Fossil eggs associated with a neoceratopsian (Mosaiceratops azumai) from the Upper Cretaceous Xiaguan Formation, Henan Province, China

Abstract The close association of osteological remains and fossil eggs sometimes leads to misinterpretations, particularly in the absence of adequate taphonomic data. A clutch of 15 fossil eggs from the Upper Cretaceous Xiaguan Formation, Henan Province, China occurs in close association to a partial skeleton of the neoceratopsian, Mosaiceratops azumai . Two centimeters of sediment separate several eggs on the edge of the clutch from the rostrum of the skull. However, preservation of aragonite crystals in the eggshell allows assignment of the eggs to a turtle. Physical characteristics of the bones and eggs suggest the specimen was prepared upside-down. We estimate an egg mass of 89.3 g and calculate water vapor conductance (GH2O) as 288 mg H2O day −1  Torr −1 . Using a formula that correlates egg size (53 × 58 mm) and carapace length, we estimate the carapace of the turtle that produced the clutch as 1.5 m. This egg size exceeds that of all previously reported fossil turtle eggs.