The Hekou Formation is a Cretaceous geologic formation in China. Pterosaur fossils have been recovered from the formation. It is a unit of the Guifeng Group and dates to the Late Cretaceous.^[2] Dinosaur fossils from the formation include a nearly perfect oviraptorid embryo nicknamed Baby Yingliang, an unnamed large hadrosaurid, and hadrosauroid eggs with embryos.^[3][4][5] Other reptiles include the alligatoroid Eurycephalosuchus^[6] and the polyglyphanodontian lizards Xenodontolacerta and Yechilacerta.^[7][8] The mammal Erythrobaatar and Yubaatar qianzhouensis have also been described from the formation.^[9][10]

Description

The Hekou Formation is a constituent of the Guifeng Group; a sequence of formations that were deposited in the Xinjiang Basin, including the Hekou, Tangbian, and Lianhe formations, which record aeolian-alluvial interactions in a palaeoplateau desert. Both a successional and coeval model of the deposition of these units have been proposed, with estimated ages of the Hekou formation ranging from Coniacian-Santonian to Maastrichtian.^[11][12] The associated facies include alluvial fans and adjacent wadi river channels, with mudcracks indicating subaerial exposure of the deposits. Oxygen-18 isotope values recorded in Dinosaur eggshells indicated low annual precipitation and humidity, suggesting an arid to semi-arid environment. The occurrence of striated cobbles in the alluvial facies suggests glacial activity in the catchment areas of the Cretaceous plateau.^[13][14] Subsequent research has reinterpreted many of the vertebrate fossils from the Nanxiong Formation as instead coming from the Hekou Formation, with the "Nanxiong Formation" instead equivalent to the Guifeng Group.^[15] In the Yudu district, the boundaries between the Hekou, Tangbian, and Lianhe formations are unclear, leading some researchers to merge these strata into a single unit, referred to as the Hekou Formation.^[16]

See also

• List of pterosaur-bearing stratigraphic units
• List of dinosaur-bearing stratigraphic units

References

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