Category: Mazon Creek
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Mazon Monday #332: Tom Testa Winter Freeze/Thaw
Sorry, this is a bit of a repeat… But, Tom Testa has been on our minds lately and we’ve all been enduring a stretch of hot weather, so here’s a post that will cool you off!
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Fossil Friday #326: Rhacophyllum cornutum from the Mazon River
This is a very beautiful Rhacophyllum cornutum (see Mazon Monday #266) from the Mazon River. Lil Magnussen showed me this stunner at the spring 2026 Danville field trip. Lil is a long-time ESCONI member… She joined in the 1960’s.
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Mazon Monday #331: Recap of Tom Testa Day at the Carbon Hill School Museum
Back in Mazon Tuesday #328, we did a post about Tom Testa and his amazing Mazon Creek fossil collection. There was a great turnout at the Carbon Hill School Museum special event “The Legacy of Tom Testa” on June 25th, 2026.
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Fossil Friday #325: Radstockia kidstonii
Jeremy Zimmerman sent in photos of this breathtaking Radstockia kidstonii. R. kidstonii is a very rare true fern from Mazon Creek. Its pinnules and fertile structures are similar to the modern fern Marattia alata.
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Mazon Monday #330: A New Mazon Creek Worm
While you were getting ready to celebrate our nation’s 250th birthday, a new fossil polychaete from Mazon Creek was being introduced to the world! It’s the first in annelid from Mazon Creek in over 20 years! Mazovermes magnaterminus was described in “The first new polychaete from the Mazon Creek fossil site in 20 years suggests…
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Happy 4th of July… the 250th Edition!
What better way to celebrate the 4th of July than with some beautiful Annularia fossils?!? We have a variety of species here, so sit back and enjoy the fireworks!
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Fossil Friday #324: A Big Beautiful Acanthotelson stimpsoni
It’s not exactly fireworks, but this week’s beautiful Acanthotelson stimpsoni will leave you speechless. A. stimpsoni is a syncarid shrimp and one of the most common shrimp found amongst the fauna of Mazon Creek. Syncarida is a superorder of crustaceans. It consists of two extant orders Anaaspidacea and Bathynellacea, and one extinct order Paleocaridacea, to…
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Mazon Monday #329: Danville Spoil Pile May 2026
Saturday, May 2nd, 2026 was a fairly nice day. It was partly cloudy with some wind. It was a little cooler than previous trips.
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Fossil Friday #323: Laveineopteris rarinervis from the Mazon River
This is the “Fossil Friday” post #323. Expect this to be a regular feature of the website. We will post fossil pictures you send in to esconi.info@gmail.com. Please include a short description or story. Check the #FossilFriday Bluesky/Twitter hash tag for contributions from around the world! Marie Angkuw sent us these photos of a gorgeous…
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Mazon Tuesday #328: The Legacy of Tom Testa
Michele Micetich, curator of the Carbon Hill School Museum, will host a special event on Saturday, June 27, 2026, celebrating the life and legacy of Tom Testa. A lifelong fossil collector with a passion for Mazon Creek fossils, Tom assembled one of the finest private collections of its kind. In 2015, he gave his collection…
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Mazon Monday #327: Direct development of stem tetrapods across the fin-to-limb transition
A significant paper on tetrapod development was published last week, and Mazon Creek fossils played a central role. “Direct Development of Stem Tetrapods Across the Fin-to-Limb Transition” by Jason Pardo and Arjan Mann of the Field Museum appeared in the journal Science. Lauer Foundation for Paleontology, Science, and Education also contributed to the study. The…
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Fossil Friday #322: Macroneuropteris scheuchzeri from Dresden
For this week’s Fossil Friday, we have a very nice Macroneuropteris scheuchzeri (see Mazon Monday #39). Macroneuropteris scheuchzeri is a fairly common seed fern, which is found in many Carboniferous fossil deposits. In some Mazon Creek localities like the Mazon River, it’s a dominant component of the flora. It was called Neuropteris scheuchzeri until 1977,…
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Mazon Monday #326: More Mazon Creek at the 2026 CGMA Show
This is Mazon Monday post #326. What’s your favorite Mazon Creek fossil? Tell us at email:esconi.info@gmail.com. Long-time ESCONI member Rich Rock had an amazing display of Mazon Creek fossils at the CGMA show. There’s a little a bit of everything here, from clams to ferns to spiders to an absolutely breathtaking Alethopteris serlii. Enjoy!
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Fossil Friday #321: A Large Crenulopteris acadica from the Mazon River
Marie Angkuw sent us these photos of a beautiful Mazon Creek fern. It’s a Crenulopteris acadica from the Mazon River. Crenulopteris acadica is a common fern from Mazon Creek, but this one is very large with multiple fronds. Marie collected this one a few years ago at the I&M Canal Corridor Benefit. The concretion opened…
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Mazon Monday #325: Braceville Spring 2026 Field Trip Report
We held our spring Braceville field trip a few weeks ago. The weather was nearly perfect… partly cloudy with temperatures in the high 70’s and low 80’s each day.
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Fossil Friday #320: Tully Monster Repeat!
For this week’s Fossil Friday, we’re featuring our first-ever repeat fossil. It was special before and you’ll see why it’s even more special now. This remarkable Tully Monster specimen comes from longtime ESCONI member Jeremy Zimmerman. You could even say that this particular fossil is getting its third chance at fame.
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Mazon Monday #324: Stepwise loss of complexity in hagfish eyes prior to deep sea colonization
Mazon Creek hagfish made headlines again last week. New research led by Victoria McCoy, Assistant Professor in the Department of Geosciences at the University of Wisconsin–Milwaukee, was published in the journal Biology Letters. In the paper, “Stepwise Loss of Complexity in Hagfish Eyes Prior to Deep-Sea Colonization,” McCoy collaborated with several familiar names… Arjan Mann…
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Fossil Friday #319: First Tully!
Back in late March, I went fossil collecting with a couple Field Museum researchers, including Lazaro Viñola López (see “Ancient bees found nesting inside fossil bones in rare cave discovery” for some of his recent work), a postdoctoral researcher. This was his first trip to Pit 11. Bet you can guess where this is headed…
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Throwback Thursday #319: Happy 150th Birthday, George Langford!
May 26th, 2026 marks George Langford’s 150th birthday! He was born on May 26th, 1876 in Denver, Colorado. George Langford Sr. is giant in the history of Mazon Creek. Before Jack Wittry’s books, George’s books were the go-to source of information about Mazon Creek. George wrote three books about Mazon Creek fossils. The first was…
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Mazon Monday #323: Mazon Creek at the 2026 CGMA Show
Jack Wittry had a breathtaking display at the 2026 CGMA Show at the Kane County Fairgrounds this past weekend. It featured Mazon Creek fossils named for ESCONI members.
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Mazon Monday #322: Asterophyllites longifolius
Asterophyllites longifolius like its sister taxon Asterophyllites equisetiformis (see Mazon Monday #103), formed part of the foliage of the giant horsetail-like plant Calamites. Both species are known from Mazon Creek, but while A. equisetiformis is common, A. longifolius is a very rare. One distinguishing characteristic of A. longifolius is that the leaves are longer than…
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Mazon Monday #321: So, where’s the shrimp?!?
Andy Jansen wrote this article for the December 2007 edition of the ESCONI newsletter. Andy has been an ESCONI board member for many years. He’s currently our Treasurer and Librarian. If you attended our show in March, he was in his usually position at the book display and sale tables.
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Fossil Friday #316: Asterophyllites longifolius
Recently, Marie Angkuw mentioned that she had required a large, and very sweet example of Asterophyllites longifolius. She found this specimen at an antique mall. The fossil was part of an old collection. I wonder if it was the “oldest” antique at the mall?
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Mazon Monday #320: A shoot at the root? Unique development and evolution of the stigmarian apical meristem
Our friends at the Field Museum have been busy… this time it’s paleobotany. The paper “A shoot at the root? Unique development and evolution of the stigmarian apical meristem” was published in the journal Proceedings of the Royal Society B a few days ago. The authors should be familiar… Michael P. D’Antonio, C. Kevin Boyce,…
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Fossil Friday #315: Eubleptus danielsi
Eubleptus danielsi belongs to the Palaeodictyoptera an extinct order of medium-sized to very large, primitive Palaeozoic paleopterous insects. E. danielsi was described by Anton Handlirsch in 1906. Handlirsch (1865 – 1935) was an Austrian entomologist, who worked extensively on many insect orders. He did significant work studying of fossil insects. Handlirsch described E. danielsi in “Revision of American Paleozoic insects. Proceedings of…
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ESCONI Field Trip to Braceville, IL for Mazon Creek Fossils – Saturday, May 30th and Sunday, May 31st, 2026
The ESCONI field trips to Braceville for Mazon Creek fossils are set for May 30th and 31st, 2026 from 9 AM to 3 PM. You can attend one or the other, but not both days. There is an attendance limit of 50 people each day. You must register to go on this trip. See rule…
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Mazon Monday #319: ESCONI Braceville Trip Spring 2005
Our spring trip to Braceville Spoil Pile is coming up in May. The sign-up will kick off very soon. We have been going there for many years. For the spring trip in 2005, Barbara Brotman, a reporter for the Chicago Tribune was there to talk to a few ESCONI members and talk about ESCONI.
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Fossil Friday #314: Kellibrooksia macrogaster
For today’s fossil, we have a beautiful specimen of Kellibrooksia macrogaster, which was a species of mantis shrimp (see Mazon Monday #105). This rare animal was described by Frederick Schram in 1973. It was named in honor of Harold Kelly Brooks, who published the first well-illustrated modern account of Mazon Creek crustaceans. A pdf of his work is…
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Mazon Monday #318: Eusphenopteris neuropteroides
Eusphenopteris neuropteroides is an extinct seed fern species that is relatively uncommon, though it is primarily known from the terrestrial deposits of Mazon Creek. It was originally described as Pseudopecopteris anceps by Leo Lesquereux, but its classification has shifted over time as its relationships to other taxa became better understood. Over the years, it has…
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Fossil Friday #313: Mazonomya mazonensis
George Witaszek sent us this breathtaking plate platter of Mazonomya mazonensis (see Mazon Monday #25). This animal was called “clam-clam” by collectors. Mazonomya mazonensis was known incorrectly as Edmondia for a long time. It was redescribed by Jack Bailey in the book “Paleobiology, Paleoecology, and Systematics of Solemyidae (Mollusca: Bivalvia: Protobranchia) from the Mazon Creek…
