Jeff Allen recently sent us photos of a fossil he found at Braceville. The specimen is Stigmaria, the underground rooting structure associated with arborescent lycophytes such as Sigillaria and Lepidodendron.

Recently, Matt Brown, McCarter Collections Manager, Fossil Vertebrates at the Field Museum, showed me a book that is special on several levels.

For some, the Carboniferous is synonymous with large arthropods including the millipede Arthropleura (pictured) and giant “dragonflies” Meganeura (see below). Image courtesy and copyright of Netflix. We haven't posted about Palaeocast in a little while. Recently, David Marshall posted two episodes about "Insect Gigantism." These podcasts feature an interview with insect physiologist Prof. Jon Harrison from Arizona State University.

For the October General Meeting, we are doing something new. Lazaro Vinola from The Field Museum will be presenting live from the field in the Dominican Republic. Earlier this year, you may recall Lazaro found a Tully Monster on his first visit to Pit 11. We used the fossil for Fossil Friday #319. For this meeting, Lazaro’s team will be processing sediment for microfossils.

The Mazon Creek Open House was first held in early 1984. It was an extension of the Mazon Creek Project at Eastern Illinois University. Both the Mazon Creek Project (see Mazon Monday #5) were sponsored by Northeastern Illinois University.

The "big block" containing the articulated arm and ribcage of "Rex Junior," a sub-adult Tyrannosaurus rex from the Zerbst Ranch in eastern Wyoming. This specimen, being studied at the University of Chicago's Fossil Lab, could be the best-preserved and most important T.rex specimen ever found. (Paul Sereno) Cowboy State Daily has a story about "Rex Junior." First discovered in the 1950's on a ranch near Newcastle, Wyoming, a partial skeleton of a sub-adult…

More horrible museum news... this time the Sternberg Museum in Hays, Kansas. See the story at KWCH News 12. The fundraising campaign started by the Fort Hays State University Foundation can be found here. HAYS, Kan. (KWCH) - The Sternberg Museum in Hays will be closing before the end of the year. The President of Fort Hays State University, Tisa Mason, shared a statement with the school sharing details on the decision to close the historic museum.

Lepidostrobus is a cone from lepidodendron tree.  It was named in 1828 by Adolphe-Theodore Brongniart (1801 – 1876), who was a French paleontologist, considered by many to be the father of paleobotany.  He also named Lepidostrobophyllum which are the individual cone bracts of which Lepidostrobus is the whole reproductive organ. See Mazon Monday #202.

Field trips require membership, but visitors are welcome at all meetings! Friday, October 9th General Meeting - 8:00 PM via Zoom. Lazaro Vinola from The Field Museum will be presenting live from the field in the Dominican Republic. Saturday, October 10th Junior Study Group Meeting - 2:00 PM at College of DuPage, TEC, Room 1038A Earthquakes! Junior members will watch videos about earthquakes, make seismographs and test them.

ESCONI highlights from 25, 50, and 70 years ago

The 2026 Mazon Creek Fossil Day will be held on Saturday, October 10th, 2026 at the Coal City Library from 10 AM to 3 PM. See you there! Previous events October 16th, 2023 October 21st, 2024 October 11th, 2025

Scientists studied fossilized teeth, including two from “Thomas,” a famous T. rex in the collection of the National History Museum of Los Angeles County, to prove that the species was warm-blooded.Credit...Dinosaur Institute, Natural History Museum of Los Angeles County The New York Times has a story about recent T. rex research. There's been a long running debate about whether dinosaurs were warm or cold blooded - endothermic or exothermic.

The Mazon Creek fossil biota has a new member... a vertebrate, which are rare. Jeanerpeton mazonensis, which means "Jean’s crawler from Mazon Creek", was named by two student-scientists from the Field Museum. The name honors their mothers, who are both named Jean.

An amateur astronomer scouting campsites accidentally uncovered a massive 390-million-year-old impact crater hidden in the Quebec wilderness. (The subtle circular shape of the Uhackatik impact structure in Quebec, with Lake Marsal near the center, is visible in this image captured on October 12, 2025, by the OLI (Operational Land Imager) on Landsat 8.) Credit: NASA Earth Observatory/Lauren Dauphin Science Daily has a…

A tiny bird feather in the fossilized excrement of a dinosaur, found at the Hell Creek Formation in Montana.Credit...David DeMar, Jr. The New York Times has a story about an amazing, chance discovery. In 2016, a researcher in the Hell Creek Formation in Montana picked up a small rock that turned out to be a small piece of fossilized dinosaur dung.

Here's a beautiful Palaeoxyris prendeli from Chowder Flats. It's a shark egg case thought to have been produced by hybodont sharks. P. prendeli was named by Leo Lesquereux in 1870. At that time, it was believed to be a plant part, maybe a seed pod. The name palaeoxyris comes from the the flowering plant genus Xyris, which grows in swampy environments in the tropics and subtropics. There are a number of species found in India. There, they are commonly known as yellow-eyed grasses and are characterized by their grass-like leaves and yellow iris-like flowers.

The October 1959 edition of the ESCONI newsletter included this little burb from the newsletter editor, George Darrow, about his vacation to Oregon during the summer of 1959.

ESCONI held our annual "Brag Night" 2026 on September 19th, 2026. 20 members braved the torrential rains to share fossils (and a few minerals) with their fellow members. Here's a quick photo recap...

View this post on Instagram A post shared by Eons (@eonsshow) PBS Eons posted this video a few days ago on Instagram. In making Life and Death on Pangea, not only did we get to tell the story of one of the most dramatic times in Earth's history, but we got visit places that were dreams come true for our natural-history-loving hearts! ⁠

Titanoscorpio douglassi is known from just three specimens, but the holotype is a breathtaking three-inch claw on display at the Prehistoric Life Museum in the basement of Dave's Down to Earth Rock Shop (see Throwback Thursday #94) in Evanston, Illinois. And yes, it really is breathtaking!

PBS Eons has a new video. This is another one about the Great Dying about 252 million years ago. What was it about the Great Dying that caused a global age of mutant plants? And could figuring it out help us avoid triggering the next one? Watch Eons: Life and Death on Pangea on the free PBS App: or on the web here: ← use this link if you are outside of the U.S.

Midpeninsula Regional Open Space District ABC Eyewitness News has a story about an "exceptionally preserved fossilized tooth." The tooth of an American mastodon was found in a creek in California’s Bay Area. It was found by a scientist doing a survey for an environmental restoration project. The fossil may be more than 10,000 years old. A fossilized Pacific mastodon tooth that scientists say is at least 10,000 years old and in “immaculate condition” was discovered recently in a creek bed in California, according to local officials.

Long-time member Marty Houdek recently sent me a couple photos of Rhacophyllum from Mazon Creek. The first one is a sweet Rhacophyllum clarkii (see Mazon Creek #170), from one of the Braidwood pits (2, 3, or maybe 4?). It's beautiful. It opened this past summer via freeze/thaw... after being collected 30 years ago!

We hope you'll come out to "Brag Night" this Saturday, September 19th, 2026! We are sure there will be some very nice treasures to see! "Brag Night" on the first meeting after summer vacation has been an ESCONI tradition for a long time. The first one seems to be 1952. Here is the announcement.

Danville Field Trip Rules for Saturday, October 17th, 2026 An ESCONI field trip to the Danville, IL Shale Pile for Pennsylvanian fossils is scheduled for Saturday October 17th, 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.

Come on out and show off your finds for 2026! "Brag Night" has been a ESCONI tradition since the very beginning!

This is Mazon Monday post #340.  What’s your favorite Mazon Creek fossil?  Tell us at esconi.info@gmail.com. Neuropteris thompsoniana was described by William Culp Darrah (1909-1989), in 1969. Darrah was an American professor of biology at Gettysburg College, in Pennsylvania. He was a specialist in paleobotany. In addition to paleontology, Darrah had a deep interest in 19th century photography, and published several works on the subject.

PBS Eons has a new video. This one is about a time when many animals had sails. This is a tale about sails, and the enigma of why, for a brief but critical phase in the history of life, sporting a big biological billboard was all the rage.

A lifelike reconstruction of a 24-legged insect that lived 324 million years ago in present-day Texas.Credit...Chao Tan The New York Times has an interesting article about research that has uncovered an early insect. The animal, Chosha praecursor, lived about 324 million years ago during the Carboniferous Period in what is now Texas. It looked very similar to modern day silverfish, with a huge difference...

I was talking to Ralph Jewell and Jeremy Zimmerman at the Braceville field trip a few weeks ago and they showed me a very nice fern fossil. Make that a seed fern... it seems to be a variety of Mariopteris, maybe Mariopteris decipens (see Mazon Monday #108) or the much rarer Mariopteris wilmingtonenese (see Mazon Monday #211). What do you think? Let's hear your thoughts...

This is "Gorgeous George", when he was on display in the main gallery in 1976. He and the Lambeosaurus were star attractions at the museum from 1956 to 1992. He was incorrectly called a Gorgosaurus for most of its “life”.  That was corrected in 1999 and he is now known as a Daspletosaurus, a rare species of tyrannosaur.  “George” originally hailed from Alberta, Canada and was found by none other than Barnum Brown of the American Museum of Natural History (AMNH).

The September 2026 General Meeting will be held on Friday, September 11th, 2026 at 8:00 PM via Zoom. Our presentation is by Franklin Duffy, PhD Student and Research Affiliate from The Field Museum and Denver Museum of Nature & Science. He will be presenting "Searching for Colorado’s Tiktaalik on the West Coast of Laurentia." This presentation is a spotlight on our fieldwork in the Late Devonian Parting Formation of Colorado and the transitional "fishapod" fossils that can be found there.

By studying the fossilized wings of ancient insects as well as the bioacoustics of their living relatives, researchers were able to use computer modeling and machine learning to replicate their sounds.Credit...Richard Bizley/Science Source The New York Times has an interesting story about the sounds of Jurassic forests. Insect chirps, trills, and clicks make up a large part of the Earth's modern soundscape.

At the end of August, ESCONI held our annual Fall field trip to the Braceville Spoil Pile, known as "Worm Hill." It was a huge success. The weather cooperated for the most part. Saturday, August 29th was a beautiful day, with no rain and highs in the mid-70's. Unfortunately, Saturday, August 30th started out with rain, but that slowed and stopped by about 10 AM. The ground soaked up most of the water and some of the shale was softened for our ready picks and shovels.

The Academy of Natural Sciences in Philadelphia opened in 1828 and is known for its Dinosaur Hall.Credit...Matt Rourke/Associated Press The New York Times has a piece about the plight of the Academy of Natural Sciences in Philadelphia. The institution first opened its door in 1828... nearly 200 years ago. It is the oldest natural history museum in the US. Due to financial difficulties since the Covid-19 pandemic, it is being forced to close at the end of September.

There's a new episode of PBS Eons. This one is about the evolution of arboreal living. Watch Eons: Life and Death on Pangea on the free PBS App: or on the web here: ← use this link if you are outside of the U.S. How and when did tetrapods move into the trees? And why? Turns out, the story of climbing may have less to do with trees and more to do with their leaves.

Today, we have a largish plate of Crossotheca sagittata. Crossotheca sagittata is the fertile form of Pecopteris fontainei (see Mazon Monday #129). Remember, paleobotany specifies separate species for different plant parts, which is why we have two names for the same plant. This concept is known as form genera.

ESCONI highlights from 25, 50, and 70 years ago

Field trips require membership, but visitors are welcome at all meetings! Friday, September 11th General Meeting - 8:00 PM via Zoom. Franklin Duffy, PhD student and research affiliate from the Field Museum and the Denver Museum of Nature & Science will be presenting "Searching for Colorado’s Tiktaalik on the West Coast of Laurentia." Saturday, September 12th Junior Study Group Meeting…

Only a few days left!!!! Step inside the world of sauropods in "The World’s Largest Dinosaurs." Stand beneath a towering, life-sized 60-foot Mamenchisaurus and discover the amazing biology behind the largest animals to ever live.

Save the date! The 2027 ESCONI Gem, Mineral, and Fossil Show will be held on March 20th and 21st, 2027 at the DuPage County Fairgrounds. See you there!

The history of Mazon Creek paleontology is filled with fossils that have been reinterpreted as new species when new information became available. Animals have been moved from one group to another, species have been renamed, and some fossils once thought to represent animals have turned out to be something else entirely. There are even some, like Tullymonstrum gregarium, whose place on the tree of life is still being determined. Another particularly interesting story is Howellitubus whitfieldorum. Howellitubus whitfieldorum was described by Eugene Richardson Jr. in the 1956 Fieldiana paper "Pennsylvanian Invertebrates of the Mazon Creek Area, Illinois - Marine Fauna". Richardson described it as an annelid worm of class Chaetopoda and family Serpulidae.

The Cromo Paleo Show has an entertaining video on Youtube. Somehow, I don't think a pet dinosaur will turn out well... Would Velociraptor make a good pet? 🦖 In this episode of the “Would It Make a Good Pet?” series, we dive deep into the REAL science behind owning one of the most famous dinosaurs of all time — Velociraptor.

ESCONI will have a field trip to Flat Run Fossils in Mt. Orab, OH on Saturday September 19, 2026. There is an attendance limit of 16 people. Flat Run Fossils is a new pay-to-dig site in the famous Mt. Orab trilobite beds. For many years, thousands of gorgeous Flexicalymene and Isotelus trilobites have been collected from this area. Other possible finds include brachiopods, graptolites, cephalopods, and crinoids.

Today, we have a Macroneuropteris scheuchzeri (see Mazon Monday #39) from the Tonganoxie Sandstone (Stranger Formation of the Douglas Group in the Virginian Stage) near Ottawa, Kansas. That formation has been dated to a range of 306 to 299 million years ago, which is younger than Mazon Creek. Many plant fossils were collected from the locality in the late 1970's. Unfortunately, the site is now closed.

Some Don Auler art was on display at the recent ESCONI Rock Swap. Rick Rock had this painting of an owl on black shale up for sale. Long-time contributors B.J. and Mike Kukulka purchased it and graciously let us post it here.

Close-up of the hip bone of an Edmontosaurus. Credit: University of Liverpool Science Daily has a story about another discovery of organic molecules in dinosaur bones. Since the early 2000's, paleontologists have been finding organic material in dinosaur bones. The discoveries have been met with skepticism by paleontologists. Now a study in the journal Analytical Chemistry adds new evidence. Professor Steve Taylor, chair of the Mass Spectrometry Research Group at the University of Liverpool's Department of Electrical Engineering & Electronics, said:

I had a chance to catch up with Jack Wittry at the Field Museum this weekend. He mentioned that he had tracked down the insect whose name we first encountered at Tom Testa Day at the Carbon Hill School Museum back in June. At the time, Jack wasn't sure whether Carbohymen testai was actually a valid name. After doing some digging, he not only confirmed the species, but also located the actual fossil in the Field Museum's collections!

RNA is supposed to fall apart within hours, yet researchers have now read it from a mammoth frozen in Siberian permafrost 39,000 years ago — and the transcripts caught his muscle tissue in the middle of a stress response

PBS Eons has a new episode. This one is about the Permian Mass Extinction, the Earth's worst mass extinction. Watch Eons: Life and Death on Pangea on the free PBS App: or on the web here: ← use this link if you are outside of the U.S. For 3 million years, microbes ruled the Earth. But were these tiny survivors just lucky? Or did they play a more sinister role in the greatest disaster our planet has ever faced?