Diplosaurus is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of goniopholidid

Goniopholididae

Goniopholididae is an extinct family of moderate-sized semi-aquatic crocodyliforms similar to living crocodiles. They lived between the Early Jurassic and the Late Cretaceous.-Geographical distribution:...

 mesoeucrocodylia

Mesoeucrocodylia

Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....

n. Fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s have been found from the western United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 and range from Late Jurassic

Late Jurassic

The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

 to Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 in age. The genus was first named and described in a paper written in 1877 by Othniel Charles Marsh

Othniel Charles Marsh

Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...

. The generic name, derived from Greek διπλόος, diploos, "double", probably refers to the "biconcave vertebrae" Marsh mentions as a distinctive trait compared to modern forms. The type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 is Diplosaurus felix. In 1890 Karl Alfred von Zittel

Karl Alfred von Zittel

Karl Alfred Ritter von Zittel was a German palaeontologist.-Biography:He was born at Bahlingen in Baden, and educated at Heidelberg, Paris and Vienna. For a short period he served on the Geological Survey of Austria, and as assistant in the mineralogical museum at Vienna...

 recombined this with Goniopholis

Goniopholis

Goniopholis is an extinct genus of crocodyliform that lived in North America, Europe and Asia during the Late Jurassic and Early Cretaceous. Being semi-aquatic it is very similar to modern crocodiles...

into a Goniopholis felix, but today this is generally rejected.

Along with D. felix, a second species of Diplosaurus was constructed in 1877 by Marsh after he recombined Hyposaurus vebbii

Hyposaurus

Hyposaurus is a genus of extinct dyrosaurid crocodyliform. Fossils have been found in Paleocene aged rocks of the Maria Farinha Formation in Pernambuco, Brazil and Iullemmeden Basin in West Africa and Maastrichtian strata in New Jersey. It was related to Dyrosaurus....

, named by 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 1874, with Diplosaurus into a new combination, Diplosaurus vebbii. D. nanus was named by Marsh in 1895 but is now considered to be a nomen dubium

Nomen dubium

In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...

. In 1999, Diplosaurus felise was named on the basis of a specimen found in Lakes' Quarry 1 at Como Bluff

Como Bluff

Como Bluff is a long ridge extending east-west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing...

, Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

, part of the Morrison Formation

Morrison Formation

The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...

.