Modern Shark Teeth

[jbstedman]

It strikes me that, despite the large number of teeth that a shark loses in its lifetime, I don't find modern shark teeth washed ashore in areas where there are living sharks. Is the modern time frame much too short, compared to the fossil record, for a walk along the beach to turn up those white modern teeth? Or, have I just not been looking hard enough or in the right places?

I'd love to acquire some but don't want to contribute, even in any small way, to the destruction of current shark populations.

[Guest N.AL.hunter]

I have found some modern shark teeth, but only two or three. So you ask a good question. Perhaps the population of sharks in the past was much higher? Let's see if anyone knows the answer.

[jax]

I would think you would find some. not sure how active sharks are up toward Maryland, but you figure off the shores of south Africa and areas in Australia you would find GW teeth. Watch Shark week next week and they might bring it up then

[Gatorman]

Good question, I've often wondered why you dont find more modern shark teeth at the beach or something.

[Sharktoothguy11222]

I know its illegal to hunt for GW's for their teeth and jaws, but why won't someone dredge them up from the seafloor of South Africa or Australia. Surely, that must be somewhat legal*looks for loophole*

As a side note, I will be leaving around 8 tonight to go and take a flight to Lebanon. I will try and pick up some fish fossils while I am there*crosses fngers*

[Sharktoothguy11222]

As for a reason as to why fossil teeth are more plentiful than modern ones. They aren't.

Part of North America was once shallow sea that contained all sorts of marine life, including sharks. As these seas receded, the sharks left their legacy behind them. And now, those fossils, exposed from carious formations, are those that you find. You find remnants of a once shallow sea, that is now on land. If you were t dredge the open ocean, their will most likely be a great deal of teeth down there.

The reason why you don't find modern teeth on beaches, is that, well, why would the teeth even end up on the beaches. Most sharks are pelagic, or open ocean, and when they lose teeth, they sink. Maybe, once the oceans recede in a few million years, the next dominant species of this planet will find and collect them.

[jbstedman]

As for a reason as to why fossil teeth are more plentiful than modern ones. They aren't.

Part of North America was once shallow sea that contained all sorts of marine life, including sharks. As these seas receded, the sharks left their legacy behind them. And now, those fossils, exposed from carious formations, are those that you find. You find remnants of a once shallow sea, that is now on land. If you were t dredge the open ocean, their will most likely be a great deal of teeth down there.

The reason why you don't find modern teeth on beaches, is that, well, why would the teeth even end up on the beaches. Most sharks are pelagic, or open ocean, and when they lose teeth, they sink. Maybe, once the oceans recede in a few million years, the next dominant species of this planet will find and collect them.

I appreciate sharktoothguy11222's response, and I recognized that the changing location of seabeds is at play in what we find. Still, I’d be interested in more discussion of two of his points – (1) most sharks are pelagic and (2) modern teeth outnumber fossil teeth.

I haven’t been able to find any definitive sources that tell me that most sharks are pelagic. (I assume that would mean they spend most of their time in the open ocean.) That may be the case, but I do know that there is a great diversity of sharks found in the littoral area of the ocean which is the shallow coastline, not the areas considered pelagic. Sharks often found in the littoral areas include nurse, spiny dogfish, sand tigers, gray reef, and other types of sharks. My understanding is that even deep ocean going sharks can be found in shallow waters at different places and different times. So, the prospect of many modern shark teeth being lost in littoral areas seems real to me. Won’t storms and wave action bring some of those teeth ashore? Other postings in this thread show that they do. So, I'll continue to look for them.

The second point about the number of teeth is intriguing. I assume that he's right. Is there any way to quantify this? At a minimum, despite the very small percentage of shark teeth that fossilize (how small a percentage?), we're talking about many millions of years of sharks and prolific tooth loss. The number of fossilized teeth has to be huge, even for all of the forces conspiring against them.

[Auspex]

I suspect that the survival rate of shark's teeth is proportional to the rapidity of their entombment. Teeth lost in the littoral environment, if not buried, might well wash up on the beach eventually if they survive the high-energy trip. If they are entombed, they will not be subjected to the forces that can destroy them, but will only be found by us air-breathers when the sediment in which they rest is exposed by either falling sea level or rising landmass.

[Guest N.AL.hunter]

As for modern teeth sinking into the depths, if my memory serves me correctly, in my college oceanography class, I learned something about the sinking of bone/shell material. There is a certain maximum depth where items made from calcium can sink to without automatically dissolving on the way down. Therefore, calcium stuff dissolves more rapidly the deeper it goes, or something like that, and very little makes it to the very deep ocean areas. Perhaps someone here knows more of what I am remembering and can elaborate.

[siteseer]

Every once in a while, I go back through old threads to see if can find some previously unseen bit of information, especially threads started and contributed to before I joined the forum (or even after - stuff I missed on days I was busy with work and/or on the road). The member who asked the original question is no longer active but I think it is something to talk about - why we don't see modern shark teeth washing up on beaches.

I know part of the answer involves local ocean currents and local ocean environments. Currents can sweep areas of the bottom clean of objects like shark teeth. That's why you won't necessarily find shark teeth where sharks frequent. Those ojects would, however, accumulate somewhere though it might be miles away - some low spot on the bottom among other objects (sometimes buried rather quickly - fossils of the future) or next to some obstacle in the path of a current.

I'm not sure if shark teeth would dissolve with some relation to depth. I can see how it's possible that water chemistry might vary to some degree from area to area and perhaps weaken a tooth. Some mollusk might drill into the root and the tooth might fragment further from that point. Most teeth would wear down from being knocked around along the bottom for some distance, getting naturally sanded down over time. They might not disintegrate completely but become so worn down that they become unrecognizable or indiscernible from surrounding rocks and debris.

It strikes me that, despite the large number of teeth that a shark loses in its lifetime, I don't find modern shark teeth washed ashore in areas where there are living sharks. Is the modern time frame much too short, compared to the fossil record, for a walk along the beach to turn up those white modern teeth? Or, have I just not been looking hard enough or in the right places?

I'd love to acquire some but don't want to contribute, even in any small way, to the destruction of current shark populations.

[Hieronymus]

Some good points you've made there siteseer. I've been wondering about the same topic as well and this is what I thought:

Most people swim in the littoral zone of the oceans or seas. Material that washes ashore is mostly

a ) debris from creatures that live close to shore/littoral

b ) debris that drifts easily (like wood, plastic, sea weed,...) which can travel larger distances.

Most sharks however are either benthic and sublittoral or pelagic (and depending on the species, they might be bottom dwellers, so they're benthic as well).

Anyway, I think it's hard for a large amount of remains of sublittoral or pelagic creatures to wash to the shoreline, especially a large enough amount to be found quite frequently and that does not immediately get covered by sand. As you said, there would have to be an ideal set of circumstances: current, depth, location of tooth loss,... I think it's easier for material that is deposited offshore to collect on the seafloor in for example benthic areas -where species diversity is large), than it would wash a large distance uphill on a beach (littoral, where shark specie diversity is lower).

That being said, I think it's easier for someone to find a dead shark on the shoreline (since it might float during a certain period while decaying) since that dead shark travels distance better in the upper water column, than a loose tooth would on the bottom of the sea (more drag,...).

Therefore, I think your luck of finding a dead shark (and hence a complete jaw with teeth) is larger than that of finding a single recent tooth on the shoreline.

I know I've seen Scyliorhinus, Squalus and rays dead on the shoreline. Of course, these species already have a littoral habitat and occur in shallow, coastal waters. Took a dead Scyliorhinus home once, to clean out its jaw. It was a hot day and I still had to travel 110 miles by car. It smelled bad for quite a while

Edited July 22, 2013 by Hieronymus

[Al Dente]

I'm not sure if shark teeth would dissolve with some relation to depth.

There is something called the "carbonate compensation depth" where calcium carbonate will dissolve below a certain depth. It is explained here: http://en.wikipedia.org/wiki/Carbonate_compensation_depth

I don't know what effect this would have on teeth, I've heard bone gets dissolved so I would image the roots of shark teeth would too.

I've found sand bar shark (C. plumbeus) teeth on the beach in association with vertebral centra. This would be an individual that washed ashore and rotted. I know of one diver that has found several modern sand tiger (C. taurus) teeth on the bottom near a wreck where sand tiger sharks are frequently seen.

The depositional environment where fossil shark teeth are found is very different from modern beaches. Fossil teeth are commonly found in area where sedimentation is minimal or where sediment has been winnowed away concentrating the teeth.