Mazon Creek Best Of The Best Esconichthys Apopyris Bardack, 1974

[RCFossils]

The Mazon Creek Deposit is known for many enigmatic creatures.

Esconichthys is one of them.

The animal has a tadpole shaped body with a usually well preserved pair of eyes.

Some specimens preserve 2 pairs of long external gills.

Muscle segments called myomeres are sometimes present on laterally preserved specimens. 

What makes it unusual is that it does not have paired fins.
It was originally suggested that Esconichthys may be a larval lungfish or possibly an amphibian.

Later studies have stated this is unlikely without offering an alternative placement.

Due to the presence of external gills, it is believed that these are likely a larval stage.

The largest specimens known can reach almost 8 centimeters.

Early collectors referred to these animals as blades or grasshoppers based on their general shape.

They are the most common vertebrate found in the Mazon Creek Deposit.

Specimens are only known from the marine (Essex) portion.

Esconichthys was named to recognize the Earth Science Club Of Illinois (ESCONI).

 

[RCFossils]

Note the eye placement on these 2 specimens.

Most specimens that I have seen preserve the eyes towards the outer edge of the skull.

The eyes on some specimens are preserved tightly together.

This may be due to preservation or possibly a different form.

[RCFossils]

This is a very large specimen.

If complete, it would measure between 7-8 centimeters.

[RCFossils]

Finding a Mazon Creek vertebrate is a rarity.

Finding multiple examples in the same concretion is almost unheard of.

Here are 2 multiple examples of Esconichthys.

One preserves the heads of 3 larger individuals.

The other preserves at lest 4 complete smaller specimens.

What I find interesting is that all animals are facing the same direction with their heads almost on top of each other.
This possibly preserves some type of behavior.

[RCFossils]

Here are 2 neat associations.

The first is an Esconichthys with a shrimp.

The second is a specimen preserved with an arrow worm.

[Tidgy's Dad]

Lovely. 

You must have heard it before, but they look sort of like ghosts.

The Caspar the Friendly Ghost of the Mazon Creek. 

[deutscheben]

Very neat, those associations are particularly evocative. 

[Nimravis]

These have always been one of my favorite fossils to find at Pit 11 and as Rob stated many collectors referred to them as “ Blades”, I have never heard the term “Grasshoppers “, but you can see why they would say that. The more common name that people that I use to collect with was “Ghosts”, and you can see where they get that name with a piece in my collection- you can see the resemblance to Casper the Friendly Ghost.

 

 

Here are a couple more in my collection and one concretion that also contains multiple specimens.