Named by American paleontologist George Gaylord Simpson in 1937, Sebecus was one of the first known sebecosuchians.
Simpson described the type species, S. icaeorhinus, from a fragmented skull and lower jaw found in the Sarmiento Formation.
The specimen was discovered by the American Museum of Natural History's First Scarritt Expedition to Patagonia.
Teeth had been known since 1906 when Argentine paleontologist Florentino Ameghino associated them with carnivorous dinosaurs.
The more complete material found by Simpson firmly established that the new animal was a crocodyliform.
Although Simpson's fossil was considered one of the best finds of the expedition, Simpson described the genus only briefly in 1937.
He noted its unusual ziphodont dentition in which the teeth were laterally compressed and serrated.
Simpson was preparing a more detailed monograph on the genus, but entered the United States Army before its completion.
Another American paleontologist, Edwin Harris Colbert, completed Simpson's work, thoroughly describing the genus and placing it in a new family, Sebecidae.
Colbert placed Sebecus and the Cretaceous baurusuchid Baurusuchus (also from South America) in the suborder Sebecosuchia (erected by Simpson for all ziphodont crocodylomorphs), as both had deep snouts and ziphodont teeth.

The name Sebecus is a Latinisation of Sebek (also called Sobek), the crocodile god of ancient Egypt.
Sebek was considered an alternative to the Greek χάμψαι, or "champsa" in crocodilian nomenclature (the Greek historian Herodotus claimed that champsa was the Egyptian word for crocodile).
The specific name icaeorhinus of the type species is derived from the Greek words εικαίοs and ρύγχος.
Εικαίοs means "random" or "not according to plan" and ρύγχος means "snout", in reference to the animal's unusually deep snout.

In 1965, American paleontologist Wann Langston, Jr. named a second species, S. huilensis, from the Miocene Honda Group at the La Venta locality in Colombia.
S. huilensis was named on the basis of skull fragments.
The deposits are Laventan in age (about 13 million years old), extending the range of the genus into the Neogene by around 40 million years.
In 1977, remains were described from the Miocene of Peru.

A third species of Sebecus, S. querejazus, was named in 1991 from the early Paleocene Santa Lucia Formation in Bolivia.
This extended the range of Sebecus back to the beginning of the Paleogene, soon after the Cretaceous–Paleogene extinction event.
In 1993, Gasparini et al.
described Sebecus carajazus.
This was not a fourth species but a misspelling, or lapsus calami, of Sebecus querejazus.

A 2007 study of sebecids reclassified several species.
The two species S. huilensis and S. querejazus were given their own genera, Zulmasuchus and Langstonia, respectively.
Langstonia huilensis, named after Langston, was distinguished from Sebecus by its narrower snout and widely spaced teeth.
Zulmasuchus querejazus, named after Zulma Gasparini, one of the authors of the study, differs from Sebecus in its wider snout.

The postcranial skeleton of S. icaeorhinus was virtually unknown until Pol et al. (
2012) described postcranial remains of several individuals of this species, including a partially articulated specimen MPEF-PV 1776 with anterior region of the dentary (allowing the identification of this individual as representing S. icaeorhinus) and most of the postcranial skeleton preserved.
Estimates of total body length and mass of MPEF-PV 1776 vary from 2.2 to 3.1 m, and from 52.2 to 113.5 kg, respectively.
The postcranial skeleton of Sebecus provides additional evidence of its terrestriality.
Its limbs, especially femora, were proportionally longer than limbs of living crocodilians; the shoulder-to-hip length of its body can be estimated at 2.3 times the length of the femur - similar to another, unrelated terrestrial crocodylomorph, Pristichampsus, while American alligators have proportionally shorter femora.
Named by American paleontologist George Gaylord Simpson in 1937, Sebecus was one of the first known sebecosuchians. Simpson described the type species, S. icaeorhinus, from a fragmented skull and lower jaw found in the Sarmiento Formation. The specimen was discovered by the American Museum of Natural History's First Scarritt Expedition to Patagonia. Teeth had been known since 1906 when Argentine paleontologist Florentino Ameghino associated them with carnivorous dinosaurs. The more complete material found by Simpson firmly established that the new animal was a crocodyliform. Although Simpson's fossil was considered one of the best finds of the expedition, Simpson described the genus only briefly in 1937. He noted its unusual ziphodont dentition in which the teeth were laterally compressed and serrated. Simpson was preparing a more detailed monograph on the genus, but entered the United States Army before its completion. Another American paleontologist, Edwin Harris Colbert, completed Simpson's work, thoroughly describing the genus and placing it in a new family, Sebecidae. Colbert placed Sebecus and the Cretaceous baurusuchid Baurusuchus (also from South America) in the suborder Sebecosuchia (erected by Simpson for all ziphodont crocodylomorphs), as both had deep snouts and ziphodont teeth.
The name Sebecus is a Latinisation of Sebek (also called Sobek), the crocodile god of ancient Egypt. Sebek was considered an alternative to the Greek χάμψαι, or "champsa" in crocodilian nomenclature (the Greek historian Herodotus claimed that champsa was the Egyptian word for crocodile). The specific name icaeorhinus of the type species is derived from the Greek words εικαίοs and ρύγχος. Εικαίοs means "random" or "not according to plan" and ρύγχος means "snout", in reference to the animal's unusually deep snout.
In 1965, American paleontologist Wann Langston, Jr. named a second species, S. huilensis, from the Miocene Honda Group at the La Venta locality in Colombia. S. huilensis was named on the basis of skull fragments. The deposits are Laventan in age (about 13 million years old), extending the range of the genus into the Neogene by around 40 million years. In 1977, remains were described from the Miocene of Peru.
A third species of Sebecus, S. querejazus, was named in 1991 from the early Paleocene Santa Lucia Formation in Bolivia. This extended the range of Sebecus back to the beginning of the Paleogene, soon after the Cretaceous–Paleogene extinction event. In 1993, Gasparini et al. described Sebecus carajazus. This was not a fourth species but a misspelling, or lapsus calami, of Sebecus querejazus.
A 2007 study of sebecids reclassified several species. The two species S. huilensis and S. querejazus were given their own genera, Zulmasuchus and Langstonia, respectively. Langstonia huilensis, named after Langston, was distinguished from Sebecus by its narrower snout and widely spaced teeth. Zulmasuchus querejazus, named after Zulma Gasparini, one of the authors of the study, differs from Sebecus in its wider snout.
The postcranial skeleton of S. icaeorhinus was virtually unknown until Pol et al. (2012) described postcranial remains of several individuals of this species, including a partially articulated specimen MPEF-PV 1776 with anterior region of the dentary (allowing the identification of this individual as representing S. icaeorhinus) and most of the postcranial skeleton preserved. Estimates of total body length and mass of MPEF-PV 1776 vary from 2.2 to 3.1 m, and from 52.2 to 113.5 kg, respectively. The postcranial skeleton of Sebecus provides additional evidence of its terrestriality. Its limbs, especially femora, were proportionally longer than limbs of living crocodilians; the shoulder-to-hip length of its body can be estimated at 2.3 times the length of the femur - similar to another, unrelated terrestrial crocodylomorph, Pristichampsus, while American alligators have proportionally shorter femora.
Sebecus