Why can I only find shark teeth and vertebrae

[FossilizedFanatic]

How come I can find (for example in Antwerp) mostly shark teeth and vertebrae and never another part of a shark?

 

[Ludwigia]

13 minutes ago, FossilizedFanatic said:

How come I can find (for example in Antwerp) mostly shark teeth and vertebrae and never another part of a shark?

 

That's because the rest of the shark is made up of other materials which are much more succeptible to decomposition and erosion and they are usually long gone before teeth and vertebra. The rest can only be preserved under relatively rare and exceptional circumstances.

[FossilizedFanatic]

2 hours ago, Ludwigia said:

That's because the rest of the shark is made up of other materials which are much more succeptible to decomposition and erosion and they are usually long gone before teeth and vertebra. The rest can only be preserved under relatively rare and exceptional circumstances.

Thank you very much!

[digit]

Indeed, sharks and rays (and skates, sawfishes, and chimaeras) belong to the taxonomic class Chondrichthyes (aka cartilaginous fishes). These are different from bony fishes (class Osteichtheys) which have skeletons made of bone tissue instead of cartilage. That is why you'll see a lot more complete fossilized (bony) fishes than sharks. Articulated fossilized sharks and rays are exceedingly rare compared to fishes. In fact, I've heard tell that the most common vertebrate fossils are the fishes preserved (quite exquisitely) in the Green River Formation fond in Colorado, Wyoming, and Utah. The Green River Formation occasionally preserves freshwater skates called Heliobatis radians that have remarkable preservation of the cartilaginous skeleton. I've also seen some articulated shark jaws and spinal columns which are very rare and wonderful specimens. Though made primarily of cartilage, some elements of sharks like the jaws and vertebrae are strengthened by small calcified areas called "tesserae" which give those parts strength without adding much additional weight.

 

It is understandable why shark teeth are preserved as they are (like most teeth) coated in a strong enamel which allows them a good chance at preserving as fossils (more so than even shark vertebrae). Of course any individual shark has a limited number of vertebrae but a continuous supply of teeth throughout its life and so that is another good reason why shark teeth are so much more commonly found than vertebrae.

 

There is another part of sharks and rays that are often found as fossils (though you have to look more carefully for them)--dermal denticles. Shark skin is covered with small tooth-like placoid scales which have a core of dentine covered by a hard enamel-like substance called vitrodentine. These shark dermal denticles are often quite tiny (just a millimeter or two) and you would not generally see them unless you are searching through fine micro-matrix. Here's a post where I added a photograph of some of these shark dermal denticles.:

 

http://www.thefossilforum.com/index.php?/topic/101540-show-us-your-fossils-though-a-macro-lens/&do=findComment&comment=1128065

 

If you search this forum for "ray dermal denticle" you'll find many examples of those larger ossified skin elements being preserved nicely.

 

The fact that generally only teeth are preserved makes fossil shark taxonomy very difficult. Think about how difficult it would be to distinguish between different species of dinosaurs that you see mounted in some of the larger natural history museums if you only had teeth to go by. It's a wonder we know much at all about ancient sharks with the limited remains they've left us as clues.

 

BTW: Welcome to the Forum. Lots of information contained within this site.

 

 

Cheers.

 

-Ken

[siteseer]

9 hours ago, digit said:

Indeed, sharks and rays (and skates, sawfishes, and chimaeras) belong to the taxonomic class Chondrichthyes (aka cartilaginous fishes). These are different from bony fishes (class Osteichtheys) which have skeletons made of bone tissue instead of cartilage. That is why you'll see a lot more complete fossilized (bony) fishes than sharks. Articulated fossilized sharks and rays are exceedingly rare compared to fishes. In fact, I've heard tell that the most common vertebrate fossils are the fishes preserved (quite exquisitely) in the Green River Formation fond in Colorado, Wyoming, and Utah. The Green River Formation occasionally preserves freshwater skates called Heliobatis radians that have remarkable preservation of the cartilaginous skeleton. I've also seen some articulated shark jaws and spinal columns which are very rare and wonderful specimens. Though made primarily of cartilage, some elements of sharks like the jaws and vertebrae are strengthened by small calcified areas called "tesserae" which give those parts strength without adding much additional weight.

 

http://www.thefossilforum.com/index.php?/topic/101540-show-us-your-fossils-though-a-macro-lens/&do=findComment&comment=1128065

 

If you search this forum for "ray dermal denticle" you'll find many examples of those larger ossified skin elements being preserved nicely.

 

The fact that generally only teeth are preserved makes fossil shark taxonomy very difficult. Think about how difficult it would be to distinguish between different species of dinosaurs that you see mounted in some of the larger natural history museums if you only had teeth to go by. It's a wonder we know much at all about ancient sharks with the limited remains they've left us as clues.

 

BTW: Welcome to the Forum. Lots of information contained within this site.

 

 

Cheers.

 

-Ken

 

Hi Ken,

 

Heliobatis is not a skate.  It's a freshwater stingray (Order Myliobatiformes).  Skates belong to the Order Rajiformes.

 

Jess

 

[PaleoNoel]

Adding to this, the extinct Hybodont shark clade are known from spines and claspers (used in reproduction). Here's an example of a hybodont spine from the Kem Kem Beds in Morocco-

Original photo posted by @britishcanuk

Here's my own partial hybodont shark spine from the Lance fm. in Wyoming

[digit]

14 hours ago, siteseer said:

Heliobatis is not a skate.  It's a freshwater stingray (Order Myliobatiformes).  Skates belong to the Order Rajiformes.

Thanks for that. I think someone had told me it was a freshwater skate as opposed to ray some many years back and it's stuck way back there in a cobwebbed corner of my mind. Will work hard to update that information so I won't make that mistake again. I just checked and there is an extant family of freshwater stingrays that have some pretty awesome coloration. Would be interesting to think that the beautifully detailed Green River specimens once had such bold coloration and patterning.

 

https://en.wikipedia.org/wiki/Potamotrygonidae

 

Cheers.

 

-Ken

[Thecosmilia Trichitoma]

Only Ossified shark vertebrae usually preserve as fossils.

[FossilizedFanatic]

On 26-1-2020 at 10:34 AM, Ludwigia said:

That's because the rest of the shark is made up of other materials which are much more succeptible to decomposition and erosion and they are usually long gone before teeth and vertebra. The rest can only be preserved under relatively rare and exceptional circumstances.

What materials in the teeth and vertebrae makes them fosssilize better than the other parts of the fish?

[Ludwigia]

2 hours ago, FossilizedFanatic said:

What materials in the teeth and vertebrae makes them fosssilize better than the other parts of the fish?

Didn't you read Digit's first post here? You'll find the answer to your question there.

[Shellseeker]

I occasionally find fish jaws:

http://www.thefossilforum.com/index.php?/topic/74383-jaws-a-tail/

http://www.thefossilforum.com/index.php?/topic/74602-fossils-to-identify/

This is entirely consistent with Ken's excellent post.

But I find these in environments that are fossil preserving!!!  made predominately of clay, mud, sand.