A procoelous dorsal vertebra collected from the Hartland Shale Member of the Late Cretaceous Greenhorn Formation represents the oldest specimen of a large squamate reptile, possibly a dolichosaur or early mosasauroid, from Kansas. The isolated vertebra was collected near the contact between the Hartland Shale and Jetmore Chalk (late Cenomanian - early Turonian) members of the Greenhorn Formation in Mitchell County, Kansas. A latest Cenomanian age was determined by analysis of the nannofossils contained in matrix recovered from the neural canal of the specimen.