fragile grey rock with holes

[anonaddict]

location: aarhus, denmark

found: loose beach rock

units: metric

date: 24/09/2024

notes: in situ image only since I don't have access to a ruler atm and im afraid it might turn to dust rapidly

ive found one of these before as a child but it completely crumbled so ive probably thrown it out

does anyone know what it is?

 

tags: aarhus, denmark, loose beach rock, beach, metric, fragment, metric scale, found loose, loose

 

Edited Wednesday at 08:20 AM by anonaddict

[Al Dente]

Pholad clams will make holes like this.

[anonaddict]

14 minutes ago, Al Dente said:

Pholad clams will make holes like this.

cool! so its modern?

[Al Dente]

Just now, anonaddict said:

so its modern?

Probably recent.

[anonaddict]

5 minutes ago, Al Dente said:

Probably recent.

still cool, i had no idea there were species capable of this level of bioerosion

[digit]

We see dugong bones in the Peace River here in Florida that have this sort of boring quite often.

 

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

 

 

Cheers.

 

-Ken

[anonaddict]

12 hours ago, digit said:

We see dugong bones in the Peace River here in Florida that have this sort of boring quite often.

 

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

 

 

Cheers.

 

-Ken

thats wild, do you have pictures of any?

[digit]

12 hours ago, anonaddict said:

thats wild, do you have pictures of any?

 

   

 

How's this?

 

The first two images are both sides of a dugong rib bone that is riddled with pholad borings. The last image is a larger bone with a deep bore hole. Dugong (and manatee) ribs are interesting in that they are oversized (much thicker than structurally necessary) and are solid to the core with no cancellous (spongy) bone. These sirenians use these bones as a diver would use a weight belt--for ballast. Being solid, they preferentially preserve very well and so places like the Peace River can have an incredible density of these dugong rib fragments. I used to keep nicer specimens and give them away to folks as "paleo paperweights". Not many people in an office can say they have a paperweight that is between 14-7 million years old.

 

Newbie fossil hunters in Florida often mistake these pholad borings for predation marks. The fact that fossil gator teeth are not uncommon in the Peace River often leads the uniformed to assume that these were made when gators attacked dugongs (a gator tooth tends to fit into these borings quite convincingly).

 

 

Cheers.

 

-Ken

[anonaddict]

5 hours ago, digit said:

 

   

 

How's this?

 

The first two images are both sides of a dugong rib bone that is riddled with pholad borings. The last image is a larger bone with a deep bore hole. Dugong (and manatee) ribs are interesting in that they are oversized (much thicker than structurally necessary) and are solid to the core with no cancellous (spongy) bone. These sirenians use these bones as a diver would use a weight belt--for ballast. Being solid, they preferentially preserve very well and so places like the Peace River can have an incredible density of these dugong rib fragments. I used to keep nicer specimens and give them away to folks as "paleo paperweights". Not many people in an office can say they have a paperweight that is between 14-7 million years old.

 

Newbie fossil hunters in Florida often mistake these pholad borings for predation marks. The fact that fossil gator teeth are not uncommon in the Peace River often leads the uniformed to assume that these were made when gators attacked dugongs (a gator tooth tends to fit into these borings quite convincingly).

 

 

Cheers.

 

-Ken

 

 

very cool, I've read a fair bit about aquatic animals and their mechanisms for adjusting density and center of mass like the siphucles of cephalopods or the swin bladders in fish. it's some very interesting mechanisms. I read ammonites could become massive thanks to adjusting its density

 

 

for clarification are the bones fossilized with fossil borings, fossil bones with modern borings  or modern with modern borings?

 

if i was a dugong i'd prefer to keep people thinking i was taken down in a brave fight against a gator instead of a clam

 

 

[digit]

Very much so fossil ribs--dugongs were around in Florida from around 14-7 million years ago. Manatees are still (for the moment) extant here in Florida. The pholad clams that created these borings were (and are) marine species so they did that a long time ago as well (the Peace River is over 20 miles from the closest beach at the present).

 

 

Cheers.

 

-Ken

[anonaddict]

20 hours ago, digit said:

Not many people in an office can say they have a paperweight that is between 14-7 million years old.

I raise you this random piece of granite

[digit]

I've got a chunk of Lewisian Gneiss that I picked up on the island of Lewis in Scotland back in 2010. It's from an Archaean age craton ranging from 3.0-1.7 Ga (more than half the age of the planet).

 

The Callanish Stones are a Neolithic stone circle (that predates Stonehenge) and is constructed of slabs of this gneiss.

 

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

 

Cheers.

 

-Ken