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The Tully Monster

Illinois's official state fossil

See Illinois (unpublished)


This little piece began as a sidebar to a much longer account of the coal industry in my never-published guide to the history and culture of Illinois. My curiosity about the geologic past was stimulated by my boyhood visits to the Illinois State Museum, where I tried to stretch my tiny brain wide enough to imagine Illinois as (among other things) a dank swamp of horsetails and club mosses the size of trees. 

Too good to throw away, and it might whet the curiosity of readers new to Illinois geology. Here's a good quick introduction to that subject from the Illinois State Geological Survey. See also my profile of geologist Richard Leary here

Three hundred million years ago, the future continent of North America straddled the equator, and Illinois was a vast lowland forest of primitive, nonflowering plants, part of a massive delta that lay along the edge of tropical southern Louisiana. Dead plants and animals that settled or were washed into low places were covered by mud; compacted under the pressure of its own weight, the muds turned into shale. 

Remains of plant and animal remains that had fallen into  the mud were preserved when carbon dioxide from their decomposition reacted with iron in the mud to form a hard protective case of what is commonly known as ironstone. These mineral coffins preserved the precise form of even the soft body parts of hundreds of species of plants and land and sea animals. Split open one of these oval or lozenge-shaped ironstone concretions and one finds exquisitely etched portraits of plant leaves, stems, and reproductive structures such as seeds and spores. “Coal balls” contain not just impressions but actual plant remains, a result of their imperfect carbonization; these remains reveal in three-dimensions the structures of the plants entombed in them, even their cellular makeup.

Outcrops of one shale formation in particular, the Francis Creek Shale laid down approximately during the Pennsylvanian Period, occur naturally along the banks of such Illinois streams as Mazon Creek. The stony pages of these abundant fossils constitute an exceptionally comprehensive and detailed catalog of Pennsylvanian-period vegetation. The Illinois State Museum, with pardonable pride, calls the Mazon Creek deposits “some of the most important fossil deposits in North America.” Mazon Creek nodules and fossils are found in museums worldwide, although the most important collections are at the Chicago’s Field Museum of Natural History and at the Illinois State Museum in Springfield. 

Among the finds is Tullimonstrum gregarium. The "Tully Monster" was a small soft-bodied animal one foot or so long . It was first found by amateur fossil-hunter Francis Tully in 195. Since then more than one hundred have been found in the Mazon Creek area, and recently they have also been found in open-pit coal mines in central Illinois.


The creature was so nicknamed because it looks as it its body was cobbled together with bits of other animals. It had a pair of vertical fins at the tail end of its vaguely submarine-like body, and at the other end  a long proboscis with up to eight small sharp teeth on each "jaw." Two thin antenna-like structures protruded from each side, at the ends of which were round organs "suggestive of a camera-type eye." (A lifelike reconstruction of which may be seen at Chicago’s Field Museum, near the famous Pennsylvanian coal forest display.)


For years, the creature defied identification; current speculation is that the Tully Monster was probably an ancient fish akin to today’s bloodsucking lampreys. Because the creature is paleontologically important, prized by collectors, and unique to the Prairie State—and no doubt because its name makes it very box office—it was voted the official Illinois state fossil in 1987. ●




John Hallwas

Essential for anyone interested in Illinois history and literature. Hallwas deservedly won the 2018 Lifetime Achievement Award from the Illinois State Historical Society.

Lee Sandlin Author

One of Illinois’s best, and least-known, writers of his generation. Take note in particular of The Distancers and Road to Nowhere.

Chicago Architecture Center

See Home Page/Learn/

Resources for a marvelous building database, architecture dictionary, even a city planning graphic novel. Handsome, useful—every Illinois culture website should be so good.

The Encyclopedia of Chicago


The online version of The Encyclopedia of Chicago. Crammed with thousands of topic entries, biographical sketches, maps and images, it is a reference work unmatched in Illinois.

Illinois Great Places

The Illinois chapter of the American Institute of Architects in 2018 selected 200 Great Places in Illinois that illustrate our  shared architectural culture across the entire period of human settlement in Illinois.

McLean County Museum

of History

A nationally accredited, award-winning project of the McLean County Historical Society whose holdings include more than 20,000 objects, more than 15,000 books on local history and genealogy, and boxes and boxes of historical papers and images.

Mr. Lincoln, Route 66, and Other Highlights of Lincoln, Illinois


Every Illinois town ought to have a chronicler like D. Leigh Henson, Ph.D. Not only Lincoln and the Mother road—the author’s curiosity ranges from cattle baron John Dean Gillett to novelist William Maxwell. An Illinois State Historical Society "Best Web Site of the Year."

Illinois Digital Archives


Created in 2000, the IDA is a repository for the digital collections of the Illinois State Library and other Illinois libraries and cultural institutions. The holdings include photographs, slides, and glass negatives, oral histories, newspapers, maps, and documents from manuscripts and letters to postcards,  posters, and videos.

The Illinois State Museum


The people's museum is a treasure house of science and the arts. A research institution of national reputation, the museum maintains four facilities across the state. Their collections in anthropology, fine and decorative arts, botany, zoology, geology, and  history are described here. A few museum publications can be obtained here.

Chronicling Illinois

“Chronicling Illinois” showcases some of the collections—mostly some 6,000 photographs—from the Illinois history holdings of the Abraham Lincoln Presidential Library.


I will leave it to the authors of this interesting site to describe it. "Chicagology is a study of Chicago history with a focus on the period prior to the Second World War. The purpose of the site is to document common and not so common stories about the City of Chicago as they are discovered." 

Illinois Labor History Society

The Illinois Labor History Society seeks to encourage the preservation and study of labor history materials of the Illinois region, and to arouse public interest in the profound significance of the past to the present. Offers books reviews, podcasts, research guides, and the like. 

Illinois Migration History 1850-2017

The University of Washington’s America’s Great Migrations Project has compiled migration histories  (mostly from the published and unpublished work by UW Professor of History James Gregory) for several states, including Illinois. The site also includes maps and charts and essays about the Great Migration of African Americans to the north, in which Illinois figured importantly. 

History on the Fox

An interesting resource about the history of one of Illinois’s more interesting places, the Fox Valley of Kendall County. History on the Fox is the work of Roger Matile, an amateur historian of the best sort. Matile’s site is a couple of cuts above the typical buff’s blog. (An entry on the French attempt to cash in on the trade in bison pelts runs more than

2,000 words.)




Southern Illinois University Press 2017

A work of solid history, entertainingly told.

Michael Burlingame,

author of Abraham 

Lincoln: A Life 

One of the ten best books on Illinois history I have read in a decade.

Superior Achievement Award citation, ISHS Awards, 2018

A lively and engaging study . . .  an enthralling narrative.

James Edstrom

The Annals of Iowa

A book that merits the attention of all Illinois historians

as well as local historians generally.

John Hoffman

Journal of Illinois HIstory

A model for the kind of detailed and honest history other states and regions could use.

Harold Henderson 

Midwestern Microhistory

A fine example of a resurgence of Midwest historical scholarship.

Greg Hall

Journal of the Illinois

State Historical Society

Click  here 

to read about

the book 

Click  here 

to buy the book 


Southern Illinois University Press

SIU Press is one of the four major university publishing houses in Illinois. Its catalog offers much of local interest, including biographies of Illinois political figures, the history (human and natural) and folklore of southern Illinois, the Civil War and Lincoln, and quality reprints in the Shawnee Classics series.

University of

Illinois Press

The U of I Press was founded in 1918. A search of the online catalog  (Books/Browse by subject/Illinois) will reveal more than 150 Illinois titles, books on history mostly but also butteflies, nature , painting, poetry and fiction, and more.  Of particular note are its Prairie State Books,  quality new paperback editions of worthy titles about all parts of Illinois, augmented with scholarly introductions.

University of

Chicago Press

The U of C publishing operation is the oldest (1891) and largest university press in Illinois. Its reach is international, but it has not neglected its own neighborhood. Any good Illinois library will include dozens of titles about Chicago and Illinois from Fort Dearborn to

Vivian Maier.

Northern Illinois University Press

The newest (1965) and the smallest of the university presses with an interest in Illinois, Northern Illinois University Press gave us important titles such as the standard one-volume history of the state (Biles' Illinois:
A History of the Land and Its People) and contributions to the history of Chicago, Illinois transportation, and the Civil War. Now an imprint of Cornell University Press.


Reviews and significant mentions by James Krohe Jr. of more than 50 Illinois books, arranged in alphabetical order

by book title. 


Illinois Center for the Book

Run by the Illinois State Library, The Center promotes reading, writing and author programs meant to honor the state's rich literary heritage. An affiliate of the Library of Congress’s Center for the Book, the site offers award competitions, a directory of Illinois authors, literary landmarks, and reading programs.

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