Irritator lived during the Albian stage of the Cretaceous Period around 110 million years ago and is a genus of spinosaurid dinosaur. It was estimated to be about 26 feet long with an unusually shaped crest at the rear of its head. According to research, it likely ate fish, as well as other carrion. Only one fossil has been found: an 80 centimeter long skull found in the Brazilian Santana formation, which resembles the fossils of the Suchomimus and Spinosaurus. This skull was tampered with by fossil-poachers who illegally sold it in Brazil. Portions of the skull fossil were fabricated in plaster, such as the posterior portion of the sagittal crest.

The name of the genus came from the feeling of irritation that the authors felt when discovering that the snout had been artificially elongated by these poachers.

The Irritator is characterized especially by its curved lip region and the unusual length of its head, although these features are also similar to another spinosaurid, the Angaturama limai. This curious similarity could mean the bones belong to the same specimen. The Angaturama limai was described by A. Kellner and Diogenes A. Campos in 1996, and later 60% of a complete skeleton was discovered and displayed at the Federal University-owned Rio de Janeiro National Museum. It is suspected that the two partial fossil skulls came from the same individual specimen.

The specimen was found near what was probably a brackish lake, and it is assumed due to its teeth and the size of its head that it may be related to today’s alligators.

The nostrils of the dinosaur were shifted toward the back of the skull and the secondary palate made respiration possible even if the creature was partially under water or holding prey. Its sagittal crest is an indication for a pronounced neck musculature, which would have been necessary to withdraw the head quickly against water resistance and snap the jaw shut.

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