First complete Isotelus

[ScarpedCliff]

I came down with a cold this week, but after a couple days I decided I would rather be out hunting fossils sick than sitting around the house sick and staring at a computer. So, Tuesday afternoon my wife and I went fossil hunting at a well-known Richmondian road cut in Indiana. The ground was already wet, and it rained heavily while we were there, but we brought raincoats. After a while, the sun came back out, and we found a good array of fossils from the Liberty Formation. There were plenty of horn corals, brachiopods, and gastropods, but we were primarily after trilobites. Between the two of us, we found 6-7 complete, enrolled Flexicalymene retrorsa minuens, as well as what I believe is a Rusophycus ichnofossil.

My favorite find of the afternoon was my first complete Isotelus. Large fragments of adult Isotelus are common at this site (and through much of the Cincinnatian series), but the large ones are almost never complete. Isotelus is not only larger than Flexicalymene, but they also roll into a flattened crescent shape instead of a tight sphere like Flexicalymene. I suppose this might explain why they're not preserved whole as often. Anyway, I found two juvenile, enrolled specimens, though the thorax of one is partially broken off. Here are both sitting on top of a rock containing the pygidium of a much larger Isotelus.

Here's a close-up of the complete Isotelus. It measures about 17 mm wide across the cephalon.

I assume it is Isotelus maximus, but does anyone have thoughts on how to differentiate a smaller specimen from Isotelus gigas?

Edited February 6, 2016 by ScarpedCliff

[Raggedy Man]

Wonderful find! Definitely worthy for FOTM.

Best regards,

Paul

[erose]

Just too cool. I'm suffering serious Cincinnatian envy.

PS that picture of me is on another well known Richmondian cut near Richmnond, IN.

Edited February 6, 2016 by erose

[ScarpedCliff]

Just too cool. I'm suffering serious Cincinnatian envy.

PS that picture of me is on another well known Richmondian cut near Richmnond, IN.

I have a bit of Texas Cretaceous envy, myself. Last summer, I only got to spend a few hours collecting in the North Sulphur River, and I loved it. There's a planetarium conference I'll probably be going to in Arlington, TX in the Fall, so I hope to hit some more sites when I'm out there.

I haven't been to that cut near Richmond yet, but it's been on my to-do list.

[piranha]

On 2/6/2016 at 9:16 AM, ScarpedCliff said:

...I assume it is Isotelus maximus, but does anyone have thoughts on how to differentiate a smaller specimen from Isotelus gigas?

 

This paper has excellent drawings, figures and info:

 

Raymond, P.E. (1914)

Notes on the Ontogeny of Isotelus gigas Dekay.

Bulletin of the Museum of Comparative Zoology, 58(5):247-263

LINK

 

 

Higher quality figures from:

 

Ludvigsen, R. (1979)

The Ordovician trilobite Pseudogygites Kobayashi in eastern and arctic North America.

Royal Ontario Museum - Life Sciences Contributions, 120:1-41

 

 

 

[Jeffrey P]

Finding an Isotelus piece like that can help any one feel better. Great way to spend a "sick" day. Big congratulations and I agree. definate nomination for FOTM. Like to see your other finds from the day if you get a chance to post them.

[ScarpedCliff]

piranha, thank you for the recommendations! I'll need to do some research.

Raggedy Man and Jeffrey P, thank you for the kind words. Let me make clear, though--lest I mislead anyone--that I didn't find the smaller Isotelus on the same rock with the large Isotelus pygidium. Each was found separately, and I just poised them there for scale.

By the way, I know the macro photo isn't perfect (it has a small depth of field), but I was still amazed at how good a photo I got with just my hand lens / loupe and a smartphone. My smartphone has an Otterbox case, and bracing the loupe against the back of the case sets it at the right distance to magnify the subject.

[ScarpedCliff]

Finding an Isotelus piece like that can help any one feel better. Great way to spend a "sick" day. Big congratulations and I agree. definate nomination for FOTM. Like to see your other finds from the day if you get a chance to post them.

I posted photos of other finds from this trip here.