[N] 2007 Dromomeron romeri
Irmis, R.B., Nesbitt, S. J., Padian, K. Smith, N.D., Turner, A,H., Woody, D., and Downs, A. (2007). \\\\\\\"A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs\\\\\\\". Science 317: 358-
Dromomeron (meaning \\\\\\\"running femur\\\\\\\") is a genus of dinosauromorph archosaur (not a dinosaur) from Late Triassic-age Chinle Formation rocks at Hayden Quarry, Ghost Ranch, New Mexico (USA). It is known from partial remains including a thigh bone, belonging to an animal less than 1.0 meters (3.3 ft) long. It is described as most closely related to the earlier Lagerpeton of Argentina, but was found among remains of true dinosaurs like Chindesaurus, indicating that the first dinosaurs did not immediately replace related groups.
The species name honors influential 20th century vertebrate paleontologist Alfred Sherwood Romer. Holotype GR 218 a complete left thigh bone from the Hayden Quarry at Ghost Ranch. The rocks there are in the lower portion of the Petrified Forest Member of the Chinle Formation, and are Norian in age (between 216 and 203 million years old). Additional hindlimb bones, some probably from the same individual, are also known. These bones are most similar to those of the older dinosauromorph Lagerpeton. Other specimens, from the Chinle Formation of Arizona and a roughly contemporaneous part of the Dockum Group of Texas, also have been assigned to this genus.
Also found at Hayden Quarry are the remains of phytosaurs, aetosaurs, rauisuchians, and several types of dinosaurs and dinosaur relatives, including a Silesaurus-like animal, the herrerasaurid Chindesaurus, and an unnamed coelophysoid theropod. Finding the remains of four types of dinosaurus and dinosaur relatives (including Dromomeron itself) is noteworthy because it shows that dinosaurs did not immediately replace related groups; that some of these groups, like the lagerpetonids, persisted for longer than previously known and diversified; and that dinosaurian replacement may have occurred at different times in different areas. It has generally been thought that the first dinosaurs quickly replaced more archaic Late Triassic faunas, either by outcompeting them or when the more archaic faunas suddenly became extinct.
Fossils from the Hayden Quarry, in the Upper Triassic Chinle Formation of New Mexico, and an analysis of other regional Upper Triassic assemblages instead imply that the transition was gradual. Some dinosaur relatives preserved in this Chinle assemblage belong to groups previously known only from the Middle and lowermost Upper Triassic outside North America. Thus, the transition may have extended for 15 to 20 million years and was probably diachronous at different paleolatitudes.
The paper is not suggesting that Dromomeron is a dinosaur or the ancestor of dinosaurs, not even that Dromomeron is the direct descendant of Lagerpeton.
Dromomeron (meaning \\\\\\\"running femur\\\\\\\") is a genus of dinosauromorph archosaur (not a dinosaur) from Late Triassic-age Chinle Formation rocks at Hayden Quarry, Ghost Ranch, New Mexico (USA). It is known from partial remains including a thigh bone, belonging to an animal less than 1.0 meters (3.3 ft) long. It is described as most closely related to the earlier Lagerpeton of Argentina, but was found among remains of true dinosaurs like Chindesaurus, indicating that the first dinosaurs did not immediately replace related groups.
The species name honors influential 20th century vertebrate paleontologist Alfred Sherwood Romer. Holotype GR 218 a complete left thigh bone from the Hayden Quarry at Ghost Ranch. The rocks there are in the lower portion of the Petrified Forest Member of the Chinle Formation, and are Norian in age (between 216 and 203 million years old). Additional hindlimb bones, some probably from the same individual, are also known. These bones are most similar to those of the older dinosauromorph Lagerpeton. Other specimens, from the Chinle Formation of Arizona and a roughly contemporaneous part of the Dockum Group of Texas, also have been assigned to this genus.
Also found at Hayden Quarry are the remains of phytosaurs, aetosaurs, rauisuchians, and several types of dinosaurs and dinosaur relatives, including a Silesaurus-like animal, the herrerasaurid Chindesaurus, and an unnamed coelophysoid theropod. Finding the remains of four types of dinosaurus and dinosaur relatives (including Dromomeron itself) is noteworthy because it shows that dinosaurs did not immediately replace related groups; that some of these groups, like the lagerpetonids, persisted for longer than previously known and diversified; and that dinosaurian replacement may have occurred at different times in different areas. It has generally been thought that the first dinosaurs quickly replaced more archaic Late Triassic faunas, either by outcompeting them or when the more archaic faunas suddenly became extinct.
Fossils from the Hayden Quarry, in the Upper Triassic Chinle Formation of New Mexico, and an analysis of other regional Upper Triassic assemblages instead imply that the transition was gradual. Some dinosaur relatives preserved in this Chinle assemblage belong to groups previously known only from the Middle and lowermost Upper Triassic outside North America. Thus, the transition may have extended for 15 to 20 million years and was probably diachronous at different paleolatitudes.
The paper is not suggesting that Dromomeron is a dinosaur or the ancestor of dinosaurs, not even that Dromomeron is the direct descendant of Lagerpeton.