Why no Ptychodus in NJ?

[Parthicus]

Teeth of the shell-crushing shark Ptychodus sp. are fairly common in the Late Cretaceous deposits of Texas and are also found in Alabama and Kansas (and maybe other states).  However, Ptychodus seems to be completely absent from the Late Cretaceous deposits of New Jersey.  Why is this?  

 

One explanation I can think of is differences in age- the Late Cretaceous formations at Big Brook and other famous NJ sites are Campanian or Maastrichtian, while my understanding is that the Late Cretaceous deposits of Texas and Kansas are a bit earlier.  

So perhaps Ptychodus became extinct after the Texas/Kansas/etc. formations were deposited, and just before the New Jersey formations?

 

 Or was there some subtle difference in the environment between those other sites and New Jersey?  All theories are welcome; theories solidly backed by fact, or that have been published by professionals, even more so.  Thanks.

[LSCHNELLE]

Parthicus:  I can check into it more.  But, @erose has hunted shark's teeth in both New Jersey and Texas and he may have a more detailed answer.  My best guess is that you are correct about the age difference being a big factor. The last surviving Ptychodus species per Shawn Hamm's NMMNH Bulletin 81 were P. mortoni in the late Santonian and P. polygyrus in the early Campanian.  Both species were likely  becoming rarer at those times due to changes in climate, increased competition with other predators, and the lowering of sea levels over the current North American continent. Certainly, you theoretically could find a Ptychodus fossil there - because New Jersey was part of the Gulf and Atlantic Coast subprovince in the Cretaceous.  The closest Ptychodus in records found nearest you are in Alabama. 

[siteseer]

9 hours ago, Parthicus said:

Teeth of the shell-crushing shark Ptychodus sp. are fairly common in the Late Cretaceous deposits of Texas and are also found in Alabama and Kansas (and maybe other states).  However, Ptychodus seems to be completely absent from the Late Cretaceous deposits of New Jersey.  Why is this?  One explanation I can think of is differences in age- the Late Cretaceous formations at Big Brook and other famous NJ sites are Campanian or Maastrichtian, while my understanding is that the Late Cretaceous deposits of Texas and Kansas are a bit earlier.  So perhaps Ptychodus became extinct after the Texas/Kansas/etc. formations were deposited, and just before the New Jersey formations?  Or was there some subtle difference in the environment between those other sites and New Jersey?  All theories are welcome; theories solidly backed by fact, or that have been published by professionals, even more so.  Thanks.

 

Oh yeah, you can find Ptychodus teeth in New Mexico, Colorado, Montana, and South Dakota as well.  I might have one from Oklahoma too.  I've seen them from England, France, eastern Europe, and Japan as well.

 

Ptychodus was largely gone by the late Santonian - just the rare teeth of one or two species are found in the Campanian.  Most NJ collectors go to Big Brook or Willow Brook and the teeth from there are from late Campanian-Maastrichtian formations.  There are Santonian-age rocks (Magothy Formation) in NJ but I've never seen teeth from them.

 

Cretoxyrhina is another shark genus you don't find in the NJ sites.  Cretoxyrhina also survived into the Campanian but its teeth are rare in rocks of that age.  In fact, Cretoxyrhina appears to have reached its largest size in the time represented by the lower half of the Niobrara Chalk (early Santonian).  Teeth found in the upper half (mid-late Santonian to early Campanian) become smaller and more uncommon as you sample higher in the Chalk.  

 

You should consult Hamm's article in any case.

[erose]

14 hours ago, LSCHNELLE said:

Parthicus:  I can check into it more.  But, @erose has hunted shark's teeth in both New Jersey and Texas and he may have a more detailed answer.  My best guess is that you are correct about the age difference being a big factor. The last surviving Ptychodus species per Shawn Hamm's NMMNH Bulletin 81 were P. mortoni in the late Santonian and P. polygyrus in the early Campanian.  Both species were likely  becoming rarer at those times due to changes in climate, increased competition with other predators, and the lowering of sea levels over the current North American continent. Certainly, you theoretically could find a Ptychodus fossil there - because New Jersey was part of the Gulf and Atlantic Coast subprovince in the Cretaceous.  The closest Ptychodus in records found nearest you are in Alabama. 

Yes, I also think it is most likely a difference in the ages represented.  But there would also have been a large difference in the environments.  Texas deposits are from the relatively shallow central north American seaway and were mostly carbonaceous.  Where NJ and the east coast deposits were on a deeper continental shelf and tend to be made up of more silty clastics.   I don't know much about the European deposits.  Ptychodus may have preferred shallow seas rich in shellfish.