Culebrasuchus was first described and named by Alexander K. Hastings, Jonathan I. Bloch, Carlos A. Jaramillo, Aldo F. Rincona and Bruce J. Macfadden in2013 based on a singleholotype skull and three neckvertebrae from theCulebra Formation.Culebrasuchus is thought to be the mostbasal member ofCaimaninae, meaning that it represents the earliest radiation of caimans in the Americas. The ancestor ofCulebrasuchus likely lived farther north, perhaps in what is now southern Mexico, because before theMiocene most of Panama was underwater. The movement ofCulebrasuchus into the Panama Canal Zone was an early part of theGreat American Interchange in which animals dispersed between North and South America across the newly formedIsthmus of Panama (although during the Early Miocene it had not yet formed, with 20 km of ocean still separating the continents). However,Culebrasuchus was not the earliest caimanine;Orthogenysuchus andTsoabichi are known from theEocene of North America andEocaiman 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.[1]
Like many living caimans,Culebrasuchus was small in size. Other caimans that lived during the same time in South America (including those in the generaMourasuchus andPurussaurus) were much larger thanCulebrasuchus. Features thatCulebrasuchus shares in common with other caimanines include nostrils that open upward (rather than slightly forward, as in alligatorines), and bones that do not overlap the edges of two openings in theskull table calledsupratemporal fenestrae. Like living caimanines,Culebrasuchushas 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 inCulebrasuchusthat 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 beplesiomorphic ("primitive") for alligatorids.Culebrasuchus also has a straighter lower jaw than most other alligatorids, it lacks the ridges on thefrontal bone between the eye sockets that are common among crocodylians, and the fourth tooth of the maxilla (rather than third, as in almost all other alligatorids) is the largest in the upper jaw.[1]
Alternatively, a 2018 study by Bonaet al. noted thatCulebrasuchus was enigmatic and difficult to interpret, and instead proposed it to be a member ofAlligatorinae, closely related to the livingAmerican Alligator andChinese Alligator, as shown in the cladogram below:[4]
