Irritator challengeri
By José Carlos Cortés
Etymology: The One That Irritated
First Described By: Martill et al., 1996
Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Megalosauroidea, Megalosauria, Spinosauridae, Spinosaurinae
Status: Extinct
Time and Place: Between 110 and 108 million years ago, in the Albian of the Early Cretaceous
Irritator is known from the Romualdo Member of the Santana Formation in Brazil
Physical Description: Irritator was a Spinosaurid, so the weird crocodile-mimicking theropods that roamed the Cretaceous landscape across the Southern hemisphere (and some of Europe). Irritator, however, is not known from very much material, despite having loads written about it. It was one of the smaller members of the Spinosaur group, only about 7.5 meters long and not weigh more than one tonne - which may actually indicate it could have still had some sort of fluffy integument, though this still seems unlikely based on its ecology. As a Spinosaur, Irritator would have been fairly bulky, with a long and vaguely crocodilian skull. Its skull also featured a long thin crest going from the midline to the eye, where it flattened into a bulge - this was probably some sort of display structure. Little is known of the rest of its skeleton, but it is known to have had a long and well-clawed hand. It probably had some sort of sail on its back, but it probably was a shorter one, and whether or not its legs were a normal size is unknown.
By Alexander Vieira, CC BY-SA 4.0 (Irritator is on the far right, in green)
Diet: Irritator would have mainly fed upon fish and other aquatic organisms.
Behavior: Irritator, being a Spinosaur, spent most of its time in the water, swimming about and searching for food. Since it was rather small, it would have been able to fit in smaller streams of water than most of its other relatives. Though, since it probably still had fairly decent legs, it also would have spent a good amount of time on the land, surveying the shore for food and seeking out prey. Its long snout would then be used to grab fish and other animals from the water, using the lightweight instrument to grab food it might not be able to reach otherwise. While swimming, it would be able to use that snout to reach even more food than before, ducking its head underwater or doing the reverse to hide from land sources of prey. Its very powerful neck muscles would have also been extremely helpful in grabbing and holding onto thrashing prey.
By Fred Wierum, CC BY 3.0
Irritator was probably warm-blooded, and used its sail more for display than for keeping warm. This display structure may have been able to change color based on blood circulation or environment in order to send different messages to other members of the species. The crest on the center of the snout also probably served similar features, for displaying to one another. It seems likely that Irritator, like most other dinosaurs, took care of its young; but there is no evidence either way to support that hypothesis.
By PaleoGeekSquared, CC BY 3.0
Ecosystem: Irritator lived in the Romualdo Environment of Brazil, which was a basin of lakes surrounded by rivers and other wetland environments, filled to the brim with a wide variety of plantlife. Nearby was the burgeoning Atlantic Ocean, making this a Spinosaur’s favorite place of all. Here there were a wide variety of early flowering plants like magnolias, seagrasses, and lilies - all of which were associated heavily with this aquatic environment. There were many types of ray-finned fish, which would have been the primary source of prey for Irritator, as well as lobe-finned fish which would have also been decent sources of food. Sharks seem to have been rare. There were plenty of turtles too, including one of the earliest sea turtles Santanachelys. This was the land of extreme pterosaurs, including Anhanguera, Arirpesaurus, Barbosania, Brasileodactylus, Cearadacytlus, Maaradactylus, Santanadactylus, Tapejara, Thalassodromeus, Tropeognathus, Tupuxuara, and Unwindia. There was also a Notosuchian, Araripesuchus. There were other dinosaurs there too - the compsognathid Mirischia and the Tyrannosauroid Santanaraptor, which would have mainly fed on small animal prey.
By Scott Reid
Other: Irritator was found as part of the illegal fossil trade, initially mistake for a pterosaur, then a maniraptoran, before being finally identified as a spinosaur. The confusion surrounding this fossil - and the fact that the snout had been artificially elongated by the fossil traders - lead to its name. Its position within the Spinosaurs is well supported, and it seems to have been at least somewhat closely related to Spinosaurus itself, rather than Baryonyx on the other end of the family tree.
~ By Meig Dickson
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