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Nimravis

Dugong Bone Question

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Nimravis

I collected this Dugong bone near Sarasota, Florida today and was wondering what would make this indentation/ boring?

 

5D6CB5F8-EE80-4065-9F8E-63B2D1E606F8.thumb.jpeg.ff4caa71ffa1428a7a0b4e377386f68b.jpeg

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Brett Breakin' Rocks
19 minutes ago, Nimravis said:

I collected this Dugong bone near Sarasota, Florida today and was wondering what would make this indentation/ boring?

Hi There, usually they are burrowing or boring clams that can make marks and holes in fossils like these.  You can see similar marks in other bones, meg teeth etc ...

 

Cheers,

Brett

 

Image Credit: MegaTeeth

Clam_Boring.thumb.jpg.b1feea85637276e1fff53f37a82e0e1d.jpg

 

Dugong rib section - Peace River

Image Credit: Galactic Stone and Iron Works

 

dugong-worm-2__32569.1502474917.jpg.a656061b72a5dacf6212173575f5bc09.jpg

 

Modern 'ship worms' a type of boring clam.

https://www.smithsonianmag.com/science-nature/tunneling-clam-bedeviled-humans-sank-ships-conquered-oceans-180961288/

ShipWorm.jpg.ead9f2584936cd83e6071bcf4697b43e.jpg

 

 

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Nimravis

@Brett Breakin' Rocks Cool Brett- I appreciate the quick response.

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digit

Yup. Bored dugong ribs make an appearance on this forum every once in a while. Here's my comments from a couple of years ago:

 

http://www.thefossilforum.com/index.php?/topic/71805-peace-river-fossil-sirenian-rib/&do=findComment&comment=756096

 

 

And some information about the boring mollusks (which are, in fact, quite interesting):

 

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

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

 

Dugong bones are quite dense and do not have the spongy cancellous interior of many other bones. Dugongs (and modern day manatee) have developed these heavy bones to act as ballast to enable them to do more than just buoyantly float around on the surface. Sometimes you can quite clearly see the growth rings in the cross-section of a break in the bone--much like tree rings. Those layers are quite evident and display well in the beginnings of a boring in your specimen. That simple item comes packed with lots of stories to tell. :)

 

 

Cheers.

 

-Ken

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Brett Breakin' Rocks
8 hours ago, Nimravis said:

Cool Brett- I appreciate the quick response.

No worries... I'm a bit of a night owl. Cool piece. 

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Bronzviking

More on Shell Wars Boreholes. Gastropods and bivalves drill in other shells to eat them. Single, circular boreholes were likely eaten by a predatory gastropod. Oyster drills (Urosalpinx app.) leave a straight hole, whereas thick lipped drills (Eupleura caudata) leave a slightly beveled hole. Shark eye snails (Neverita duplicata) leave a countersunk hole, circular borehole that has a outer diameter twice the inner diameter. Reference: "Florida's Seashells A Beachcomber's Guide" by Blair and Dawn Witherington


I've seen bore holes in rock so, I don't see why that can't drill in bone. Would you say yours is a beveled or countersunk hole?

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Nimravis
6 minutes ago, Bronzviking said:

Would you say yours is a beveled or countersunk hole?

I would say beveled- though pics of beveled and countersunk holes look the same to me. :)

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digit

Keep in mind that the predatory gastropods mentioned above (murex and shark eyes) drill tiny holes into the shells of other mollusks (usually bivalves) in order to breach the protective shell and feed upon the soft tissue within. These holes are usually much smaller than the larger boring holes made by burrowing pholad bivalves and shipworms. Here are some examples of the tiny predatory holes that are evidence the demise of these mollusks.

 

Cheers.

 

-Ken

 

lady-in-waiting-venus-clam-with-drill-hole-1.jpg    Moon-snail-drill-hole-in-Dallarca-idonea.jpg    2-Bivalve-shells-with-a-smooth-round-hole-in-them.jpg

 

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Bronzviking
12 minutes ago, Nimravis said:

I would say beveled- though pics of beveled and countersunk holes look the same to me. :)

Can you measure the diameter of the hole? Thanks

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Nimravis
12 minutes ago, Bronzviking said:

Can you measure the diameter of the hole? Thanks

I will go find that piece in a bit, but I believe that it is a tad over 1 cm.

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digit

Which is much larger than the smaller drill holes that the predatory mollusks would drill into other shells. There would be no point for these predators to drill into dugong bones as it would not gain them any food. The larger holes would be the burrows of the pholad type mollusks. I've seen newbie fossil hunters on the Peace River who, upon discovering their first fossil gator teeth, try to convince themselves that the teeth fit nicely into the holes left in the dugong bones and must have come from gator predation. A classic mistake made by a simple assumption unencumbered by the thought process. :P

 

 

Cheers.

 

-Ken

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Harry Pristis

 

Pholadid clams (Fam. Pholadidae - "rock-boring clams") burrow into any hard substrate.  Here's a fossil coral from South Florida with two pholadids still embedded.

 

 

 

 

coral_dichocoeniaB.JPG

coral_dichocoeniaD.JPG

dugongribpair.JPG

dugongribborings.JPG

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Nimravis

7A8A4150-288F-4C03-8564-58DF58B4135C.thumb.jpeg.9420a1e5ee8d382d60c3b451ea981023.jpeg

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Nimravis
2 hours ago, digit said:

Here are some examples of the tiny predatory holes that are evidence the demise of these mollusks.

I agree- and I like collecting them and have tons of examples of these.

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digit
11 minutes ago, Bronzviking said:

Don't ship worms just bore in wood and drift wood?

Likely. I expect that is their primary choice for burrowing into. I can see how these were a real pain back in the days when all boats were made of wood. :blink:

 

 

Cheers.

 

-Ken

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Bronzviking

 

1 hour ago, Nimravis said:

7A8A4150-288F-4C03-8564-58DF58B4135C.thumb.jpeg.9420a1e5ee8d382d60c3b451ea981023.jpeg

@digit So what your saying is these circles exposed by the boring pholadid clams is growth rings in the bone? At first glance it looked like a beveled hole made by boring shells.

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digit

It is both--this hole is made by the larger boring pholad bivalves as a burrow and it is exposing the layers of the dugong bone since the bottom of the hole has a nice curvature to it. :)

 

 

Cheers.

 

-Ken

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Harry Pristis

Shipworms and rock-boring clams are placed in the same Superfamily (Pholadoidea),  but they are in two different Families, Teredinidae and Pholadidae, respectively.  In other words, they are as closely related to one another as pronghorn antelopes are related to whitetail deer or as gomphotheres are related to mammoths.

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