Spinosaurid nostrils were set far back on the skull, at least behind the teeth of the premaxillae, instead of at the front of the snout as in most theropods. Those of "Baryonyx" and "Suchomimus" were large and started between the first and fourth maxillary teeth, while "Spinosaurus"'s nostrils were far smaller and more retracted. "Irritator"'s nostrils were positioned similarly to those of "Baryonyx" and "Suchomimus", and were between those of "Spinosaurus" and "Suchomimus" in size. Spinosaurids had long secondary palates, bony and rugose structures on the roof of their mouths that are also found in extant crocodilians, but not in most theropod dinosaurs. "Oxalaia" had a particularly elaborate secondary palate, while most spinosaurs had smoother ones. The teeth of spinosaurids were conical, with an oval to circular cross section and either absent or very fine serrations. Their teeth ranged from slightly recurved, such as those of "Baryonyx" and "Suchomimus", to straight, such as those of "Spinosaurus" and "Siamosaurus", and the crown was often ornamented with longitudinal grooves or ridges.