''Aciprion'' is an extinct genus of lizard from the

Middle Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

and

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

. It was named in 1873 by American paleontologist

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...

for a jaw fragment from the Cedar Creek Member of the

White River Formation The White River Formation is a geologic formation of the Paleogene Period, in the northern Great Plains and central Rocky Mountains, within the United States. It has been found in northeastern Colorado, Dawes County in western Nebraska, Badland ...

in Colorado, as the

binomial Binomial may refer to: In mathematics *Binomial (polynomial), a polynomial with two terms *Binomial coefficient, numbers appearing in the expansions of powers of binomials *Binomial QMF, a perfect-reconstruction orthogonal wavelet decomposition * ...

''A. formosum''. Multiple additional specimens have been referred to the genus, including the second species ''A. majus'' named by Gilmore in 1928 for a partial skull. However, the differences between ''A. formosum'' and ''A. majus'' relate to slight size differences, so ''A. majus'' is considered a junior synonym of ''A. formosum''. Cope originally named ''Aciprion'' as a genus of teiid lizard, but Gilmore reclassified it as a member of

Iguanidae The Iguanidae is a family of lizards composed of the iguanas, chuckwallas, and their prehistoric relatives, including the widespread green iguana. Taxonomy Iguanidae is thought to be the sister group to the Crotaphytidae, collared lizards (fam ...

References

{{Taxonbar, from=Q131625237 Oligocene reptiles of North America Iguanidae Prehistoric lizard genera