Segisaurus ‭(‬Segi lizard‭ ‬-‭ ‬after Tsegi Canyon‭)

Short Info

Segisaurus ‭(‬Segi lizard‭ ‬-‭ ‬after Tsegi Canyon‭)

Phonetic : Seg-e-sore-us

Named By : Lewis Camp‭ ‬-‭ ‬1936

Diet : Insectivore/Carnivore

Size : Estimated 1.5 meters long

Type of Dinosaur : Small Theropod

Type Species : S.‭ ‬halli‭ (‬type‭)‬

Found in : USA,‭ ‬Arizona,‭ ‬Tsegi Canyon‭ ‬-‭ ‬Navajo Sandstone Formation

When it Lived : Mid Jurassic, 195-180 million years ago

Segisaurus (meaning “Segi canyon lizard”) is an genus belonging to the small coelophysid dinosaurs that was approximately 1 meter (3.3 feet) in length. The sole known specimen was discovered in the early Jurassic strata of Tsegi Canyon, Arizona, the place it was named. Segisaurus was the sole dinosaur that has ever been discovered in the area.


Segisaurus halliCamp, C. L., Public domain, via Wikimedia Commons


Segisaurus was alive around 18 million years ago in its Jurassic period. It was a bipedal, primitive theropod that was roughly the size of an average goose. Segisaurus was 1 meters (3.3 feet) long and a half-meter (1.65 feet) tall and weighed approximately 4-7 kilograms. It was agile and insectivorous however, it could have also scavenged meat. Its structure was reminiscent of birds with a flexible extended neck and a strong body. Segisaurus was three-toed with strong legs that were lengthy when compared to the length of its body. Similar to its legs, Segisaurus had a tail that was long and forearms that were long. The collar bone of the dinosaur was as bird-like, bolstering the argument of scientists that dinosaurs are closely related to birds. Segisaurus is mentioned from the sole specimen ever discovered that was a holotype, UCMP 32101 that was an infant. The exact dimensions of Segisaurus as an adult could not be discovered. It is interesting to note that clavicles were observed within the Segisaurus specimen, which was not found in other dinosaurs of the time period. An speculative explanation from Charles Lewis Camp was that the “splint-like” neck ribs supported a patagium that resembled a Draco along the neck to increase the ability of the animal to move swiftly. Segisaurus is significant as it proves that the clavicle was a primitive structure found in early theropods.

It was in 1933 that Max Littlesalt, a Navajo Indian, discovered the Holotype found within Tsegi Canyon of the Navajo Sandstone of Coconino County, Arizona. The specimen was discovered in calcareous sandstone. It was laid down in the Pliensbachian and Toarcian phases of the Jurassic roughly from 190-174 million years in the past. When the remains were discovered, Littlesalt, who had animals in the canyon, was able to point out these fossils for archeologists conducting an exploration in the canyon. In addition to the first discovery of Segisaurus there are no other fossils that were found.

When the fossil of Segisaurus was found, Camp likened its posture to the posture of an “sitting hen”, due to the position that the remains of the dinosaur were located in. Theropods also used this position to rest or remain sheltered during ash and sand storms.

Source: Wikipedia