Irritator is a genus of spinosaurid theropod dinosaur. The theropod lived in what is now Brazil during the Early Cretaceous Period, about 110 million years ago.
Discovery & NamingEdit
It is known from a nearly complete skull. Fossil dealers had acquired this skull and illegally sold it to the State Museum of Natural History Stuttgart.
In 1996, the specimen became the holotype of the type species Irritator challengeri. The genus name comes from the word "irritation", reflecting the feelings of paleontologists who found the skull had been heavily damaged and altered by the collectors. The species name is an homage to the fictional character Professor Challenge. 
Irritator is a member of Spinosauridae, in the inner family of Spinosaurinae; it was a rather closer relative of Spinosaurus and Siamosaurus.
Estimated at between 7.5 and 8 meters (20 to 26 ft) in length, Irritator weighed around 1 tonne, making it one of the 'smaller' spinosaurids.
The diet of Irritator has been identified as a Generalistic Carnivorous theropod and stands as an example for spinosaurid diet. A research made in 2002, by Sues and colleagues pointed out, that there would be no reason to assume that the Spinosauridae specialized completely in fishing. They stressed rather that this head morphology indicates generalist feeding, particularly on small prey animals. In fact, portions of a young Iguanodon, a terrestrial herbivore, were found inside the fossil skeleton of one Baryonyx. 
Naish and colleagues in 2004 supported the theory that Irritator hunted both aquatic and terrestrial animals as a generalist within the coastal area and in addition probably searched for carrion 
This conclusion has been bolstered by the evidence such as; tooth belonging to Irritator was discovered still inserted into the fossil neck vertebral column of an ornithocheirid pterosaur, likely with a wingspan of 3.3 m (11 ft). This indicates that Irritator ate pterosaurs as well. 
In 2018, Aureliano and colleagues presented a possible scenario for the food web of the Romualdo Formation. The researchers proposed that spinosaurines from the formation may have also preyed on terrestrial and aquatic crocodyliforms, juveniles of their own species, turtles, and small to medium-sized dinosaurs. This would strongly indicates the fact that the spinosaurines are indeed the primary apex predators within their ecosystem 
- ↑ https://jgs.lyellcollection.org/content/153/1/5
- ↑ https://www.nature.com/news/brazil-clamps-down-on-illegal-fossil-trade-1.14808
- ↑ https://www.researchgate.net/publication/254314432_Irritator_challengeri_a_Spinosaurid_Dinosauria_Theropoda_from_the_Lower_Cretaceous_of_Brazil
- ↑ https://www.researchgate.net/publication/40663003_Ecology_Systematics_and_Biogeographical_Relationships_of_Dinosaurs_Including_a_New_Theropod_from_the_Santana_Formation_Albian_Early_Cretaceous_of_Brazil
- ↑ https://www.tandfonline.com/doi/abs/10.1080/08912960410001674200
- ↑ https://www.nature.com/articles/430033a
- ↑ https://sp.lyellcollection.org/content/455/1/7
- ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3665537/
- ↑ https://paleorxiv.org/mjt95/
- ↑ https://osf.io/bjkg6/files/
- ↑ https://www.researchgate.net/publication/324950412_Semi-aquatic_adaptations_in_a_spinosaur_from_the_Lower_Cretaceous_of_Brazil
- ↑ https://www.sciencedirect.com/science/article/pii/S0195667117305153