| Twin Mountains Formation | |
|---|---|
| Stratigraphic range: Aptian | |
| Type | Geological formation |
| Unit of | Trinity Group |
| Underlies | Glen Rose Formation |
| Thickness | 150 ft (46 m) |
| Lithology | |
| Primary | Claystone, sandstone |
| Other | Conglomerate |
| Location | |
| Region |  Texas |
| Country |  United States |
The Twin Mountains Formation, also known as the Twin Mak Formation, is a sedimentary rock formation, within the Trinity Group, found in Texas of the United States of America. It is a terrestrial formation of Aptian age (Lower Cretaceous), and is notable for its dinosaur fossils. Dinosaurs from this formation include the large theropod Acrocanthosaurus, the sauropod Sauroposeidon, as well as the ornithopods Tenontosaurus and Convolosaurus.[1] [2] It is the lowermost unit of the lower Cretaceous, lying unconformably on Carboniferous strata. It is overlain by the Glen Rose Formation. It is the lateral equivalent of the lower part of the Antlers Formation.[3]
- ^ Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loueff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth M.P.; Noto, Christopher N. (2004). "Dinosaur distribution". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 517–606. ISBN 0-520-24209-2.
- ^ Rose, Peter J. (2007). "A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships" (web pages). Palaeontologia Electronica. 10 (2).
- ^ "Geologic Unit: Twin Mountains". National Geologic Map Database. USGS. Retrieved 31 May 2014.