Day 374#: Segisaurus halli
Today's animal of the day is Segisaurus halli!
Image credit: Nobu Tamura
Named after the Tsegi Canyon in Arizona, where it was found, this small species of theropod dinosaur lived during the Early Jurassic period between 200 and 195 million years ago. It was a member of the Coelophysid clade, which was a group of slender carnivorous theropods that lived around the world throughout the Triassic and Early Jurassic. As the group's name suggests, the Coelophysid clade also includes the Triassic Coelophysis, and both Coelophysis and Segisaurus looked very similar to each other, with long, slender necks and stout bodies. Segisaurus is also believed to be a tad smaller than Coelophysis, but since the only fossils we have of it belong to a subadult specimen, its full adult size is currently unknown. It was also once believed that Segisaurus had solid bones, unlike the hollow bird-like bones of Coelophysis. This made scientists doubt whether Segisaurus was even a theropod or not, until it was eventually discovered that Segisaurus did in fact have hollow bones like its close relatives had.
Image credit: cisiopurple on DeviantArt
Segisaurus is often described as being about the size of a large goose and was around 1.65 ft tall and 3.3 ft long. It had muscular hind legs and a long tail to help with balance, which would have allowed it to better chase after small fast-moving prey, like insects and small lizards. Based on the type of sandstone its remains were found in, paleontologists think it would have lived in a sandy desert environment with lots of shifting sand dunes.
Image credit: Timothy J. Bradley (Jurassic Park Institute)
Segisaurus is currently the only species of dinosaur discovered in the Tsegi Canyon region, and was first discovered in 1933 by a Navajo man named Max Littlesalt. This specimen was found in a posture similar to that of a sitting chicken, and it's believed that this individual may have gotten caught in a sandstorm and had sat down in an area it thought was well-sheltered (perhaps in a den or nest), but ended up being buried by the sand and dying in the storm. Though that's just speculation since no nesting materials were found near the specimen. Other than this individual, no other remains of Segisaurus have been discovered. Regardless, its bird-like posture and appearance were actually key pieces of evidence that would eventually lead to the discovery that dinosaurs and birds were closely related.
Image credit: Frontier Developments plc (game: Jurassic World Evolution 2)
Also, fun fact: Segisaurus is technically canon in the Jurassic Park movie universe. It appears in a lot of the promotional materials for some of the movies, including the original Jurassic Park. However, it hasn't appeared in any of the movies yet, though it is in Jurassic World Evolution 2.
