Recent Cretaceous microfossil sorting at the Field Museum of Natural History in Chicago

[Joseph Fossil]

The past few weeks, I've been doing awesome Internship work with Late Cretaceous microfossils at the Chicago Field Museum of Natural History (aka the Best Museum in Chicago). The micro fossils are 68-66 Million Years old and are from the Maastrichtian Cretaceous age Hell Creek Formation in what is now the U.S. States of North Dakota, South Dakota, and Montana. My job is to sort out the collected micro fossils into the correct taxonomic categories and I wanted to some of my best current finds with this project.

 

 

I've discovered at least 7 Tyrannosaurus rex teeth and tooth fragments (some even mislabeled as fish teeth)

 

 

 

 

 

 

[Joseph Fossil]

 

 

 

 

 

 

 

 

 

 

 

Lots and Lots of Atractosteus sp. Gar fish scales!!!

 

[Joseph Fossil]

Actinopterygii Fish Vertebrae 

 

 

Thescelosaurus teeth

 

 

 

Mylepaphus teeth

 

 

 

Hiotonid fish vertebrae 

 

 

 

Acheroraptor teeth

 

 

 

Alongside lots more!!!

 

 

 

 

 

Hope you all enjoyed these awesome fossils as much as I do!!!

[JamieLynn]

Dang, that looks like a dream job! Do you know what formation these are from?

[jdp]

Thinking that vertebra is amiid rather than hiodontid. Check with Lance?

[Joseph Fossil]

4 hours ago, JamieLynn said:

Dang, that looks like a dream job! Do you know what formation these are from?

 

@JamieLynn Yes, they're all from the Maastrichtian Cretaceous age parts of the Hell Creek Formation dating 68-66 Million Years ago in what is now the Western U.S.

[jpc]

9 hours ago, Joseph Fossil said:

 

Lots and Lots of Atractosteus sp. Gar fish scales!!!

 

 

Atracosteus or Lepisosoteus?  Having found thousands of these, how do you tell the difference?  

 

... and are you sure that is Thescelosaurus?  It looks crocodilian from here.

 

Meanwhile, have fun.  these microsites are genuine bucket of coolness.  

Edited October 11 by jpc

[Kohler Palaeontology]

Very cool!

 

From what I'm seeing, I'd agree that my first thought when looking at the supposed Thescelosaur tooth was that it looks more crocodillian to me.

[ThePhysicist]

 

Looks like great fun! The HCF is particularly enjoyable for its richness and diversity.

 

This one I believe is Richardoestesia isosceles.

On 10/10/2024 at 9:22 AM, Joseph Fossil said:

[Joseph Fossil]

On 10/10/2024 at 8:09 PM, jpc said:

Atracosteus or Lepisosoteus?  Having found thousands of these, how do you tell the difference?  

 

... and are you sure that is Thescelosaurus?  It looks crocodilian from here.

 

Meanwhile, have fun.  these microsites are genuine bucket of coolness.  

 

@jpc I actually thought that, until you pointed it out, the genus Atracosteus was the only gar genus present at the formation, so I really appreciate the information. For the microfossil sorting, we utilize a guide book named Atlas To Fossils Of The Hell Creek Formation: A Carthage Institute of Paleontology Field Guide Companion by Thomas D. Carr, PhD, Megan E. Seitz, PhD, and Dino Pulerà, MScBMC, CMI. The guide book is a few years old and only lists Atracosteus as the gar genus present in the formation.

 

I'll double check with the possible Thescelosaurus tooth, but if it is a Crocodilian what genus would it be?

 

I also agree, the microsites are genuine buckets of coolness and awesomeness!!!

[jpc]

Interesting. 

 

I winder why they went with A. rather than L.  

I found this paper from 2022.

file:///C:/Users/Owner/Downloads/brownstein-lyson-2022-giant-gar-from-directly-above-the-cretaceous-palaeogene-boundary-suggests-healthy-freshwater%20(1).pdf

 

Their cladogram shows one species of A going into the Cretaceous.  It is from Morocco.  As a guy who has catalogued countless gar scales and a few less skull pieces as L,  I am really curious as to why Carr et al call the Cretaceous gar an A. 

 

Can you PM me a pdf of the Atlas, if you have one available?  

 

Thanks

jpc

[Nimravis]

Fun work, I am doing the same with micros from Shark Tooth Hill, Bakersfield, California: Mid-Miocene Round Mountain Silt Unit / Temblor Formation.

 

 

 

 

 

 

 

 

 

[ThePhysicist]

On 10/12/2024 at 12:20 PM, Joseph Fossil said:

 

@jpc I actually thought that, until you pointed it out, the genus Atracosteus was the only gar genus present at the formation, so I really appreciate the information. For the microfossil sorting, we utilize a guide book named Atlas To Fossils Of The Hell Creek Formation: A Carthage Institute of Paleontology Field Guide Companion by Thomas D. Carr, PhD, Megan E. Seitz, PhD, and Dino Pulerà, MScBMC, CMI. The guide book is a few years old and only lists Atracosteus as the gar genus present in the formation.

 

I'll double check with the possible Thescelosaurus tooth, but if it is a Crocodilian what genus would it be?

 

I also agree, the microsites are genuine buckets of coolness and awesomeness!!!

I'm familiar with this guide, but haven't been privy to most of its content, as it apparently has been in limited print, unpublished, and Carr has made it explicit that it is not for the eyes of private collectors. Are there any references cited? I have not seen Atracosteus from the HCF referred to in any peer-reviewed work, so I also doubt this assignment.

 

As for the croc, only the bulbous posterior teeth of Brachychampsa are distinctive enough to ID at the genus level, all others should be considered Crocodyliformes indet.

[Joseph Fossil]

On 10/13/2024 at 2:02 PM, ThePhysicist said:

I'm familiar with this guide, but haven't been privy to most of its content, as it apparently has been in limited print, unpublished, and Carr has made it explicit that it is not for the eyes of private collectors. Are there any references cited? I have not seen Atracosteus from the HCF referred to in any peer-reviewed work, so I also doubt this assignment.

 

As for the croc, only the bulbous posterior teeth of Brachychampsa are distinctive enough to ID at the genus level, all others should be considered Crocodyliformes indet.

 

@ThePhysicist After your comment I did check the guidebook again on the subject of Gar diversity of the Hell Creek Formation and it stated on Page 68 that the authors (Carr, Seitz, and Pulerà) no longer consider the prehistoric gars from that formation belonging to the genus Lepisosteus since it appears Lepisosteus is only distantly related to Hell Creek Formation Gar species than species of the genus Atractosteus, hence assigning all the gar fossils at the formation to the genus Atractosteus as Atractosteus sp..

[jpc]

Joseph...

do you have a pdf of this paper available you could send me?  

 

thx

 

[doushantuo]

some of you may like:

Giant gar from directly above the Cretaceous–Palaeogene boundary
suggests healthy freshwater ecosystems existed within thousands of years of the
asteroid impact
Chase Doran Brownstein and Tyler R. Lyson

Roy. Soc Biol. Lett. 18: 20220118.
https://doi.org/10.1098/rsbl.2022.0118

specific epithet grandei as a tribute to giant in the field Lance Grande

(size: 1.4 Mb )

brownstein-lyson-2022-giant-gar-from-directly-above-the-cretaceous-palaeogene-boundary-suggests-healthy-freshwater (1).pdf

Edited 10 hours ago by doushantuo

[Joseph Fossil]

30 minutes ago, jpc said:

Joseph...

do you have a pdf of this paper available you could send me?  

 

thx

 

 

@jpc I'm sorry but I currently don't have a pdf copy. However, I do have a Google Books link which might help you find a online copy.

 

https://books.google.com/books/about/Fossils_of_the_Hell_Creek_Formation.html?id=Z2f6zgEACAAJ

 

Hope this helps. I also have photos of the cover and some of the pages in order to help with the sorting project.

[Joseph Fossil]

[jpc]

Thanks for this.  Unfortunately, they don't tell us how the HCF gars are more similar to A than L.  : (

 

I will try to contact Carr and ask him.  

 

Edited 2 hours ago by jpc