Twin Mountains Formation
Encyclopedia
The Twin Mountains Formation, also known as the Twin Mountain 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
fossil
s. Dinosaurs from this formation include the large theropod Acrocanthosaurus
, the sauropod Paluxysaurus
, and the ornithopod
Tenontosaurus
.
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
of the United States of America. It is a terrestrial
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
formation of Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
age (Lower Cretaceous), and is notable for its dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s. Dinosaurs from this formation include the large theropod Acrocanthosaurus
Acrocanthosaurus
Acrocanthosaurus is a genus of theropod dinosaur that existed in what is now North America during the Aptian and early Albian stages of the Early Cretaceous. Like most dinosaur genera, Acrocanthosaurus contains only a single species, A. atokensis. Its fossil remains are found mainly in the U.S...
, the sauropod Paluxysaurus
Paluxysaurus
Paluxysaurus is a genus of basal titanosauriform sauropod dinosaur from the late Aptian or early Albian-age Lower Cretaceous Twin Mountains Formation of Hood County, Texas, USA...
, and the ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
Tenontosaurus
Tenontosaurus
Tenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...
.
Paleobiota
- Acrocanthosaurus atokensis
- DromaeosauridaeDromaeosauridaeDromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
indet. - TheropodaTheropodaTheropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
indet. - SauropodaSauropodaSauropoda , or the sauropods , are an infraorder of saurischian dinosaurs. They had long necks, long tails, small heads , and thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land...
indet. - Pleurocoelus sp.
- Unnamed Euornithopod
- TenontosaurusTenontosaurusTenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...
dossi - "Skull and postcranial skeleton, several individuals." - Iguanodontia indet.