Sunday, June 16, 2019

The Dinosaurs and Prehistoric Animals of Illinois.

Tyrannosaurus Rex
No dinosaur bones or fossils have ever been discovered in Illinois -- for the simple reason that this state's geologic sediments were being eroded away, rather than actively deposited, during most of the Mesozoic Era [1] (250,000,000 BC to 65,000 BC). No dinosaur bones or fossils have been found in Wisconsin, Michigan, Indiana or Ohio either.

Still, Illinois can boast a significant number of amphibians and invertebrates dating to the Paleozoic Era [2] (541,000,000 BC to 251,900,000), as well as a handful of Pleistocene period (2,600,00 BC to 12,000 BC) pachyderms (Woolly Mammoths, Mastodons and other elephant type mammals). For much of the Mesozoic and Cenozoic Eras (250,000,000 BC to 2,000,000 BC), Illinois was geologically unproductive -- hence the lack of fossils dating from this vast expanse of time.
Woolly Mammoths
American Mastodon
However, conditions improved tremendously during the Pleistocene period when herds of Woolly Mammoths and American Mastodons tramped across this state's endless plains (and left scattered fossil remains to be discovered, piecemeal, by 19th and 20th-century paleontologists).

Joe Devera, has been a geologist with the Illinois State Geological Survey for over 30 years. "Other dinosaurs, such as T-Rex, could be found in Illinois but they're covered up by vegetation and soil," he said. "People think of dinosaur bones out West, because the ground is dry and eroded, and bones are much easier to find." Devera said he believes dinosaurs roamed the state during the Cretaceous period (145,000,000 BC to 66,000,000 BC).

Devera is particularly interested in finding the bones of duckbilled dinosaurs -- plant-eaters known as hadrosaurs -- because their remains have already been detected in northeastern Missouri. Devera said a researcher got "darn lucky" in Missouri and found dinosaur fossils when a well was being dug. Three kinds of dinosaur fossils have been found in Missouri: Hadrosaurs, Parrosaurus, a small Tyrannosaurid (perhaps Albertosaurus).

After hours of research, I finally found Tyrannosaurus Rex bones in Illinois. It's SUE, the famous T. Rex we all know and love. 
SUE in the Main Hall of the Field Museum in Chicago.
She is no longer featured in the main entrance hall of the Field Museum in Chicago.
SUE in the 'Griffin Halls of Evolving Planet' of the Field Museum in Chicago.
SUE is in her new home in the 'Griffin Halls of Evolving Planet' display in the upper level of the Field Museum.

Is it possible to find dinosaur fossils in Illinois?
To find dinosaurs you need Jurassic or Cretaceous age rocks. Unfortunately, there are no Jurassic rock outcroppings in Illinois and very little Cretaceous. As yu can see, there is just a tiny bit of dark green at the southern point of Illinois and an even smaller patch in western Illinois. These dark green colored locations are mapped as "Undifferentiated" Cretaceous -- which means their age has not been accurately determined yet. It's not hopeful. If the rocks contained common well-preserved fossils, we would already know their age.
Compiled by Neil Gale, Ph.D. 


[1] The Mesozoic Era includes the Triassic, Jurassic, and Cretaceous periods.

[2] The Paleozoic Era is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from 541,000,000 BC to 251,900,000, and is subdivided into six geologic periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

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