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bthemoose

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I acquired the tooth below a little over a year ago along with some Cretodus crassidens teeth from a Texas collector. They're from a Dallas County, Texas, site that exposes a buffer zone between the Eagle Ford and Woodbine Formations (Cenomanian-Turonian). All of the teeth were identified to me as Cretodus, and that appears to be correct for the others, but I'm pretty sure the ID on this one is incorrect. On further examination, it appears to be a cardabiodontid, though I'm not sure whether Dwardius or Cardabiodon. The slant length is just under 39 mm.

 

@ThePhysicist @siteseer, you helped ID a previous Cardabiodon tooth that I picked up from Kansas--any thoughts on this one? @MikaelS if you see this, your expertise would of course also be much appreciated. Thanks!

 

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You're right, this is definitely not Cretodus (side note, the other Cretodus teeth are probably not C. crassidens since they differ from the type so much. They also don't compare well with the recently described C. houghtonorum, and C. semiplicatus; my amateur guess is they're an undescribed sepcies).

 

To my knowledge, no one has found a North American Dwardius, so this is most likely Cardabiodon sp. Dr. Siversson is the expert so I would defer to his judgement.

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"Argumentation cannot suffice for the discovery of new work, since the subtlety of Nature is greater many times than the subtlety of argument." - Carl Sagan

"I was born not knowing and have had only a little time to change that here and there." - Richard Feynman

 

Collections: Hell Creek Microsite | Hell Creek/Lance | Dinosaurs | Sharks | SquamatesPost Oak Creek | North Sulphur RiverLee Creek | Aguja | Permian | Devonian | Triassic | Harding Sandstone

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2 hours ago, ThePhysicist said:

You're right, this is definitely not Cretodus (side note, the other Cretodus teeth are probably not C. crassidens since they differ from the type so much. They also don't compare well with the recently described C. houghtonorum, and C. semiplicatus; my amateur guess is they're an undescribed sepcies).

 

To my knowledge, no one has found a North American Dwardius, so this is most likely Cardabiodon sp. Dr. Siversson is the expert so I would defer to his judgement.


That’s helpful to know that Dwardius possibly hasn’t been found in North America!
 

Re: Cretodus, are you saying that the teeth found in Texas generally seem to be from an undescribed species? Here are some photos of the ones that I acquired alongside the likely Cardabiodon tooth (slant lengths are 49, 43, and 38 mm respectively):

 

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2 hours ago, bthemoose said:

Re: Cretodus, are you saying that the teeth found in Texas generally seem to be from an undescribed species? Here are some photos of the ones that I acquired alongside the likely Cardabiodon tooth (slant lengths are 49, 43, and 38 mm respectively):

 

Not all teeth in Texas may be undescribed, but the gracile ones (like yours) could be. C. crassidens has huge teeth with broad crowns and weak basal ridges:

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Amalfitano et al. (2022)

 

It may be present in TX, judging by this truly awesome tooth found by @sharko69 :wub:

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C. houghtonorum has recently been described from KS as a more gracile form. "Teeth of the gigantea/houghtonorum-grade Cretodus also have a gracile principal cusp, but their root lobes may be long (C. gigantea) or short (C. houghtonorum) and the crown base exhibit weak costulae."

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^ Shimada & Everhart (2019)

 

The authors of the previous paper also formed a 3rd "category" of Cretodus: "Teeth of the longiplicatus/semiplicatus-grade Cretodus are characterized by having a gracile principal cusp and root lobes and strong costulae along the crown base."

 

So clearly these Texan gracile teeth are either gigantea/houghtonorum-grade or longiplicatus/semiplicatus-grade. I don't understand their categorization well enough right now to place these teeth more precisely. I would doubt them being C. houghtonorum since I've yet to see a double cusplet'ed Texan Cretodus, and they don't look a lot like C. semiplicatus. That leaves us with a couple of more known species to investigate, and I'm still trying to learn about those remaining. I'm sticking with labeling mine as Cretodus sp. for now. 

"Argumentation cannot suffice for the discovery of new work, since the subtlety of Nature is greater many times than the subtlety of argument." - Carl Sagan

"I was born not knowing and have had only a little time to change that here and there." - Richard Feynman

 

Collections: Hell Creek Microsite | Hell Creek/Lance | Dinosaurs | Sharks | SquamatesPost Oak Creek | North Sulphur RiverLee Creek | Aguja | Permian | Devonian | Triassic | Harding Sandstone

Instagram: @thephysicist_tff

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Thanks for the great info and summary, @ThePhysicist! I actually have two potential Cretodus teeth that are likely from Texas and that have double cusplets. I got both of these in a group of teeth from the estate of a Dallas area collector. I believe the teeth were all or mostly collected in northern Texas but unfortunately none of them came with geographic or stratigraphic data.

 

The first is one that @siteseer ID'ed a while back as a potential Cretodus intermediate tooth. It measures just over 17 mm on the slant. The second tooth is a partial and measures 24 mm.

 

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5 hours ago, bthemoose said:

Thanks for the great info and summary, @ThePhysicist! I actually have two potential Cretodus teeth that are likely from Texas and that have double cusplets. I got both of these in a group of teeth from the estate of a Dallas area collector. I believe the teeth were all or mostly collected in northern Texas but unfortunately none of them came with geographic or stratigraphic data.

 

The first is one that @siteseer ID'ed a while back as a potential Cretodus intermediate tooth. It measures just over 17 mm on the slant. The second tooth is a partial and measures 24 mm.

Interesting teeth, wish we had better provenance. I would lean towards the first being Protolamna, considering how narrow the main cusp is compared to the root. Cretodus symphyseals seem to have a thicker cusp, but there could of course be some variation between species and individuals. The right image is one I'm very sure is a Cretodus symphyseal from POC found by @Caaaleb (I haven't seen any definite Protolamna from POC). They are difficult to distinguish for sure.

 

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Compare to Protolamna:

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^ Welton & Farish

 

The second tooth is interesting, could indeed be a "houghtonorum-grade" Cretodus, could be a pathology. Thanks for showing! All your teeth are just great btw. 

 

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"Argumentation cannot suffice for the discovery of new work, since the subtlety of Nature is greater many times than the subtlety of argument." - Carl Sagan

"I was born not knowing and have had only a little time to change that here and there." - Richard Feynman

 

Collections: Hell Creek Microsite | Hell Creek/Lance | Dinosaurs | Sharks | SquamatesPost Oak Creek | North Sulphur RiverLee Creek | Aguja | Permian | Devonian | Triassic | Harding Sandstone

Instagram: @thephysicist_tff

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I think that first tooth is a Cardabiodon.  I haven't seen enough Dwardius teeth to really have a solid understanding of the genus.

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  • 5 weeks later...
On 7/7/2022 at 5:44 AM, bthemoose said:

I acquired the tooth below a little over a year ago along with some Cretodus crassidens teeth from a Texas collector. They're from a Dallas County, Texas, site that exposes a buffer zone between the Eagle Ford and Woodbine Formations (Cenomanian-Turonian). All of the teeth were identified to me as Cretodus, and that appears to be correct for the others, but I'm pretty sure the ID on this one is incorrect. On further examination, it appears to be a cardabiodontid, though I'm not sure whether Dwardius or Cardabiodon. The slant length is just under 39 mm.

 

@ThePhysicist @siteseer, you helped ID a previous Cardabiodon tooth that I picked up from Kansas--any thoughts on this one? @MikaelS if you see this, your expertise would of course also be much appreciated. Thanks!

 

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I have seen possible Dwardius teeth from the Cenomanian/Turonian of Texas but not further north, within the WIS. In general Cardabiodon teeth have a noticeably convex labial side whereas it is flatter in Dwardius. Another difference enabling separation  between C. venator and coeval Dwardius is the development of the labial foramina along the root/crown boundary. Dwardius teeth are similar to the older C. ricki in this regard (see Siverson & Lindgren 2005). Associated dentitions with vertebrae are very easy to assign to either Dwardius or Cardabiodon as the former has enlarged anterior teeth whereas Cardabiodon does not. The tallest anterior teeth in Cardabiodon are about 40% of the maximum vertebral diameter whereas in Dwardius they are about 60% (undescribed specimen). If you have a homogeneous monospecific collection of Dwardius teeth, the anteriors will be about 50% taller than the tallest laterals whereas in Cardabiodon they will be the same height (see Siverson, 1999). So returning to this particular tooth it resembles Dwardius but I would like to see a sample of teeth rather than just a single one and good images of cleaned up teeth with the labial side photographed after coating with ammonium chloride. If the sample has laterals about as tall as the anteriors then that would indicate Cardabiodon. The largest Dwardius vertebrae I have seen are about 50mm in diameter (undescribed material from Poland and Western Australia) whereas Cardabiodon vertebrae max out around 100mm. Dwardius was a large-toothed taxon (like a mako) whereas Cardabiodon was a much larger type of shark but not large-toothed in relative terms.

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I should add that Cardabiodon venator does occur in the Turonian of Texas (Kamp Ranch Limestone) but it is possible that we have Dwardius there as well (not necessarily in the same unit though).

 

3 hours ago, MikaelS said:

Dwardius was a large-toothed taxon (like a mako) whereas Cardabiodon was a much larger type of shark but not large-toothed in relative terms.

To clarify; by 'large-toothed' I am referring to the anterior tooth-files. Other 'large-toothed' taxa include eg Cretoxyrhina.

 

In a couple of years time I hope to have time to submit a description of the paratype dentition of Dwardius woodwardi along with a 'very minor' revision of the dentition of Cardabiodon ricki (we have collected more teeth of the holotype dentition so its more complete with some of the gaps filled).

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Thank you so much for this detailed explanation, @MikaelS!
 

I wish I had other potential Dwardius/Cardabiodon teeth from this site to enable more analysis—perhaps in the future.

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5 minutes ago, MikaelS said:

In a couple of years time I hope to have time to submit a description of the paratype dentition of Dwardius woodwardi along with a 'very minor' revision of the dentition of Cardabiodon ricki (we have collected more teeth of the holotype dentition so its more complete with some of the gaps filled).

 

I know many of us will look forward to reading that paper! Thanks again for providing all of your thoughts here.

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