Segisaurus

Name Origin

Lizard from Segi Canyon

Family

Coelophysidae

Classification

Diapsida, Saurischia, Theropoda

Habitat (Discovery Location)

United States

Period

Approximately 183 million years ago (Early Jurassic)

Length

Approximately 1 meter

Weight

Approximately 5 kilograms

Diet

Carnivore (Meat-eater)

Description

Segisaurus was a small carnivorous dinosaur that lived in North America, in what is now Tsegi Canyon, Arizona, during the Early Jurassic period.
Its name means “lizard from Segi Canyon,” in reference to the location where its fossil was excavated.

A Goose-Sized, Swift Hunter

Segisaurus was an extremely small dinosaur, measuring about 1 meter in length and weighing only 5 kg, roughly the size of a modern goose.

Physical Characteristics

Segisaurus had a bird-like body structure, characterized by a slender, flexible neck and a long tail and forelimbs.
Its bones were hollow, and it is presumed to have had a very lightweight build.

Agility

Its slender physique and developed hind limbs were adapted for running fast, and it is believed to have been extremely agile.

Weaponry

It had claws on its hands, indicating that Segisaurus was a carnivorous dinosaur.

A Diet Shrouded in Mystery: The Missing Skull

Although fossils of Segisaurus have been discovered, its skull and teeth have not yet been found.
Post-cranial fossils have been found, but the skull and teeth are missing. Because of this, there is no definitive proof of what it specifically ate.

However, based on its lightweight body and claws, it is speculated to have been an agile hunter that preyed on small animals like insects and lizards, and perhaps also scavenged on the carcasses of larger animals.

The Most Important Feature: The Discovery of “Clavicles” and Its Evolutionary Significance

The reason the discovery of Segisaurus is considered highly significant in the field of paleontology lies in its chest.

The Segisaurus fossil was found to possess clavicles (collarbones), a feature that many dinosaurs were thought to lack.
The presence of these clavicles is a trait shared with modern birds.

This fact implies that Segisaurus was not merely a small carnivore, but that it potentially represents a crucial snapshot of an early evolutionary stage, before dinosaurs and birds diverged onto their separate paths.
Segisaurus holds an extremely important key to unlocking the mystery of the evolution from dinosaurs to birds.

Jurassic
Park / World Featured Dinosaur

Role in the Film (Spoiler Alert!)

Appearance in Jurassic Park
It never makes an appearance as a living creature in the film.

However, it does exist purely in the park's lore as one of the dinosaurs being housed there. According to this lore, a dedicated paddock was prepared for Segisaurus, and its marker (featuring a skull design) can be seen on the park map.

Given its complete lack of any role in the movie, it's likely that only the most dedicated fans would even know that Segisaurus was (in theory) supposed to be living on Isla Nublar.