Conglomerate fossil bone puerto rico

[GallinaPinta]

Hello, I think I found my first serious fossil!! Up until now, I always found invertebrate and plant fossils like echinoids and giant oysters, but recently after fossil hunting last week at my favorite spot, the San Sebastián Limestone, I stumbled upon something absolutely incredible. I was rushing to get home cause it was getting dark and the river was getting pretty cold, but I tripped over this huge stone. I saw the shadow of something stuck and quickly put it in my backpack, swam and crossed the river and bought it home thinking it was some kind of fossilized wood. It is very, very heavy. However, after checking it closely, it looks like it's actually a bone! Those are extremely rare in the island and I've never seen one, so I'm hoping some bone experts can help me properly identify this fossil. 

Edited December 23, 2022 by GallinaPinta
More accurate title

[GallinaPinta]

There's some crystal minerals embracing the fossil, but I'm not quite sure what they are. Is it quartz? I attached a chart of fossil formations, San Sebastián limestone's is oligocene and paleogene according to the source https://en.wikipedia.org/wiki/List_of_fossiliferous_stratigraphic_units_in_the_Caribbean#Puerto_Rico. There was one sirenian fossil found in the same town. But not much has been reported on it aside from one article. 

[FranzBernhard]

Nice!! I always love fossils in conglomerate. But this superb bone, nicely placed in conglomerate matrix, is a bummer! Lovely!

I am throwing out dugong rib as a wild guess for that one, not knowing if they were already around during that time.

Franz Bernhard

Edited December 23, 2022 by FranzBernhard

[GallinaPinta]

13 minutes ago, FranzBernhard said:

Nice!! I always love fossils in conglomerate. But this superb bone, nicely placed in conglomerate matrix, is a bummer! Lovely!

I am throwing out dugong rib as a wild guess for that one, not knowing if they were already around during that time.

Franz Bernhard

Wow! Conglomerate fossil bone!! Learned how this type of matrix is called now. So it is quartz? That's amazing. How many years did this fossil take to form? 

[Mahnmut]

Hi,

I´ll join the sirenian camp, as the fractures surfaces seem to show a very dense bone.

Concerning age, the other sirenian fossil your source mentions is of miocene age, thats between 20 and 5 million years roughly. Aquatic Sirenians have been around for 40 million, and with much luck and help will stay some more...

Best Regards,

J

[FranzBernhard]

The bone seems to be bone, consisting mainly of the mineral apatite (calcium phosphate).

 

2 hours ago, GallinaPinta said:

There's some crystal minerals embracing the fossil, but I'm not quite sure what they are. Is it quartz?

Could be quartz, could be calcite. Put a small fragment in vinegar or hydrochloric acid and see, what happens.

 

I don´t know what the clasts of the conglomerate are composed of, they look like fragments of rocks, not pure quartz. But could be a few quartz clasts among them.

 

1 hour ago, GallinaPinta said:

How many years did this fossil take to form? 

Few, very few .

 

Major questions for me is, does this specimen belong to the formations you mentioned. Are similar conglomerates know in outcrops?

 

Franz Bernhard

 

[GallinaPinta]

14 hours ago, FranzBernhard said:

Few, very few 

Just how few? could it be...a few million years? 

 

14 hours ago, FranzBernhard said:

Major questions for me is, does this specimen belong to the formations you mentioned. Are similar conglomerates know in outcrops?

Yes, I've found steinkern and other fossils in the same matrix in the same location, but I've never found this matrix containing so many white crystals. So there are a lot of similar conglomerates in the san Sebastián limestone. Never as eye catching as this fossil, though! 

[hemipristis]

16 hours ago, GallinaPinta said:

Wow! Conglomerate fossil bone!! Learned how this type of matrix is called now. So it is quartz? That's amazing. How many years did this fossil take to form? 

Think of conglomerate as a pile of sand and gravel glued together.
 

The amount of time required for conglomerates to lithify (turn to solid rock) varies greatly, depending on the mineral “cementing” the sand and gravel together. There are ironstone conglomerates where iron oxide is the cementing mineral that formed in thousands of years. Conglomerates where silica (quartz) or calcite are the cement take longer, perhaps into the millions of years.

Edited December 24, 2022 by hemipristis

[GallinaPinta]

22 minutes ago, hemipristis said:

Think of conglomerate as a pile of sand and gravel glued together.
 

The amount of time required for conglomerates to lithify (turn to solid rock) varies greatly, depending on the mineral “cementing” the sand and gravel together. There are ironstone conglomerates where iron oxide is the cementing mineral that formed in thousands of years. Conglomerates where silica (quartz) or calcite are the cement take longer, perhaps into the millions of years.

Absolutely mind blowing. Thank you

[FranzBernhard]

7 hours ago, GallinaPinta said:

Yes, I've found steinkern and other fossils in the same matrix in the same location, but I've never found this matrix containing so many white crystals. So there are a lot of similar conglomerates in the San Sebastián limestone. Never as eye catching as this fossil, though!

Great, other fossils in the same rock give that bone some context. What are the other fossils?

 

White crystals may come from a localized crack or (very minor) fault in the rock.

 

@hemipristis is right, hardening of conglomerates can be very fast or very slow.

For example, the postglazial gravel I life on is locally hardened to conglomerate by precipitated calcite, so less than about 10.000 years old.

On the other hand, in my usual Cretaceous hunting ground, there are very hard conglomerate beds interlayered with very crumbly conglomerate beds. It all depends on local factors.

 

The fossil itself, the bone, does not take "any" time to fossilize, its probably still the bone it was during lifetime of the animal, minus the organic components.

 

Franz Bernhard

[westcoast]

We have coastal sand dunes that are cemented by precipitating calcite that are less than 5,000 years old, and beachrock can form in tropical regions in a matter of a few years, some have coke cans cemented into them.

[GallinaPinta]

7 hours ago, FranzBernhard said:

What are the other fossils?

All the same I find locally, there was an echinoid, steinkerns, corals and oysters. They were all marine fossils.

 

7 hours ago, FranzBernhard said:

The fossil itself, the bone, does not take "any" time to fossilize,

I'm confused now, dugong bones are different from other bones in the context of fossilization? 

 

7 hours ago, FranzBernhard said:

the postglazial gravel I life on is locally hardened to conglomerate by precipitated calcite, so less than about 10.000 years old.

The postglaziel gravel you live on is 10 thousand years old? That's still very impressive and might hold some more modern fossils...have you checked it out? 

 

8 hours ago, FranzBernhard said:

there are very hard conglomerate beds interlayered with very crumbly conglomerate beds

Interestingly, the upper part of the river has huge stones with oysters cemented in them in a very hard conglomerate bed, but the lower part has the same huge stones but with a bit of a more flaky consistency where if you try to climb it, the stones fall off. The fossil I found was found in the upper side. 

 

[GallinaPinta]

8 hours ago, FranzBernhard said:

Great, other fossils in the same rock give that bone some context.

 

On 12/23/2022 at 5:52 AM, FranzBernhard said:

does this specimen belong to the formations you mentioned.

 

On 12/23/2022 at 5:51 AM, Mahnmut said:

Concerning age, the other sirenian fossil your source mentions is of miocene age, thats between 20 and 5 million years roughly.

I hope this information can help us shed some light as to the fossil's age and era. I translated the article's information from spanish to english. https://manatipr.org/2014/09/28/descubren-sirenio-fosil-en-san-sebastian-puerto-rico/ The sirenia fossil found in the same location I found my fossil bone was a brand new species of ancient Sirenia.

 

"The fossil was baptized with the scientific name of Priscosiren atlantica, which in Latin means "ancestral siren of the Atlantic". This one was discovered in San Sebastián, Puerto Rico, and another specimen comes from South Carolina. Although today San Sebastián is over 250 feet above sea level, 30 million years ago, the landscape in that area was totally different.“The island of Puerto Rico has changed many through the millennia, either due to global or local processes. During the Oligocene (33.9-23.0 Ma ago), parts of what is now Moca, San Sebastián, Lares and Utuado, among other municipalities, formed part of the coast facing the Atlantic Ocean. In San Sebastián there were mangroves, beaches, and marine lagoons near the mouth of a river. Based on the analysis of Priscosiren atlantica, doctors speculate that this prehistoric sirenian could not adapt to the climatic changes that began 28 Ma ago and culminated 15 Ma ago."

Edited December 24, 2022 by GallinaPinta

[FranzBernhard]

2 hours ago, GallinaPinta said:

dugong bones are different from other bones in the context of fossilization?

Dugong rib bones are very dense, low organic content, mainly hard mineral substance. Other bones not so. Often very porous, lots of space occupied by organic substance during lifetime, that is later filled by other stuff.

I am not into bones, other members are much better suited to explain this special aspect .

 

2 hours ago, GallinaPinta said:

might hold some more modern fossils

I have rarely visited the gravel pits in my area (tens of years ago, but for minerals), other people do this quite often. fossils are very, very rare, I can not remember only a single one! Which is rather surprising. There must have been some found during the centuries, but I don´t know.

Franz Bernhard

 

 

 

 

 

 

[Mahnmut]

Hi,

the miocene sirenian I was referring to above was from the quotation on the page you linked to in your earlier post: https://en.wikipedia.org/wiki/List_of_fossiliferous_stratigraphic_units_in_the_Caribbean#Puerto_Rico.

"L. S. Varona. 1972. Un Dugongido del Mioceno de Cuba (Mammalia: Sirenia). Sociedad de Ciencias Naturales La Salle: Caracas, Venezuela Memoria 91(32):5-19"

 

But as I realize  now there are sirenian fossils of very different ages in the Caribbean, it could be of any age between about 40 million years and nearly recent.

When there is an oligocene sirenian described from close by or even the same formation, that is of course a good candidate.

 

The Bone structure of sirenians is very characteristic, often nearly massive bone without the porous interior typical for most other mammals, as FranzBernhard mentioned above. The additional weight helps them to stay underwater in spite of their buoyant fat. I think I see that structure in your fossil. Search "dugong rib" on the forum and you will find many examples.

And being that solid increases the chances to remain intact in a conglomerate, which tends to destroy more delicate bones, think of the things you find on a pebble beach vs sand.

Best regards

J