Smithian (early Triassic) Ammonoid Biostratigraphy at Crittenden Springs, Elko County, Nevada and a New Ammonoid from the Meekoceras Gracilitatis Zone

Crittenden Springs in northeastern Nevada yields M. gracilitatis Zone ammonoids renowned for the finely detailed, exquisite preservation of the test, which sometimes even displays relict color patterns. Evidence reveals most of the fossiliferous Lower Triassic beds in the Crittenden Springs area are overturned and this conclusion places the Meekoceras gracilitatis Zone portion of the section and the immediately adjacent, but condensed Anasibirites fauna in the proper biostratigraphic sequence. The paleoequatorial affinity of the western US Smithian ammonoid fauna is affirmed, and the co-occurrence of certain ammonoids from western US and Tethyan low paleolatitude localities demonstrates faunal exchange between both sides of Panthalassa during the Early Triassic. One of these co-occurring ammonoids, Churkites noblei n. sp. from the Meekoceras gracilitatis Zone is herein described and compared to two species of Churkites from the Anasibirites nevolini Zone of the