Culebrasuchus was first described and named by Alexander K. Hastings, Jonathan I. Bloch, Carlos A. Jaramillo, Aldo F. Rincona and Bruce J. Macfadden in 2013 based on a single holotype skull and three neck vertebrae from the Culebra Formation. Culebrasuchus is thought to be the most basal member of Caimaninae, meaning that it represents the earliest radiation of caimans in the Americas. The ancestor of Culebrasuchus likely lived farther north, perhaps in what is now southern Mexico, because before the Miocene most of Panama was underwater. The movement of Culebrasuchus into the Panama CanalZone was an early part of the Great American Interchange in which animals dispersed between North and South America across the newly formed Isthmus of Panama. However, Culebrasuchus was not the earliest caimanine; Orthogenysuchus and Tsoabichi are known from the Eocene of North America and Eocaiman is known from the Eocene of South America, indicating that caimanines were dispersing between the continents across large expanses of ocean long before the isthmus formed.
Description
Like many living caimans, Culebrasuchus was small in size. Other caimans that lived during the same time in South America were much larger than Culebrasuchus. Features that Culebrasuchusshares in common with other caimanines include nostrils that open upward, and bones that do not overlap the edges of two openings in the skull table called supratemporal fenestrae. Like living caimanines, Culebrasuchus has blunter teeth at the back of the jaw, and the teeth in the upper jaw completely overly the teeth in the lower jaw when the mouth is closed. Features in Culebrasuchus that are not found in other caimanines include the lack of ridges above the eye sockets and the large size of a hole in the lower jaw called the external mandibular fenestra. These features may be plesiomorphic for alligatorids. Culebrasuchus also has a straighter lower jaw than most other alligatorids, it lacks the ridges on the frontal bone between the eye sockets that are common among crocodylians, and the fourth tooth of the maxilla is the largest in the upper jaw.
Phylogeny
Below is a cladogram from the 2013 description of Culebrasuchus showing its phylogenetic position as the most basal caimanine:
