Coelophysis, the New Mexico State Fossil

summer 2017 COELOPHYSIS, THE NEW MEXICO STATE FOSSIL any of us are aware that the State of credited with jump-starting American He sent the sack, along with some MNew Mexico has a state gemstone science in the late 19th century. additional specimens from near Gallina, to (Turquoise), a state flower (Yucca), a state In February 1881, while living in Cope in Philadelphia. Cope named them bird (Roadrunner), and even a state ques- Abiquiu, Baldwin explored the Upper two species of a genus of small meat-eating tion (Red or Green?). But how many know Triassic deposits of what is called the dinosaur (theropod) previously named by that New Mexico also has an official state Chinle Formation a few miles north of Marsh; Coelurus longicollis and Coelurus fossil? And that this particular fossil is one town, in exposures along the Chama bauri, writing that Coelurus bauri was of the scientifically best-known and most River at a locality he knew as Arroyo Seco. “… about the size of a greyhound.” After important dinosaurs in the world? New Baldwin often collected in winter, when further consideration, Cope moved Mexico has an incredibly rich fossil record a steady source of water was available as both species to a different genus, first and many remarkable fossil organisms have snow. He found a small concentration Tanystrophaeus and then the new genus been recovered here. But one in particular, of delicate bones, which he picked up Coelophysis. The name Coelophysis is a relatively small, and at first glance, and placed in a sack. He included a note derived from two Greek roots meaning unassuming, animal was chosen by the written in flowing black script,“Contains “hollow form,” referring to the hollow New Mexico state legislature on March 17, Triassic or Jurassic bones all small and bones of the small animal. 1981, to be the New Mexico State fossil. tender — Those marked little bones are many That honor was bestowed on the uniquely of them almost microscopic. All in this sack Ghost Ranch Coelophysis Quarry New Mexican dinosaur Coelophysis bauri found together in same place. About four Several decades later, in 1947, Edwin (pronounced “see-low-fy-sis”). This is a hundred feet below gypsum stratum Arroyo Colbert, a curator of the American brief account of its initial finding, and Seco Rio Arriba Co New Mexico February Museum of Natural History (AMNH), subsequent discovery of one of the most 1881. No feet — no head — only one tooth. visited the Arroyo Seco area, which is near famous dinosaur quarries in the world, the D. Baldwin—Abiquiu.” Ghost Ranch, while on his way to explore Ghost Ranch Coelophysis Quarry. When discovered, Coelophysis was one of the old- est dinosaurs in the world, and the remains of this animal continue to inform us about the world of the Late Triassic (about 225 to 202 million years ago) and the rise of the ruling reptiles, the dinosaurs. Discovery The bones of Coelophysis were first discovered by David Baldwin, a little-known figure who worked as a packer for the 1875 Wheeler Survey in northern New Mexico. Baldwin later roamed throughout northwestern New Mexico and collected and sold vertebrate fossils first to Othniel Charles Marsh of Yale University, and later, through the 1880s, to Marsh’s nem- esis Edward Drinker Cope of Philadelphia. The rivalry and feud between Marsh and Cope, sometimes referred to as “The Bone A “flock” of Coelophysis bauri running across a Late Triassic landscape near what would become Wars,” are legendary and sometimes are Ghost Ranch, New Mexico. Illustration by Matt Celeskey and Mary Sundstrom. Published by the New Mexico Bureau of Geology and Mineral Resources • A Division of New Mexico Tech the Triassic in what is now the Petrified Forest National Park of Arizona. George Whitaker, a preparator on the American Museum’s staff and part of Colbert’s field crew, stumbled across a remarkable site in the Chinle Formation on Sunday, June 22, shortly before noon. Several days of careful excavation revealed what has become one of the most famous dinosaur localities in the world — the Ghost Ranch Coelophysis Quarry (also known as the Whitaker Quarry). Crews from the AMNH continued collecting through the next two summers, retrieving numerous blocks, some weighing several thousand pounds, containing complete skeletons of Coelophysis and other animals. The Ghost Ranch Coelophysis Quarry was reopened in 1981 by crews from the Carnegie Museum of Natural History Portion of a block from the Ghost Ranch Coelophysis Quarry collected in 1981 on display at the working cooperatively with several other New Mexico Museum of Natural History and Science, showing a partial skeleton of Coelophysis institutions, including the then newly bauri including the base of the tail, hind limbs and pelvic bones, dorsal vertebrae, and skull. founded New Mexico Museum of Natural History, the Museum of Northern Some workers have estimated that What’s in a Name? Arizona, and others. They recovered about a thousand complete or nearly com- The name and identity of Coelophysis has plete skeletons lie within the Ghost Ranch been controversial. The original fossils Coelophysis Quarry, a truly extraordinary collected by Baldwin, and described accumulation of dinosaurs. Coelophysis is by Cope, are fragmentary and may not represented by young to old individuals, be complete enough to allow precise with bodies commonly intertwined and identification. In the early 1990s, a pair tangled. The quarry is overwhelmingly of New Mexican paleontologists therefore dominated by Coelophysis, but it also argued that Coelophysis bauri is a “nomen contains other animals including the dubium” (doubtful name), and proposed small invertebrate chonchostracans (clam a new name for the more complete Ghost shrimp) and ostracodes (seed shrimp), Ranch specimens, Rioarribasaurus colberti. complete fish, a variety of archosaurs However, another team of paleontologists (archosaurs are a group of vertebrate argued that since the name Coelophysis animals that includes crocodiles, dinosaurs bauri has been applied to the Ghost Ranch and birds, and their close relatives), includ- specimens since 1947, it is best to designate ing a crocodile-like phytosaur, long-limbed one of the Coelophysis Quarry specimens crocodile relatives (Effigia and Vancleavea), a new type, or neotype, to maintain small reptiles like drepanosaurs and sphen- taxonomic stability. They petitioned the odontids, and at least one other small, Commission of Zoological Nomenclature, meat-eating dinosaur, Daemonosaurus. which ruled in their favor in June 1996. What led to this accumulation of In the late 1990s, two paleontologists fossilized animals in a single location? announced that they had discovered the Taphonomic studies (studies that look into area where Baldwin had collected the what happens to organisms after death Ghost Ranch Coelophysis Quarry undergoing original type specimen of Coelophysis bauri, excavation in late June, 1981. Photo courtesy of until their discovery as a fossil) of the and named a new dinosaur from a partial Timothy Rowe. quarry indicated that the bone bed is the skeleton that they had collected from the numerous additional blocks that have been result of transport of carcasses by running area, Eucoelophysis baldwini (meaning widely distributed in museums across the water and burial in silt, possibly in a small “Baldwin’s true Coelophysis”). However, United States for preparation and research. depression occupied by a pond. What several years later, a pair of other studies Several of the original blocks collected by killed the many hundreds of Coelophysis demonstrated that Euceolophysis is not a the AMNH in the 1940s were opened only and other animals? That cannot yet be dinosaur, but rather a close dinosaur rela- within the last ten years or so, and found determined. Possibly the animals died in tive. Most paleontologists consider that the to contain skeletons of animals other a drought. Perhaps animals congregated exact position of Baldwin’s Arroyo Seco than Coelophysis, and several of the larger around a shrinking water source when remains a mystery, although it likely was blocks collected by the Carnegie Museum flood waters overcame and drowned them along the cliffs near Ghost Ranch. continue to undergo preparation at the and transported them to the Coelophysis time of this writing. Quarry site. new mexico earth matters 2 summer 2017 Paleobiology that of birds. The neck vertebrae had side pockets that may have held airs sacks tied to Coelophysis is a small dinosaur, belonging the respiratory system, such as are found in 84 to the group Theropoda, that contains birds. Birds and many dinosaurs, including all meat-eating dinosaurs and birds. The Coelophysis, had an ultra-efficient breathing ! many skeletons of Coelophysis provide for Ghost Ranch system in which air is circulated in one an incomparable knowledge of its skeletal direction across the lungs, enabled by the anatomy. Coelophysis resembles other early action of air sacks that were distributed dinosaurs in being bipedal (moved by throughout the body, and indeed even Abiquiu means of its two rear legs) with a fully erect Reservoir pervading many of the bones. These helped gait. Their bodies were long, with a rela- pump air through a rigid lung located tively small head atop a long and sinuous within the chest cavity, and even allowed neck. A long tail helped to balance their oxygen to pass across the lungs during both 84 bodies over their hind legs. Early dinosaurs inhalation and exhalation. 96 differed from other archosaurs in having a ! Some specimens from the Ghost Ranch Abiquiu specialized hip-joint where the head of the Coelophysis Quarry even preserve the femur bent at right angles and was securely extremely delicate, thin, plate-like bones socketed within a cartilage-lined hole that helped to support the eye, the sclerotic within the pelvic bones. The ankle bones Location map of Ghost Ranch area.

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