Mesojassoides is a genus of extinct leaf hopper from the Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

, approximately 70-65 million years ago, Fox Hills Formation

Fox Hills Formation

The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south....

. The genus contains a single

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 species Mesojassoides gigantea, described from a fore wing found in 1932 by C.H. Dane and W. G. Pierce in Adams County, Colorado

Adams County, Colorado

Adams County is the fifth most populous of the 64 counties of the state of Colorado of the United States. The United States Census Bureau estimates that the county population was 441,603 in 2010 census, a 21.4% increase since 2000 census. Adams County is named for Alva Adams, Governor of the...

. Described by Paul W. Oman

Paul W. Oman

Paul Wilson Oman An entomologist and specialist on leafhopper taxonomy, Paul Oman was born in Kansas in 1908 and was educated at the University of Kansas and the George Washington University...

 in 1937, the genus was named for the similarity in vein structure between the holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 and the modern genus Jassus. The holotype specimen, National Museum of Natural History

National Museum of Natural History

The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. Admission is free and the museum is open 364 days a year....

#75521, is 12 millimetre (0.47244094488189 in) long and nearly complete, missing the clavus and a small section of the costal margin. The specimen indicates M. gigantea was similar in size to the largest modern leaf hopper species.