Suchomimus lived in a fluvial environment of vast floodplains alongside many other dinosaurs, in addition to pterosaurs, crocodylomorphs, bony fishes, testudines, and bivalves.

In 1997, American palaeontologist Paul Sereno and his team at Gadoufaoua discovered Fossils that represented about two-thirds of a large theropod dinosaur skeleton in Niger.

[2] S. tenerensis is potentially a junior synonym of another spinosaurid from the Elrhaz Formation, Cristatusaurus lapparenti, named the same year based on jaw fragments and vertebrae.

[3] The skull elements were considered indistinguishable from those of Baryonyx walkeri from the Barremian of England by British paleontologists Alan Charig and Angela Milner.

[6] In a 2004 conference abstract, Hutt and Newberry supported the synonymy based on a large theropod vertebra from the Isle of Wight which they attributed to an animal closely related to Baryonyx and Suchomimus.

[8][9][10][11][12] A 2017 review paper by the palaeontologist Carlos Roberto A. Candeiro and colleagues stated that this debate was more in the realm of semantics than science, as it is generally agreed that B. walkeri and S. tenerensis are distinct, related species.

The tip of the snout was enlarged sideways and carried a "terminal rosette" of longer teeth, seven per side in the premaxillae and about the same number in the corresponding part of the lower jaw.

[1] The upper jaw had a prominent kink just behind the rosette, protruding downwards; this convexly curved part of the maxilla had the longest teeth of the entire skull.

The external nares were long, narrow and horizontally positioned; the same was true of the larger antorbital fenestrae, a pair of bony openings in front of the eyes.

The lower jaws were greatly elongated and narrow, forming a rigid structure as their dentaries touched each other at the midline, reinforcing the mandible against torsional (bending and twisting) forces.

Accordingly, the ulna of the lower arm was well-developed with an enormous olecranon (upper process set-off from the shaft), an exceptional trait shared with Baryonyx.

Sereno and colleagues pointed out that the more retracted nostrils in Irritator and the tall sail of Spinosaurus could also be unique traits of spinosaurines, though material from other taxa is needed to know for sure.

[1][19] Sereno and colleagues in 1998 analyzed the distribution of forty-five traits to produce a cladogram that showed Suchomimus and Baryonyx to be distinct but closely related.

[20] They shared features such as long, narrow, crocodile-like skulls; sub-circular teeth, with fine to no serrations; the terminal rosette of the snout; and a secondary palate that made them more resistant to torsion.

Since Suchomimus was more closely related to Baryonyx (from Europe) than to Spinosaurus—although that genus also lived in Africa—the distribution of spinosaurids cannot be explained as vicariance resulting from continental rifting.

[19] In 1998 Sereno and colleagues suggested the same dietary preference for Suchomimus, based on its elongated jaws, spoon-shaped terminal rosette, and long teeth reminiscent of those of piscivorous crocodilians.

[1] American palaeontologist Thomas Holtz noted that spinosaurid teeth were adapted for grasping rather than slicing, hence their reduced serrations, which in most other theropods were more prominent.

Suchomimus's extensive secondary palate, which would have made the roof of the mouth more solid, allowed it to better resist twisting forces exerted by prey.

[29][19] A 2005 study by Canadian paleontologist François Therrien and colleagues posited that spinosaur forelimbs were probably used for hunting larger prey items, given that their snouts could not resist the bending stress.

[30] In a 2017 review of the family, David Hone and Holtz also considered possible functions in digging for water sources or hard to reach prey, as well as burrowing into soil to construct nests.

Suchomimus itself was more adapted to a life hunting in shallow water due to its hollow bones, while Baryonyx and Spinosaurus were capable of fully submerging underwater and diving after prey.

[31][32][33] The Elrhaz Formation, part of the Tegama Group, consists mainly of fluvial sandstones with low relief, much of which is obscured by sand dunes.

[37][38] The sediment layers of the formation have been interpreted as an inland habitat of extensive freshwater floodplains and fast-moving rivers, with a tropical climate that likely experienced seasonal dry periods.

Crocodylomorphs were abundant; represented by the giant pholidosaur species Sarcosuchus imperator, as well as small notosuchians like Anatosuchus minor, Araripesuchus wegeneri, and Stolokrosuchus lapparenti.