Fishes are the oldest known of the animals which have backbones – the vertebrates. Recently they have been found in rocks from the Cambrian Period, dating some 500 million years old. Myriad forms have evolved and disappeared over the past 1/2 billion years, but thousands of varieties still exist in the seas, oceans, lakes and rivers. Even with the vast variety of fishes, most, living or extinct, can easily be classified on the basis of how much of the skeleton is bone, and the shapes of the bones.

Chondrichthyean fishes are those with skeletons comprised primarily of cartilage, with little real bone present. These are best typified by the sharks. Fossils readily identifiable as sharks are first known from mid-Paleozoic rocks. Many cartilaginous fish forms have appeared and disappeared, to be found only as fossils, but the basic ‘shark’ form has persisted nearly 400 million years.

steichthyean fishes are those with bony skeletons. Though they first appeared soon after the sharks, they remained relatively obscure until Mesozoic times. Soon they diversified into the varied forms familiar to us today ranging from angelfish, catfish, and sailfish, to minnows.


The Institute has collected fish from around the world, but the majority of specimens come from several formations including Green River, Niobrara and the country of Lebanon.

Green River Formation

The Green River Formation is a series of Eocene Epoch freshwater lakebed deposits in southwestern Wyoming, northeastern Utah, and northwestern Colorado. These deposits are known for the tremendous volume of fossils they contain. Fishes, turtles, crocodiles and other vertebrates are found, as well as plants, insects, and other invertebrates. They show that this region once had a tropical climate.


Perhaps the oldest continuously collected fossil locality, the area near the towns of Hakel and Hadjula, Lebanon is known for fossil fishes. The limestone rocks there preserve a wide variety of mid-Cretaceous fossils. The fishes are of particular interest because the age is right to capture early members of many of today’s most common ocean fish groups, as well as many extinct groups.

The Institute has numerous fossil fish for sale. These include specimens from the Green River Formation, the country of Lebanon, and the Niobrara Chalk Formation of Kansas.