In the 1840s explorers to the American West began recovering fossils from a unit of rocks later named the Green River Formation. These first finds consisted of invertebrate fossils but within a decade vertebrate varieties cropped up when in 1856 American geologist John Evans found fish remains in a stone nodule.
Evans’s discovery opened up an era of paleontological exploration that continues to this day and has resulted in more than a million specimens recovered by fossil collectors. In fact, today this is one of the most-collected vertebrate fossils in the world.
Discovery and Early Description of Knightia eocaena
After Evans discovered the fish fossils in 1856, he sent them to prominent American paleontologist Joseph Leidy in Philadelphia to study. Leidy was one of the country’s leading experts on a variety of fossils, including the first nearly complete skeleton of a dinosaur – Hadrosaurus foulkii – ever found.
In a brief description published in the Proceedings of the Academy of Natural Sciences of Philadelphia, Leidy attributed the fish fossils to a new species, Clypea humilis.
Soon, Leidy protégé Edward Drinker Cope began exhaustive studies of these fish and other animal remains from the Green River beds. Besides doing his own field work, he also paid collectors to find and send him specimens, which he used as the basis for several important descriptive publications. In his classic 1884 publication informally referred to as “Cope’s Bible”, he reassigned Clypea humilis to a new genus, Diplomystus.
In 1907, ichthyologist and future Stanford University president David Starr Jordan realized that some of the fossils previously attributed to the genus Diplomystis displayed enough different characteristics to warrant separation into two genera, and thus he christened the genus Knightia, named after former University of Wyoming geologist Wilbur Clinton Knight.
Jordan also determined that the specific name, humilis, was preoccupied under a different genus and so introduced the name eocaena, in recognition of the Eocene-aged rocks from which the fossils are extracted. Leidy’s original Clypea humilis is now thus known as Knightia eoceaena.
Nature of a Prehistoric Herring from Wyoming
Knightia eoceaena lived in lakes about 40-50 million years ago in modern-day southwestern Wyoming. It grew up to about ten inches long and its fossil are very common and well preserved.
Knightia was a relatively slender fish with four fins, a large head, deeply forked tail, and double row of scutes extending form the back of the head to the middle of the body.
Scientists believe Knightia was an important component of the food cycle, feeding on algae and plankton and being consumed by other fish and crocodiles. It was a schooling fish and its fossils are often found in mass concentrations totaling hundreds of individuals.
Lawmakers Designate Green River Fish as State Fossil in 1987
Today the Green River Formation and its fossils, especially Knightia eocaena, are legendary in the field of paleontology.
The effort to designate this fish as Wyoming’s state fossil was spearheaded by teacher Madie Barker and students from Cheyenne’s Anderson Elementary School. This group gained the support of Senator Liz Byrd and lobbied other politicians to push through a state fossil bill.
Finally, on February 18, 1987, in the same year that Wyoming designated the cutthroat trout as its state fish, Governor Mike Sullivan signed into law Knightia as the state fossil. Wyoming Statutes Title 8, Chapter 3, Section 112 reads, “The fossilized fish Knightia is the state fossil of Wyoming.”
Sources
Grande, Lance, 1984. "Paleontology of the Green River Formation, with a Review of the Fish Fauna". Geological Survey of Wyoming, Bulletin 63.
Jordan, David. 1907. "The Fossil Fishes of California". University of California Publications, Bulletin of the Department of Geology Volume 5 (7).
Leidy, Joseph.1856 (1857). "Notice of Some Remains of Fishes Discovered by Dr. John E. Evans". Proceedings of the Academy of Natural Sciences of Philadelphia Volume 8.
Kevin Schindler - I have worked at scientific institutions for more than 20 years written more than 200 articles about science, history, and baseball.
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