Bull or dusky shark teeth? ID help

[hokietech96]

Hi are these bull shark or dusky shark teeth. How in the world to you tell the difference?  Thanks for any feedback!

[The Jersey Devil]

Bull and dusky are different species in the genus Carcharhinus. It’s hard to tell the species apart.

[hokietech96]

Thanks for the feedback. I guess when I separate the 800+ teeth I put all the Carcharhinus together and not guess what is bull versus dusky. That makes it so much easier on me. Haha

[hemipristis]

4 hours ago, hokietech96 said:

Thanks for the feedback. I guess when I separate the 800+ teeth I put all the Carcharhinus together and not guess what is bull versus dusky. That makes it so much easier on me. Haha

As @The Jersey Devil noted, they're difficult to tell apart.  There are some methods, but they're not foolproof; I'd say 60-70% accurate. I describe them below

 

 Further complicating matters is. the fact that there are a few other species whose teeth also closely resemble huskies and bulls:  Caribbean reef, oceanic white tip, and Galapagos shark.  The latter two are rather rare, but the Caribbean reef shark is common. It resembles a dusky but is usually smaller and usually has a noticeable notch on the distal side of the blade, viewed lingually

 

First question usually is where did you find them?  Duskies dominate from NC northward, while bulls dominate in Florida.

 

A somewhat reliable indicator of distinguishing between the duskies and bulls  is the location of the nutrient pore on the lingual side of the tooth.  Orient the tooth in question with the tip pointed "up", as you have done.  Find the nutrient pore if you can,  In duskies, the pore is located at or above the bulge or thickest part of the root.  In bulls it is generally below, and close to the root base.. But there are a lot of teeth where they are on the thickest part but other characteristics suggest bulls. So this isn't foolproof.  

 

I've zoomed in your photo and found the nutrient pore on 7 of the teeth (below). In all 7, the pore appears to be 'below' the thickest part of the root, suggesting bulls.  With 7 bulls out of 10 teeth, these likely came from Florida.

 

Other, less reliable characteristics:

• Dusky teeth tend to have coarser, irregular serrations, bulls finer and more  uniform
• The tips of Type I dusky teeth (two general tooth styles seem to exist--perhaps gender?) are 'kinked'' distally at an observable angle. This is not present in the Type I anterior A1-A3 teeth, nor the Type II teeth. In bulls, the distal curvature in bull teeth tend to more gently recurved (compare yours with the second photo of identified dusky Type I teeth courtesy of elasmo.com). I've added the Type II dusky teeth as the third photo.

 

I have several hundred of these teeth, and three categories:  

1. Likely dusky
2. Likely bull
3. Can't tell

[hokietech96]

Wow. This is so helpful. So all these teeth are fro FL. I found these 3 in NJ this summer. I first thought they where bull but based on above I’m second guessing

[The Jersey Devil]

10 hours ago, hokietech96 said:

Wow. This is so helpful. So all these teeth are fro FL. I found these 3 in NJ this summer. I first thought they where bull but based on above I’m second guessing

 

That’s really cool. I’ve never seen that many NJ beach teeth before. 

[hokietech96]

I know. I have been crazy lucky.  I found another one today on the beach.