Hill Annex Mine Fossil Gallery

Fossils From the Cretaceous Era Coleraine Formation in Calumet, Minnesota

The Cretaceous era Coleraine Formation at Hill Annex Mine State Park in Calumet, Minnesota
preserves fossils from the inhabitants of the Western Interior Seaway and its shores.



Minnesota's Fossil Crocodile

Teleorhinus mesabiensis now known as Terminonaris robusta.

Illustration by Ken Sander for Minnesota Volunteer Magazine. This image is displayed at the Hill Annex Mine State Park Museum.

This article is on display at the
Hill Annex State Park Museum

Iron Range Crocodile

This article is from the MN DNR Publication

"The Minnesota Volunteer"
Volume 46 Number 271
November-December 1983

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(Terminonaris text modified from Wikipedia entry Terminonaris)

Terminonaris is a genus of extinct crocodyliforms that lived in the Late Cretaceous (Cenomanian and Turonian).
They were similar in appearance to the modern Gharial. The name means: “enlarged snout or nose” at the front of the skull.

Only seven Terminonaris fossil specimens have been discovered and all are from the
Northern Hemisphere: six from North America and one from Europe.

All of the Terminonaris fossils found in North America were done so along the shores of the former Western Interior Seaway.
One of those fossils was found at Hill Annex Mine in Calumet, MN.

The snout fragment was found by brothers Vincent Garlough and Gary Garlough in 1967.
They found it on the same hill that tourists at the park find fossils today.
The fossil was donated to the Science Museum of Minnesota where it was described
as a new species of Teleorhinus by Dr. Bruce Erickson. He named it Teleorhinus mesabiensis.

Biologists now classify Teleorhinus as Terminonaris.

Display case replica at Hill Annex State Park Museum.

Terminonaris was a predator that could reach a length of about 6 meters or 20 feet.
The skull of the largest individual is 98.3 cm (38.7 in) long.
The elongated snout and the long, relatively thin teeth suggest that Terminonaris
was a hunter of fish, small mammals and possibly small dinosaurs.

A modern gharial eating a fish at Indira Gandhi Zoological Park, Visakhapatnam, India.

Image credit: Author - Siddhartha Lammata from Bangalore, India
This file is licensed under the Creative Commons Attribution 2.0 Generic license.

A reptile tooth found at Hill Annex in 2019 by a tourist. This may be from a Terminonaris.

(I've never found one)