Oddities from the Hell Creek formation

[Jared C]

Recently, I had the special privilege of exploring some South Dakota Hell Creek outcrops with a friend who has access to land. Lots of cool things were found and a thorough trip report is coming soon. This is an alien fauna to me, so hoping some of y'all have can point me into the right direction with these mysteries.

 

1). From what I've seen, I'm leaning into Pachycephalosaurus tooth, but I know those are rare finds so I don't want to jump the gun. 

 

 

2) No clue what this vert is 

 

 

 

3.) This tooth has me leaning in to fish, but of what type I'm not sure. It is bicarinate.

 

 

 

4.) Odd little (toebone?). Is this diagnostic enough for any ID?

 

 

 

5.) This jaw reminds me of some of the Texas cretaceous fish jaws I'm used to, but I do not know if that's a fair comparison.

 

 

 

6.) These jaws were surprisingly common. Croc? Champsosaurus? What would be the difference?

 

 

 

7.) Lastly - though realistically these might be the edges of turtle shells, the perceived vascularity of these pieces and rounded edges remind me of tiny ceratopsian frills. Is there a chance these are edge pieces of a Leptoceratops frill? Baby Triceratops? Any input welcome

Edited July 8 by Jared C

[debivort]

I think 3 is croc.

[Mikrogeophagus]

3) Also resembles fish to me

 

4) looks like this from the Duck Creek:

 

No idea what it is, but my best guess was turtle vert at the time. The texture of your specimen's cortical bone might be a little turtley too?

[Jared C]

29 minutes ago, debivort said:

I think 3 is croc.

The pinch half way down is throwing me off. Is that typical of croc?

[Jared C]

10 minutes ago, Mikrogeophagus said:

3) Also resembles fish to me

 

4) looks like this from the Duck Creek:

 

No idea what it is, but my best guess was turtle vert at the time. The texture of your specimen's cortical bone might be a little turtley too?

I should’ve included that bone 4 is well concave on the side I didn’t picture, so I easily see vert now

[debivort]

14 minutes ago, Jared C said:

The pinch half way down is throwing me off. Is that typical of croc?

I've only collected HC once, but my guide said similar teeth were croc.
Compare: https://prehistoricfossils.com/product/champsosaurus-reptile-tooth-15

 

edit: here's another for comparison:

Edited July 8 by debivort

[Mikrogeophagus]

I did a little digging cuz I thought those teeth look so strongly Amiid I must be going crazy. Looks like they are from the Amiid Melvius thomasi

[PaleoNoel]

1 hour ago, Jared C said:

Recently, I had the special privilege of exploring some South Dakota Hell Creek outcrops with a friend who has access to land. Lots of cool things were found and a thorough trip report is coming soon. This is an alien fauna to me, so hoping some of y'all have can point me into the right direction with these mysteries.

 

1). From what I've seen, I'm leaning into Pachycephalosaurus tooth, but I know those are rare finds so I don't want to jump the gun.

 

2) No clue what this vert is 

 

3.) This tooth has me leaning in to fish, but of what type I'm not sure. It is bicarinate.

 

4.) Odd little (toebone?). Is this diagnostic enough for any ID?

 

5.) This jaw reminds me of some of the Texas cretaceous fish jaws I'm used to, but I do not know if that's a fair comparison.

 

6.) These jaws were surprisingly common. Croc? Champsosaurus? What would be the difference?

 

7.) Lastly - though realistically these might be the edges of turtle shells, the perceived vascularity of these pieces and rounded edges remind me of tiny ceratopsian frills. Is there a chance these are edge pieces of a Leptoceratops frill? Baby Triceratops? Any input welcome

1. I believe is more likely to be ceratopsid

2. Croc caudal vert.

3. Juvenile croc tooth.

4. Turtle vert?

5. Seems like fish, could be bowfin, but not sure.

6. Jaw A seems to be croc, B could be large fish, but may also be reptile.

7. I agree, could be young ceratopsian.

[ClearLake]

As a couple others have suggested, #4 looks like a turtle vert. to me.

[Al Dente]

6 hours ago, Jared C said:

3.) This tooth has me leaning in to fish, but of what type I'm not sure. It is bicarinate.

Melvius?

[Jared C]

@ThePhysicist curious if you have any thoughts? 

[Frightmares]

On 7/7/2024 at 11:22 PM, PaleoNoel said:

1. I believe is more likely to be ceratopsid

I agree

[Jared C]

@PaleoNoel @Frightmares what are the characteristics that point to ceratopsian?

 

I just have trouble seeing it compared to another juvenile ceratopsian tooth - unless i'm wrong about the other one being ceratopsian 

 

 

 

Another difference is in the rear view, where the white tooth has exposed enamel while the juvenile ceratopsian tooth is covered by the root

Edited July 9 by Jared C

[ThePhysicist]

Seems like the wisdom of the crowd has got you the answers! 

 

On 7/7/2024 at 8:28 PM, debivort said:

I've only collected HC once, but my guide said similar teeth were croc.
Compare: https://prehistoricfossils.com/product/champsosaurus-reptile-tooth-15

 

edit: here's another for comparison:

These are the amiid Melvius as @Mikrogeophagus suggested. They're commonly called Champsosaurus by fossil sellers for some reason (see real champ teeth here).

 

1. juvenile ceratopsid dentary tooth - note in pachycephalosaurids the crown is distinct from the root, the crown width is larger. (Note, you also can't identify HCF pachycephalosaurids to the genus level as there are many genera present with similar teeth.)

3. crocodyliform tooth - they are bicarinate with constriction at the base of the crown being more prominent in juveniles, and labio-lingually compressed being a juvenile feature too

6. A crocodyliform, B Champsosaurus - note the dentine infolding features, they look like "stars" in the sockets (sorry best image I could find atm):

^ https://carnegiemnh.org/mesozoic-monthly-champsosaurus/

[debivort]

59 minutes ago, ThePhysicist said:

These are the amiid Melvius as @Mikrogeophagus suggested. They're commonly called Champsosaurus by fossil sellers for some reason (see real champ teeth here).

So, do I understand correctly that the comparison images I linked are actually Melvius, but erroneously labeled by the sellers as Champ/croc — whereas OP's #3 is indeed Champ/croc?

[ThePhysicist]

1 hour ago, debivort said:

So, do I understand correctly that the comparison images I linked are actually Melvius, but erroneously labeled by the sellers as Champ/croc — whereas OP's #3 is indeed Champ/croc?

Correct - except #3 is a crocodyliform, for certain not Champsosaurus. Champsosaurus is not closely related to croc's, it only convergently evolved to look like them.

[Mikrogeophagus]

Very interesting! I underestimated the diversity of croc teeth which is never a good idea

[debivort]

9 hours ago, ThePhysicist said:

Correct - except #3 is a crocodyliform, for certain not Champsosaurus. Champsosaurus is not closely related to croc's, it only convergently evolved to look like them.

Amazing. Thanks for your expertise. Do you have any guidance on how to distinguish Melvius from crocodyliform (non-Champ) teeth? I would reassess my finds with this info.

[jpc]

If I had these in my collection I would label them as such:

1.   Leptoceratops tooth... or maybe a very young larger ceratopsian, but the (missing) root looks possibly single rooted.

2.  Mammal caudal vert... good find

3.  possibly Melvius

4.  vert of a very young turtle?... note the texture seen on the side views.  

5. a jaw  : )

6.  Not sure what champs jaws look like, but Melvius has the radiating patterns at the tooth base like I see in at least one tooth position here. 

7.  yeah, possible youthful frill pieces, or pieces of ankylosaur osteoderm.  

[Anomotodon]

Cool finds!! I’d love to visit hell creek myself someday.

 

I agree with the comments above. Champsosaurus jaws are easy to distinguish from crocs - crocs had thecodont dentition, meaning their teeth were placed in sockets,

while champsosaurs I think were acrodont, meaning their teeth were fused with the top of the jaw bone, hence the circular markings. A third type of tooth placentation is pleurodonty, where teeth are attached to the side of the jaw - that’s the case in squamates.

 

As for your jaw #5, I think it might be a posterior part of the jaw from an aspidorhynchid fish, like Belonostomus which is known from Hell Creek.

[ThePhysicist]

15 hours ago, debivort said:

Amazing. Thanks for your expertise. Do you have any guidance on how to distinguish Melvius from crocodyliform (non-Champ) teeth? I would reassess my finds with this info.

Melvius teeth are described as being lanceolate (like the head of lances) with sharp, pronounced carinae that proceed the full length of the crown. The enamel is glass-smooth and often translucent. Given they're from fish the tooth implantation means they are not rooted, though more complete teeth may possess finely striated cylindrical basal "collars" (so-described in Wick & Brink 2022). 

 

Here are a few Campanian examples from the Aguja (they're identical in the HCF, I just don't have many good examples):

 

Crocodyliforms when complete will have full roots with a basal cavity where the replacement tooth would be developing. Their enamel is textured. If there any teeth you're not sure about, we can take a look.

 

9 hours ago, jpc said:

1.   Leptoceratops tooth... or maybe a very young larger ceratopsian, but the (missing) root looks possibly single rooted.

I would disagree, every Leptoceratops I've seen has very strong cingula that form a shelf a the base of the crown.

Ryan, Michael & Evans, David & Currie, Philip & Brown, Caleb & Brinkman, Donald. (2012). New leptoceratopsids from the Upper Cretaceous of Alberta, Canada. Cretaceous Research. 35. 69-80. 10.1016/j.cretres.2011.11.018. 

 

vs. a juvenile ceratopsid (image from online seller),

 

 

Suffice to say, you could just call it ceratopsian without being more specific and call it a day.

 

9 hours ago, jpc said:

6.  Not sure what champs jaws look like, but Melvius has the radiating patterns at the tooth base like I see in at least one tooth position here. 

I change my mind, I also now think B could be amiid. The descibers of M. thompsoni describe the aveoli as having crenulated borders. The flat outer surface and foramina look similar too.

 

Laurie J. Bryant (1988) A new genus and species of Amiidae (Holostei; Osteichthyes) from the Late Cretaceous of North America, with comments on the phylogeny of the Amiidae, Journal of Vertebrate Paleontology, 7:4, 349-361, DOI: 10.1080/02724634.1988.10011669