"Crocodylus" acer is an extinct species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of crocodyloid from the Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 of Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

. A single well preserved skull was described by paleontologist Edward Drinker Cope

Edward Drinker Cope

Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...

 in 1882 and remains the only known fossil of the species. It was found from the Wasatchian

Wasatchian

The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 55,400,000 to 50,300,000 years BP lasting . It is usually considered to be within the Eocene, more specifically the...

-age Green River Formation

Green River Formation

The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...

. "C." acer had a long, narrow snout and a low, flattened skull.

Some postcranial bones have been attributed to "C." acer but they have more recently been suggested to belong to the related species "C." affinis

Crocodylus affinis

"Crocodylus" affinis is an extinct species of crocodyloid from the Eocene of Wyoming. Fossils were first described from the Bridger Formation by American paleontologist Othniel Charles Marsh in 1871. Marsh described the species, along with every other species of crocodyloid in the Bridger...

. Although they were first placed in the genus Crocodylus

Crocodylus

Crocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family.Established species include three extinct species:* † Crocodylus acer - probably represents a distinct genus....

, "C." acer and "C." affinis are not crocodiles. Recent studies place them as early members of Crocodyloidea

Crocodyloidea

Crocodyloidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, it is defined as Crocodylus niloticus and all crocodylians more closely related to C. niloticus than to either Alligator mississippiensis or Gavialis gangeticus .- Phylogeny :Cladogram after...

, only distantly related to Crocodylus. Although it represents a distinct genus, a generic name has not yet been proposed for "C." acer.