Field Collection at St. Leon

[FossilSniper]

On my eighth trip to the locality, I collected fossils at the famous St. Leon roadcut. Exposed were the Waynesville and Liberty formations, which date to the immense coral reefs of the upper Ordovician, or 450 ±5 MYA. The site was heavily picked, its erosive forces slowed during Indiana's summer heat. My drops of sweat evaporated on the sun-tempered limestone faster than I could count to ten. Despite the setbacks, acquisitions were generous. Best for last.

 

Behold my brachiopods. The top row is Strophomena sp., the top-left sample demonstrating encrusting bryozoan. The second row is Vinlandostrophia ponderosa. The third and fourth rows are Lepidocyclus/Hiscobeccus, though I am of the opinion the genera are synonymous and are just sexual dimorphs given their identical ages, appearances, and regional occurrences. I am curious what other brachiopod enthusiasts think of this similarity. (Four boxes on the grid is 25 millimeters.)

I continue with the bivalves. The top row is Caritodens sp, the top-left sample being a particularly well-preserved example. The bottom-left sample is Anomaladonta sp., and the bottom-right sample is a near-perfect Ambonychia sp.

Life is incomplete without the gastropods! I didn't take French in high school for nothing! The top sample is unknown to me, despite being the second I have found of its type. The middle-left sample is too buried. The remaining four are all Paupospira sp., the middle sample being a good example. Interestingly, the bottommost Paupospira has a partial Flexicalymene sp. trilobite cephalon on it, which makes me question if the trilobite was consuming the calcium to augment its own development. However, considering the sample is a messy storm deposit, it is likely pure luck.

I have to mention the numerous Isotelus maximus fragments at the site. When looking for fossils at St. Leon, one must wonder how many beautiful I. maximus lie under the surface, only to crumble down the slopes of the roadcut and into my hands. Of interest is the long, delicate genal spine on the top right.

Now to the more interesting fossils. I follow with three of six total straight-shelled nautiloid cephalopods. The middle sample is a rare, (calcified) Anaspyroceras sp., and the right sample is also calcified.

The beautiful, ancient calcite crystals within the dull-appearing right sample:

Now to the next three. The left orthocone is all associated and is very large. The middle sample is also quite large. Species-level identification of orthocones can be difficult even with a clear cross-section of the siphuncle, so "straight-shelled nautiloid cephalopod" will have to suffice. However, I suspect these three samples are likely Treptoceras sp. Excellent samples to say the least.

I kept saying "straight-shelled," so perhaps some of you guessed it: I found a coiled nautiloid cephalopod! These are very rare. I have found only a handful of these. Behold the curved Beloitoceras sp., a member of Oncocerida, to which the modern nautilus owes its existence to! It's unbelievable how this rock from half a billion years ago directly led to the existence of modern nautiloids! The continuity of life is incredible. 

The penultimate is a bryozoan fan. Yes, a fan! The bryozoan tapers off at the upper edges. I have never seen anything like it! It is 8x4 cm.

And finally...

 

...a giant bryozoan! This is my biggest single fossil find ever! The caliper on the left is set all the way out to 15.00 cm! It is easily 15 inches in diameter and four inches thick! After crashing my bicycle a few weeks ago, this immense find could be my new wheel! 

 

Hear me out. In ten years of collecting, I have found many rare trilobites, behemoth cephalopods, and more, but this colony of tens of thousands of individual animals takes the cake for the most interesting fossil I've ever had the privilege to collect. On top of being huge and complete, it's riddled with trypanites (trace burrows for you bone hunters out there) from all a manner of creatures that used to reside in the Ordovician. I'm sure my fellow amateur paleontologists appreciate that this isn't just a fossil coral, it's an entire ecosystem! It's literally a window into life 450 million years ago! It's riddled with traces left by crinoid stems, scolecodonts (boring worms), parasitic encrusting bryozoans, brachiopods, bivalves, and so much else! I'm considering donating it to a museum.

 

Thank you so much for reading! I hope you enjoyed.

[connorp]

Could you post some closer up pictures? Based on size it’s probably a tabulate coral, perhaps Tetradium. 
 

[FossilSniper]

25 minutes ago, connorp said:

Could you post some closer up pictures? Based on size it’s probably a tabulate coral, perhaps Tetradium. 
 

I'd be happy to! I'm pretty confident this is a bryozoan (Stigmatella personata), as similar samples have been discovered by the Dry Dredgers (see link) but I'm always looking for corrections!

Here is a cross-section: 

Here is a closer view from above:

The width of the individual zooids (0.7-0.8mm in diameter) is consistent with the colonial bryozoan species. Tabulate coral would have corallites of significantly larger diameter (2.4-1.5 mm).

[connorp]

53 minutes ago, FossilSniper said:

I'd be happy to! I'm pretty confident this is a bryozoan (Stigmatella personata), as similar samples have been discovered by the Dry Dredgers (see link) but I'm always looking for corrections!

Here is a cross-section: 

Here is a closer view from above:

The width of the individual zooids (0.7-0.8mm in diameter) is consistent with the colonial bryozoan species. Tabulate coral would have corallites of significantly larger diameter (2.4-1.5 mm).

Sorry, I meant colonial not tabulate. This looks like Tetradium to me though. I have found some large pieces in the Saluda at St. Leon.

[FossilSniper]

28 minutes ago, connorp said:

Sorry, I meant colonial not tabulate. This looks like Tetradium to me though. I have found some large pieces in the Saluda at St. Leon.

Interesting! May you post some pictures?