morning on the symphysis and ascending ramus of the now stabilized jawbone, the matrix removal on this side of the specimen was complete. At this point she let it dry for the rest of the day before adding more stabilizing polymer to prepare the fossil for complete removal from the jacket. The specimen will then be carefully lifted out and the opposite side will also be dried and saturated to complete the prepping of this mustelid dentary.

While they have drawer after drawer of some species (like Parahippus leonensis) from the Thomas Farm site, Kristen mentioned that the material they have for this species would likely fit comfortably within a single shoebox. I'm proud to have contributed in my own minimal way to the story of the fossil assemblage of Thomas Farm. And of course if the micro mammal tooth turns out to be from a new species, my wife will find me impossible to live with for quite some time....

Some more photos to document the unveiling.

Tin snips make short work of trimming away the now excess wall from the plaster jacket.

The "underside" of the jawbone at the end of the first (long) day of prepping.

The remaining bits at the front tip and rear of the jawbone are exposed on the second morning after stabilizing with polymer.

-Ken

[digit]

Here's a bonus higher resolution close-up of the nearly finished mustelid dentary for those who wish to get a closer look.

Cheers.

-Ken

[Auspex]

What a saga! Congratulations on the outcome of your efforts, thank you very much for the fascinating write-up, and happy birthday!

[jcbshark]

Really interesting and Happy Bday!

[digit]

Thanks. It was quite a fossiliferous day. It's currently quite soggily raining where I am at the moment (about 45 minutes from where we were hunting Mazon Creek nodules). Hoping to get back out for a repeat but wondering if the rain may make that problematic. I weighed up my haul from my birthday dig and I came away with just under 40 pounds of nodules. I brought 3 suitcases so I could spread the weight around.

I plan on making a return trip to Gainesville to see "my" mustelid jawbone once it is fully prepped. Maybe I'll pose for some photos with it. I'm even more interested in the micro carnivore tooth that may turn out to be something new. These things usually turn out to be false alarms upon closer inspection but I've got my phalanges crossed just in case.

-Ken

[GaRockhound]

Thank you so much for sharing ! Very, very interesting !

[dirtdauber]

Nice follow-up, Ken. Great job! -- George

[digit]

Conclusion:

Kristen MacKenzie sent me some wrap-up photos of the jawbone (dentary) now positively identified as Leptarctus ancipidens.

The remaining matrix was cleared from the specimen and some heavier glue was used to stabilize it before it was picked-up and flipped. Once removed from the jacket the jawbone was stabilized vertically in a bed of sand for support while the teeth got a good cleaning (Paleo-floss?) before the specimen received its new moniker: UF295000.

Specimen with last of matrix removed from jacket.

Stabilized with heavier glue before removal.

Supported to allow good dental hygiene.

-Ken

Edited June 12, 2014 by digit

[digit]

Here are the three views of the fully prepped (and accessioned) specimen.

Lingual view:

Labial view:

Occlusal view:

-Ken

[digit]

Thanks to all the TFF members who have followed the saga this far. Thanks also to the Florida Museum of Natural History for making volunteer opportunities available to novice enthusiasts like me and to Dr. Richard Hulbert and Kristen MacKenzie (as well as the other volunteers) for making the fieldwork enjoyable. Special thanks go to Kristen who not only took a special interest in this rare little jawbone but did a great job prepping AND documenting the process for my benefit (and the members of TFF).

'nuff said.....

Cheers.

-Ken

Edited June 12, 2014 by digit

[digit]

I'd also like to remind everybody to check the FLMNH website in early 2015 for announcements for next season's dig at the Thomas Farm site. If I'm in country during the next volunteer dig I'm definitely in--who knows what I'll find next time.

Cheers.

-Ken

[beachbum]

That was some adventure. Thanks for letting all of us share it with you. Happy B'day,Jim

[jpc]

Thanks for the great report and nice set of pix on how to make a plaster jacket. Great little find, too.

Somehow, I have always pictured Thomas Farm to look like... Oh, I don't know... a farm, not a forest.