Tooth Id And Question Re: Cutting Edge

[jbstedman]

I have been struck by the vast amount of knowledge that resides within the forum. I was hoping that I might take advantage of that knowledge. Is this what I think it is? I have identified the tooth shown below as a Carcharias reticulata. This tooth’s slant length is 1.5 cm (lingual view on the left, labial on the right). It was found in the surf drop-off deposits at Randle Cliff Beach on the Chesapeake Bay. This is the Calvert Formation. I find sand tigers to be very frustrating teeth since I usually find them too worn to make any reasonable identification. But this one has its cusplets and secondary cusplets so I assumed I could nail this one. A careful look at the tooth reveals what I consider slight striations at the base of the crown on the lingual side. I based my identification on Kent (Fossil Sharks of the Chesapeake Bay Region) who, in part, says that reticulata can be mistaken for Odontaspis winkleri except for the reticulata’s weak striations on lingual face of crown and its nearly complete cutting edge. I originally thought the tooth was winkleri but winkleri is too old – it’s not found in the Calvert Formation.

A follow-up question: I am stumped by the various descriptions (e.g., “incomplete”) of a tooth’s cutting edge. What do they mean and where might I see some examples?

[Northern Sharks]

I have been struck by the vast amount of knowledge that resides within the forum. I was hoping that I might take advantage of that knowledge. Is this what I think it is? I have identified the tooth shown below as a Carcharias reticulata. This tooth’s slant length is 1.5 cm (lingual view on the left, labial on the right). It was found in the surf drop-off deposits at Randle Cliff Beach on the Chesapeake Bay. This is the Calvert Formation. I find sand tigers to be very frustrating teeth since I usually find them too worn to make any reasonable identification. But this one has its cusplets and secondary cusplets so I assumed I could nail this one. A careful look at the tooth reveals what I consider slight striations at the base of the crown on the lingual side. I based my identification on Kent (Fossil Sharks of the Chesapeake Bay Region) who, in part, says that reticulata can be mistaken for Odontaspis winkleri except for the reticulata’s weak striations on lingual face of crown and its nearly complete cutting edge. I originally thought the tooth was winkleri but winkleri is too old – it’s not found in the Calvert Formation.

A follow-up question: I am stumped by the various descriptions (e.g., “incomplete”) of a tooth’s cutting edge. What do they mean and where might I see some examples?

Let me preface this by saying sand-tigers are not a particularly strong point with me. Its easier to say what a species is not than to say what it is. Assuming your ID is correct, Elasmo.com describes this tooth as Odontapsis reticulata aka Carcharias reticulata aka Odontapsis cf. acutissma. The difference in the 2 genus' being Carcharias teeth morph into more of a crushing dentition in the posteriors while Odontapsis does not. I'll have a look tonite and see what I can come up with to confirm your idea. With regards to your second question, I believe an incomplete cutting edge means that the "razor" sharp edge between the lingual and labial sides of the tooth doesn't stay razor sharp the whole length of the blade. Near the root or cusps, the sharp edge fades and there is a rounded edge between the 2 sides. I hope that makes sense. I'll try to get picture of what I mean when I get home tonite.

[Northern Sharks]

I hope this clarifies things a bit. Here are 2 photos: a Striatolamia with an incomplete cutting edge and an Otodus with a complete cutting edge. This is my understanding only, if I'm wrong, please feel free to correct me.

[jbstedman]

Thanks. That helps a great deal in distinguishing among cutting edges.