#12DaysofFossils

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I try to share and show people something new. I'm glad you're enjoying learning about trilobites.

I also share lots of fossil crinoids. Flip through my #12DaysofFossils to see some of my collection.

Thank you to everyone that has enjoyed, liked and shared my #12DaysofFossils.

I appreciate all the kind comments about my collection.

I try to post on #TrilobiteTuesday and #FossilFriday. I have more fossils to share. Let me know if there is something you'd like to see!

2 fossil brittle stars.

I will finish with the 12th species highlighted from Crawfordsville.

These are Aganaster brittle stars. Starfish and brittle stars disarticulate into small pieces very quickly after death. It's rare to find complete ones.

So on Christmas day, here are some "stars" for your tree.

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Fossil Eretmocrinus crinoid with paddle like arms

This is another one of my favorite Crawfordsville crinoids.

Eretmocrinus has broad paddle-like ends of the arms. There is some speculation that this design may have stabilized fluid dynamics of the crinoid during waves or storm events.

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Fossil brittle star curled up

There are also at least 4 species of starfish or brittle stars found at Crawfordsville. Onychaster is probably the most common. They are usually found curled around a crinoid anal tube stealing food. This one is loose and coiled up to protect itself during a storm event.

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Agaricocrinus fossil crinoid

Close up of regenerating arm

This is another Agaricocrinus and was the first Crawfordsville crinoid in my collection. I didn't realize until a couple years ago that one of the arms was starting to regenerate.

Just like starfish, when an arm was damaged, it could regenerate.

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Juvenile fossil crinoid

There is actually a 4th crinoid on the large plate. There's a juvenile (probably) Cyathocrinus right next to the Halysiocrinus. It's only about 1 mm across. These are usually destroyed during aggressive preparation, so the are uncommon to see.

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Close up of Scytalocrinus fossil crinoid

Scytalocrinus arms don't branch after the calyx. The calyx plates are very clearly defined. The shape and number of sides are important when describing different species.

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Close up of Halysiocrinus fossil crinoid.

Halysiocrinus may be one of my favorite crinoids from Crawfordsville. The calyx has very different plates that allowed it to hinge and lay on the seafloor and bend back towards the stem.

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Close up of Agaricocrinus fossil crinoid.

Agaricocrinus has beautiful arms that really highlight the delicate pinnules that filter the water for food.

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Large plate of 3 crinoids

This is a huge plate I found 10+ years ago. I kept pushing it to the side of my prep pile, but I finished it last year and it was worth the wait.

Left to right: Agaricocrinus, Halysiocrinus and Scytalocrinus

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Normal Macrocrinus crinoid fossil

Macrocrinus crinoid with damaged, forked and regenerated anal tube.

These are the 2 Macrocrinus on the plate. The one on the left is a typical specimen. The right specimen is missing arms, which shows the anal tube used to expel waste above the arms. This one was damaged, split and damaged again and starting to regenerate.

Maybe it was predation?

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Close up of fossil crinoid.

This is the Abrotocrinus from the plate. Note the branching arms and the delicate pinnules (feathers) on each arm that would filter water for food.

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Large plate with 4 fossil crinoids.

This is a large plate with 3 different crinoids and 4 total.

The tiny one in the center is another Cyathocrinus. There are 2 Macrocrinus and an Abrotocrinus.

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Fossil crinoid calyx and stem with cirri.

Diagram of Camptocrinus crinoid

Camptocrinus was a very strange crinoid that did not stand up straight on the seafloor. The calyx bent back towards the cirri or branches off the stem.

My specimen has a very 3D section of stem preserved.

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Close up of two crinoid calyxes

Here's a closer view of the calyxes. You can see the very different arm structure.

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Fossil crinoid plate with 2 different crinoids.

This plate has 2 crinoids. The Camptocrinus calyx is to the left. It's a small and simple calyx. Cyathocrinus is "faceplanted" to the right. There is also the stem of a Camptocrinus to the far right of the plate.

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Fossil crinoid with curled arms.

Forbesiocrinus is a Flexible crinoid. It doesn't mean it's super bendy.

Flexible is a superorder of crinoids. They have very distinct arms that tend to be curled in. There are other traits with the stem and calyx plates too.

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Fossil crinoid with long arms.

Hylodecrinus has long arms that branch multiple times.

For my new followers, crinoids are echinoderms related to starfish and sand dollars. They have 5 point symmetry. Think of them as a starfish on a stem with arms in multiples of 5 that filter the water for food.

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Multiple fossil crinoids displayed.

Plate of 3 crinoid fossils.

On the 12th day of fossils, my true love gave to me...

12 Crawfordsville echinoderms!

Crawfordsville, Indiana is home to the Mississippian aged Edwardsville formation, famous for an amazing diversity and density of crinoids. 95+ different crinoids are found here.

1/x

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Very spiny trilobite fossil

Olenellus fowleri is a very spiny beast. Imagine something trying to make a meal out of this trilobite.

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Brown trilobite with small cheek spines

This is another rare trilobite, Eofallotaspis.

It's the second oldest trilobite found in North America. It's around 520 million years old.

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Trilobite fossil with long tail segments

Nephrolenellus genticulatus is a strange trilobite with many tail segments called opistothorax. There are also long cheek (genal) and body spines, but they are hard to see on this specimen.

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Gogia fossil with spiral arms.

I love echinoderms and this is one of the first.

Gogia spiralis is an eocrinoid. It has very simple arms to grab food and a short holdfast. This is a complete specimen.

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Red tube like fossil - algae or worm tube?

Margaretia dorus is another soft tissue fossil. It's been debated if it's a worm tube or a long algae.

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Fossil sponge with x shaped spicules.

Another soft tissue fossil.

This is Diagonella cyathiformis, a siliceous sponge. You can see the spicules, especially near the bottom.

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Fossil hair cyanobacteria

I love soft tissue preservation and there are a few spots in the Great Basin where you can find these fossils.

Marpolia spissa is a filamentous cyanobacteria or algae. This specimen is less than 1 cm.

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Rock with trilobite heads that were molted.

This is just a mess of molted trilobite heads. However, Bristolia anteros is an exceptionally rare trilobite. The head has large cheek spines that splay out.

Only a few complete specimens have been found. Partial specimens are worth keeping.

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Bite mark on the trilobite fossil is rounded and healed.

The left side of the Asaphiscus was attacked. The one segment and tail section are rounded and healed. This damage occurred when the trilobite was alive and it survived.

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Asaphiscus trilobite fossil with bite marks on the left side.

Asaphiscus wheeleri is uncommon. This one is special because there is a juvenile Elrathia and signs the Asaphiscus survived an attack.

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