Tully monster

The Tully monster is the common name for *Tullimonstrum gregarium*, an extinct soft-bodied animal from the late Carboniferous period.

The Tully monster, scientifically named *Tullimonstrum gregarium*, is an extinct soft-bodied animal from the late Carboniferous period. It is best known from the Mazon Creek fossil beds in Illinois, where it was first discovered in 1958 and later designated Illinois’s state fossil. Its exact evolutionary placement was debated for decades, but a 2016 study concluded it was a vertebrate related to lampreys.

Discovery and naming

The first specimen of the Tully monster was discovered in 1958 by amateur fossil collector Francis Tully in the Mazon Creek area of northeastern Illinois. The animal was later named *Tullimonstrum gregarium* in his honour and became widely known as the Tully monster.

Fossil record and habitat

Tully monster fossils are best known from the Essex biota in the Mazon Creek fossil beds. They are interpreted as having lived in shallow tropical coastal waters and estuaries during the late Carboniferous.

Anatomy and appearance

The Tully monster had a soft body, a long trunk-like proboscis ending in a claw with teeth, and eyes mounted on a rigid bar. Its distinctive body plan made it difficult to classify for many years.

Scientific classification

The Tully monster was long considered an enigmatic invertebrate, but a 2016 analysis of more than 1,000 fossils concluded it was a vertebrate and likely related to lampreys. This interpretation is widely cited, though the animal has remained unusual enough to invite continued discussion.