Are there earliest Paleocene records of Tyrannosaurus rex

[Joseph Fossil]

Image Reconstruction of Western North America during the winter caused by the Asteroid impact 66 Million Years ago, with two Tyrannosaurus rex chicks foraging for food.
Image Credit: James McKay
https://eos.org/science-updates/a-post-impact-deep-freeze-for-dinosaurs

 

 

This is a topic I'd thought I'd never ask about on the forum, but I think it's worthy of discussion. 

 

I recently watched Youtube Channel ExtinctZoo’s recent video on how long the Non-Avian Dinosaurs survived the initial Asteroid impact that struck Earth 66 Million Years ago and the winter (caused by the dust and debris the asteroid kicked up) that followed. 

 

 

The video made some pretty good points and I do agree with the point that a very few non-avian dinosaur species likely survived the asteroid impact and the subsequent 1-15 year long winter it caused for between 15-100 years to a max of 33,000 years. I also agree with its point that Carnivores Theropods, not Herbivorous, Dinosaurs would likely have survived the longest due to the dramatic decline in plant diversity and the massive number of carcasses lying around due to the impact and winter.

 

https://www.sci.news/paleontology/chicxulub-asteroid-dust-12406.html

https://www.nature.com/articles/s41561-023-01290-4.epdf?sharing_token=LlrRnU14xAo8_BrQc95oZ9RgN0jAjWel9jnR3ZoTv0MOr-zLbWfWnMUrUoeF8AP4MvNe11eJCtA6H3n5nWnRpR271jYN4Fz73kXdSUZ6xQVgMVXxTx3Vnh3yvBZlkYemKPpfcbtmV6M4jq6PZazABiMNdKVJxKckIOlT3R3_qstwUGqDfrSo2UqyCCPAKx_SyDYKuQdZV8QV4GUVTLJwUYBE5yq_urGjvNgYtdkfnNM%3D&tracking_referrer=www.washingtonpost.com

https://www.uv.es/pardomv/pe/2009_2/199/199.pdf

 

https://www.pure.ed.ac.uk/ws/files/21561904/PDF_for_PUREID21368259_Brusatte.pdf

https://dinodata.de/bibliothek/pdf_a/2020/2006087117.full_dd.pdf

https://yibs.yale.edu/sites/default/files/FALL10.pdf
(Vertebrate Evolution Across the Cretaceous– Tertiary Boundary in Eastern Montana page 6.)

https://royalsocietypublishing.org/doi/abs/10.1098/rsbl.2011.0470

https://eps.harvard.edu/files/eps/files/renne.kt_.science.2013.pdf

 

After watching the video, I decided to investigate old paleontological archives and papers to see if I could find any evidence of catalogued specimens of Non-Avian Theropod Dinosaurs collected in earliest Paleocene deposits. After a week of searching, I think I found two promising records. The first I would like to talk about in much greater detail: a potential earliest Paleocene record of Tyrannosaurus rex.

[Joseph Fossil]

These are a series of fossilized theropod teeth discovered in 1957 in Garfield County, Montana. Originally labeled as belonging to the taxon “Aublysodon mirandus”, it’s now known “Aublysodon mirandus” is a synonym for the giant theropod dinosaur Tyrannosaurs rex. These teeth are now part of the collections of the University of California’s Museum of Paleontology (UCMP). But what is truly remarkable about these teeth is that according to the IDiGBiO (Integrated Digitized Biocollections), they were all collected from geologic deposits of the Tullock Member of the Fort Union Formation. The Tullock Member does not date to the latest Cretaceous, but rather the earliest parts of the Danian Paleocene between 66-63 Million Years ago.

https://pubs.usgs.gov/bul/1917f/report.pdf

 

“Aublysodon mirandus”
UCMP = University of California Museum of Paleontology
Specimen UCMP: V:125231
Collected 1957
Garfield County, Montana, U.S. 
Horsethief Canyon 2
Tullock Member, Fort Union Formation
https://www.idigbio.org/portal/records/7bd4a731-47e6-4e3a-a309-af8cdf88a587

 

“Aublysodon mirandus”
UCMP = University of California Museum of Paleontology
Specimen UCMP: V:125232
Collected 1957
Garfield County, Montana, U.S. 
Horsethief Canyon 2
Tullock Member, Fort Union Formation
https://www.idigbio.org/portal/records/bdd6ea5e-9f69-4ece-8a31-7f3aa63e0ebc

 

“Aublysodon mirandus”
UCMP = University of California Museum of Paleontology
Specimen UCMP: V:125235
Collected 1957
Garfield County, Montana, U.S. 
Horsethief Canyon 2
Tullock Member, Fort Union Formation
https://www.idigbio.org/portal/records/1f11d071-36d8-45a5-9335-1cebdcdda8e7
 
“Aublysodon mirandus”
UCMP = University of California Museum of Paleontology
Specimen UCMP: V:125236
Collected 1957
Garfield County, Montana, U.S. 
Horsethief Canyon 2
Tullock Member, Fort Union Formation
https://www.idigbio.org/portal/records/65ce5a67-ca48-41b6-9a64-0231f751fc8b
 

[Joseph Fossil]

Image Reconstruction of a Tyrannosaurus rex by a couple Baenid turtles of the species Saxochelys gilberti during Late Cretaceous in what is now Western North America.

Image Credit: Lyson, Sayler & Joyce, 2019

http://novataxa.blogspot.com/2020/02/saxochelys.html

 

Based on its size fully grown and metabolism requirements, it would seem a Theropod like Tyrannosaurus rex would have the worst time surviving (even briefly) the effects of the asteroid impact (especially since the vast majority of most terrestrial animals that survived the extinction event weighed only about or less than 25kg or 55lbs).

 

But T-rex did have a few adaptations that might have given it some small advantages during the worst of the post asteroid winter. Liked other advanced Tyrannosaurids It had exceptional vision and smell, allowing it to easily find any large prey and carcasses within several miles.

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6571463/

 

 

T-rex, like other non-avian theropods, was also able to swim remarkably well due to their hollow bone structure and long legs. 

 

https://academic.oup.com/zoolinnean/article/198/1/202/7153107
https://www.researchgate.net/publication/260359854_Were_non-avian_theropod_dinosaurs_able_to_swim_Supportive_evidence_from_an_Early_Cretaceous_trackway_Cameros_Basin_La_Rioja_Spain

This could have allowed them more access to food sources in what remained of the Western Interior Seaway including Sea Turtles (a group that did survive the Cretaceous-Paleocene Mass Extinction Event) such as Euclastes.

 

https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=67331
https://www.sciencedirect.com/science/article/abs/pii/S0195667114000445
 

 

Image Map Reconstruction of North America 72-66 Million Years ago (note the map hasn’t included Tyrannosaurus fossils found in the Ojo Alamo Formation, Willow Creek Formation, and Frenchmen Formation).
Image Credit: Paleoartist A. E. Charters
https://www.reddit.com/r/Paleontology/comments/l6c47f/map_i_made_mapping_nonavian_dinosaur_species_and/#lightbox
 

 

[Joseph Fossil]

Though these traits wouldn’t have saved Tyrannosaurus rex from total extinction, these traits likely could have still given Tyrannosaurus an edge over other non-avian theropod dinosaurs in Maastrichtian North America (excluding smaller dromaeosaurs) post impact and allowed some scattered individuals to survive into the Earliest Paleocene before dying out likely 15-1,000 years after the impact event. A true case of a “Dead Clade Walking” species. 

 

However, to verify without doubt the dates of these fossils, direct zircon crystal testing should be conducted to determine whether they date to the Maastrichtian Cretaceous or within the first hundred-thousand so years of the Danian Paleocene.

[Joseph Fossil]

I would like to know if anyone on the forum has heard of these specimens before and how likely it is a very few individuals of Tyrannosaurus rex (alongside other smaller Tyrannosauroid species also alive during the Maastrichtian Cretaceous like Asiatyrannus and Dryptosaurus) survived the Astroid impact, the subsequent 15 year long winter, and into the first days of the Danian Paleocene as "Dead Clade Walking"?

[Al Dente]

3 hours ago, Joseph Fossil said:

But what is truly remarkable about these teeth is that according to the IDiGBiO (Integrated Digitized Biocollections), they were all collected from geologic deposits of the Tullock Member of the Fort Union Formation. The Tullock Member does not date to the latest Cretaceous, but rather the earliest parts of the Danian Paleocene between 66-63 Million Years ago.

It is not uncommon for older fossils to be reworked into younger sediment. Here in North Carolina, Cretaceous fossils, including dinosaur material, can be found in the basal lag of the Eocene Castle Hayne Formation.

[Joseph Fossil]

2 minutes ago, Al Dente said:

It is not uncommon for older fossils to be reworked into younger sediment. Here in North Carolina, Cretaceous fossils, including dinosaur material, can be found in the basal lag of the Eocene Castle Hayne Formation.

 

@Al Dente You're absolutely correct. I also do believe that was the case for a Hadrosaur specimen from the Ojo Alamo Formation thought to date to the Paleocene but actually was Cretaceous in age, being reworked into the younger sediment.

 

https://www.uv.es/pardomv/pe/2009_2/199/199.pdf

 

However, I'm not aware of how common reworking of fossils is for the Fort Union Formation and the formation apparently right below it (the Hell Creek Formation) to my knowledge has not too many records of reworked fossils. I do believe a Zircon crystal test of these specimens would best solve the question of the actual age (either Maastrichtian or Danian) of the specimens.

[Joseph Fossil]

@jpc @hadrosauridae Do you guys have any your input on this topic (also have you heard of these particular specimens before)? Would really appreciate your thoughts on this as I've been trying to figure out and verify the age of these specimens for at least a week now? 

[hadrosauridae]

12 minutes ago, Joseph Fossil said:

@jpc @hadrosauridae Do you guys have any your input on this topic (also have you heard of these particular specimens before)? Would really appreciate your thoughts on this as I've been trying to figure out and verify the age of these specimens for at least a week now? 

 

You;ve made quite a few posts in this thread, can you sum up the idea you want input on?

[Joseph Fossil]

6 hours ago, hadrosauridae said:

 

You;ve made quite a few posts in this thread, can you sum up the idea you want input on?

 

I'm trying to get input on the veracity of the claims made by IDiGBiO (Integrated Digitized Biocollections) that specimens UCMP V 125231, 125232, 125235, and 125236 were indeed collected from the earliest Paleocene Tullock Member of the Fort Union Formation, If any of the traits I listed above would (hypothetically) allow a few T-rex individuals to survive the post impact winter as a dead clade walking (if the UCMP specimens are indeed early Paleocene in age), and if anyone on the forum had heard about these particular UCMP specimens before?

[Joseph Fossil]

I know this topic might be a little bit of an unusual one to bring up. But this is something I've only just heard about and for two reputable institutions and databases (the University of California Museum of Paleontology and IDiGBiO (Integrated Digitized Biocollections)) to make such a bold claim for the age of their specimens, I do believe this does merits discussion.

 

If the two are correct, it would mean the first confirmed specimens belonging to a "Dead Clade Walking" Non-Avian Dinosaur have been discovered and would have enormous implications for the study of earliest Paleocene ecosystems.

[Joseph Fossil]

I also don't blame anyone here for being skeptical of the veracity of these specimens ages (I know I am). But it's still worthwhile investigating the true age of these specimens!!!

[Joseph Fossil]

Update: Was able to contact the scientist who initially identified the UCMP fossils as belonging to Tyrannosaurids in 1981. He thinks they are likely reworked. He points out some scientists like Fassett do support the idea some non-avian dinosaurs survived into the earliest Paleocene as "dead clade walking" but there are flaws in his studies. Debate on topic still continues.

[TriVeratops]

That matches what I’ve read about the current state of evidence for non-avian dinosaur survival into the paleocene. I think about this too. It’s hard to imagine that a few didn’t make it through, but the evidence to support it seems debatable at best.

 

A few weeks ago I saw a youtube video (yeah, yeah, I know) that cited a discovery of multiple hadrosaur bones from the Paleocene that were postulated to be from a single individual. If they were from a single animal, this would argue against reworking. But I haven’t seen any studies of this alleged discovery and I feel that if the evidence were reliable, it would be better known.

[Joseph Fossil]

29 minutes ago, TriVeratops said:

That matches what I’ve read about the current state of evidence for non-avian dinosaur survival into the paleocene. I think about this too. It’s hard to imagine that a few didn’t make it through, but the evidence to support it seems debatable at best.

 

A few weeks ago I saw a youtube video (yeah, yeah, I know) that cited a discovery of multiple hadrosaur bones from the Paleocene that were postulated to be from a single individual. If they were from a single animal, this would argue against reworking. But I haven’t seen any studies of this alleged discovery and I feel that if the evidence were reliable, it would be better known.

 

@TriVeratops Your absolutely correct and I appreciate your response. There were so many dinosaur species of so many varying sizes during the Maastrichtian Cretaceous that there's a decent chance at least some (by mathematics alone) could have survived the astroid impact and the 15 year winter. But I also do agree any that did likely didn't last long afterwards and at best could've lasted between 10 and 1,000 years (maybe 33,000 if one is especially generous) after impact. This is definitely not the million or so years as Fassett proposed with the San Juan Basin Hadrosaur specimens which, despite their remarkable condition, are likely reworked. All surviving non-avian dinosaurs that would have made it into the Danian would have been "dead clade walking"...the last of a great dynasty living on borrowed time. 

 

As for the short update I gave earlier, I want to actually clarify the scientist didn't say the specimens I listed weren't Danian in age....just that he couldn't confirm it for certain and currently no other definitive non-avian dinosaur specimens are known from the Danian, Paleocene.

 

The question how long the non-avian dinosaurs lasted after the astroid impact 66 million years ago is probably amongst the greatest paleontological questions yet to be answered. One we likely all think about with wonder and curiosity from time to time. Only confirmed specimens that can be said with absolute certainty are not reworked from Cretaceous formations into earliest Paleocene formations could answer this question. For now, we keep on researching as we always do to solve this question, other paleontological questions, and to learn more about the awesome ecosystems of our planet past and present. This includes those of the Maastrichtian stage of the Cretaceous period 66 Million Years ago in North America and Globally.

[Joseph Fossil]

+ Additional Tyrannosaurus Maastricthian/earliest Paleocene specimen for this topic:

 

Unnamed Tyrannosaurus sp. 

UCMP = University of California Museum of Paleontology

Specimen UCMP: 187215
(Field No: 87DLL7-20-4)
Collected July 20, 1987
McCone County, Montana, U.S.
Tedrow Quarry D
Upper section, Hell Creek Formation

https://ucmpdb.berkeley.edu/cgi/ucmp_query2?admin=&query_src=ucmp_index&table=ucmp2&spec_id=V187215&one=T