Category: Mazon Creek
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Mazon Monday #325: Braceville Spring 2026 Field Trip Report
This is Mazon Monday post #325. What’s your favorite Mazon Creek fossil? Tell us at email:esconi.info@gmail.com. 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. Field Trip Chairman Jeremy Zimmerman was working hard to get everyone…
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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 #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…
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Mazon Monday #317: Pohlsepia Revisited — Not an Octopus After All
A new paper “Synchrotron data reveal nautiloid characters inPohlsepia mazonensis, refuting a Palaeozoic origin for octobrachians” in the journal Proceedings of the Royal Society B Biological Sciences refutes the classification of Pohlsepia mazonensis as an octopus and reclassifies it as a soft-bodied nautiloid with the new name Paleocadmus pohli.
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Fossil Friday #312: Sublepidophloios protuberans with a spray of Cyperites bicarinatus
At first glance, today’s fossil might look like a cone. But, closer examination reveals it to be a nice specimen of Sublepidophloios protuberans with a spray of Cyperites bicarinatus at the top. Sublepidophloios protuberans is a species of lycopsid branch (see Mazon Monday #316) and Cyperites bicarinatus was the sterile leaves for the Lycopsida (see Mazon…
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Throwback Thursday #312: Ron Schinderle Donation
Barb Schinderle stopped by ESCONI Show last month to drop off a donation of her late husband Ron’s fossils. Ron passed away in 2021. He was a long time ESCONI member and an avid fossil collector . He went on many ESCONI field trips. A group of us remember him fondly from our many trips…
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Mazon Monday #316: Sublepidophloios protuberans
Today, we have Sublepidophloios protuberans, which is a species of lycopsid branch. It’s very common, actually the most common form of lycopsid bark in the Mazon Creek fossil flora.
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ESCONI Field Trip to Danville Shale Pile Fossils – Saturday, May 2nd, 2026
An ESCONI field trip to the Danville IL Shale Pile for Pennsylvanian fossils is scheduled for Saturday May 2nd, 2026 starting at 10 AM. This is on private property and there is an attendance limit of 25 people. The gate will be secured once we are in and locked when we leave. Plan on being…
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Mazon Monday #315: Another Langford Book Inscription
From time to time, we run across some old book inscriptions. Back in Mazon Monday #18, we highlighted a few… Well, here’s another interesting inscription.
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Fossil Friday #310: Mazon Creek Scallop
Another small concretion with a treasure inside… this one has a scallop (see Mazon Monday #35). This one is Aviculopecten mazonensis. There’s no information about where this concretion was collected, but Pit 11 is very likely. We ran across it while preparing for the 2026 ESCONI Show. Do you think these were as tasty as…
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Mazon Monday #314: Smithixerxes juliarum
Smithixerxes juliarum is among the rarest animals found in the Mazon Creek fossil deposit. It belongs to an extinct group of arthropods known as the euthycarcinoids, which ranged from the Cambrian to the Triassic periods. Some researchers believe euthycarcinoids may have been amphibious, capable of venturing between water and land.
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2026 ESCONI Gem, Mineral, and Fossil Show – Preview #38: Reticulopteris munsterii var. dawsonii from Mazon Creek
How about another Mazon Creek seed fern? This one is Neuropteris jacksonii (see Mazon Monday #250). If you are reading this… today is the day!
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2026 ESCONI Gem, Mineral, and Fossil Show – Preview #28: Coelocanth Scale from Pit 11
Here’s beautiful example of a Coelocanth scale Mazon Creek’s Pit 11 locality. Look closely, the preservation is very detailed. Did we mention the tomorrow is the show… see you there!
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2026 ESCONI Gem, Mineral, and Fossil Show – Preview #25: Calomostachys Cone
We have a bunch of Mazon Creek fossils this year… here’s another nice cone – Calomostachys, sp. One day away from the show… are you coming?!?
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Fossil Friday #309: Acanthotelson stimpsoni
Today, we have a cute little Acanthotelson stimpsoni (see Mazon Monday #52) from the Mazon River. Acanthotelson stimpsoni is a syncarid shrimp. It’s the most common shrimp found in the Braidwood fauna.
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Mazon Monday #313: Mazon Creek Studies – the first 120 years
For this week, we have an article from the September 1978 edition of the Field Museum’s Bulletin. The full edition, which includes Jaunary thru December, is available on the Biodiversity Heritage Library (BHL) website.
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Fossil Friday #308: Beautiful things in small packages…
For this week, we have a nice and detailed orbicular pinnule from a Macroneuropteris scheuchzeri. The concretion is very small., but the “hairs” are there. Unfortunately, they may not show up in the photos. This concretion was collected from Pit 2 and opened via freeze/thaw. Check out the last photo to see the size and…
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Mazon Monday #312: Sigillaria tessellata
Sigillaria tessellata is an extinct species of spore bearing, arborescent (tree-like) lycophyte from the Mazon Creek fossil deposit. Arborescent lycophytes (or scale trees) belong to the group Lepidodendrales. Sigillaria is known from as early as the Middle Devonian. It went extinct during the Early Permian Period.
