Coelophysis - Meaning: Hollow Form

One of the earliest known dinosaurs, Coelophysis (seel-OH-fie-sis) meaning "hollow form" in reference to its hollow bones is a small, carnivorous biped from North America.

It first appeared in the Late Triassic Period, around 210 million years ago.

Coelophysis is an earliest well known dinosaur. Coelophysis was a lightly built dinosaur, between two to three metres in length, and less than a metre tall at the hips. The name Coelophysis means "hollow form" or "hollow process", so named because of its hollow limb bones.

Coelophysis lived in what was then a seasonally dry, desert-like environment, a savanna-type climate perhaps like modern-day Kenya without the grasses (since flowering plants hadn't evolved yet).

Coelophysis was a carnivore, a meat eater. It may also have been a scavenger. Coelophysis' fossilized stomach remains have been found containing small reptiles, fish, and other Coelophysis bones of different sizes, indicating that it was a cannibal.

Coelophysis most likely reproduced by laying eggs. Thousands of fossilized Coelophysis skeletons were found at the Ghost Ranch, New Mexico, USA. Many of them contained the bones of young Coelophysis in their abdomens - this evidence showed that Coelophysis either ate its young or gave birth to live young. It is more likely that they were cannibalistic (like many modern-day reptiles) since the tiny Coelophysis skeletons within the adult Coelophysis were not embryos, but young Coelophysis.

Despite being an early dinosaur, the evolution of the theropod body form had already advanced greatly from creatures like Herrerasaurus and Eoraptor. Coelophysis had an elongated snout with large fenestrae (small pores in epithelial cells) which helped to reduce skull weight, while narrow struts of bones preserved the structural integrity of the skull. The neck had a pronounced sigmoid curve.

The torso of Coelophysis conforms to the basic theropod body shape, but the pectoral girdle displays some interesting special characteristics wishbone, the earliest known example in a dinosaur. Coelophysis also preserves the ancestral condition of possessing four digits on the hand. It had only three functional digits, the fourth embedded in the flesh of the hand.