Mazon Creek Best Of The Best Glaphurochiton Concinnus Richardson, 1956

[RCFossils]

Chitons are the most primitive of all living mollusks. They belong to a class called Polyplacophora (bearer of many plates). There lineage extends as far back as the late Cambrian.

There are over 430 described species in the fossil record. Almost all  are only  known from individual body plates or valves.

The Mazon Creek deposit is one of the only  sites in the world where complete examples have been collected.

Modern chitons have changed little from Glaphurochiton concinnus.

The basic chiton body plan consists of 8 valves made of Aragonite. The front plate is named the cephalic plate and the rear plate the anal.

The plates have fine ornamentation which is a key feature in differentiating species.

Modern chitons can roll into a ball when threatened.

The muscular body is known as the girdle. This girdle is covered with tiny spicules that are sometimes preserved on Mazon specimens.

Most modern chitons use this girdle to attach themselves to rocks.

To feed, the animal has a radula that can have over a hundred rows of denticles. Each row consists of 17 each.

Most modern chitons attach to rocks and feed on algae.

Glaphurochiton was a mud dweller feeding on detritus.

Like all chitons, Glaphurochiton is strictly marine and is only found in the Essex portion of the deposit.

Glaphurochiton is rare but 2 concentrations of chitons have been found. The areas have been termed “chiton hills”.

It has been noted that modern chitons have a homing ability to return to there same resting spots despite lacking eyes.

 

This first example is the largest chiton that I am aware of that has ever been found in the Mazon Creek deposit. Not including the skirt, the animal measures 70 millimeters.

The typical size is usually between 30-40 millimeters.

[RCFossils]

Here is a close up showing the valve ornamentation.

[RCFossils]

Here you can see an incredible radula.

Each row has 17 denticles.

[RCFossils]

This next specimen is the smallest example that I am aware of.

It measures approximately 12 millimeters.

[Tidgy's Dad]

Wonderful fossils of a member of an amazing group of animals. 

A few modern day chitons are carniverous and use their anterior girdle to form a sort of cave which unwary invertebrates such as shrimps wander into to use as a shelter. 

Then, "Gobble!" they slam down the girdle onto the rock trapping the victim within to be devoured. 

[RCFossils]

1 hour ago, Tidgy's Dad said:

Wonderful fossils of a member of an amazing group of animals. 

A few modern day chitons are carniverous and use their anterior girdle to form a sort of cave which unwary invertebrates such as shrimps wander into to use as a shelter. 

Then, "Gobble!" they slam down the girdle onto the rock trapping the victim within to be devoured. 

That’s quite interesting.

I had no idea.

[bigred97]

Beautiful! Thanks for sharing, @RCFossils!

 

I think I was in the area of Pit 11 that has been labeled in the past as a chiton hotspot. I suppose that may be what you are referring to as "chiton hill". Unfortunately I had very little luck in that area this year. I found few concretions and they were mostly very small. In freeze-thaw they have been mostly crumbling away. I soaked them for close to 2 weeks before starting freeze-thaw, so I'm guessing I just did not find good concretions. I'll have to do some more exploring in that area, though, for future trips. Finding one of these would be fantastic.

[Carboniferouspat]

Awesome pieces. I had no idea they grew that large here.

Thanks

[RCFossils]

2 hours ago, bigred97 said:

Beautiful! Thanks for sharing, @RCFossils!

 

I think I was in the area of Pit 11 that has been labeled in the past as a chiton hotspot. I suppose that may be what you are referring to as "chiton hill". Unfortunately I had very little luck in that area this year. I found few concretions and they were mostly very small. In freeze-thaw they have been mostly crumbling away. I soaked them for close to 2 weeks before starting freeze-thaw, so I'm guessing I just did not find good concretions. I'll have to do some more exploring in that area, though, for future trips. Finding one of these would be fantastic.

To my understanding, the “chiton hills” were leveled many years ago and unfortunately no longer collectible.

They do occasionally pop up in the South unit but they are few and far between.

[Coco]

Here is a recent chiton in my collection

 

 

You can see the 8 plates and girdle.

 

Coco

[Coco]

And other ones

 

 

 

 

Coco

 

[deutscheben]

Thank you @RCFossils and @Coco for sharing your collections. That tiny Glaphurochiton is simply too dang cute!