| Miaogou Formation | |
| Type: | Geological formation |
| Age: | late Early Cretaceous, |
| Period: | Early Cretaceous |
| Region: | Inner Mongolia |
| Country: |  China |
| Coordinates: | 40.2°N 149°W |
| Unitof: | Yangtaiwatan Basin[1] |
| Underlies: | Baiyanghe Formation[2] |
| Prilithology: | Sandstone, mudstone, muddy limestone and sandy conglomerate |
The Miaogou Formation is a geological formation in Inner Mongolia, north China. While its absolute age is uncertain, it has been estimated to represent Early Cretaceous (around Aptian–Albian) sediments based on the faunal composition. Dinosaur remains are among the fossils that have been recovered from the formation.
The primary fossil-producing outcrop of the Miaogou Formation is the Maortu locality, which was discovered in 1959 by a joint expedition of Chinese and Russian paleontologists.[3] Initial reports of the locality's fauna incorrectly assigned the fossils to either the Ulansuhai or Dashuigou formations, but a later discussion corrected this.
Analysis of the formation's geology indicates that it represents a hot, humid environment with large lake systems. The formation's lower member preserves alluvial fan to braided stream deposits, while the upper member preserves meandering stream and lacustrine deposits.[4]
| Genus | Species | Region | Material | Notes | Images | |
|---|---|---|---|---|---|---|
| Gobisaurus | G. domoculus | Maortu locality, Chilantai | A skull, with undescribed postcranial remains belonging to the same individual[5] | An ankylosaurid closely related to Shamosaurus; originally interpreted as from the nearby Ulansuhai Formation | ||
| Probactrosaurus | P. gobiensis | Maortu locality, Chilantai | Partial skulls and skeletons[6] | A hadrosauroid ornithopod; originally interpreted as from the nearby Dashuigou Formation | ||
| Shaochilong | S. maortuensis | Maortu locality, Chilantai | Partial skull, axis, and caudal vertebrae[7] | A carcharodontosaurid theropod, formerly "Chilantaisaurus" maortuensis; originally interpreted as from the nearby Ulansuhai Formation | ||
| Yuanyanglong | Y. bainian | Maortu locality, Chilantai | Two associated partial skeletons of similarly sized individuals[8] | A basal oviraptorosaurian theropod |