Ptychodus Id Quick Guide

[Tony Eaton 33]

I'm recycling some content from a prior post to cobble together a quick, non technical guide to ID Ptychodus teeth. Many of the pictures below are from CreekCrawler.

A few terms:

1. transverse ridges = the lines going across the tooth
   
2. crown = the abrasive "eating" surface of the tooth
   
3. margin = the area around the crown above the root
   

flat crowned, from oldest to youngest:

Ptychodus decurrens

• low crown with ridges that split (bifurcate) to the end of the marginal area
  

Ptychodus marginalis (polygyrus)

• crown only moderately raised
  
• ridges circle crown at marginal area and margin has a circular "finger print" pattern unlike decurrens
  

Ptychodus latissimus

• few, thick, "sharp" ridges on the low crown
  
• little marginal area
  

Ptychodus martini

• very low crown, unlike decurrens and marginalis
  
• the marginal area is rough or non existent and has no discernable pattern
  
• more ridges and generally more rectangular compared to litissimus
  

high crowned, oldest to newest:

Ptychodus anonymus

• small in general
  
• 10+ ridges
  
• rough margin
  
• crown lower than whipplei and more rounded than mammillaris
  

Ptychodus occidentalis

• gently curved high crown at a slight angle to margin unlike mammillaris
  
• 10+ fine ridges
  
• ridges branch into the marginal area unlike anonymous
  

Ptychodus mammillaris

• crown attached at a steep angle to the marginal area unlike occidentalis
  
• ridges are course and crown wider/squarer than anonymous
  
• marginal area has a circular pattern around the crown
  

Ptychodus whipplei

very high crowned, peg like

transverse ridges generally do not extend to the margin

Ptychodus mortoni

• the crown is pointed with ridges running together meeting at a single point at the top of the crown
  

Ptychodus atcoensis (sp.)

• front to back (labial to lengual) median line
  
• thick ridges that form a "chevron" pattern
  
• recenly named by Shawn Hamm, previously Ptychodus sp.
  

Ptychodus rugosus

• most rare Ptychodus at least in Texas, no pictures to post ;-)
  
• transverse ridges are rough and poorly defined, almost giving the ridges a heavily "rusted" outline
  

Orginal post with some other great picks from kknight.

http://www.thefossilforum.com/index.php/topic/14366-ptychodus-occidentalis/

Edited July 29, 2010 by Tony Eaton

[barefootgirl 17]

Thank you so much for this. We should tag this.

[Guest N.AL.hunter]

Great guide. Thanks

[siteseer 822]

That is a nice guide - great photos. The only information I would add would be the formations/sites each of the species is known from.

[JohnJ 2,293]

Good work, Tony and Barry. I once wanted to do something like this for the resident species of Salenia echinoids in Texas. You have assimilated something useful beyond state boundaries. I also agree it would be good to include the formation, age, or period typical for each species....

[Hieronymus 5]

Interesting!

But personally, I don't see many differences (if any) between anonymous and mammillaris.

Can you point the differences out with more detail?

I can't really remember, but don't some authors consider anonymous and mammilaris as nomen dubium, resulting in one species, namely mammillaris? I'm not at home right now so I can't check any sources.

[Tony Eaton 33]

Hieronymus, thanks for the feedback. I enjoy the debate :-)

I have just taken a picture that might be a better diagnostic example. Here is a picture of 2 teeth roughly the same size from the same site (middle Turonian, Kamp Ranch Fm., Denton Co.)

The tooth on the left is mammilaris, the one on the right anonymous. They have more or the same margin design and same ridge count, but the difference is that mammilaris is much more squared off (flat) at the top of the crown.

I have several teeth that are less clear cut and seem to be variations between mammilaris, anonymous, and even a bit like mortoni or atcoensis.

The picture of anonymous in my post above includes a tooth, (second tooth on the bottom left) that I might consider mammilaris judging by just that picture. In the pictures I included originally of mammilaris, the tooth on the right has a flat crown, but it is more narrow compared to most "mammilaris" that I've collected and at the angle I picked it is not clear. Here is another view where the flat crown is more obvious.

Unless I saw a naturally associated tooth set that showed morphology of both the flat and rounded crowns I would not agree that anonymous is a nomen dubium (doubtful name).

Edited July 27, 2010 by Tony Eaton

[Tony Eaton 33]

Regarding adding more info, to do it right I'd need to drive to a University Library and get access to some work (namely Shawn Hamm's master's thesis).

I have a number of articles and websites I'll use to ID Ptychodus, but my two "go to" sources:

http://www.texassharks.org/

http://www.dallaspaleo.org/dpsstorepubs.htm (DPS volume 8)

Edited July 27, 2010 by Tony Eaton

[Coco 751]

Hi,

Thanks for this very interesting subject.

But I ask a question : did not Ptychodus have different teeth forms according to their place in the mouth ?

Coco

[Harry Pristis 3,411]

Hi,

Thanks for this very interesting subject.

But I ask a question : did not Ptychodus have different teeth forms according to their place in the mouth ?

Coco

Thank you, 'Coco'. Yes, of course, there are positional variations and individual variations and perhaps variations over time. Those variations make the ID of a single tooth or even a handful of these teeth such a dicey game.

But, it's a game that's entertaining. A few people actually make a living at museums playing this game. And, it keeps some of us collectors out of the juke joints.

[Tony Eaton 33]

Yah, fossil collecting is healthy living provided I ignore any temptation to trespass LOL.

Coco, there is heterodonty in Ptychodus, most notable with symphysials that are sometimes quite odd, but the outer files or posterior teeth can also be tricky. However, these teeth are easy to single out and none are pictured above. Most Ptychodus toothsets I've seen pictured the teeth are very similar to each other, especially the general features of the marginal pattern. The Oceans of Kansas site details a few toothsets. http://www.oceansofkansas.com/Ptychodus.html

[Hieronymus 5]

Hieronymus, thanks for the feedback. I enjoy the debate :-)

I have just taken a picture that might be a better diagnostic example. Here is a picture of 2 teeth roughly the same size from the same site (middle Turonian, Kamp Ranch Fm., Denton Co.)

The tooth on the left is mammilaris, the one on the right anonymous. They have more or the same margin design and same ridge count, but the difference is that mammilaris is much more squared off (flat) at the top of the crown.

I have several teeth that are less clear cut and seem to be variations between mammilaris, anonymous, and even a bit like mortoni or atcoensis.

The picture of anonymous in my post above includes a tooth, (second tooth on the bottom left) that I might consider mammilaris judging by just that picture. In the pictures I included originally of mammilaris, the tooth on the right has a flat crown, but it is more narrow compared to most "mammilaris" that I've collected and at the angle I picked it is not clear. Here is another view where the flat crown is more obvious.

Unless I saw a naturally associated tooth set that showed morphology of both the flat and rounded crowns I would not agree that anonymous is a nomen dubium (doubtful name).

Thank you for the explanation!

I'm going to wrestle trough my literature a little bit more now:-)

[MB 123]

Thankyou, that's a great job

[Coco 751]

Hi,

I like this file ! Thanks for this very interesting link. All your teeth are nice, and it is marvelous to see plate jaws of this shark. Many thanks.

Coco

[siteseer 822]

I'm bumping this great thread because someone just asked about a Ptychodus ID. The additional notes on mammilaris vs. anonymus are a cool bonus. For anyone who has picked up - whether in the field or through trades - a variety of Ptychodus teeth from various sites/ages, this is the guide you hoped existed somewhere.

Jess

Yah, fossil collecting is healthy living provided I ignore any temptation to trespass LOL.

Coco, there is heterodonty in Ptychodus, most notable with symphysials that are sometimes quite odd, but the outer files or posterior teeth can also be tricky. However, these teeth are easy to single out and none are pictured above. Most Ptychodus toothsets I've seen pictured the teeth are very similar to each other, especially the general features of the marginal pattern. The Oceans of Kansas site details a few toothsets. http://www.oceansofkansas.com/Ptychodus.html

Edited September 9, 2013 by siteseer

[truceburner 33]

I recall someone on this forum mentioning a reclassification of Ptychodus teeth was forthcoming. Does anyone know whether this has been published?

[Uncle Siphuncle 2,347]

The closest reference I've seen is Systematic, Stratigraphic, Geographic and Paleocological Distribution of the Late Cretaceous Shark Genus Ptychodus within the Western Interior Seaway, Hamm (2008). I think this was his Masters thesis. I happen to have a hard copy of this 400+ page magnum opus in my library.

[Eddie78 0]

Just want to thank you for posting this. I think I've IDed this as a ptychodus martoni thanks to this guide. Cheers!

[LSCHNELLE 43]

Tony, thanks for your post. My wife found a complete 1.5 cm wide ptychodus in Walnut Creek metropolitan Park in Austin. The ridges are highly bifurcated as you drop from the crown to the margin. A British website pic says that crowns on P. decurrens are generally flat but can be bulbous (with higher ridge?). They also have a decurrens pic that looks more like the tooth she found. Is that your understanding as well? See pics.

[LSCHNELLE 43]

Two more pics.

[siteseer 822]

That tooth has a rather high, more bulbous crown than decurrens (which I still like calling P. decurrens) so I think it's P. occidentalis, which is an uncommon species for its time.

Two more pics.

[Pilobolus 31]

http://www.elasmo.com/refs/pdf/hamm2008-ptychodusMS.pdf

[Tony Eaton 33]

I recall someone on this forum mentioning a reclassification of Ptychodus teeth was forthcoming. Does anyone know whether this has been published?

I'm not too sure as I haven't reviewed the latest work in the last few years.

Paraptychodus washitaensis and Ptychodus rhombodus are two "new" species that need some attention. P. washitaensis is a tiny raisin like tooth from the lower Cretaceous that is rare. P. rhombodus is also a small tooth from the middle Cenomanian but has been lumped in with other species. I'll try to post pics from my collection when I get a chance.

[Tony Eaton 33]

Here are some pics of Ptychodus rhombodus that turn up in the Woodbine / Eagleford contact zones (Middle Cenomanian) in Texas.

Very similar to P. decurrens except for the quick transitioned "speed bump" labial to lengual crown. P. decurrens has a more evenly rounded crown. P. rhombodus is like P. anonymus but occurs earlier (sometimes just feet below) P. anonymus and lacks the more developed marginal area (more elaborately textured sides) of P. anonymus. P. rhombodus also has a lower crown compared to P. anonymus although some teeth seem to be "in between". The tooth is named for the rhombic outline which combined with the "speed bump" crown and the "primitive" decurrens like ridge patterns warranted this tooth being designated it's own species (Underwood / Cumbaa 2009). I have collected several additional teeth that seem to be between P. rhombodus and P. anonymous and may simply get lumped in with P. decurrens?

Edited July 3, 2016 by Tony Eaton

[Tony Eaton 33]

A broken Paraptychodus washitaensis from the Duck Creek Fm. lower Cretaceous. This is less than 1cm in length. Note the raisin like appearance of the crown with a more primitive enamel design comparable to Ptychodus decurrens. Also, note how thin the enamel is compared to typical broken Ptychodus teeth. Some tooth positions lack multiple transverse ridges and have a hybodont like pointed crown. Perhaps if this tooth where whole the crown (top) would come to a single point more like other shark teeth?

See recent publications from Shawn Hamm who had named the Genus and Species i.e Hamm 2008.

Edited July 3, 2016 by Tony Eaton