Commercial fossil-poachers excavated a chalk concretion containing the rear of a large skull with lower jaws near the town of Santana do Cariri in northeastern Brazil.
This fossil was acquired by dealers who illegally sold it—fossil trade has been prohibited by law in Brazil since 1942—to Rupert Wild of the State Museum of Natural History Stuttgart, Germany.
At the time it was assumed to be the skull of a giant basal pterosaur, or flying reptile, since the Chapada do Araripe region is famous for its copious pterosaur finds, and the German museum often bought such pieces.
As it promised to be a unique discovery of singular importance, German and British pterosaur experts were contacted to study the exemplar.
A paper describing it as a pterosaur had already been submitted for publication when the authors, German paleontologists Eberhard Frey and Hans-Dieter Sues, were disabused of this notion by the peer reviewers, who suggested the fossil belonged to a theropod dinosaur.

The skull was flattened somewhat sideways and, as is common with fossils, was partly crushed.
The right side was well-preserved, while the left was extensively damaged during collection.
Some of the skull's hindmost upper surface had eroded, and the lower jaw lacked its front end, both owing to breakage during fossilization.
Parts of the specimen were also cracked due to being part of a septarian concretion.
The tip of the upper jaw was also missing.
Since there were no signs of erosion, it had most probably broken off during or after the fossil's collection.
Evident corrosion on certain bones indicates acid preparation had been attempted.
A vertical fracture was present across the middle of the skull, which had apparently been sealed with car body filler.
In hopes of making it look more complete and valuable, the fossil traders had severely obscured the skull beneath plaster; a widespread practice among local collectors in the Chapada do Araripe, especially on fish fossils.
The buyers were unaware of the modifications to the illegally collected specimen until it was sent to universities in the United Kingdom for CT scan imaging.
This revealed the collectors had tried to reconstruct the skull by grafting parts of the maxilla (main upper jaw bone) onto the front of the rostrum (snout).
The skull (designated SMNS 58022) became the holotype specimen of the new genus and species Irritator challengeri in February 1996, when it was first scientifically described by paleontologists David M. Martill, Arthur R.I. Cruickshank, Eberhard Frey, Philip G. Small and Malcolm Clarke.
In this paper, Martill and his team wrote that the generic name Irritator came "from irritation, the feeling the authors felt (understated here) when discovering that the snout had been artificially elongated."
The type species, Irritator challengeri, was named after Professor Challenger, a character in Arthur Conan Doyle's novels, specifically The Lost World.
Two years earlier, Frey and Martill had named a new pterosaur species from the Crato Formation Arthurdactylus conandoylei, after the novelist himself.

When Martill and colleagues first described Irritator challengeri, the holotype was still extensively encased in calcareous rock matrix.
Researcher Diane M. Scott from the University of Toronto assumed the task of fully cleaning out the skull, allowing for a detailed redescription in 2002.
Written by Sues, Frey, Martill, and Scott, this inspection of the now fully prepared specimen negated many of Martill and colleagues' original observations, which were based on misinterpretations of the damaged and largely concealed skull.
The estimated length of the complete skull was 24 cm (9.4 in) shorter than previously proposed.
What was originally thought to be a prominent head crest proved to be an unattached, indeterminate bone fragment.
Furthermore, additional skull bones were identified.
As in the previous study, Sues and colleagues regarded the African genus Spinosaurus as the most similar taxon to Irritator, because they shared many dental features, including mostly straight conical tooth cr
Commercial fossil-poachers excavated a chalk concretion containing the rear of a large skull with lower jaws near the town of Santana do Cariri in northeastern Brazil. This fossil was acquired by dealers who illegally sold it—fossil trade has been prohibited by law in Brazil since 1942—to Rupert Wild of the State Museum of Natural History Stuttgart, Germany. At the time it was assumed to be the skull of a giant basal pterosaur, or flying reptile, since the Chapada do Araripe region is famous for its copious pterosaur finds, and the German museum often bought such pieces. As it promised to be a unique discovery of singular importance, German and British pterosaur experts were contacted to study the exemplar. A paper describing it as a pterosaur had already been submitted for publication when the authors, German paleontologists Eberhard Frey and Hans-Dieter Sues, were disabused of this notion by the peer reviewers, who suggested the fossil belonged to a theropod dinosaur.
The skull was flattened somewhat sideways and, as is common with fossils, was partly crushed. The right side was well-preserved, while the left was extensively damaged during collection. Some of the skull's hindmost upper surface had eroded, and the lower jaw lacked its front end, both owing to breakage during fossilization. Parts of the specimen were also cracked due to being part of a septarian concretion. The tip of the upper jaw was also missing. Since there were no signs of erosion, it had most probably broken off during or after the fossil's collection. Evident corrosion on certain bones indicates acid preparation had been attempted. A vertical fracture was present across the middle of the skull, which had apparently been sealed with car body filler. In hopes of making it look more complete and valuable, the fossil traders had severely obscured the skull beneath plaster; a widespread practice among local collectors in the Chapada do Araripe, especially on fish fossils. The buyers were unaware of the modifications to the illegally collected specimen until it was sent to universities in the United Kingdom for CT scan imaging. This revealed the collectors had tried to reconstruct the skull by grafting parts of the maxilla (main upper jaw bone) onto the front of the rostrum (snout). The skull (designated SMNS 58022) became the holotype specimen of the new genus and species Irritator challengeri in February 1996, when it was first scientifically described by paleontologists David M. Martill, Arthur R.I. Cruickshank, Eberhard Frey, Philip G. Small and Malcolm Clarke. In this paper, Martill and his team wrote that the generic name Irritator came "from irritation, the feeling the authors felt (understated here) when discovering that the snout had been artificially elongated." The type species, Irritator challengeri, was named after Professor Challenger, a character in Arthur Conan Doyle's novels, specifically The Lost World. Two years earlier, Frey and Martill had named a new pterosaur species from the Crato Formation Arthurdactylus conandoylei, after the novelist himself.
When Martill and colleagues first described Irritator challengeri, the holotype was still extensively encased in calcareous rock matrix. Researcher Diane M. Scott from the University of Toronto assumed the task of fully cleaning out the skull, allowing for a detailed redescription in 2002. Written by Sues, Frey, Martill, and Scott, this inspection of the now fully prepared specimen negated many of Martill and colleagues' original observations, which were based on misinterpretations of the damaged and largely concealed skull. The estimated length of the complete skull was 24 cm (9.4 in) shorter than previously proposed. What was originally thought to be a prominent head crest proved to be an unattached, indeterminate bone fragment. Furthermore, additional skull bones were identified. As in the previous study, Sues and colleagues regarded the African genus Spinosaurus as the most similar taxon to Irritator, because they shared many dental features, including mostly straight conical tooth cr
Irritator