Additional Information about the Discovery
Summary of key findings:
- Tawa is known from entire skeletons, is well preserved, and is one of the most completely known theropods from the Triassic.
- Tawa is found in the same deposits as the primitive carnivorous dinosaur Chindesaurus (closely related to Herrerasaurus) and an animal closely related to Coelophysis.
- These three animals are not each other's closest relatives, demonstrating that Triassic carnivorous dinosaurs from the Hayden Quarry at Ghost Ranch dispersed multiple times into North America.
- Dispersal of early dinosaurs was widespread during the Triassic, suggesting that the lack of sauropodomorph dinosaurs in North America was not a result of physical barriers.
- Anatomical information from Tawa helps unite all Triassic carnivorous dinosaurs into one group, called Theropoda. Previously, some scientists thought that carnivorous dinosaurs such as Herrerasaurus and Eoraptor evolved before the split of sauropodomorphs and true theropods.
- Theropoda is the clade (natural group) of dinosaurs containing the carnivorous dinosaurs, including Tyrannosaurus rex, Velociraptor, and birds.
- Dinosaurs lived with their closest relatives ("protodinosaurs" or "dinosaur precursors") towards the end of the Triassic Period.
- The Triassic Period lasted from 250 to 201 million years ago, and the following animals arose during this time: dinosaurs, crocodile relatives, mammals, pterosaurs, turtles, frogs, and lizards.
- Tawa is a theropod dinosaur and most likely ate meat.
- Tawa is known from multiple individuals ranging from small juveniles to sub adults.
- Tawa is between 2 and 4 meters long and stood at 1-1.5 meters tall at the hips.
- The braincase and neck of Tawa were surrounded by airsacs, just like living birds.
- Tawa has features of Herrerasaurus and coelophysid dinosaurs like Coelophysis and Herrerasaurus. This mix of features shows that Herrerasaurus is the most primitive theropod known (more closely related to birds than to sauropods).
- The Hayden Quarry is between 215-213 million years old.
- The fossils described in this paper were found at Ghost Ranch, in northern New Mexico, near the town of Abiquiu. Ghost Ranch is famous for its Triassic fossils, and has been visited throughout the last 130 years by scientists from the University of California, Berkeley; American Museum of Natural History; Carnegie Museum of Natural History; and the famous paleontologist Edward Drinker Cope.
- The fossils are from a locality known as the Hayden Quarry. This locality is probably several million years older than the famous Coelophysis Quarry, also on Ghost Ranch land.
- The Hayden Quarry was near the equator during the Late Triassic Period (it is currently at 36.2° latitude).
- Dinosaurs may have originated in South America
- During the Triassic, the continents were coalesced into a single landmass named Pangea.
- The specimens of Tawa were collected during the filming of the NSF-sponsored IMAX® 3-D film "Dinosaurs Alive!"
- Sauropodomorph dinosaurs apparently did not live in North America during the Triassic even though they had to pass through North America when dispersing between South America, Africa, and Europe.
- The name Tawa is from the Hopi name for the Puebloan sun god. The second part of the species name, hallae, is for Ruth Hall, who collected many of the specimens that formed the genesis of the Ghost Ranch Ruth Hall Museum of Paleontology (GR) collections.
Tawa hallae- Ta-WA Hall-A
Coelophysis - See-low-phy-sis
Coelophysoid - See-low-phy-soyd
Theropod - THER-o-pod
Chinle - Chin-lee
A fleshed-out reconstruction shows the newly discovered Triassic, carnivorous dinosaur, Tawa hallae
Ghost Ranch contains fossil-rich, Upper Triassic beds.
Paleontologists Nathan Smith (left) and Sterling Nesbitt (right) dig for fossils at the Ghost Ranch dig site in New Mexico.
The complete right hand of Tawa hallae
shows the excellent preservation of the Tawa
Sterling Nesbitt (left, of the American Museum of Natural History at the time, now at the University of Texas at Austin), Nathan Smith (of the University of Chicago and the Chicago Field Museum), Alan Turner (of Stony Brook University), and Randall Irmis (of the Utah Museum of Natural History and the University of Utah) were filmed for the NSF-supported IMAX® film Dinosaurs Alive! The scene above was captured soon after the paleontologists had wrapped a block of sediment containing Tawa
fossils in preparation for transport to the American Museum of Natural History.