Shark tooth discolouration

[Mike from North Queensland]

Ever now and then while looking through matrix for small finds I get a discoloured / degraded shark tooth.

this preservation is actually quite rare in the quarry

My theory is that this is caused by the shark swallowing the tooth as it is shed when eating.

Then the sharks stomach acids start to eat into the enamel causing the damage.

The layer I get the teeth out of was laid down in the cretaceous and has not been reworked since then being a single thin undulating layer in a quarry.

I do find the occasional small bit of bone in a similar condition but not very often, hence the digested theory.

These teeth are found by digging down to a specific layer so the discolouration is not caused by surface bleaching.

thoughts or any other theories welcome as these are a bit of an enigma.

Tooth on the left is normal preservation and the white / black tooth on the right is the discoloured one.

These have been removed from the matrix by softening the matrix with tap water and a little mechanical scratching only.

 

Mike D'Arcy

[Doctor Mud]

Your theory sounds reasonable to me.

 

The tooth on the right looks acid etched to me. Reminds me of teeth I extracted when I messed up the acid extraction one time and the acid started to etch the enamel.

 

[Past Hunter]

I have found several teeth in the same condition. Someone at the Aurora Fossil Museum told me that is what happens when the tooth was digested also.

 I have not verified that with any other source though.

[Al Dente]

Digestion is a possibility. When I find a few teeth that are much lighter (both in weight and color) than most of the other teeth I assume that the teeth have been leached of minerals. Usually happens when the tooth was close to the surface for a long period.

[Plax]

A single layer with abundant teeth sounds like a lag deposit of some sort. Transgressive lags often incorporate resistant clasts such as sharks teeth from the existing sediment and previous sedimentation events. Even winnowing because of shoaling will time average resistant clasts. Very little time may have elapsed between the original clast placement and the concentration in the lag so the same teeth may be variously preserved. I can believe the tooth in question is acid etched but the usual variation in tooth preservation is the result of variable dissolution of fossils by ground water or abrasion/dissolution from reworking in lag deposits. It would be interesting to see if aquarists notice such things in the bottom of shark tanks. Your tooth definitely looks acid etched.