Sarcosuchus

Sarcosuchus (meaning 'flesh crocodile' and commonly called "SuperCroc", is an extinct genus of crocodyliform and distant relative of the crocodile. It dates from the early Cretaceous Period of what is now Africa and is one of the largest giant crocodile-like reptiles that ever lived. It was almost twice as long as the modern saltwater crocodile and weighed approximately 8 tonnes.

Until recently, all that was known of the genus was a few fossilized teeth and armour scutes, which were discovered in the Sahara Desert by the French paleontologist Albert-Félix de Lapparent, in the 1940s or 1950s. However, in 1997 and 2000, Paul Sereno discovered half a dozen new specimens, including one with about half the skeleton intact and most of the spine. All of the other giant crocodiles are known only from a few partial skulls, so which is actually the biggest is an open question.

Description
When fully mature, Sarcosuchus is believed to have been almost as long as a city bus (9 – 12.2 meters or 29–40 ft) and weighed up to 8 tonnes.The largest living crocodilian, the saltwater crocodile, is less than two-thirds of that length (6.3 meters or 20.6 ft is the longest confirmed individual) and a small fraction of the weight (1,200 kg, or 1.3 tons).

The very largest Sarcosuchus is believed to have been the oldest. Osteoderm growth rings taken from an 80% grown individual (based on comparison to largest individual found) suggest that Sarcosuchus kept growing throughout its entire 50–60 year average life span (Sereno et al., 2001). Modern crocodiles grow at a rapid rate, reaching their adult size in about a decade, then growing more slowly afterwards.

Its skull alone was as big as a human adult (1.78 m, or 5 ft 10 inches). The upper jaw overlapped the lower jaw, creating an overbite. The jaws were relatively narrow (especially in juveniles). The snout comprises about 75% of the skull's length (Sereno et al., 2001).

The huge jaw contained 132 thick teeth (Larsson said they were like "railroad spikes" [citation needed]). The teeth were conical, adapted for grabbing and holding; instead of narrow, adapted for slashing (like the teeth of some land-dwelling carnivores), and more like that of true crocodilians. Sarcosuchus could probably exert a force of 80 kN (18,000 lbf) with its jaw, making it very unlikely that prey could escape.

It had a row of bony plates or osteoderms, running down its back, the largest of which were 1 m (3 ft) long. The scutes served as armor and may have helped support its great mass, but also restricted its flexibility.[citation needed]

Sarcosuchus also had a strange depression at the end of its snout. Called a bulla, it has been compared to the ghara seen in gharials. Unlike the ghara, though, the bulla is present in all Sarcosuchus skulls that have been found so far. This suggests it was not a sexually selected character (only the male gharial has a ghara). The purpose of this structure remains enigmatic. Sereno and others asked various reptile researchers what their thoughts on this bulla were. Opinions ranged from it being an olfactory enhancer to being connected to a vocalization device (Geology News, 2001).

Behavior and diet
Like true crocodiles, Sarcosuchus might have made a wide range of vocalisations, from grunts and squeaks to hisses, growls, barks, bellows and roars. These sounds may have been used by Sarcosuchus to stake out territory, attract mates and to communicate with their progeny. The eye sockets of Sarcosuchus rotated upwards and were somewhat telescoped (Sereno et al., 2001). This suggests that the animal probably spent most of its time with the majority of its body submerged, watching the shore for prey.

It seems likely that it ate the large fish and turtles of the Cretaceous. As the overhanging jaw and stout teeth are designed for grabbing and crushing, its primary prey may have been large animals and smaller dinosaurs, which it ambushed, dragged into the water, crushed, drowned and then tore apart.

It may have come into conflict with Suchomimus, an 11 m (36 ft) theropod dinosaur with a gharial-like snout, whose fossils were found in the same geological formation as Sarcosuchus. According to Sereno [citation needed], "because the ancient animal was so large, it could easily handle huge dinosaurs, including the massive long-necked, small-headed sauropods that were common in that African region".

Other crocodilian biologists are skeptical of the animal's "giant killing" capabilities.[citation needed] The long, thin snout of Sarcosuchus was very similar to the thin snouts of the modern gharial, the false gharial and the slender-snouted crocodile, all of which are nearly exclusive fish-eaters and incapable of tackling large prey. This can be contrasted to both the modern Nile crocodile and the extinct Deinosuchus, both of which exhibit very broad, heavy skulls, suitable for dealing with large prey. This, coupled with the abundance of large, lobe-finned fish in its environment, leads many to suggest that, far from being a dinosaur killer, Sarcosuchus was simply a large piscivore, a scaled-up version of the modern gharial.

However, while the snout of juvenile Sarcosuchus strongly resembled modern narrow-snouted crocodiles in width, it expands dramatically in mature individuals (Sereno et al., 2001). While still comparatively narrower than the snout of a Nile crocodile, the snout is still much wider than the snouts of crocodilians like the gharial. In addition, the teeth do not interlock [citation needed], like those of mostly piscivorous crocodilians. This suggests that, like the Nile crocodile, it may have complemented a primarily fish diet with terrestrial animals, at least upon maturity.[citation needed]

It is pertinent to note, though, that the lobe-finned fish that shared the waters with Sarcosuchus were often in excess of 1.8 m (6 ft) long and 90 kg (200 lb) in weight.[citation needed] This raises the possibility of those adaptations, which seem to indicate large or moderate-sized terrestrial prey, may instead have been adaptations for dealing with exceptionally large fish (many species of which possessed a layer of osteoderms, for protection).