guisessuch

Guisessuch is a genus of small, basal theropod dinosaur that lived during the Late Jurassic period, approximately 155 million years ago. Fossils of Guisessuch have been discovered in the Morrison Formation of western North America, specifically in what is now the state of Colorado. The name "Guisessuch" translates roughly to "Guisé's crocodile-like reptile," referencing the distinctive crocodilian-like features observed in its skull.

Guisessuch is notable for its unique anatomical traits that blend characteristics of both theropods and crocodilians. Its skull was elongated and low, with a broad snout, which is unusual for theropods but reminiscent of modern crocodiles. The teeth were slender and conical, adapted for a diet likely consisting of small prey or possibly scavenging. The forelimbs were relatively robust, suggesting a possible semi-arboreal or climbing lifestyle, though this remains debated among paleontologists.

The holotype specimen, designated as **CM 662**, consists of a nearly complete skull and partial postcranial skeleton. This fossil provides significant insights into the evolutionary diversity of theropods during the Late Jurassic. Guisessuch is often classified within the group of basal theropods known as "coelophysoids," though its exact phylogenetic placement is still under discussion due to its unusual features.

Research on Guisessuch contributes to understanding the evolutionary transitions between early theropods and more derived groups like ceratosaurs and neotheropods. Its discovery highlights the morphological variability present in theropod dinosaurs during this time period, offering clues about their ecological roles and adaptations.