Aegisuchus is an extinct genus of giant, flat-headed crocodyliform within the family Aegyptosuchidae. It existed in what is now Morocco during the Cenomanian age of the Late Cretaceous Epoch. The type species Aegisuchus witmeri was named in 2012 by paleontologists Casey Holliday and Nicholas Gardner, who nicknamed it "Shieldcroc" for the shield-like shape of its skull. A. witmeri is known from a single partial skull including the braincase and skull roof.
Holliday & Gardner, 2012
Holliday & Gardner, 2012
Aegisuchus is known only from a partial braincase and skull roof cataloged as ROM 54530. It is diagnosed by several autapomorphies, or unique features. At the center of the skull table is a raised and rough-surfaced boss on the parietal bone that is shaped like a circle. On either side of this boss are holes called dorsotemporal fenestrae, and the surrounding bone is relatively smooth. The quadrate bone in the temporal region of the skull has a rectangular projection called the adductor tubercle, which served as an attachment for muscles that closed the jaw. At the front of the skull table, projections on the laterosphenoid bones called capitate processes face out to the side. This feature is also seen in the skulls of living gharials, but evolved independently in each group. Also on the front surface are two holes of the dorsotemporal fenestrae, which pass through the skull and open at the skull table. On the front surface, a ridge of bone or torus makes up the lateral edge of each hole. The back of the skull is wide, with large projections on the exoccipital bones that would have anchored large epaxial muscles in the top part of the neck.
At 40 cubic centimetres, the braincase of Aegisuchus is much larger in volume than that of any other crocodyliform. Based on the ratio of braincase to skull length in other crocodilians, the total skull length of Aegisuchus is estimated to have been 2.08 to 2.86 metres (6.8 to 9.4 ft) in length. A similar ratio between braincase and body length puts Aegisuchus at 15 to 21 metres (49 to 69 ft) long when based on the proportions of long-snouted gharials, or 16 to 22 metres (52 to 72 ft) long when based on the proportions of short-snouted crocodiles. However, these proportions have been met with a lot of scrutiny, and it is more likely that Aegisuchus reached only 3.9 metres (13 ft) long.
The circular boss of roughened bone on the skull table is one of the most unusual features of Aegisuchus. As in most crocodilians, the rough-surfaced region was probably covered in a thick skin that tightly adhered to the skull. Surrounding the boss, the smooth-surfaced region bears several deep parallel channels for blood vessels, suggesting that thicker, more complex skin tissue covered this region. Vascularization is not seen in any other crocodilian, and may have been unique to Aegisuchus. Given that the blood vessel channels run into the braincase, the vascularized tissue may have served a thermoregulatory role by heating blood going to the brain and eyes. The central boss may have been used in mating displays, appearing as an eyespot. Modern crocodilians raise their heads out of the water as a social signal in mating displays; as a close relative of crocodilians, Aegisuchus likely had similar mating rituals.
The flattened shape of the skull of Aegisuchus suggests that it was an ambush predator resting at the surface of the water. Although only the back of the skull is known, other characteristics can be inferred from the closely related Aegyptosuchus. Aegisuchus probably had eyes that faced directly upward, with no raised ridges surrounding the sockets. A strut of bone called the postorbital bar, which in most crocodilians is vertically oriented, would have been almost flat. The flattened skull of Aegisuchus required significant alteration to jaw muscles. The adductor muscles that close the jaw shifted to a more vertical orientation in Aegisuchus. Muscles like the adductor mandibulae externus medialis, which are weak in most crocodilians, became more important as jaw closers and were greatly enlarged. The broad-surfaced occipital region at the back of the skull provides a large attachment area for the splenius capitis muscles of the neck. With a long flattened snout, Aegisuchus would have had great difficulty in raising its head and opening its mouth if it did not have large neck muscles. A depressed region in the lower part of the back of the skull suggests that the jaw adductor muscles were also large, facilitating jaw opening. A similar mechanism for lifting the head and opening the jaws is seen in the Late Triassic amphibian Gerrothorax. Aegisuchus has a very flexible articulation between the skull and vertebral column, allowing a greater degree of skull elevation than other crocodilians.
During the Late Cretaceous, northern Africa was a humid region near the Tethys Ocean, a seaway between the southern continents of Gondwana and northern land masses of Laurasia. At this time, the Kem Kem Beds of Morocco were deposited in a freshwater delta system. Aegisuchus lived within this delta alongside fishes, turtles, snakes and varanid lizards, pterosaurs, and sauropod and theropod dinosaurs. Stomatosuchids are also known from the Kem Kem Beds, and probably shared a close ecological niche with Aegisuchus as river predators.
With its flattened skull, Aegisuchus was probably an ambush predator. Possible prey include coelacanths, lungfish, and bichirs, all of which have been found in the Kem Kem beds. As an opportunistic predator, Aegisuchus may also have preyed on land vertebrates such as reptiles. Aegisuchus could have potentially fallen prey to much larger predators such as Spinosaurus.
The Late Cretaceous was an important time in crocodilian evolution because many land masses were breaking up. What is now Europe and Asia was drifting away from Africa to form the Tethys Ocean, while North America continued to separate from the rest of Laurasia as the Atlantic Ocean widened. With the presence of several early crocodilians like Borealosuchus, North America is often hypothesized as the continent of origin for Crocodylia. However, the presence of agyptosuchids such as Aegisuchus in northern Africa suggests that early crocodilian evolution was focused instead around the Tethys Ocean. The agyptosuchids represent a highly specialized and highly endemic branch of crocodyliforms at a time when crocodilian diversity and geographic range were expanding.
Aegyptosuchidae is an extinct family of eusuchian crocodyliforms from the Cretaceous period of Africa. They are characterized by their large size and flat heads. The family includes two genera, Aegyptosuchus and Aegisuchus.Aegyptosuchus
Aegyptosuchus ("Egyptian crocodile") is an extinct genus of aegyptosuchid eusuchian crocodyliform. This taxon was coined by Kuhn (1936) as a monotypic family-level taxon redundant with the Cretaceous genus Aegyptosuchus. Carroll (1988) classified the genus in the family Stomatosuchidae. Only one species is descript, Aegyptosuchus peyeri.Amphicotylus
Amphicotylus is an extinct genus of goniopholidid mesoeucrocodylian from the Tithonian of Colorado and Oklahoma.Anthracosuchus
Anthracosuchus (meaning "coal crocodile" in Greek) is an extinct genus of dyrosaurid crocodyliform from the Paleocene of Colombia. Remains of Anthracosuchus balrogus, the only known species, come from the Cerrejón Formation in the Cerrejón mine, and include four fossil specimens with partial skulls. Anthracosuchus differs from other dyrosaurids in having an extremely short (brevirostrine) snout, widely spaced eye sockets with bony protuberances around them, and osteoderms that are smooth and thick. It is one of the most basal dyrosaurids along with Chenanisuchus and Cerrejonisuchus. The species name is a reference to the Balrog, a creature in J. R. R. Tolkien's fantasy novel The Lord of the Rings that could, like the remains of Anthracosuchus, be found in a mine.Atoposauridae
Atoposauridae is a family of crocodile-line archosaurs belonging to Neosuchia. The majority of the family are known from Late Jurassic to Early Cretaceous marine deposits in France, Portugal, and Bavaria in southern Germany. The discovery of the genus Aprosuchus, however, extends the duration of the lineage to the end of the Cretaceous in Romania.Brillanceausuchus
Brillanceausuchus is an extinct genus of atoposaurid crocodylomorph. Fossils have been found in Early Cretaceous–age rocks of Cameroon. The genus is notable for the position of the secondary choana within its palate. Parts of the pterygoid bones make up the rostral margin of the choana and thus separate it from the palatines, a feature also seen in the more advanced neosuchian suborder Eusuchia. This characteristic was once thought to be characteristic of Eusuchia, but its presence in Brillanceausuchus suggests that the trait is homoplasic, thus making the evolution of the position of the choana within crocodilians more complex than previously thought.Coelosuchus
Coelosuchus is an extinct genus of goniopholidid mesoeucrocodylian. Fossils have been found from the Graneros Shale of the Benton Group in Wyoming, and are of Cenomanian age. It was slightly over 1 meter in length.Eusuchia
The Eusuchia ("true crocodiles") are a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades died out 35 and 11 million years ago, all living crocodilian species are eusuchians, as are many extinct forms.Karatausuchus
Karatausuchus is an extinct genus of atoposaurid crocodylomorph. It is known from a single specimen discovered in the Late Jurassic (Oxfordian - Kimmeridgian) Karabastau Svita from the vicinity of Mikhailovka in the Karatau Mountains of southern Kazakhstan. The type specimen is PIN 25858/1, a complete but poorly preserved juvenile skeleton with some possible soft tissue preservation. It is notable for having over 90 teeth, but its other anatomical details are difficult to discern. The length of this individual is estimated at 160 millimetres (6.3 in). Karatausuchus was described in 1976 by Mikhail Efimov, and the type species is K. sharovi.Kem Kem Beds
The Kem Kem Beds (also referred to by various names including the Continental Red Beds and Continental intercalaire) is a geological formation along the border between Morocco and Algeria in southeastern Morocco, whose strata date back to the Late Cretaceous.Dinosaur remains are among the fossils that have been recovered from the formation. Recent fossil evidence in the form of isolated large abelisaurid bones and comparisons with other similarly aged deposits elsewhere in Africa indicates that the fauna of the Kem Kem Beds (specifically in regard to the numerous predatory theropod dinosaurs) may have been mixed together due to the harsh and changing geology of the region when in reality they would likely have preferred separate habitats and likely would be separated by millions of years.Khoratosuchus
Khoratosuchus is an extinct genus of neosuchian crocodylomorph which existed in northeast Thailand during the early Cretaceous period. Its type species is Khoratosuchus jintasakuli. Khoratosuchus is the youngest and most advanced Mesozoic crocodyliform yet known from Thailand. It possesses several distinctive features that help determine its phylogenetic position among crocodylomorphs, including secondary choanae relatively posterior and almost encircled by the pterygoid bones on the palate and a smooth dorsal surface of the skull.Koumpiodontosuchus
Koumpiodontosuchus is an extinct genus of neosuchian crocodyliform that lived in the Early Cretaceous. The only species is K. aprosdokiti.Laganosuchus
Laganosuchus is an extinct genus of stomatosuchid crocodyliform. Fossils have been found from Niger and Morocco and date back to the Upper Cretaceous.Nannosuchus
Nannosuchus (meaning "dwarf crocodile") is an extinct genus of goniopholidid mesoeucrocodylian from the Berriasian of England.Sabresuchus
Sabresuchus is an extinct genus of neosuchian crocodyliform from the Cretaceous of Europe. The name is derived from 'Sabre' in reference to the enlarged and curved fifth maxillary tooth, and 'suchus' from the Ancient Greek for crocodile.Shamosuchus
Shamosuchus is an extinct genus of neosuchian crocodile that lived during the Late Cretaceous (Santonian-Campanian) period in what is now the Gobi desert of Mongolia, approximately 85 to 74 million years ago.Symptosuchus
Symptosuchus is an extinct genus of goniopholidid mesoeucrocodylian. It is known from the Late Cretaceous of Argentina. Argentine paleontologist Florentino Ameghino named the genus in 1899, along with the type species S. contortidens. It was formally described by Carlos Rusconi in 1934.Wahasuchus
Wahasuchus is a genus of extinct mesoeucrocodylian of the Middle Campanian age found in the Quseir Formation, Egypt. The generic name derives from the Arabic word واحة (waha), which means "oasis", and souchos from the Greek in honor of crocodile-headed god of ancient Egypt. The specific egyptensis (Lat.) means from Egypt.Fossils of skull and jaw fragments, dorsal vertebrae, and fragmentary appendicular remains have been recovered.