Distribution and biochronology of Camarasaurus (Dinosaria, Sauropoda) from the Jurassic Morrison Formation of the Rocky Mountain Region

Abstract

––The stratigraphic distribution of fossil remains of Camarasaurus (Dinosauria, Sauropoda) allows recognition of five biozones in the upper Jurassic Morrison Formation: (1) no Camarasaurus Zone (early-mid Kimmeridgian), (2) Camarasaurus grandis Zone (mid Kimmeridgian), (3) C. lentus Zone (late Kimmeridgian), (4) transition Zone (early Tithonian), and (5) C. supremus Zone (Tithonian). Paleobiogeographically, C. grandis is known from south and central Wyoming, central Colorado, and New Mexico; C. lentus occurs in Wyoming and Utah and C. supremus in south-central Colorado to western Oklahoma. However, the geographic occurrences may only reflect stratigraphic distribution as locally appropriate beds may not be exposed or were eroded. Camarasaurus might have a much wider distribution in the Rocky Mountain area than indicated by its distribution of the fossil remains. Additionally, the data provide new insights into the taxonomy of Camarasaurus. FIGURE 1. Geological features in the Rocky Mountain region and major dinosaur quarries in the Morrison Formation. The map is modified from King (1977, fig. 74). Areal definition of the Morrison Formation is based on Turner and Peterson (1999).