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10 Facts About Coelophysis

The Truth About the World's Best-Known Early Theropod Dinosaur



The late Triassic Coelophysis was descended from the very first dinosaurs, which evolved in South America (Wikimedia Commons)


Thousands of Coelophysis skeletons have been discovered in New Mexico's Ghost Ranch quarry (Wikimedia Commons)


Coelophysis was a fairly small dinosaur, only weighing 20 or 30 pounds (Nobu Tamura)

One of the best-represented theropod dinosaurs in the fossil record, Coelophysis holds an important place in the history of paleontology. Here are 10 facts you may (or may not) have known about this early meat-eater.

1. Coelophysis lived during the Triassic period...

Coelophysis prowled southwestern North America well before the golden age of dinosaurs: about 215 to 200 million years ago, right up to the cusp of the Jurassic period. At that time, dinosaurs were far from the dominant vertebrates on land; in fact, they were probably third in the terrestrial pecking order, behind crocodiles and archosaurs (the "ruling lizards" from which the first dinosaurs evolved).

2. ...and descended from the first South American dinosaurs.

As early as Coelophysis appeared on the scene, it wasn't quite as "basal" as the South American dinosaurs that preceded it. These middle Triassic theropods, dating from about 230 million years ago, included such important genera as Eoraptor, Herrerasaurus and Staurikosaurus; as far as paleontologists can tell, these were the first true dinosaurs.

3. The name Coelophysis means "hollow form."

Granted, Coelophysis (pronounced see-low-FIE-sis) isn't very catchy, but scientists of the mid-19th century adhered strictly to form when assigning names to their discoveries. The name Coelophysis was bestowed by the famous paleontologist Edward Drinker Cope, who was referring to this early dinosaur's hollow bones, an adaptation that helped it to remain light and nimble.

4. Coelophysis was one of the first dinosaurs with a wishbone.

Not only were Coelophysis' bones hollow, like the bones of modern birds; this early theropod also possessed a furcula, or wishbone. However, Coelophysis was only distantly ancestral to birds; it wasn't until 50 million years later, during the late Jurassic period, that small theropods like Archaeopteryx truly started evolving in an avian direction.

5. The eyes of Coelophysis were unusually large.

As a general rule, predatory animals rely more on their senses than their relatively slow-witted prey. Like many small theropods of the Mesozoic Era, Coelophysis had unusually well-developed eyesight, which helped it to home in on its prospective meals. (Bigger eyes also meant a correspondingly bigger brain, which was necessary to process the extra visual information.)

6. Thousands of Coelophyis fossils have been discovered at the Ghost Ranch quarry...

For nearly a century after it was discovered, Coelophysis was a relatively obscure dinosaur. That all changed in 1947, when the famous paleontologist Edwin H. Colbert discovered thousands of Coelophysis bones tangled together in New Mexico's Ghost Ranch quarry. That goes a long way toward explaining why Coelophysis is the state fossil of New Mexico!

7. ...a hint that this dinosaur may have congregated in packs.

Whenever paleontologists discover extensive "bone beds" belonging to a single genus of dinosaur, they're tempted to speculate that this dinosaur roamed in massive packs or herds. Today, the weight of opinion is that Coelophysis was indeed a pack animal, but it's also possible that isolated individuals drowned together in the same flash flood and wound up being washed into the same location.

8. Coelophysis was once believed to be a cannibal.

Analysis of the stomach contents of some Ghost Ranch Coelophysis specimens has revealed the fossilized remnants of smaller reptiles--which once prompted speculation that Coelophysis ate its own young. However, it turns out that these tiny meals weren't Coelophyis babies at all, or even dinosaurs, but rather small archosaurs of the late Triassic period.

9. Coelophysis may have been the same dinosaur as Megapnosaurus.

There is still a lot of confusion about the proper classification of the earliest theropods. Some paleontologists believe that Coelophysis was the same dinosaur as Megapnosaurus--which was itself known as Syntarsus until a few years ago. It's also possible that Coelophysis roamed the expanse of Triassic North America, rather than just being restricted to the southwestern quadrant.

10. Male Coelophysis were bigger than females (or vice-versa).

Because so many specimens of Coelophysis have been discovered, paleontologists have been able to establish the existence of two basic body plans: "gracile" (that is, slender) and "robust" (that is, not so slender). It's very likely that these corresponded to the males and females of the genus, though it's anyone's guess as to which was which!

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